Papers for Thursday, Jul 06 2023

Extreme emission line galaxies (EELGs) are considered the primary contributor to cosmic reionization and are valuable laboratories to study the astrophysics of massive stars. It is strongly expected that Roman's High Latitude Wide Area Survey (HLWAS) will find many strongly gravitationally lensed [O III] emitters at Cosmic Noon (1 < z < 2.8). Roman imaging and grism spectroscopy alone will simultaneously confirm these strong lens systems and probe their interstellar medium (ISM) and stellar properties on small scales ($\lesssim$ 100 pc). Moreover, these observations will synergize with ground-based and space-based follow-up observations of the discovered lensed [O III] emitters in multi-wavelength analyses of their properties (e.g., massive stars and possible escape of ionizing radiation), spatially resolved on the scales of individual star cluster complexes. Only Roman can uniquely sample a large number of lensed [O III] emitters to study the small scale (~ 100 pc) ISM and stellar properties of these extreme emission line galaxies, detailing the key physics of massive stars and the ISM that govern cosmic reionization.

We present a novel mechanism for gravitational wave generation in the early Universe. Light spectator scalar fields during inflation can acquire a blue-tilted power spectrum due to stochastic effects. We show that this effect can lead to large curvature perturbations at small scales (induced by the spectator field fluctuations) while maintaining the observed, slightly red-tilted curvature perturbations at large cosmological scales (induced by the inflaton fluctuations). Along with other observational signatures, such as enhanced dark matter substructure, large curvature perturbations can induce a stochastic gravitational wave background (SGWB). The predicted strength of SGWB in our scenario, $\Omega_{\rm GW}h^2 \simeq 10^{-20} - 10^{-15}$, can be observed with future detectors, operating between $10^{-5}$ Hz and 10 Hz. We note that, in order to accommodate the newly reported NANOGrav observation, one could consider the same class of spectator models. At the same time, one would need to go beyond the simple benchmark considered here and consider a regime in which a misalignment contribution is also important.

Understanding planetesimal formation is an essential first step to understanding planet formation. The distribution of these first solid bodies will drive the locations where planetary embryos can grow. We seek to understand the parameter space of possible protoplanetary disk formation and evolution models of our Solar System. A good protoplanetary disk scenario for the Solar System must meet at least the following three criteria: 1) an extended dust disk (at least 45 au); 2) formation of planetesimals in at least two distinct locations; and 3) transport of high temperatures condensates (i.e., calcium-aluminium-rich inclusion, CAIs) to the outer disk. We explore a large parameter space to study the effect of the disk viscosity, the timescale of infall of material into the disk, the distance within which material is deposited into the disk, and the fragmentation threshold of dust particles. We find that scenarios with a large initial disk viscosity ($\alpha>0.05$), relatively short infall timescale ($T_{infall}<100-200$ kyr), and a small centrifugal radius ($R_C\sim0.4$~au; the distance within which material falls into the disk) result in disks that satisfy the criteria for a good protoplanetary disk of the Solar System. The large initial viscosity and short infall timescale result in a rapid initial expansion of the disk, which we dub the inflationary phase of the disk. Furthermore, a temperature-dependent fragmentation threshold, which mimics that cold icy particles break more easily, results in larger and more massive disks. This results in more "icy" than "rocky" planetesimals. Such scenarios are also better in line with our Solar System, which has small terrestrial planets and massive giant planet cores. Finally, we find that scenarios with large $R_C$ cannot transport CAIs to the outer disk and do not produce planetesimals at two locations within the disk.

We present the first results from the Revealing Low-Luminosity Active Galactic Nuclei (ReveaLLAGN) survey, a JWST survey of seven nearby LLAGN. We focus on two observations with the Mid-Infrared Instrument's (MIRI) Medium Resolution Spectrograph (MRS) of the nuclei of NGC 1052 and Sombrero (NGC 4594 / M104). We also compare these data to public JWST data of a higher-luminosity AGN, NGC 7319. JWST clearly resolves the AGN component even in Sombrero, the faintest target in our survey; the AGN components have very red spectra. We find that the emission-line widths in both NGC 1052 and Sombrero increase with increasing ionization potential, with FWHM > 1000 km/s for lines with ionization potential > 50 eV. These lines are also significantly blue-shifted in both LLAGN. The high ionization potential lines in NGC 7319 show neither broad widths or significant blue shifts. Many of the lower ionization potential emission lines in Sombrero show significant blue wings extending > 1000 km/s. These features and the emission-line maps in both galaxies are consistent with outflows along the jet direction. Sombrero has the lowest luminosity high-ionization potential lines ([Ne V] and [O IV]) ever measured in the mid-IR, but the relative strengths of these lines are consistent with higher luminosity AGN. On the other hand, the [Ne V] emission is much weaker relative to the [Ne III}] and [Ne II] lines of higher-luminosity AGN. These initial results show the great promise that JWST holds for identifying and studying the physical nature of LLAGN.

According to the current concordance cosmological model, the dark matter (DM) particles are collision-less and produce self-gravitating structures with a central cusp which, generally, is not observed. The observed density tends to a central plateau or core, explained within the cosmological model through the gravitational feedback of baryons on DM. This mechanism becomes inefficient when decreasing the galaxy stellar mass so that in the low-mass regime (Mstar << 10**6 Msun) the energy provided by the baryons is insufficient to modify cusps into cores. Thus, if cores exist in these galaxies they have to reflect departures from the collision-less nature of DM. Measuring the DM mass distribution in these faint galaxies is extremely challenging, however, their stellar mass distribution can be characterized through deep photometry. Here we provide a way of using only the stellar mass distribution to constrain the underlying DM distribution. The so-called Eddington inversion method allows us to discard pairs of stellar distributions and DM potentials requiring (unphysical) negative distribution functions in the phase space. In particular, cored stellar density profiles are incompatible with the Navarro, Frenk, and White (NFW) potential expected from collision-less DM if the velocity distribution is isotropic and the system spherically symmetric. Through a case-by-case analysis, we are able to relax these assumptions to consider anisotropic velocity distributions and systems which do not have exact cores. In general, stellar distributions with radially biased orbits are difficult to reconcile with NFW-like potentials, and cores in the baryon distribution tend to require cores in the DM distribution.

Observations of the millimeter sky contain valuable information on a number of signals, including the blackbody cosmic microwave background (CMB), Galactic emissions, and the Compton-$y$ distortion due to the thermal Sunyaev-Zel'dovich (tSZ) effect. Extracting new insight into cosmological and astrophysical questions often requires combining multi-wavelength observations to spectrally isolate one component. In this work, we present a new arcminute-resolution Compton-$y$ map, which traces out the line-of-sight-integrated electron pressure, as well as maps of the CMB in intensity and E-mode polarization, across a third of the sky (around 13,000 sq.~deg.). We produce these through a joint analysis of data from the Atacama Cosmology Telescope (ACT) Data Release 4 and 6 at frequencies of roughly 93, 148, and 225 GHz, together with data from the \textit{Planck} satellite at frequencies between 30 GHz and 545 GHz. We present detailed verification of an internal linear combination pipeline implemented in a needlet frame that allows us to efficiently suppress Galactic contamination and account for spatial variations in the ACT instrument noise. These maps provide a significant advance, in noise levels and resolution, over the existing \textit{Planck} component-separated maps and will enable a host of science goals including studies of cluster and galaxy astrophysics, inferences of the cosmic velocity field, primordial non-Gaussianity searches, and gravitational lensing reconstruction of the CMB.

The Astro2020 Decadal Survey has identified the mapping of the circumgalactic medium (CGM, gaseous plasma around galaxies) as a key objective. We explore the prospects for characterizing the CGM in and around nearby galaxy halos with future large grasp X-ray microcalorimeters. We create realistic mock observations from hydrodynamical simulations (EAGLE, IllustrisTNG, and Simba) that demonstrate a wide range of potential measurements, which will address the open questions in galaxy formation and evolution. By including all background and foreground components in our mock observations, we show why it is impossible to perform these measurements with current instruments, such as X-ray CCDs, and only microcalorimeters will allow us to distinguish the faint CGM emission from the bright Milky Way (MW) foreground emission lines. We find that individual halos of MW mass can, on average, be traced out to large radii, around R500, and for larger galaxies even out to R200, using the OVII, OVIII, or FeXVII emission lines. Furthermore, we show that emission line ratios for individual halos can reveal the radial temperature structure. Substructure measurements show that it will be possible to relate azimuthal variations to the feedback mode of the galaxy. We demonstrate the ability to construct temperature, velocity, and abundance ratio maps from spectral fitting for individual galaxy halos, which reveal rotation features, AGN outbursts, and enrichment.

We present Paper II of the Eccentric Debris Disc Morphologies series to explore the effects that significant free and forced eccentricities have on high-resolution millimetre-wavelength observations of debris discs, motivated by recent ALMA images of HD53143's disc. In this work, we explore the effects of free eccentricity, and by varying disc fractional widths and observational resolutions, show for a range of narrow eccentric discs, orbital overlaps result in dust emission distributions that have either one or two radial peaks at apocentre and/or pericentre. The narrowest discs contain two radial peaks, whereas the broadest discs contain just one radial peak. For fixed eccentricities, as fractional disc widths are increased, we show that these peaks merge first at apocentre (producing apocentre glow), and then at pericentre (producing pericentre glow). Our work thus demonstrates that apocentre/pericentre glows in models with constant free and forced eccentricities can be both width and resolution dependent at millimetre wavelengths, challenging the classical assertion that apocentre/pericentre glows are purely wavelength dependent. We discuss future high-resolution observations that can distinguish between competing interpretations of underlying debris disc eccentricity distributions.

The patchy kinetic Sunyaev-Zel'dovich (kSZ) signal is an integral probe of the timing and morphology of the epoch of reionization (EoR). Recent observations have claimed a low signal-to-noise (S/N) measurement, with a dramatic increase in S/N expected in the near future. In this work, we quantify what we can learn about the EoR from the kSZ signal. We perform Bayesian inference by sampling galaxy properties and using forward-models of the kSZ as well as other EoR and galaxy observations in the likelihood. Including the recent kSZ measurement obtained by the South Pole Telescope ($\mathcal{D}_{3000}^{\rm{pkSZ}} = 1.1_{-0.7}^{+1.1} \mu$K$^2$) shifts the posterior distribution in favor of faster and later reionization models, resulting in lower values of the optical depth to the CMB: $\tau_e = 0.052_{-0.008}^{+0.009}$ with a 68$\%$ confidence interval (C.I.). The combined EoR and UV luminosity function observations also imply a typical ionizing escape fraction of $0.04_{-0.03}^{+0.05}$ (95$\%$ C.I.), without a strong dependence on halo mass. We show how the patchy kSZ power from our posterior depends on the commonly-used parameters of reionization. For a given midpoint and duration, the EoR morphology only has a few percent impact on the patchy kSZ power in our posterior. However, a physical model is needed to obtain tight constraints from the current low S/N patchy kSZ measurement, as it allows us to take advantage of complimentary high-$z$ observations. Future high S/N detections of the patchy kSZ should decrease the current uncertainties on the timing of the EoR by factors of $\sim$2 - 3.

We present six epochs of optical spectropolarimetry of the Type II supernova (SN) 2023ixf ranging from $\sim$ 2 to 15 days after the explosion. Polarimetry was obtained with the Kast double spectrograph on the Shane 3 m telescope at Lick Observatory, representing the earliest such observations ever captured for an SN. We observe a high continuum polarization $p_{\text{cont}} \approx 1$ % on days +1.4 and +2.5 before dropping to 0.5 % on day +3.5, persisting at that level up to day +14.5. Remarkably, this change coincides temporally with the disappearance of highly ionized "flash" features. The decrease of the continuum polarization is accompanied by a $\sim 70^\circ$ rotation of the polarization position angle ($PA$) as seen across the continuum. The early evolution of the polarization may indicate different geometric configurations of the electron-scattering atmosphere as seen before and after the disappearance of the emission lines associated with highly-ionized species (e.g., He II, C IV, N III), which are likely produced by elevated mass loss shortly prior to the SN explosion. We interpret the rapid change of polarization and $PA$ from days +2.5 to +4.5 as the time when the SN ejecta emerge from the dense asymmetric circumstellar material (CSM). The temporal evolution of the continuum polarization and the $PA$ is consistent with an aspherical SN explosion that exhibits a distinct geometry compared to the CSM. The rapid follow-up spectropolarimetry of SN 2023ixf during the shock ionization phase reveals an exceptionally asymmetric mass-loss process leading up to the explosion.

The hot, X-ray-emitting phase of the circumgalactic medium in galaxies is believed to be the reservoir of baryons from which gas flows onto the central galaxy and into which feedback from AGN and stars inject mass, momentum, energy, and metals. These effects shape the velocity fields of the hot gas, which can be observed by X-ray IFUs via the Doppler shifting and broadening of emission lines. In this work, we analyze the gas kinematics of the hot circumgalactic medium of Milky Way-mass disk galaxies from the TNG50 simulation with synthetic observations to determine how future instruments can probe this velocity structure. We find that the hot phase is often characterized by outflows outward from the disk driven by feedback processes, radial inflows near the galactic plane, and rotation, though in other cases the velocity field is more disorganized and turbulent. With a spectral resolution of $\sim$1 eV, fast and hot outflows ($\sim$200-500 km s$^{-1}$) can be measured, depending on the orientation of the galaxy on the sky. The rotation velocity of the hot phase ($\sim$100-200 km s$^{-1}$) can be measured using line shifts in edge-on galaxies, and is slower than that of colder gas phases but similar to stellar rotation velocities. By contrast, the slow inflows ($\sim$50-100 km s$^{-1}$) are difficult to measure in projection with these other components. We find that the velocity measured is sensitive to which emission lines are used. Measuring these flows will help constrain theories of how the gas in these galaxies forms and evolves.

We report new observations of the cool diffuse gas around 29, $2.3<z<6.3$ galaxies, using deep JWST/NIRCam slitless grism spectroscopy around the sightline to the quasar J0100+2802. The galaxies span a stellar mass range of $7.1 \leq \log M_{*}/M_{sun} \leq 10.7$, and star-formation rates of $-0.1 < \log \; SFR/M_{sun}yr^{-1} \; <2.3$. We find galaxies for seven MgII absorption systems within 300 kpc of the quasar sightline. The MgII radial absorption profile falls off sharply with radii, with most of the absorption extending out to 2-3$R_{200}$ of the host galaxies. Six out of seven MgII absorption systems are detected around galaxies with $\log M_{*}/M_{sun} >$9. MgII absorption kinematics are shifted from the systemic redshift of host galaxies with a median absolute velocity of 135 km/s and standard deviation of 85 km/s. The high kinematic offset and large radial separation ($R> 1.3 R_{200}$), suggest that five out of the seven MgII absorption systems are gravitationally not bound to the galaxies. In contrast, most cool circumgalactic media at $z<1$ are gravitationally bound. The high incidence of unbound MgII gas in this work suggests that towards the end of reionization, galaxy halos are in a state of remarkable disequilibrium, and are highly efficient in enriching the intergalactic medium. Two strongest MgII absorption systems are detected at $z\sim$ 4.22 and 4.5, the former associated with a merging galaxy system and the latter associated with three kinematically close galaxies. Both these galaxies reside in local galaxy over-densities, indicating the presence of cool MgII absorption in two "proto-groups" at $z>4$.

We look for simulated star-forming linear wakes such as the one recently discovered by van Dokkum et al. (2023) in the cosmological hydrodynamical simulation ASTRID. Amongst the runaway black holes in ASTRID, none are able to produce clear star-forming wakes. Meanwhile, fly-by encounters, typically involving a compact galaxy (with a central black hole) and a star-forming galaxy (with a duo of black holes) reproduce remarkably well many of the key properties (its length and linearity; recent star formation, etc.) of the observed star-forming linear feature. We predict the feature to persist for approximately 100 Myr in such a system and hence constitute a rare event. The feature contains a partly stripped galaxy (with $M_{\rm gal}=10^9 \sim 10^{10}M_\odot$) and a dual BH system ($M_{\rm BH}=10^5 \sim 10^7\,M_\odot$) in its brightest knot. X-ray emission from AGN in the knot should be detectable in such systems. After $100\sim 200\,{\rm Myrs}$ from the first fly-by, the galaxies merge leaving behind a triple black hole system in a (still) actively star-forming early-type remnant of mass $\sim 5\times 10^{10}\,M_\odot$. Follow-up JWST observations may be key for revealing the nature of these linear features by potentially detecting the older stellar populations constituting the bright knot. Confirmation of such detections may therefore help discriminate a fly-by encounter from a massive BH wake to reveal the origin of such features.

We derive predictions from state-of-the-art cosmological galaxy simulations for the spatial distribution of the hot circumgalactic medium (CGM, ${\rm [0.1-1]R_{200c}}$) through its emission lines in the X-ray soft band ($[0.3-1.3]$ keV). In particular, we compare IllustrisTNG, EAGLE, and SIMBA and focus on galaxies with stellar mass $10^{10-11.6}\, \MSUN$ at $z=0$. The three simulation models return significantly different surface brightness radial profiles of prominent emission lines from ionized metals such as OVII(f), OVIII, and FeXVII as a function of galaxy mass. Likewise, the three simulations predict varying azimuthal distributions of line emission with respect to the galactic stellar planes, with IllustrisTNG predicting the strongest angular modulation of CGM physical properties at radial range ${\gtrsim0.3-0.5\,R_{200c}}$. This anisotropic signal is more prominent for higher-energy lines, where it can manifest as X-ray eROSITA-like bubbles. Despite different models of stellar and supermassive black hole (SMBH) feedback, the three simulations consistently predict a dichotomy between star-forming and quiescent galaxies at the Milky-Way and Andromeda mass range, where the former are X-ray brighter than the latter. This is a signature of SMBH-driven outflows, which are responsible for quenching star formation. Finally, we explore the prospect of testing these predictions with a microcalorimeter-based X-ray mission concept with a large field-of-view. Such a mission would probe the extended hot CGM via soft X-ray line emission, determine the physical properties of the CGM, including temperature, from the measurement of line ratios, and provide critical constraints on the efficiency and impact of SMBH feedback on the CGM.

The formation of molecular clouds out of HI gas is the first step toward star formation. Its metallicity dependence plays a key role to determine star formation through the cosmic history. Previous theoretical studies with detailed chemical networks calculate thermal equilibrium states and/or thermal evolution under one-zone collapsing background. The molecular cloud formation in reality, however, involves supersonic flows, and thus resolving the cloud internal turbulence/density structure in three dimension is still essential. We here perform magnetohydrodynamics simulations of 20 km s^-1 converging flows of Warm Neutral Medium (WNM) with 1 uG mean magnetic field in the metallicity range from the Solar (1.0 Zsun) to 0.2 Zsun environment. The Cold Neutral Medium (CNM) clumps form faster with higher metallicity due to more efficient cooling. Meanwhile, their mass functions commonly follow dn/dm proportional to m^-1.7 at three cooling times regardless of the metallicity. Their total turbulence power also commonly shows the Kolmogorov spectrum with its 80 percent in the solenoidal mode, while the CNM volume alone indicates the transition towards the Larson's law. These similarities measured at the same time in the unit of the cooling time suggest that the molecular cloud formation directly from the WNM alone requires a longer physical time in a lower metallicity environment in the 1.0-0.2 Zsun range. To explain the rapid formation of molecular clouds and subsequent massive star formation possibly within 10 Myr as observed in the Large/Small Magellanic Clouds (LMC/SMC), the HI gas already contains CNM volume instead of pure WNM.

We present Version 2023-02-04 (ISO) of the Chroma+ atmospheric, spectrum, and transit light-curve modelling suite, which incorporates the VALD atomic line list. This is a major improvement as the previous versions used the much smaller NIST line list. The NIST line list is still available in Chroma+ for those projects requiring speed over completeness of line opacity. We describe a procedure for exploiting the ''Array job'' capability of the slurm workload manager on multi-cpu machines to compute broadband high resolution spectra with the VALD line list quickly using the Java version of the code (ChromaStarServer (CSS)). The inclusion of a much larger line list more completely allows for the many weaker lines that over-blanket the blue band in late-type stars and has allowed us to reduce the amount of additional ad hoc continuous opacity needed to fit the solar spectral energy distribution (SED). The additional line opacity exposed a subtle bug in the spectrum synthesis procedure that was causing residual blue line wing opacity to accumulate at shorter wavelengths. We present our latest fits to the observed solar SED and to the observed rectified high resolution visible band spectra of the Sun and the standard stars Arcturus and Vega. We also introduce the fully automated Burke-Gaffney Observatory (BGO) at Saint Mary's University (SMU) and compare our synthetic spectra to low resolution spectra obtained with our grism spectrograph that is available to students. The fully automated BGO, the spectrograph, and the BGO spectrum reduction procedure are fully described in a companion paper. All codes are available from the OpenStars www site: www.ap.smu.ca/OpenStars.

Magnetorotational instability (MRI)-driven turbulence and dynamo phenomena are analyzed using direct statistical simulations. Our approach begins by developing a unified mean-field model that combines the traditionally decoupled problems of the large-scale dynamo and angular-momentum transport in accretion disks. The model consists of a hierarchical set of equations, capturing up to the second-order cumulants, while a statistical closure approximation is employed to model the three-point correlators. We highlight the web of interactions that connect different components of stress tensors -- Maxwell, Reynolds, and Faraday -- through shear, rotation, correlators associated with mean fields, and nonlinear terms. We determine the dominant interactions crucial for the development and sustenance of MRI turbulence. Our general mean field model for the MRI-driven system allows for a self-consistent construction of the electromotive force, inclusive of inhomogeneities and anisotropies. Within the realm of large-scale magnetic field dynamo, we identify two key mechanisms -- the rotation-shear-current effect and the rotation-shear-vorticity effect -- that are responsible for generating the radial and vertical magnetic fields, respectively. We provide the explicit (nonperturbative) form of the transport coefficients associated with each of these dynamo effects. Notably, both of these mechanisms rely on the intrinsic presence of large-scale vorticity dynamo within MRI turbulence.

The nearby spiral galaxy NGC 3147 hosted three Type Ia supernovae (SNe Ia) in the past decades, which have been subjects of intense follow-up observations. Simultaneous analysis of their data provides a unique opportunity for testing the different light curve fitting methods and distance estimations. The detailed optical follow-up of SN 2021hpr allows us to revise the previous distance estimations to NGC 3147, and compare the widely used light curve fitting algorithms to each other. After the combination of the available and newly published data of SN 2021hpr, its physical properties can be also estimated with higher accuracy. We present and analyse new BVgriz and Swift photometry of SN 2021hpr to constrain its general physical properties. Together with its siblings, SNe 1997bq and 2008fv, we cross-compare the individual distance estimates of these three SNe given by the SALT code, and also check their consistency with the results from the MLCS2k2 method. The early spectral series of SN 2021hpr are also fit with the radiative spectral code TARDIS in order to verify the explosion properties and constrain the chemical distribution of the outer ejecta. After combining the distance estimates for the three SNe, the mean distance to their host galaxy, NGC 3127, is 42.5 $\pm$ 1.0 Mpc, which matches with the distance inferred by the most up-to-date LC fitters, SALT3 and BayeSN. We confirm that SN~2021hpr is a Branch-normal Type Ia SN that ejected $\sim 1.12 \pm 0.28$ M$_\odot$ from its progenitor white dwarf, and synthesized $\sim 0.44 \pm 0.14$ M$_\odot$ of radioactive $^{56}$Ni.

We derive an analytic expression for the two-point correlation function in redshift space which (i) is nonlinear; (ii) is valid on the full sky, i.e. the distant-observer limit is not assumed; (iii) can account for the effect of magnification and evolution bias due to a non-uniform selection function; and (iv) respects the fact that observations are made on the past lightcone, so naturally yields unequal-time correlations. Our model is based on an exact treatment of the streaming model in the wide-angle regime. Within this general regime, we find that the redshift-space correlation function is essentially determined by a geometric average of its real-space counterpart. We show that the linear expression for the galaxy overdensity, accurate to subleading order, can be recovered from our nonlinear framework. This work is particularly relevant for the modeling of odd multipoles of the correlation function at small separations and low redshifts, where wide-angle effects, selection effects, and nonlinearities are expected to be equally important.

Several studies have reported magnetic field fluctuations associated with umbral shock waves. We aim to study the properties and origin of magnetic field fluctuations in the umbral chromosphere. Temporal series of spectropolarimetric observations were acquired with the GREGOR telescope. The chromospheric and photospheric conditions were derived from simultaneous inversions of the He I 10830 \AA\ triplet and the Si I 10827 \AA\ line using HAZEL2. The oscillations are interpreted using wavelet analysis and context information from UV observations acquired with SDO/AIA and IRIS. The chromospheric magnetic field shows strong fluctuations in the sunspot umbra, with peak field strengths up to 2900 G. Magnetic field and velocity umbral oscillations exhibit a strong coherence, with the magnetic field lagging the shock fronts detected in the velocity fluctuations. This points to a common origin of the fluctuations in both parameters, whereas the analysis of the phase shift between photospheric and chromospheric velocity is consistent with upwards wave propagation. These results suggest that the strong inferred magnetic field fluctuations are caused by changes in the response height of the He I 10830 \AA\ line to the magnetic field, which is sensitive to high photospheric layers after the shock fronts. The coronal activity seen in EUV data could possibly have some impact on the inferred fluctuations, but it is not the main driver of the magnetic field oscillations since they are found before EUV events take place. Chromospheric magnetic field fluctuations measured with the He I 10830 \AA\ triplet arise due to variations in the opacity of the line. After shocks produced by slow magnetoacoustic waves, the response of the line to the magnetic field can be shifted down to the upper photosphere. This is seen as remarkably large fluctuations in the line of sight magnetic field strength.

The detection of gravitational waves (GW) with an electromagnetic counterpart enabled the first Hubble Constant $H_0$ measurement through the standard siren method. Current constraints suggest that $\sim 20-80\%$ of LIGO/Virgo/KAGRA (LVK) Binary Black Hole (BBH) mergers occur in Active Galactic Nuclei (AGN) disks. The claim for a possible association of several BBH mergers with flaring AGNs suggests that cosmological analyses using BBH and AGNs might be promising. We explore standard siren analyses through a method that takes into account the presence of background flaring AGNs, without requiring a unique host galaxy identification, and apply it to realistic GW simulations. Depending on the fraction of LVK BBHs that induce flares, we expect to constrain $H_0$ at the $\sim 3.5-7\%$ ($\sim 2.5-5\%$) precision with $\sim 2$ years or $\sim 160$ events ($\sim 1$ year or $500$ events) of LVK at design (A+) sensitivity, assuming that systematic BBH follow-up searches are performed. Assuming a more restrictive $\Omega_{\rm m}$ prior and that at least $20\%$ of BBHs produces detectable flares, we may reach a $3\%$ ($2\%$) precision in $H_0$ after 2 (1) year of LVK at design (A+) sensitivity. We also show that a $\sim 5-10\%$ precision is possible with complete AGN catalogs and 1 year of LVK run, without the need of time-critical follow-up observations.

Spectra of planetary nebulae (PNe) are characterised by strong forbidden emission lines and often also by an infrared (IR) excess. A few PNe show dust obscuration events and/or harbour long-period binaries. Some post-asymptotic giant branch stars, symbiotic stars, or B[e] stars may feature similar characteristics. Recently, dust clouds eclipsing white dwarfs were also detected. We report the discovery of an object with a very peculiar variability pattern that bears signatures compatible with the above-mentioned classes of objects. The object is ZTFJ201451.59+120353.4 and identifies with PM 1-322. The object was discovered in Zwicky Transient Facility archival data and investigated with historical and newly obtained photometric and spectroscopic observations. The ZTF r and g data show a one magnitude deep, eclipse-like event with a duration of about half a year that occurred in 2022. The variability pattern of the star is further characterised by several dimming events in the optical region that are accompanied by simultaneous brightenings in the red and IR regions. Apart from that, two fast eruption-like events were recorded in ZTF r data. Archival data from WISE indicate long-term variability with a possible period of 6 or 12 yr. Our follow-up time series photometry reveals a stochastic short-term variability with an amplitude of about 0.1 mag on a timescale of about one hour. The spectral energy distribution is dominated by IR radiation. Our high-resolution spectroscopy shows strong forbidden emission lines from highly ionised species and symmetric double-peaked emission in Halpha, which is very different from what is seen in earlier spectra obtained in 2007. Several explanatory scenarios are presented. Our most likely interpretation is that our target object involves a hot central star surrounded by gaseous and dusty disks, an extended nebula, and a possible companion star.

Context: Open clusters (OCs) provide homogeneous samples of white dwarfs (WDs) with known distances, extinctions, and total ages. The unprecedented astrometric precision of \textit{\textit{Gaia}} allows us to identify many novel OC--WD pairs. Studying WDs in the context of their parent OCs makes it possible to determine the properties of WD progenitors and study the initial-final mass relation (IFMR). Aims: We seek to find potential new WD members of OCs in the solar vicinity. The analysis of OC members' parallaxes allows us to determine the OC distances to a high precision, which in turn enables us to calculate WD masses and cooling ages and to constrain the IFMR. Methods: We searched for new potential WD members of nearby OCs using the density-based machine learning clustering algorithm \texttt{HDBSCAN}. The clustering analysis was applied in five astrometric dimensions -- positions in the sky, proper motions and parallaxes -- and in three dimensions where the positional information was not considered in the clustering analysis. The identified candidate OC WDs were further filtered using the photometric criteria and properties of their putative host OCs. The masses and cooling ages of the WDs were calculated via a photometric method using all available \textit{\textit{Gaia}}, Pan-STARRS, SDSS, and GALEX photometry. The WD progenitor masses were determined using the ages and metallicities of their host OCs. Results: Altogether, 63 OC WD candidates were recovered, 27 of which are already known in the literature. We provide characterization for 36 novel WDs that have significant OC membership probabilities. Six of them fall into relatively unconstrained sections of the IFMR where the relation seems to exhibit nonlinear behavior. We were not able to identify any WDs originating from massive progenitors that would even remotely approach the widely adopted WD progenitor mass limit. (abridged)

We present the operating principle and the first observing run of a novel kind of direct detector for axions and axion-like particles in the galactic halo. Our experiment is sensitive to the polarisation rotation of linearly polarised laser light induced by an axion field, and the first detector of its kind collecting science data. We discuss our current peak sensitivity of $1.44\times 10^{-10}$ GeV$^{-1}$ (95 % confidence level) to the axion-photon coupling strength in the axion mass range of 1.97-2.01 neV which is, for instance, motivated by supersymmetric grand-unified theories. We also report on effects that arise in our high-finesse in-vacuum cavity at unprecedented optical continuous-wave intensity. Our detector already belongs to the most sensitive direct searches within its measurement band, and our first results pave the way towards surpassing the current sensitivity limits in the mass range from $10^{-8}$ eV down to $10^{-16}$ eV via quantum-enhanced laser interferometry.

Previous survey studies reported that coronal mass ejections (CMEs) can exhibit various structures in white-light coronagraphs, and $\sim$30\% of them have the typical three-part feature in the high corona (e.g., 2--6 $R_\odot$), which has been taken as the prototypical structure of CMEs. It is widely accepted that CMEs result from eruption of magnetic flux ropes (MFRs), and the three-part structure can be understood easily by means of the MFR eruption. It is interesting and significant to answer why only $\sim$30\% of CMEs have the three-part feature in previous studies. Here we conduct a synthesis of the CME structure in the field of view (FOV) of K-Coronagraph (1.05--3 $R_\odot$). In total, 369 CMEs are observed from 2013 September to 2022 November. After inspecting the CMEs one by one through joint observations of the AIA, K-Coronagraph and LASCO/C2, we find 71 events according to the criteria: 1) limb event; 2) normal CME, i.e., angular width $\geq$ 30$^{\circ}$; 3) K-Coronagraph caught the early eruption stage. All (or more than 90\% considering several ambiguous events) of the 71 CMEs exhibit the three-part feature in the FOV of K-Coronagraph, while only 30--40\% have the feature in the C2 FOV (2--6 $R_\odot$). For the first time, our studies show that 90--100\% and 30--40\% of normal CMEs possess the three-part structure in the low and high corona, respectively, which demonstrates that many CMEs can lose the three-part feature during their early evolutions, and strongly supports that most (if not all) CMEs have the MFR structures.

Using the SWIFT simulation code we study different forms of active galactic nuclei (AGN) feedback in idealized galaxy groups and clusters. We first present a physically motivated model of black hole (BH) spin evolution and a numerical implementation of thermal isotropic feedback (representing the effects of energy-driven winds) and collimated kinetic jets that they launch at different accretion rates. We find that kinetic jet feedback is more efficient at quenching star formation in the brightest cluster galaxies (BCGs) than thermal isotropic feedback, while simultaneously yielding cooler cores in the intracluster medium (ICM). A hybrid model with both types of AGN feedback yields moderate star formation rates, while having the coolest cores. We then consider a simplified implementation of AGN feedback by fixing the feedback efficiencies and the jet direction, finding that the same general conclusions hold. We vary the feedback energetics (the kick velocity and the heating temperature), the fixed efficiencies and the type of energy (kinetic versus thermal) in both the isotropic and the jet case. The isotropic case is largely insensitive to these variations. In particular, we highlight that kinetic isotropic feedback (used e.g. in IllustrisTNG) is similar in its effects to its thermal counterpart (used e.g. in EAGLE). On the other hand, jet feedback must be kinetic in order to be efficient at quenching. We also find that it is much more sensitive to the choice of energy per feedback event (the jet velocity), as well as the efficiency. The former indicates that jet velocities need to be carefully chosen in cosmological simulations, while the latter motivates the use of BH spin evolution models.

The past two decades have witnessed the rapid growth of our knowledge of the X-ray Universe thanks to flagship X-ray space observatories like XMM-Newton and Chandra. A significant portion of discoveries would have been impossible without the X-ray diffractive grating spectrometers aboard these two space observatories. We briefly overview the physical principles of diffractive grating spectrometers as the background to the beginning of a new era with the next-generation (diffractive and non-diffractive) high-resolution X-ray spectrometers. This chapter focuses on the Reflection Grating Spectrometer aboard XMM-Newton, which provides high-quality high-resolution spectra in the soft X-ray band. Its performance and excellent calibration quality have allowed breakthrough advancements in a wide range of astrophysical topics. For the benefit of new learners, we illustrate how to reduce RGS imaging, timing, and spectral data.

Gravitational waves emitted from stellar binary black hole (sBBH) mergers can be gravitationally lensed by intervening galaxies and detected by future ground-based detectors. A large amount of effort has been put into the estimation of the detection rate of lensed sBBH originating from the evolution of massive binary stars (EMBS channel). However, sBBHs produced by the dynamical interaction in dense clusters (dynamical channel) may also be dominant in our universe and their intrinsic distribution of physical properties can be significantly different from those produced by massive stars, especially mass and redshift distribution. In this paper, we investigate the event rate of lensed sBBHs produced via dynamical channel by Monte Carlo simulations and the number is $16_{-12}^{+4.7} $ $\rm yr^{-1}$ for the Einstein telescope and $24_{-17}^{+6.8}$ $ \rm yr^{-1}$ for Cosmic Explorer, of which the median is about $\sim 2$ times the rate of sBBHs originated from EMBS channel (calibrated by the local merger rate density estimated for the dynamical and the EMBS channel, i.e., $\sim 14_{-10}^{+4.0}$ and $19_{-3.0}^{+42} \rm Gpc^{-3}yr^{-1}$ respectively). Therefore, one may constrain the fraction of both EMBS and dynamical channels through the comparison of the predicted and observed number of lensed sBBH events statistically.

The Universe is pervaded by magnetic fields in different scales, although for simplicity, they are ignored in most cosmological simulations. In this paper, we use the TNG50, which is a large cosmological galaxy formation simulation that incorporates magnetic fields with unprecedented resolution. We study the correlation of the magnetic field with various galaxy properties such as the total, stellar and gaseous mass, circular velocity, size and star formation rate. We find a linear correlation between the average magnetic field pervading the disc of galaxies in relative isolation and their circular velocities. In addition we observed that in this sample the average magnetic field in the disc is correlated with the total mass as $\overline{B}\sim M_{\mathrm{tot,\,R_{\star}}}^{0.2}$. We also find that the massive galaxies with active wind-driven black hole feedback, do not follow this trend, as their magnetic field is substantially decreased by this feedback mode. We show that the correlation of the magnetic field with the star formation rate is a little weaker than the circular velocity. Moreover, we compare the magnetic field components of the above sample with a compiled observational sample of non-cluster non-interacting nearby galaxies. Similar to the observation, we find a coupling between the ordered magnetic field and the circular velocity of the flat part of the rotation curve in the simulation, although contrary to the observation, the ordered component is the dominant one in the simulation.

Aerocapture is a technique which uses atmospheric drag to decelerate a spacecraft and achieve nearly fuel-free orbit insertion from an interplanetary trajectory. The present study performs a historical review of the field, and a bibliometric data analysis of the literature from 1980 to 2023. The data offers insights into the evolution of the field, current state of research, and pathways for its continued development. The data reveal a pattern in the rise of publications, followed by a period of stagnation, which repeats itself approximately once every decade. Mars is the most studied destination, while Uranus is the least studied. Prior to 2013, NASA centers produced the most publications and are the most cited in the field. However, academic institutions produced the majority of publications in the last decade. The United States continues to be the leading country in terms of publications, followed by China. The Journal of Spacecraft and Rockets is the leading source of publications, both in terms of number and citations. NASA is the leading funding source, followed by the National Natural Science Foundation of China. A proposed low-cost Earth flight demonstration of aerocapture will greatly reduce the risk for future science missions.

Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have flown on small satellites with the goal "to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth's ionosphere and thermosphere". The primary science instrument is the Amptek X123 X-ray spectrometer that has improved with each generation of the MinXSS experiment. This third generation MinXSS-3 has higher energy resolution and larger effective area than its predecessors and is also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022 February 14, and INSPIRESat-1 has successfully completed its 6-month prime mission. The INSPIRESat-1 is in a dawn-dusk, Sun-Synchronous Orbit (SSO) and therefore has 24-hour coverage of the Sun during most of its mission so far. The rise of Solar Cycle 25 (SC-25) has been observed by DAXSS. This paper introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the science results here on a solar occultation experiment and multiple flares on 2022 April 24. One key flare result is that the reduction of elemental abundances is greatest during the flare impulsive phase and thus highlighting the important role of chromospheric evaporation during flares to inject warmer plasma into the coronal loops. Furthermore, these results are suggestive that the amount of chromospheric evaporation is related to flare temperature and intensity.

Recent observations have granted to us two unique insights into the early universe: the presence of a low-frequency stochastic gravitational wave background detected by the NANOGrav and Pulsar Timing Array (PTA) experiments and the emergence of unusually massive galaxy candidates at high redshifts reported by the James Webb Space Telescope (JWST). In this letter, we consider the possibility that both observations have a common origin, namely primordial black holes (PBHs) in the mass range between $10^{6}~M_{\odot}$ and $10^{13}~M_{\odot}$. While superheavy PBHs act as seeds of accelerated galaxy formation capable of explaining the JWST extreme galaxies, they can also form binary mergers that source gravitational waves which can be potentially identified as the PTA signal. The analysis is performed taking into account the constraints on the relevant region of the PBH parameter space including the novel bound imposed by the so-called Ultraviolet Luminosity Function of galaxies observed by the Hubble Space Telescope. We conclude that PTA's and JWST's interpretations in terms of PBH binary mergers and Poissonian gas of PBHs, respectively, are strongly excluded.

We report on the results of our simultaneous observations of three large stellar flares with soft X-rays (SXRs) and an H$\mathrm{\alpha}$ emission line from two binary systems of RS CVn type. The energies released in the X-ray and H$\mathrm{\alpha}$ emissions during the flares were $10^{36}$--$10^{38}$ and $10^{35}$--$10^{37}$ erg, respectively. It renders the set of the observations as the first successful simultaneous X-ray/H$\mathrm{\alpha}$ observations of the stellar flares with energies above $10^{35}$ erg; although the coverage of the H$\mathrm{\alpha}$ observations of the stellar flares with energies above $10^{35}$ erg; although the coverage of the H$\mathrm{\alpha}$ observations was limited, with $\sim$10\% of the $e$-folding time in the decay phase of the flares, that of the SXR ones was complete. Combining the obtained physical parameters and those in literature for solar and stellar flares, we obtained a good proportional relation between the emitted energies of X-ray and H$\mathrm{\alpha}$ emissions for a flare energy range of $10^{29}$--$10^{38}$ erg. The ratio of the H$\mathrm{\alpha}$-line to bolometric X-ray emissions was $\sim$0.1, where the latter was estimated by converting the observed SXR emission to that in the 0.1--100 keV band according to the best-fitting thin thermal model. We also found that the $e$-folding times of the SXR and H$\mathrm{\alpha}$ light curves in the decaying phase of a flare are in agreement for a time range of $1$--$10^4$~s. Even very large stellar flares with energies of six orders of magnitude larger than the most energetic solar flares follow the same scaling relationships with solar and much less energetic stellar flares. This fact suggests that their physical parameters can be estimated on the basis of the known physics of solar and stellar flares.

Many pulsars in the known population exhibit nulling, which is characterised by a sudden cessation and subsequent restoration of radio emission. In this work, we present the localization, timing, and emission properties of a GHRSS discovered pulsar J1244-4708. Moreover, we find that this pulsar shows nulling with a nulling fraction close to 60%. A quasi-periodicity is also seen in the nulling from this pulsar with two timescales. We demonstrate the broadband nature of nulling in this pulsar using simultaneous observations in band-3 (300-500 MHz) and band-4 (550-750 MHz) with the uGMRT. We also present a comparison of the efficiency of various search approaches such as single pulse search, Fast Folding Algorithm (FFA) based search, and Fast Fourier Transform (FFT) based search to search for nulling pulsars. We demonstrated that the FFA search is advantageous for detecting extreme nulling pulsars, which is also confirmed with multiple epochs of observations for the nulling pulsars using the GMRT.

We have found that the 2+2 quadruple star system BU CMi is currently the most compact quadruple system known, with an extremely short outer period of only 121 days. The previous record holder was TIC 219006972 (Kostov et al. 2023), with a period of 168 days. The quadruple nature of BU CMi was established by Volkov et al. (2021), but they misidentified the outer period as 6.6 years. BU CMi contains two eclipsing binaries (EBs), each with a period near 3 days, and a substantial eccentricity of about 0.22. All four stars are within about 0.1 solar mass of 2.4 solar masses. Both binaries exhibit dynamically driven apsidal motion with fairly short apsidal periods of about 30 years, thanks to the short outer orbital period. The outer period of 121 days is found both from the dynamical perturbations, with this period imprinted on the eclipse timing variations (ETV) curve of each EB by the other binary, and by modeling the complex line profiles in a collection of spectra. We find that the three orbital planes are all mutually aligned to within 1 degree, but the overall system has an inclination angle near 83.5 degrees. We utilize a complex spectro-photodynamical analysis to compute and tabulate all the interesting stellar and orbital parameters of the system. Finally, we also find an unexpected dynamical perturbation on a timescale of several years whose origin we explore. This latter effect was misinterpreted by Volkov et al. (2021) and led them to conclude that the outer period was 6.6 years rather than the 121 days that we establish here.

We explore sources of ionization of diffuse gas at different altitudes in galaxies in dependence of their stellar mass, \Ha\ luminosity, and specific star formation rate. We use the MaNGA data from SDSS-IV data release DR16 together with photoionization and shock ionization models provided by the 3MdB database. Our sample comprises 239 edge-on galaxies, which makes our results statistically valuable. We reach very high galactic altitudes with the help of spectra stacking. We demonstrate that models of the gas photoionization in a combination of young OB-stars and hot low-mass evolved stars (HOLMES) describes the gas ionization state in the galaxies of all types on diagnostic diagrams. Nevertheless, the shock waves may contribute to the gas ionization in massive galaxies with passive star formation. We observe a general trend of decreasing the fraction of the ionizing flux from OB-stars and the ionization parameter with the altitude, while the role of the ionization by the HOLMES increases. The biggest difference in the contribution from these types of ionizing sources correlates with the specific star formation rate and with stellar masses of galaxies. The HOLMES are the principal gas ionization sources in massive galaxies with passive star formation, while OB-stars dominate the gas ionization in low-mass galaxies with active star formation.

Many models have been proposed to minimize the dark matter (DM) content in various astronomical objects at every scale in the Universe. The most widely known model isMOdified Newtonian Dynamics (MOND). MOND was first published by Mordehai Milgromin 1983 (Milgrom, 1983; 2015; see also Banik and Zhao, 2022 for a review). A second concurrent model is modified gravity (MOG), which is a covariant scalar-tensor-vector (STVG)extension of general relativity (Moffat, 2006; 2020). Other theories also exist but have notbeen broadly applied to a large list of astronomical objects (Mannheim and Kazanas, 1989;Capozziello and De Laurentis, 2012; O'Brien and Moss, 2015; Verlinde, 2017). A new model,called $\kappa$-model, based on very elementary phenomenological considerations, has recently beenproposed in the astrophysics field. This model shows that the presence of dark matter canbe considerably minimized with regard to the dynamics of galaxies (Pascoli, 2022 a,b). The$\kappa$-model belongs to the general family of theories descended from MOND. Under this familyof theories, there is no need to develop a highly uncertain dark matter sector of physics toexplain the observations.

Kuiper-like belts of planetesimals orbiting stars other than the Sun are most commonly detected from the thermal emission of small dust produced in collisions. Emission from gas, most notably CO, highlights the cometary nature of these planetesimals. Here we present models for the release of gas from comet-like bodies in these belts, both due to their thermophysical evolution, most notably the decay of long-lived radioactive nuclides and collisional evolution, including catastrophic and gentler resurfacing collisions. We show that the rate of gas release is not proportional to the rate of dust release, if non-catastrophic collisions or thermal evolution dominate the release of CO gas. In this case, care must be taken when inferring the composition of comets. Non-catastrophic collisions dominate the gas production at earlier times than catastrophic collisions, depending on the properties of the planetesimal belt. We highlight the importance of the thermal evolution of comets, including crucially the decay of long-lived radioactive nuclides, as a source of CO gas around young (<50Myr) planetary systems, if large (10-100s kms) planetesimals are present.

Massive stars blow powerful winds and eventually explode as supernovae. By doing so, they inject energy and momentum in the circumstellar medium, which is pushed away from the star and piles up to form a dense and expanding shell of gas. The effect is larger when many massive stars are grouped together in bound clusters or associations. Large cavities form around clusters as a result of the stellar feedback on the ambient medium. They are called superbubbles and are characterised by the presence of turbulent and supersonic gas motions. This makes star clusters ideal environments for particle acceleration, and potential contributors to the observed Galactic cosmic ray intensity.

We present a forecast of the cosmological parameter estimation using fast radio bursts (FRBs) from the upcoming Square Kilometre Array (SKA), focusing on the issues of dark energy, the Hubble constant, and baryon density. We simulate $10^5$ and $10^6$ localized FRBs from a 10-year SKA observation, and find that: (i) using $10^6$ FRB data alone can tightly constrain dark-energy equation of state parameters better than CMB+BAO+SN, providing a single cosmological probe to explore dark energy; (ii) combining the FRB data with gravitational wave standard siren data from 10-year observation with the Einstein Telescope, the Hubble constant can be constrained to a sub-percent level, serving as a powerful low-redshift probe; (iii) using $10^6$ FRB data can constrain the baryon density $\Omega_{\rm b}h$ to a precision of $\sim 0.1\%$. Our results indicate that SKA-era FRBs will provide precise cosmological measurements to shed light on both dark energy and the missing baryon problem, and help resolve the Hubble tension.

FU Orionis objects (FUors) are eruptive young stars, which exhibit outbursts that last from decades to a century. Due to the duration of their outbursts, and to the fact that only about two dozens of such sources are known, information on the end of their outbursts is limited. Here we analyse follow-up photometry and spectroscopy of Gaia21elv, a young stellar object, which had a several decades long outburst. It was reported as a Gaia science alert due to its recent fading by more than a magnitude. To study the fading of the source and look for signatures characteristic of FUors, we have obtained follow-up near infrared (NIR) spectra using Gemini South/IGRINS, and both optical and NIR spectra using VLT/X-SHOOTER. The spectra at both epochs show typical FUor signatures, such as a triangular shaped $H$-band continuum, absorption-line dominated spectrum, and P Cygni profiles. In addition to the typical FUor signatures, [OI], [FeII], and [SII] were detected, suggesting the presence of a jet or disk wind. Fitting the spectral energy distributions with an accretion disc model suggests a decrease of the accretion rate between the brightest and faintest states. The rapid fading of the source in 2021 was most likely dominated by an increase of circumstellar extinction. The spectroscopy presented here confirms that Gaia21elv is a classical FUor, the third such object discovered among the Gaia science alerts.

We investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe II lines of the 279.3-280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a comprehensive Fe II atomic model to solve the problem of the generation and transfer of polarized radiation in semi-empirical models of the solar atmosphere, comparing the region of formation of the Fe II spectral lines with those of the Mg II h and k and the Mn I resonance lines. These are present in the same near ultraviolet (near-UV) spectral region and allowed the mapping of the longitudinal component of the magnetic field ($B_{\rm L}$) through several layers of the solar chromosphere in an active region plage. We compare our synthetic intensity profiles with observations from the IRIS and CLASP2 missions, proving the suitability of our model atom to characterize these Fe II spectral lines. The CLASP2 observations show two Fe II spectral lines at 279.79 and 280.66 nm with significant circular polarization signals. We demonstrate the suitability of the Weak-Field Approximation (WFA) applied to the Stokes $I$ and $V$ profiles of these Fe II lines to infer $B_{\rm L}$ in the plage atmosphere. We conclude that the near-UV spectral region of CLASP2 allows to determine $B_{\rm L}$ from the upper photosphere to the top of the chromosphere of active region plages.

The evidence of the nano-Hertz stochastic gravitational wave (GW) background is reported by multiple pulsar timing array collaborations. While a prominent candidate of the origin is astrophysical from supermassive black hole binaries, alternative models involving GWs induced by primordial curvature perturbations can explain the inferred GW spectrum. Serendipitously, the nano-Hertz range coincides with the Hubble scale during the cosmological quantum chromodynamics (QCD) phase transition. The influence of the QCD phase transition can modify the spectrum of induced GWs within the nano-Hertz frequency range, necessitating careful analysis. We estimate GWs induced by power-law power spectra of primordial curvature perturbations taking account of the QCD phase transition. Then we translate the implication of the NANOGrav data into the constraint on the power spectrum of the primordial curvature perturbation, which suggests that one may miss the correct interpretation if neglecting the QCD effect. We also derive fitting formulae for their amplitude and scale dependence, helping to update the constraint in future experiments.

The dissertation presents result from study of Pre-main sequence (PMS) stars that are in the earliest stages of stellar evolution. These young stellar objects are still in the process of formation, and the energy they emit is produced only by gravitational contraction. The main results were obtained with the telescopes at the National Astronomical Observatory Rozhen, as well as with the use of archival photographic observations and spectral observations obtained in collaboration with colleagues from abroad. Our results are obtained by studying the photometric and spectral variability of PMS stars. Our main goal is to study the processes of star formation, the formation of circumstellar disks, the structure of the circumstellar environment and the interaction of the star-disk system. The results of our research have been published in 65 scientific papers that have been cited over 300 times. The photometric and spectral variability of PMS stars is of great importance for modeling star formation processes. On the one hand, photometric variability allows us to easily detect young objects, since they are characterized by rapid variability and in many cases with large amplitudes. On the other hand, stars form in groups and are physically located in the same geometric space, and several variable objects that are at approximately the same stage of evolution can be observed simultaneously. Comparing star systems of different ages can be used to trace the stages of stellar evolution.

The Hubble Tension is a well-known issue in modern cosmology that refers to the apparent disagreement in inferences of the Hubble constant $H_0$ as found through low-redshift observations and those derived from the $\Lambda$CDM model utilizing early universe observations. Several extensions to $\Lambda$CDM have been proposed to address the Hubble Tension that involve new ingredients or dynamics in the early universe. Reversing the effects of gravitational lensing on cosmic microwave background (CMB) maps produces sharper acoustic peaks in power spectra and allows for tighter constraints on cosmological parameters. We investigate the efficacy of CMB delensing for improving the constraints on parameters used in extensions of the $\Lambda$CDM model that are aimed at resolving the Hubble Tension (such as varying fundamental constants, contributions from early dark energy, and self-interacting dark radiation). We use Fisher forecasting to predict the expected constraints with and without this delensing procedure. We demonstrate that CMB delensing improves constraints on $H_0$ by $\sim$ 20% for viable models and significantly improves constraints on parameters across the board in the low-noise regime.

The magnetic activity level of low-mass stars is known to vary as a function of the physical properties of the star. Many studies have shown that the stellar mass and rotation are both important parameters that determine magnetic activity levels. In contrast, the impact of a star's chemical composition on magnetic activity has received comparatively little attention. Data sets for traditional activity proxies, e.g. X-ray emission or calcium emission, are not large enough to search for metallicity trends in a statistically meaningful way. Recently, studies have used the photometric variability amplitude as a proxy for magnetic activity to investigate the role of metallicity because it can be relatively easily measured for large samples of stars. These studies find that magnetic activity and metallicity are positively correlated. In this work, we investigate the link between activity and metallicity further by studying the flaring properties of stars in the Kepler field. Similar to the photometric variability, we find that flaring activity is stronger in more metal-rich stars for a fixed mass and rotation period. This result adds to a growing body of evidence that magnetic field generation is correlated with metallicity.

In July 2021, PKS 1510-089 exhibited a significant flux drop in the high-energy gamma-ray (by a factor 10) and optical (by a factor 5) bands and remained in this low state throughout 2022. Similarly, the optical polarization in the source vanished, resulting in the optical spectrum being fully explained through the steady flux of the accretion disk and the broad-line region. Unlike the aforementioned bands, the very-high-energy gamma-ray and X-ray fluxes did not exhibit a significant flux drop from year to year. This suggests that the steady-state very-high-energy gamma-ray and X-ray fluxes originate from a different emission region than the vanished parts of the high-energy gamma-ray and optical jet fluxes. The latter component has disappeared through either a swing of the jet away from the line-of-sight or a significant drop in the photon production efficiency of the jet close to the black hole. Either change could become visible in high-resolution radio images.

Taiji program is a space mission aiming to detect gravitational waves in the low frequency band. Taiji-1 is the first technology demonstration satellite of the Taiji Program in Space, with the gravitational reference sensor (GRS) serving as one of its key scientific payloads. For accurate accelerometer measurements, the test-mass center of the GRS must be positioned precisely at the center of gravity of the satellite to avoid measurement disturbances caused by angular acceleration and gradient. Due to installation and measurement errors, fuel consumption during in-flight phase, and other factors, the offset between the test-mass center and the center-of-mass (COM) of the satellite can be significant, degrading the measurement accuracy of the accelerometer. Therefore, the offset needs to be estimated and controlled within the required range by the center-of-mass adjustment mechanism during the satellite's lifetime. In this paper, we present a novel method, the Extended Kalman Filter combined with Rauch-Tung-Striebel Smoother, to estimate the offset, while utilizing the chi-square test to eliminate outliers. Additionally, the nonlinear Least Squares estimation algorithm is employed as a crosscheck to estimate the offset of COM. The two methods are shown to give consistent results, with the offset estimated to be $dx \approx $$-$$0.19$ mm, $dy \approx 0.64$ mm, and $dz \approx $$-$$0.82$ mm. The results indicate a significant improvement on the noise level of GRS after the COM calibration, which will be of great help for the future Taiji program.

The LOFAR Two-Metre Sky Survey (LoTSS) is an invaluable new tool for investigating the properties of sources at low frequencies and has helped to open up the study of galaxy populations in this regime. In this work, we perform a search for host galaxies of gamma-ray bursts (GRBs). We use the relative density of sources in Data Release 2 of LoTSS to define the probability of a chance alignment, $P_{\rm chance}$, and find 18 sources corresponding to 17 GRBs which meet a $P_{\rm chance}$<1% criterion. We examine the nature and properties of these radio sources using both LOFAR data and broadband information, including their radio spectral index, star formation rate estimates and any contributions from active galactic nucleus emission. Assuming the radio emission is dominated by star formation, we find that our sources show high star formation rates ($10^1$-$10^3$ $M_{\odot}$ yr$^{-1}$) compared with both a field galaxy sample and a sample of core-collapse supernova hosts, and the majority of putative hosts are consistent with ultraluminous infrared galaxy (ULIRG) classifications. As a result of our analyses, we define a final sample of eight likely GRB host candidates in the LoTSS DR2 survey.

Based on a novel laboratory method, 14 mm-wave lines of the molecular ion H$_2$CCCH$^+$ have been measured in high resolution, and the spectroscopic constants of this asymmetric rotor determined with high accuracy. Using the Yebes 40 m and IRAM 30 m radio telescopes, we detect four lines of H$_2$CCCH$^+$ towards the cold dense core TMC-1. With a dipole moment of about 0.55 Debye obtained from high-level ab initio calculations, we derive a column density of 5.4$\pm$1$\times$10$^{11}$ cm$^{-2}$ and 1.6$\pm$0.5$\times$10$^{11}$ cm$^{-2}$ for the ortho and para species, respectively, and an abundance ratio N(H$_2$CCC)/N(H$_2$CCCH$^+$)= 2.8$\pm$0.7. The chemistry of H$_2$CCCH$^+$ is modelled using the most recent chemical network for the reactions involving the formation of H$_2$CCCH$^+$. We find a reasonable agreement between model predictions and observations, and new insights into the chemistry of C$_3$ bearing species in TMC-1 are obtained.

A comprehensive multi-wavelength campaign has been carried out to probe stellar activity and variability in the young Sun-like star $\iota$-Horologii. We present the results from long-term spectropolarimetric monitoring of the system by using the ultra-stable spectropolarimeter/velocimeter HARPS at the ESO 3.6-m telescope. Additionally, we included high-precision photometry from the NASA Transiting Exoplanet Survey Satellite (TESS) and observations in the far- and near-ultraviolet spectral regions using the STIS instrument on the NASA/ESA Hubble Space Telescope (HST). The high-quality dataset allows a robust characterisation of the star's rotation period, as well as a probe of the variability using a range of spectroscopic and photometric activity proxies. By analyzing the gradient of the power spectra (GPS) of the TESS lightcurves we constrained the faculae-to-spot driver ratio ($\rm S_{fac}/S_{spot}$) to 0.510$\pm$0.023, which indicates that the stellar surface is spot dominated during the time of the observations. We compared the photospheric activity properties derived from the GPS method with a magnetic field map of the star derived using Zeeman-Doppler imaging (ZDI) from simultaneous spectropolarimetric data for the first time. Different stellar activity proxies enable a more complete interpretation of the observed variability. For example, we observed enhanced emission in the HST transition line diagnostics C IV and C III, suggesting a flaring event. From the analysis of TESS data acquired simultaneously with the HST data, we investigate the photometric variability at the precise moment that the emission increased and derive correlations between different observables, probing the star from its photosphere to its corona.

Multispacecraft and multiwavelength observations of solar eruptions such as flares and coronal mass ejections are essential to understand the complex processes behind these events. The study of solar burst events in the radio-frequency spectrum has relied almost exclusively on data from ground-based radiotelescopes and dedicated heliophysics missions such as STEREO or Wind. Reanalysing existing data from the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) instrument, a Martian planetary radar sounder, we have detected 38 solar radio burst events with a correlated observation by at least one dedicated solar mission. The very high resolution of the instrument, both in temporal and frequency directions, its bandwidth, and its position in the solar system enable SHARAD to make significant contributions to heliophysics; it could inform on plasma processes on the site of the burst generation and also along the propagation path of associated fast electron beams. In this letter, we characterise the sensitivity of the instrument to type-III solar radio bursts through a statistical analysis of correlated observations, using STEREO and Wind as references. We establish the conditions under which SHARAD can observe solar bursts in terms of acquisition geometry, laying the foundation for its use as a solar radio-observatory. We also present the first analysis of type-III characteristic times at high resolution beyond 1 AU. The scaling laws are also comparable to results found on Earth, except for the fall time; a clearer distinction between fundamental and harmonic components of the bursts may be needed to resolve the discrepancy.

We use angular clustering of luminous red galaxies from the Dark Energy Spectroscopic Instrument (DESI) imaging surveys to constrain the local primordial non-Gaussianity parameter fNL. Our sample comprises over 12 million targets, covering 14,000 square degrees of the sky, with redshifts in the range 0.2< z < 1.35. We identify Galactic extinction, survey depth, and astronomical seeing as the primary sources of systematic error, and employ linear regression and artificial neural networks to alleviate non-cosmological excess clustering on large scales. Our methods are tested against log-normal simulations with and without fNL and systematics, showing superior performance of the neural network treatment in reducing remaining systematics. Assuming the universality relation, we find fNL $= 47^{+14(+29)}_{-11(-22)}$ at 68\%(95\%) confidence. With a more aggressive treatment, including regression against the full set of imaging maps, our maximum likelihood value shifts slightly to fNL$ \sim 50$ and the uncertainty on fNL increases due to the removal of large-scale clustering information. We apply a series of robustness tests (e.g., cuts on imaging, declination, or scales used) that show consistency in the obtained constraints. Despite extensive efforts to mitigate systematics, our measurements indicate fNL > 0 with a 99.9 percent confidence level. This outcome raises concerns as it could be attributed to unforeseen systematics, including calibration errors or uncertainties associated with low-\ell systematics in the extinction template. Alternatively, it could suggest a scale-dependent fNL model--causing significant non-Gaussianity around large-scale structure while leaving cosmic microwave background scales unaffected. Our results encourage further studies of fNL with DESI spectroscopic samples, where the inclusion of 3D clustering modes should help separate imaging systematics.

Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT, AT2023fhn. The Hubble Space Telescope data reveal a large offset (greater than 3.5 half-light radii) from the two closest galaxies, both at a redshift of 0.24. The isolated environment of AT 2023fhn is in stark contrast with previous events, is challenging to explain with most LFBOT progenitor models, and calls into question the homogeneity of LFBOTs as a class.

Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H$_2$O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive multi-Myr disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust-traps, which loses its icy content to sublimation upon reaching the snow line. We find that vapor abundance in the inner disk is strongly affected by fragmentation velocity (v$_{\rm f}$) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence ($\alpha$ $\le$ 1 $\times$ 10$^{-3}$) and for a range of v$_{\rm f}$, radial location, and gap depth (especially that of the innermost gaps), can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that the for realistic v$_{\rm f}$ ($\le$ 10 m s$^{-1}$), presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk.

Nearly a hundred of binary black holes (BBHs) have been discovered with gravitational-wave signals emitted at their merging events. Thus, it is quite natural to expect that significantly more abundant BBHs with wider separations remain undetected in the universe, or even in our Galaxy. We consider a possibility that star-BH binary candidates may indeed host an inner BBH, instead of a single BH. We present a detailed feasibility study of constraining the binarity of the currently available two targets, Gaia BH1 and Gaia BH2. Specifically, we examine three types of radial velocity (RV) modulations of a tertiary star in star-BBH triple systems; short-term RV modulations induced by the inner BBH, long-term RV modulations induced by the nodal precession, and long-term RV modulations induced by the von Zeipel-Kozai-Lidov oscillations. Direct three-body simulations combined with approximate analytic models reveal that Gaia BH1 system may exhibit observable signatures of the hidden inner BBH if it exists at all. The methodology that we examine here is quite generic, and is expected to be readily applicable to future star-BH binary candidates in a straightforward manner.

Tidal Disruption Events (TDEs) are rare transients, which are considered as promising tools in probing supermassive black holes in quiescent galaxies. The majority of $\approx 60$ known TDEs has been discovered with time-domain surveys in the last two decades. Currently, $\approx 10$ TDEs are discovered per year, and this number will increase with the Legacy Survey of Space and Time (LSST) at Rubin Observatory. This work evaluates LSST survey strategies in view of their performance in identifying TDEs. We assume that TDEs can be identified photometrically based on their colors, particularly $u$-band, and will be scientifically useful if we can detect the light curve peak to derive physical quantities. We define requirements for the Rubin light curves needed to achieve this (detections pre-peak, post-peak, in different bands to measure colour). We then inject model light curves into the Operations Simulator, and calculate the fraction of TDEs passing our requirements for several strategies. We find that under the baseline strategy, $\approx 1.5$\% of simulated TDEs fulfil our detection criteria, while this number increases when more time is devoted to $u$-band observations. An ideal observing strategy for photometric identification of TDEs would have longer $u$-band exposures, which should not come at the expense of fewer $u$-band visits. A filter distribution weighted towards more observing time in bluer bands, intra-night visits in different filters, and strategies with frequent sampling leading to higher quality light curves are preferred. We find that these strategies benefiting TDE science do not impact significantly other science cases.

Studying the feedback process of Active Galactic Nuclei (AGN) requires characterising multiple kinematical components, such as rotating gas and stellar disks, outflows, inflows, and jets. To compare the observed properties with theoretical predictions of galaxy evolution and feedback models and to assess the mutual interaction and energy injection rate into the interstellar medium (ISM), one usually relies on simplified kinematic models. These models have several limitations, as they often do not take into account projection effects, beam smearing and the surface brightness distribution of the emitting medium. Here, we present MOKA3D, an innovative approach to model the 3D gas kinematics from integral field spectroscopy observations. In this first paper, we discuss its application to the case of AGN ionised outflows, whose observed clumpy emission and apparently irregular kinematics are only marginally accounted for by existing kinematical models. Unlike previous works, our model does not assume the surface brightness distribution of the gas, but exploits a novel procedure to derive it from the observations by reconstructing the 3D distribution of emitting clouds and providing accurate estimates of the spatially resolved outflow physical properties (e.g. mass rate, kinetic energy). As an example, we demonstrate the capabilities of our method by applying it to three nearby Seyfert-II galaxies observed with MUSE at the VLT and selected from the MAGNUM survey, showing that the complex kinematic features observed can be described by a conical outflow with a constant radial velocity field and a clumpy distribution of clouds.

Several prominent forthcoming Cosmic Microwave Background polarisation experiments will employ a Continuously Rotating Half-Wave Plate (CRHWP), the primary purpose of which is to mitigate instrumental systematic effects on relatively large angular scales, where the $B$-mode polarisation signal generated by primordial gravitational waves is expected to peak. The use of a CRHWP necessitates demodulating the time-ordered data during the early stages of data processing. The standard approach is to ``lock in'' on the polarisation signal using the known polarisation modulation frequency and then use Fourier techniques to filter out the remaining unwanted components in the data. However, an alternative less well-studied option is to incorporate the demodulation directly into the map-making step. Using simulations, we compare the performance of these two approaches to determine which is most effective for $B$-mode signal recovery. Testing the two techniques in multiple experimental scenarios, we find that the lock-in technique performs best over the full multipole range explored. However, for the recovery of the largest angular scales ($\ell < 100$) we find essentially no difference in the recovery of the signal between the lock-in and map-making approaches, suggesting that a parallel analysis based on the latter approach could represent a powerful consistency check for primordial $B$-mode experiments employing a CRHWP. We also investigate the impact of a detector-differencing step, implemented prior to demodulation, finding that in most scenarios it makes no difference whether differencing is used or not. However, analysing detectors individually allows the point at which information from multiple detectors is combined to be moved to later stages in the analysis pipeline. This presents alternative options for dealing with instrumental systematic effects that are not mitigated by the CRHWP.

We present Hubble Space Telescope photometry in optical (F475X) and near-infrared (F110W) bands of the globular cluster (GC) systems of the inner halos of a sample of 15 massive elliptical galaxies. The targets are selected from the volume-limited MASSIVE survey, and chosen to sample a range of environments from sparsely populated groups to BCGs in dense clusters. We also present a quantitative model of the relation between (F475X - F110W) colour and cluster metallicity [M/H], using simulated GCs. Because much of the GC population in such galaxies is built up through accretion, the metallicity distribution of the GC systems might be expected to vary with galaxy environment. The photometry is used to create a completeness-corrected metallicity distribution for each galaxy in the sample, and to fit a double Gaussian curve to each histogram in order to model the two standard red and blue subpopulations. Finally, the properties of the GC metallicity distribution are correlated against galaxy environment. We find that almost no GCS properties and host galaxy environmental properties are correlated, with the exception of a weak but consistent correlation between blue fraction and nth-nearest neighbour surface density. The results suggest that the systemic properties of the GCS, at least in the inner to mid-halo regions, are influenced more strongly by the local environment at early times, rather than by the environmental properties we see today.

I analyze the K2 and TESS data taken in 2016, 2019 and 2021 of the symbiotic X-ray binaries GX 1+4 and IGR J16194-2810. GX 1+4 consists of a pulsar accreting from a red giant companion in a 1160 days orbit. Since 1984, the pulsar has shown a continuous spin-down rate of $\dot{P}$=-0.1177(3) mHZ/yr. I report the detection of the spin period at an average value of 180.426(1) seconds as observed with the K2 mission and confirm that the spin period continues to increase at a rate of $\sim$1.61$\times$10$^{-7}$ s/s. The K2 and hard X-rays, as observed with Swift/BAT, varied in tandem, in agreement with other authors who proposed that the optical light arise from reprocessed X-ray emission. In the case of IGR J16194-2810, the X-ray and optical spectroscopy have been interpreted as arising from a neutron star accreting from a M2 III red giant companion. Its orbital period is unknown, while I report here the detection of a modulation with a period of 242.837 min, interpreted as the neutron star spin period. IGR J16194-2810 is thus the second symbiotic X-ray binary where the spin period is detected in optical wavelengths. This period, however, was only detected during the TESS observations of Sector 12 in 2019. The non-detection of this modulation during the observations of Sector 39 in 2021 is perhaps related with the orbital modulation, i.e. a low inclination of the orbit.

The present work is devoted to the analysis of the internal structure of relativistic jets under the condition that the velocity of the plasma flow at the jet axis vanishes. It is shown that in spite of the seemingly fundamental difference in the formulation of the problem at the axis, the key properties of the internal structure of such relativistic jets remain the same as for nonzero velocity along the axis. In both cases, at a sufficiently low ambient pressure, a dense core appears near the axis, the radius of which is close to the size of the light cylinder.

Solar radio emissions provide several unique diagnostics to estimate different physical parameters of the solar corona, which are otherwise simply inaccessible. However, imaging the highly dynamic solar coronal emissions spanning a large range of angular scales at radio wavelengths is extremely challenging. At GHz frequencies, the MeerKAT radio telescope is possibly globally the best-suited instrument at the present time and can provide high-fidelity spectroscopic snapshot solar images. Here, we present the first images of the Sun made using the observations with the MeerKAT at L-band (856 -- 1711 MHz). This work demonstrates the high fidelity of the MeerKAT solar images through a comparison with simulated radio images at the MeerKAT frequencies. The observed images show extremely good mophological similarities with the simulated images. A detailed comparison between the simulated radio map and observed MeerKAT radio images demonstrates that there is significant missing flux density in MeerKAT images at the higher frequencies of the observing band, though it can potentially be estimated and corrected for. We believe once solar observations with the MeerKAT are commissioned, they will not only enable a host of novel studies but also open the door to a large unexplored phase space with significant discovery potential.

We report on the development of millimeter-wave, lumped-element reflectionless filters using an advanced thin-film fabrication process. Based on previously demonstrated circuit topologies capable of achieving 50{\Omega} impedance match at all frequencies, these circuits have been implemented at higher frequencies than ever before by leveraging a thin-film process with better than 2 {\mu}m feature size and integrated elements such as SiN Metal-Insulator-Metal (MIM) capacitors, bridges, and TaN Thin-Film Resistors (TFRs).

We use data from the pilot observations of the EMU/POSSUM surveys to study the "missing supernova remnant (SNR) problem", the discrepancy between the number of Galactic SNRs that have been observed and the number that are estimated to exist. The Evolutionary Map of the Universe (EMU) and the Polarization Sky Survey of the Universe's Magnetism (POSSUM) are radio sky surveys that are conducted using the Australian Square Kilometre Array Pathfinder (ASKAP). We report on the properties of 7 known SNRs in the joint Galactic pilot field, with an approximate longitude and latitude of 323$^\circ\leq$ l $\leq$ 330$^\circ$ and -4$^\circ\leq$ b $\leq$ 2$^\circ$ respectively, and identify 21 SNR candidates. Of these, 4 have been previously identified as SNR candidates, 3 were previously listed as a single SNR, 13 have not been previously studied, and 1 has been studied in the infrared. These are the first discoveries of Galactic SNR candidates with EMU/POSSUM and, if confirmed, they will increase the SNR density in this field by a factor of 4. By comparing our SNR candidates to the known Galactic SNR population, we demonstrate that many of these sources were likely missed in previous surveys due to their small angular size and/or low surface brightness. We suspect that there are SNRs in this field that remain undetected due to limitations set by the local background and confusion with other radio sources. The results of this paper demonstrate the potential of the full EMU/POSSUM surveys to uncover more of the missing Galactic SNR population.

Humanity is close to characterizing the atmospheres of rocky exoplanets due to the advent of JWST. These astronomical observations motivate us to understand exoplanetary atmospheres to constrain habitability. We study the influence greenhouse gas supplement has on the atmosphere of TRAPPIST-1e, an Earth-like exoplanet, and Earth itself by analyzing ExoCAM and CMIP6 model simulations. We find an analogous relationship between CO2 supplement and amplified warming at non-irradiated regions (night side and polar) - such spatial heterogeneity results in significant global circulation changes. A dynamical systems framework provides additional insight into the vertical dynamics of the atmospheres. Indeed, we demonstrate that adding CO2 increases temporal stability near the surface and decreases stability at low pressures. Although Earth and TRAPPIST-1e take entirely different climate states, they share the relative response between climate dynamics and greenhouse gas supplements.

The Stardust mission captured comet Wild 2 particles in aerogel at 6.1 km/sec. We performed high resolution three-dimensional imaging and X-ray fluorescence mapping of whole cometary tracks in aerogel. We present the results of a survey of track structures using Laser Scanning Confocal Microscopy, including measurements of track volumes, entry hole size and cross-sectional profiles. We compare various methods for measuring track parameters. We demonstrate a methodology for discerning hypervelocity particle ablation rates using synchrotron-based X-ray fluorescence, combined with mass and volume estimates of original impactors derived from measured track properties. Finally, we present a rough framework for reconstruction of original impactor size, and volume of volatilized material, using our measured parameters. The bulk of this work is in direct support of non-destructive analysis and identification of cometary grains in whole tracks, and its eventual application to the reconstruction of the size, shape, porosity and chemical composition of whole Stardust impactors.

One of the major unresolved problems in cosmochemistry is the origin of chondrules, once molten, spherical silicate droplets with diameters of 0.2 to 2 mm. Chondrules are an essential component of primitive meteorites and perhaps of all early solar system materials including the terrestrial planets. Numerous hypotheses have been proposed for their origin. Many carbonaceous chondrites are composed of about equal amounts of chondrules and fine-grained matrix. Recent data confirm that matrix in carbonaceous chondrites has high Si/Mg and Fe/Mg ratios when compared to bulk carbonaceous chondrites with solar abundance ratios. Chondrules have the opposite signature, low Si/Mg and Fe/Mg ratios. In some carbonaceous chondrites chondrules have low Al/Ti ratios, matrix has the opposite signature and the bulk is chondritic. It is shown in detail that these complementary relationships cannot have evolved on the parent asteroid(s) of carbonaceous chondrites. They reflect preaccretionary processes. Both chondrules and matrix must have formed from a single, solar-like reservoir. Consequences of complementarity for chondrule formation models are discussed. An independent origin and/or random mixing of chondrules and matrix can be excluded. Hence, complementarity is a strong constraint for all astrophysical-cosmochemical models of chondrule formation. Although chondrules and matrix formed from a single reservoir, the chondrule-matrix system was open to the addition of oxygen and other gaseous components.

The connection between quenching mechanisms, which rapidly turn star-forming systems into quiescent, and the properties of the galaxy population remains difficult to discern. In this work we investigate the physical properties of MaNGA and SAMI galaxies at different stages of their star formation history. Specifically, we compare galaxies with signatures of recent quenching (Quenched) -- $\rm H(\alpha)$ in absorption and low $D_n(4000)$ -- with the rest of the low star-forming and active population (Retired and Ageing, respectively). The analysis is performed in terms of characteristics such as the total stellar mass, half-light radius, velocity-to-dispersion ratio, metallicity, and environment. We find that the Ageing population comprises a heterogeneous mixture of galaxies, preferentially late-type systems, with diverse physical properties. Retired galaxies, formerly Ageing or Quenched systems, are dominated by early-type high-mass galaxies found both at low and dense environments. Most importantly, we find that recently quenched galaxies are consistent with a population of compact low-mass satellite systems, with higher metallicities than their Ageing analogues. We argue that this is compatible with being quenched after undergoing a star-burst phase induced by environmental processes (e.g. ram pressure). However, we also detect a non-negligible fraction of field central galaxies likely quenched by internal processes. This study highlights that, in order to constrain the mechanisms driving galaxy evolution, it is crucial to distinguish between old (Retired) and recently quenched galaxies, thus requiring at least two estimates of the specific star formation rate over different timescales.

We present the results of ALMA-ACA 7 m-array observations in $^{12}$CO($J=2-1$), $^{13}$CO($J=2-1$), and C$^{18}$O($J=2-1$) line emission toward the molecular-gas disk in the Local Group spiral galaxy M33 at an angular resolution of 7''.31 $\times$ 6''.50 (30 pc $\times$ 26 pc). We combined the ACA 7 m-array $^{12}$CO($J=2-1$) data with the IRAM 30 m data to compensate for emission from diffuse molecular-gas components. The ACA+IRAM combined $^{12}$CO($J=2-1$) map clearly depicts the cloud-scale molecular-gas structure over the M33 disk. Based on the ACA+IRAM $^{12}$CO($J=2-1$) cube data, we cataloged 848 molecular clouds with a mass range from $10^3$ $M_{\odot}$ to $10^6$ $M_{\odot}$. We found that high-mass clouds ($\geq 10^5 M_{\odot}$) tend to associate with the $8 \mu$m-bright sources in the spiral arm region, while low-mass clouds ($< 10^5 M_{\odot}$) tend to be apart from such $8 \mu$m-bright sources and to exist in the inter-arm region. We compared the cataloged clouds with GMCs observed by the IRAM 30 m telescope at 49 pc resolution (IRAM GMC: Corbelli et al. 2017), and found that a small IRAM GMC is likely to be identified as a single molecular cloud even in ACA+IRAM CO data, while a large IRAM GMC can be resolved into multiple ACA+IRAM clouds. The velocity dispersion of a large IRAM GMC is mainly dominated by the line-of-sight velocity difference between small clouds inside the GMC rather than the internal cloud velocity broadening.

We investigate the second order energy density perturbation $\delta^{(2)}$ induced by small-scale Gaussian and local-type non-Gaussian primordial curvature perturbations. The relative abundance of primordial black hole is calculated in terms of the probability density function of total energy density perturbation $\delta_r=\delta^{(1)}+\frac{1}{2}\delta^{(2)}$. The effects of second order density perturbation greatly reduce the upper bounds of small-scale power spectra of primordial curvature perturbations by one to two orders of magnitude. For log-normal primordial power spectrum, its amplitude $A_{\zeta}$ is constrained to be about $A_{\zeta}\sim 3\times10^{-3}$. And for local-type non-Gaussianity with $f_{\mathrm{NL}}=10$, the upper bound of $A_{\zeta}$ is about $2.5\times10^{-4}$.

The knee of cosmic ray spectra reflects the maximum energy accelerated by galactic cosmic ray sources or the limit to the ability of galaxy to bind cosmic rays. The measuring of individual energy spectra is a crucial tool to ascertain the origin of the knee. The Extensive Air Shower of cosmic rays in the knee energy region is simulated via CORSIKA software. The energy resolution for different secondary components and primary nuclei identification capability are studied. The energy reconstruction by using electromagnetic particles in the energy around knee is better than by using other secondary particles. The resolution is 10-19 percent for proton, and 4-8 percent for iron. For the case of primary nuclei identification capability, the discriminability of density of muons is best both at low (around 100 TeV) and high (around 10 PeV) energy, the discriminability of the shape of lateral distribution of electron and gamma-rays are good at low energy and the discriminability of density of neutrons is good at high energy. The differences between the lateral distributions of secondary particles simulated by EPOS-LHC and QGSJet-II-04 hadronic model are also studied. The results in this work can provide important information for selecting the secondary components and detector type during energy reconstruction and identifying the primary nuclei of cosmic rays in the knee region.

MeerKAT imaging of the globular cluster 47 Tucanae (47 Tuc) reveals 1.28 GHz continuum emission at the locations of 20 known millisecond pulsars (MSPs). We use time series and spectral imaging to investigate the image-domain characteristics of the MSPs, and search for previously unknown sources of interest. The MSPs exhibit a range of differences in their temporal and spectral properties compared the general background radio source population. Temporal variability differs strongly from pulsar to pulsar, some appearing to vary randomly on 15 min timescales, others varying coherently by factors of >10 on timescales of hours. The error in the typical power law fit to the spectrum emerges as a powerful parameter for indentifying the MSPs. This behaviour is likely due to differing diffractive scintillation conditions along the sight lines to the MSPs. One MSP exhibits tentative periodic variations that are consistent with modulation due the orbit of an eclipsing binary system. One radio source has spectro-temporal properites closely resembling those of the MSP population in the cluster, and we report its position as a candidate new MSP, or alternatively an interferometric localisation of one of six MSPs which do not yet have an accurate position from the timing solutions.

Experimental and theoretical infrared spectra, between 4000-500 cm$^{-1}$ (2.5-20 microns), and infrared band strengths of two solid phases of indene, amorphous and crystalline, are given for the first time. The samples were generated via vapor deposition under high vacuum conditions on a cold surface. Density functional theory was employed for the calculations of the IR spectra. Lacking of previous information, a monoclinic symmetry is suggested for the theoretical crystalline phase of indene, based on the comparison of the calculated and experimental IR spectra. Assignments, based on the calculations, are given for the main indene IR absorptions. The infrared spectra of highly diluted mixtures of indene in amorphous solid water at 10 K are also provided, evidencing that the indene spectrum is not much altered by the water ice environment. These data are expected to be useful for the search of this species in the solid phase in astrophysical environments with the JWST. With the band strengths obtained in this work, and applying a simple literature model, we find that indene could represent at most 2-5 percent of the intensity of a weak absorption feature at 3.3 microns recently reported for Elias 16. A column density of (1.5 -0.6) 10$^{16}$ cm$^{-2}$ is estimated for indene in the ice mantles of TMC-1. It would correspond to aprox. (2 - 0.8) 10$^{-2}$ of cosmic carbon, which is probably too high for a single small hydrocarbon.

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process). These heavy elements include some of great geophysical, biological and cultural importance, such as thorium, iodine and gold. Here we present observations of the exceptionally bright gamma-ray burst GRB 230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW170817. We obtained James Webb Space Telescope mid-infrared (mid-IR) imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns which we interpret as tellurium (atomic mass A=130), and a very red source, emitting most of its light in the mid-IR due to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the Universe.

Molecular outflows are expected to play a key role in galaxy evolution at high redshift. To study the impact of outflows on star formation at the epoch of reionization, we performed sensitive ALMA observations of OH 119 $\mu$m toward J2054-0005, a luminous quasar at $z=6.04$. The OH line is detected and exhibits a P-Cygni profile that can be fitted with a broad blue-shifted absorption component, providing unambiguous evidence of an outflow, and an emission component at near-systemic velocity. The mean and terminal outflow velocities are estimated to be $v_\mathrm{out}\approx670~\mathrm{km~s}^{-1}$ and $1500~\mathrm{km~s}^{-1}$, respectively, making the molecular outflow in this quasar one of the fastest at the epoch of reionization. The OH line is marginally resolved for the first time in a quasar at $z>6$, revealing that the outflow extends over the central 2 kpc region. The mass outflow rate is comparable to the star formation rate ($\dot{M}_\mathrm{out}/\mathrm{SFR}\sim1$), indicating rapid ($\sim10^7~\mathrm{yr}$) quenching of star formation. The mass outflow rate in a sample star-forming galaxies and quasars at $4<z<6.4$ exhibits a near-linear correlation with the total infrared luminosity, although the scatter is large. Owing to the high outflow velocity, a large fraction (up to $\sim50\%$) of the outflowing molecular gas may be able to escape from the host galaxy into the intergalactic medium.

It is proposed that one-off fast radio burst (FRB) with periodic structures may be produced during the inspiral phase of a binary neutron-star (BNS) merger. In this paper, we study the event rate of such kind of FRB. We first investigate the properties of two one-off FRBs with periodic structures (i.e., FRB~20191221A and FRB~20210213A) in this scenario, by assuming the fast magnetosonic wave is responsible for their radio emission. For the luminosities and periods of these bursts, it is found that the pre-merger BNS with magnetic field strength $B\gtrsim 10^{12}\,{\rm Gs}$ is required. This is relatively high compared with that of the most of the BNSs observed in our Galaxy, of which the magnetic field is around $10^{9}\,{\rm Gs}$. Since the observed BNSs in our Galaxy are the binaries without suffering merger, a credited event rate of BNS-merger originated FRBs should be estimated by considering the evolution of both the BNS systems and their magnetic fields. Based on the population synthesis and adopting a decaying magnetic field of NSs, we estimate the event rate of BNS-mergers relative to their final magnetic fields. We find that the rapid merged BNSs tend to merge with high magnetization, and the event rate of BNS-merger originated FRBs, i.e., the BNS-mergers with both NSs' magnetic field being higher than $10^{12}\,{\rm Gs}$ is $\sim8\times10^{4}\,\rm{yr}^{-1}$ ($19 \%$ of the total BNS-mergers) in redshift $z<1$.

A new and promising avenue was recently developed for analyzing large-scale structure data with a model-independent approach, in which the linear power spectrum shape is parametrized with a large number of freely varying wavebands rather than by assuming specific cosmological models. We call this method FreePower. Here we show, using a Fisher matrix approach, that precision of this method for the case of the one-loop power spectrum is greatly improved with the inclusion of the tree-level bispectrum. We also show that accuracy can be similarly improved by employing perturbation theory kernels whose structure is entirely determined by symmetries instead of evolution equations valid in particular models (like in the usual Einstein-deSitter approximation). The main result is that with the Euclid survey one can precisely measure the Hubble function, distance and ($k$-independent) growth rate $f(z)$ in seven redshift bins in the range $z\in [0.6,\, 2.0]$. The typical errors for the lowest $z$bins are around 1\% (for $H$), 0.5--1\% (for $D$), and 1--3\% (for $f$). The use of general perturbation theory allows us, for the first time, to study constraints on the nonlinear kernels of cosmological perturbations, that is, beyond the linear growth factor, showing that they can be probed at the 10--20\% level. We find that the combination of spectrum and bispectrum is particularly effective in constraining the perturbation parameters, both at linear and quadratic order.

PSR~J0631+1036 is a middle-aged pulsar with properties similar to those of the nearby Geminga pulsar. It is bright in $\gamma$-rays, and has been noted as the only source possibly associated with the TeV source 3HWC J0631+107 (also the LHAASO J0631+1040). For understanding the nature of the TeV source, we analyze the GeV $\gamma$-ray data obtained with the Large Area Telescope (LAT) onboard {\it the Fermi Gamma-ray Space Telescope} for the source region. We are able to remove the pulsar's emission from the region from timing analysis, and find that the region is rather clean without possible GeV $\gamma$-ray emission present as the counterpart to the TeV source. By comparing this pulsar to Geminga and considering the spectral feature of the TeV source, we argue that it is likely the TeV halo powered by the pulsar.

POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42{\deg} and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy (corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of $\beta^+$ decay with a typical for this process gamma-ray energy line of 511 keV.

We present the results of optical spectroscopy of stellar companions to three binary millisecond pulsars, PSRs J0621$+$2514, J2317$+$1439 and J2302$+$4442, obtained with the Gran Telescopio Canarias. The spectrum of the J0621$+$2514 companion shows a blue continuum and prominent Balmer absorption lines. The latter are also resolved in the spectrum of the J2317$+$1439 companion, showing that both are DA-type white dwarfs. No spectral features are detected for the J2302$+$4442 companion, however, its broadband magnitudes and the spectral shape of the continuum emission imply that this is also a DA-type white dwarf. Based on the spectral analyses, we conclude that the companions of J0621$+$2514 and J2317$+$1439 are relatively hot, with effective temperatures $T_{\rm eff}$$=$8600$\pm$200 and 9600$\pm$2000~K, respectively, while the J2302$+$4442 companion is significantly cooler, $T_{\rm eff}$$<$6000~K. We also estimated the distance to J0621$+$2514 of 1.1$\pm$0.3 kpc and argue that its companion and the companion of J2317$+$1439 are He-core white dwarfs providing constraints on their cooling ages of $\lesssim$2 Gyr.

Type Ia supernovae (SNe Ia) arise from the thermonuclear explosion in binary systems involving carbon-oxygen white dwarfs (WDs). The pathway of WDs acquiring mass may produce circumstellar material (CSM). Observing SNe Ia within a few hours to a few days after the explosion can provide insight into the nature of CSM relating to the progenitor systems. In this paper, we propose a CSM model to investigate the effect of ejecta-CSM interaction on the early-time multi-band light curves of SNe Ia. By varying the mass-loss history of the progenitor system, we apply the ejecta-CSM interaction model to fit the optical and ultraviolet (UV) photometric data of eight SNe Ia with early excess. The photometric data of SNe Ia in our sample can be well-matched by our CSM model except for the UV-band light curve of iPTF14atg, indicating its early excess may not be due to the ejecta-CSM interaction. Meanwhile, the CSM interaction can generate synchrotron radiation from relativistic electrons in the shocked gas, making radio observations a distinctive probe of CSM. The radio luminosity based on our models suggests that positive detection of the radio signal is only possible within a few days after the explosion at higher radio frequencies (e.g., ~250 GHz); at lower frequencies (e.g., ~1.5 GHz) the detection is difficult. These models lead us to conclude that a multi-messenger approach that involves UV, optical, and radio observations of SNe Ia a few days past explosion is needed to address many of the outstanding questions concerning the progenitor systems of SNe Ia.

Herein, we describe the design, implementation and operation principles of an astronomical camera system, based on a large-format CCD261-84 detector with an extremely thick 200 mkm substrate. The DINACON-V controller was used with the CCD to achieve high performance and low noise. The CCD system photometric characteristics are presented. A spatial autocorrelation analysis of flat-field images was performed to reveal the dependence of substrate voltage on the lateral charge spreading. The investigation of the dispersion index for the optimal choice of exposure time is discussed. Studies of the patterns of fringes were carried out in comparison with previous detectors. The amplitude of fringes with CCD261-84 was significantly lower, compared to previous-generation detectors. The results of using a new camera for imaging and spectral observations at the Russian 6 m telescope with the SCORPIO-2 multimode focal reducer are considered. The developed CCD camera system makes it possible to significantly increase the sensitivity in the 800-1000 spectral range.

We investigate the impact of a galaxy's merger history on its system of satellites using the new \textsc{vintergatan-gm} suite of zoom-in hydrodynamical simulations of Milky Way-mass systems. The suite simulates five realizations of the same halo with targeted `genetic modifications' (GMs) of a $z \approx 2$ merger, but resulting in the same halo mass at $z=0$. We find that differences in the satellite stellar mass functions last for 2.25-4.25 Gyr after the $z \approx 2$ merger; specifically, the haloes that have undergone smaller mergers host up to 60% more satellites than those of the larger merger scenarios. However, by $z=0$ these differences in the satellite stellar mass functions have been erased. The differences in satellite numbers seen soon after the mergers are driven by several factors, including the timings of major mergers, the masses and satellite populations of the central and merging systems, and the subsequent extended history of minor mergers. The results persist when measured at fixed central stellar mass rather than fixed time, implying that a host's recent merger history can be a significant source of scatter when reconstructing its dynamical properties from its satellite population.

We investigate the origin of mesoscale structures in the solar wind called microstreams defined as enhancements in solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind data and are now omnipresent in the "young" solar wind measured by Parker Solar Probe and Solar Orbiter. These recent data reveal that microstreams transport a profusion of Alfv\'enic perturbations in the form of velocity spikes and magnetic switchbacks. In this study we use a very high-resolution 2.5 MHD model of the corona and the solar wind to simulate the emergence of magnetic bipoles interacting with the pre-existing ambient corona and the creation of jets that become microstreams propagating in the solar wind. Our high-resolution simulations reach sufficiently high Lundquist numbers to capture the tearing mode instability that develops in the reconnection region and produces plasmo\"ids released with the jet into the solar wind. Our domain runs from the lower corona to 20 Rs, this allows us to track the formation process of plasmo\"ids and their evolution into Alfv\'enic velocity spikes. We obtain perturbed solar wind flows lasting several hours with velocity spikes occurring at characteristic periodicities of about 19 minutes. We retrieve several properties of microstreams measured in the pristine solar wind by Parker Solar Probe, namely an increase in wind velocity of about 100 km/s during the streams passage together with superposed velocity spikes of also about 100 km/s released into the solar wind.

Nucleosynthetic isotope anomalies in meteorites allow distinguishing between the non-carbonaceous (NC) and carbonaceous (CC) meteorite reservoirs and show that correlated isotope anomalies exist in both reservoirs. It is debated, however, whether these anomalies reflect thermal processing of presolar dust in the disk or are primordial heterogeneities inherited from the Solar System's parental molecular cloud. Here, using new high-precision 84Sr isotope data, we show that NC meteorites, Mars, and the Earth and Moon are characterized by the same 84Sr isotopic composition. This 84Sr homogeneity of the inner Solar System contrasts with the well-resolved and correlated isotope anomalies among NC meteorites observed for other elements, and most likely reflects correlated s- and (r-, p-)-process heterogeneities leading to 84Sr excess and deficits of similar magnitude which cancel each other. For the same reason there is no clearly resolved 84Sr difference between NC and CC meteorites, because in some carbonaceous chondrites the characteristic 84Sr excess of the CC reservoir is counterbalanced by an 84Sr deficit resulting from s-process variations. Nevertheless, most carbonaceous chondrites exhibit 84Sr excesses, which reflect admixture of refractory inclusions and more pronounced s-process heterogeneities in these samples. Together, the correlated variations of s-, (r-, p-)-process nuclides revealed by the 84Sr data of this study refute an origin of these isotope anomalies solely by processing of presolar dust grains, but points to primordial mixing of isotopically distinct dust reservoirs as the dominant process producing the isotopic heterogeneity of the Solar System.

FRB 180916.J0158+65 is a well-known repeating fast radio burst with a period ($16.35~\rm days$) and an active window ($5.0~\rm days$). We give out the statistical results of the dispersion measures and waiting times of bursts of FRB 180916.J0158+65. We find the dispersion measures at the different frequencies show a bimodal distribution. The peaking dispersion measures of the left mode of the bimodal distributions increase with frequency, but the right one is inverse. The waiting times also present the bimodal distribution, peaking at 0.05622s and 1612.91266s. The peaking time is irrelevant to the properties of bursts, either for the preceding or subsequent burst. By comparing the statistical results with possible theoretical models, we suggest that FRB 180916.J0158+65 suffered from the plasma lensing effects in the propagation path. Moreover, this source may be originated from a highly magnetized neutron star in a high-mass X-ray binary.

Magnetic fields are expected to be efficiently amplified during the formation of the first massive black holes via the small-scale dynamo and in the presence of strong accretion shocks occurring during gravitational collapse. Here, we analyze high-resolution cosmological magneto-hydrodynamical simulations of gravitational collapse in atomic cooling halos, exploring the dynamical role of magnetic fields, particularly concerning the effect of magnetic braking and angular momentum transport. We find that after the initial amplification, magnetic fields contribute to the transport of angular momentum and reduce it compared to pure hydrodynamical simulations. However, the magnetic and Reynolds torques do not fully compensate for the inward advection of angular momentum, which still accumulates over timescales of $\sim1$~Myr. A Jeans analysis further shows that magnetic pressure strongly contributes to suppressing fragmentation on scales of $0.1-10$~pc. Overall, the presence of magnetic fields thus aids in the transport of angular momentum and favors the formation of massive objects.

In this paper, we analyse sound waves arising from a cosmic phase transition where the full velocity profile is taken into account as an explanation for the gravitational wave spectrum observed by multiple pulsar timing array groups. Unlike the broken power law used in the literature, in this scenario the power law after the peak depends on the macroscopic properties of the phase transition, allowing for a better fit with pulsar timing array (PTA) data. We compare the best fit with that obtained using the usual broken power law and, unsurprisingly, find a better fit with the gravitational wave (GW) spectrum that utilizes the full velocity profile. We then discuss models that can produce the best-fit point and complementary probes using CMB experiments and searches for light particles in DUNE, IceCUBE-Gen2, neutrinoless double beta decay, and forward physics facilities at the LHC like FASER nu, etc.

The advancement of neutrino observatories has sparked a surge in multi-messenger astronomy. Multiple neutrino associations among blazars are reported while neutrino production site is located within their central (sub)parsecs. Yet many questions remain on the nature of those processes. The next generation Event Horizon Telescope (ngEHT) is uniquely positioned for these studies, as its high frequency and resolution can probe both the accretion disk region and the parsec-scale jet. This opens up new opportunities for connecting the two regions and unraveling the proton acceleration and neutrino production in blazars. We outline observational strategies for ngEHT and highlight what it can contribute to the multi-messenger study of blazars.

Insight into the formation and global distribution of cloud particles in exoplanet atmospheres continues to be a key problem to tackle going into the JWST era. Understanding microphysical cloud processes and atmospheric feedback mechanisms in 3D has proven to be a challenging prospect for exoplaneteers. In an effort to address the large computational burden of coupling these models in 3D simulations, we develop an open source, lightweight and efficient microphysical cloud model for exoplanet atmospheres. `Mini-cloud' is a microphysical based cloud model for exoplanet condensate clouds that can be coupled to contemporary general circulation models (GCMs) and other time dependent simulations. We couple mini-cloud to the Exo-FMS GCM and use a prime JWST target, the hot Jupiter HAT-P-1b, as a test case for the cloud formation module. After 1000+ of days of integration with mini-cloud, our results show a complex 3D cloud structure with cloud properties relating closely the dynamical and temperature properties of the atmosphere. Current transit and emission spectra data are best fit with a reduced cloud particle number density compared to the nominal simulation, with our simulated JWST NIRISS SOSS spectra showing promising prospects for characterising the atmosphere in detail. Overall, our study is another small step in first principles 3D exoplanet cloud formation microphysical modelling. We suggest that additional physics not included in the present model, such as coagulation, are required to reduce the number density of particles to appropriately observed levels.

We use the spectral lag data of 32 long GRBs detected by Fermi/GBM, which has been recently collated in Liu et al (2022) to carry out a search for Lorentz Invariance violation (LIV) using Bayesian model selection. We use two different parametric functions to model the null hypothesis of only intrinsic emission: a smooth broken power law model (SBPL) (proposed in Liu et al) as well as a simple power law model, which has been widely used before in literature. We find that using the SBPL model as the null hypothesis, only three GRBs show decisive evidence for linear LIV, of which only one shows decisive evidence for quadratic LIV. When we use the simple power-law model as the null hypothesis, we find 15 and 16 GRBs showing decisive evidence for linear and quadratic LIV, respectively. Finally, when we apply the SBPL model to model the intrinsic emission in GRB 1606025B, the evidence for LIV (which was previously reported using the simple power law model) disappears. This underscores the importance of adequately modelling the intrinsic emission while searching for evidence of LIV using spectral lags.

Fast radio bursts (FRBs) are extragalactic transients with typical durations of milliseconds. FRBs have been shown, however, to fluctuate on a wide range of timescales: some show sub-microsecond sub-bursts while others last up to a few seconds in total. Probing FRBs on a range of timescales is crucial for understanding their emission physics, how to detect them effectively, and how to maximize their utility as astrophysical probes FRB 20121102A is the first-known repeating FRB source. Here we show that FRB 20121102A is able to produce isolated microsecond-duration bursts whose total durations are more than ten times shorter than all other known FRBs. The polarimetric properties of these micro-bursts resemble those of the longer-lasting bursts, suggesting a common emission mechanism producing FRBs spanning a factor of 1,000 in duration. Furthermore, this work shows that there exists a population of ultra-fast radio bursts that current wide-field FRB searches are missing due to insufficient time-resolution.

We report on observations of 68 satellites belonging to the SpaceX Starlink constellation with the LOFAR radio telescope. Radiation associated with Starlink satellites was detected at observing frequencies between 110 and 188 MHz. A combination of broad-band features, covering the entire observed bandwidth, as well as narrow-band (bandwidth < 12.2 kHz) emission at frequencies of 125, 135, 143.05, 150, and 175 MHz, was observed. The presence and properties of both the narrow- and broad-band features vary between satellites at different orbital altitudes. While the narrow-band detections at 143.05 MHz can be attributed to reflections of radar signals from the French GRAVES Space Surveillance Radar, the signal properties of the broad- and narrow-band features at the other frequencies suggest that this radiation is intrinsic to the Starlink satellites and it is seen for 47 out of the 68 Starlink satellites that were observed. We observed spectral power flux densities vary from 0.1 to 10 Jy for broad-band radiation, to 10 to 500 Jy for some of the narrow-band radiation, equivalent to electric field strengths of up to 49 dB[uV/m] (as measured at a 10 m distance from the satellites, with a measurement bandwidth of 120 kHz). In addition, we present equivalent power flux density simulations of the full Starlink phase 1 constellation, as well as other satellite constellations, for one frequency band allocated to radio astronomy by the International Telecommunication Union (ITU). With these, we calculate the maximum radiation level that each satellite constellation would need to have to comply with regulatory limits for intended emissions in that band. However, these limits do not apply if the radiation is unintended, that is to say if it does not originate from intentionally radiated signals for radio communication or other purposes. (shortened)

We present an imaging molecular line survey in the 3-mm band (85-114 GHz) focused on one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068, based on observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA). Distributions of 23 molecular transitions are obtained in the central ~3 kpc region, including both the circumnuclear disk (CND) and starburst ring (SBR) with 60 and 350 pc resolution. The column densities and relative abundances of all the detected molecules are estimated under the assumption of local thermodynamic equilibrium in the CND and SBR. Then, we discuss the physical and chemical effects of the AGN on molecular abundance corresponding to the observation scale. We found that H13CN, SiO, HCN, and H13CO+ are abundant in the CND relative to the SBR. In contrast, 13CO is more abundant in the SBR. Based on the calculated column density ratios of N(HCN)/N(HCO+), N(HCN)/N(CN), and other molecular distributions, we conclude that the enhancement of HCN in the CND may be due to high-temperature environments resulting from strong shocks, which are traced by the SiO emission. Moreover, the abundance of CN in the CND is significantly lower than the expected value of the model calculations in the region affected by strong radiation. The expected strong X-ray irradiation from the AGN has a relatively lower impact on the molecular abundance in the CND than mechanical feedback.

We demonstrate that the recently announced signal for a stochastic gravitational wave background (SGWB) from pulsar timing array (PTA) observations, if attributed to new physics, is compatible with primordial GW production due to axion-gauge dynamics during inflation. More specifically we find that axion-$U(1)$ models may lead to sufficient particle production to explain the signal while simultaneously source some fraction of sub-solar mass primordial black holes (PBHs) as a signature. Moreover there is a parity violation in GW sector, hence the model suggests chiral GW search as a concrete target for future. We further analyze the axion-$SU(2)$ coupling signatures and find that in the low backreaction regime, it is incapable of producing PTA evidence and violates PBH constraints.

The recent detection of high-energy neutrinos by IceCube in the direction of the nearby Seyfert/starburst galaxy NGC 1068 implies that radio-quiet active galactic nuclei can accelerate cosmic-ray ions. Dedicated multi-messenger analyses suggest that the interaction of these high-energy ions { with ambient gas or photons} happens in a region of the galaxy that is highly opaque for GeV-TeV gamma rays. Otherwise, the GeV-TeV emission would violate existing constraints provided by {\it Fermi}-LAT and MAGIC. The conditions of high optical depth are realized near the central super-massive black hole (SMBH). At the same time, the GeV emission detected by the {\it Fermi}-Large Area Telescope (LAT) is likely related to the galaxy's sustained star-formation activity. In this work, we derive a 20\,MeV - 1\,TeV spectrum of NGC 1068 using 14\,yrs of {\it Fermi}-LAT observations. We find that the starburst hadronic component is responsible for NGC 1068's emission above $\sim$500\,MeV. However, below this energy an additional component is required. In the 20-500\,MeV range the {\it Fermi}-LAT data are consistent with hadronic emission {initiated by non-thermal ions interacting with gas or photons} in the vicinity of the central SMBH. This highlights the importance of the MeV band to discover hidden cosmic-ray accelerators.

By applying our previously developed two-step scheme for galaxy morphology classification, we present a catalog of galaxy morphology for H-band selected massive galaxies in the COSMOS-DASH field, which includes 17292 galaxies with stellar mass $M_{\star}>10^{10}~M_{\odot}$ at $0.5<z<2.5$. The classification scheme is designed to provide a complete morphology classification for galaxies via a combination of two machine-learning steps. We first use an unsupervised machine learning method (i.e., bagging-based multi-clustering) to cluster galaxies into five categories: spherical (SPH), early-type disk (ETD), late-type disk (LTD), irregular (IRR), and unclassified (UNC). About 48\% of galaxies (8258/17292) are successfully clustered during this step. For the remaining sample, we adopt a supervised machine learning method (i.e., GoogLeNet) to classify them, during which galaxies that are well-classified in the previous step are taken as our training set. Consequently, we obtain a morphology classification result for the full sample. The t-SNE test shows that galaxies in our sample can be well aggregated. We also measure the parametric and nonparametric morphologies of these galaxies. We find that the S\'{e}rsic index increases from IRR to SPH and the effective radius decreases from IRR to SPH, consistent with the corresponding definitions. Galaxies from different categories are separately distributed in the $G$--$M_{20}$ space. Such consistencies with other characteristic descriptions of galaxy morphology demonstrate the reliability of our classification result, ensuring that it can be used as a basic catalog for further galaxy studies.

We present an International LOFAR Telescope sub-arcsecond resolution image of the nearby galaxy M 51 with a beam size of 0.436" x 0.366" and rms of 46 $\mu$Jy. We compare this image with an European VLBI Network study of M 51, and discuss the supernovae in this galaxy, which have not yet been probed at these low radio frequencies. We find a flux density of 0.97 mJy for SN 2011dh in the ILT image, which is about five times smaller than the flux density reported by the LOFAR Twometre Sky Survey at 6" resolution using the same dataset without the international stations. This difference makes evident the need for LOFAR international baselines to reliably obtain flux density measurements of compact objects in nearby galaxies. Our LOFAR flux density measurement of SN 2011dh directly translates into fitting the radio light curves for the supernova and constraining massloss rates of progenitor star. We do not detect two other supernovae in the same galaxy, SN 1994I and SN 2005cs, and our observations place limits on the evolution of both supernovae at radio wavelengths. We also discuss the radio emission from the centre of M 51, in which we detect the Active Galactic Nucleus and other parts of the nuclear emission in the galaxy, and a possible detection of Component N. We discuss a few other sources, including the detection of a High mass X-ray Binary not detected by LoTSS, but with a flux density in the ILT image that matches well with higher frequency catalogues.

The observations of the energy spectra of cosmic-ray have revealed complicated structures. Especially, spectral hardenings in the boron-to-carbon and boron-to-oxygen ratios above $\sim 200$ GV has been revealed by AMS-02 and DAMPE experiments. One scenario to account for the hardenings of secondary-to-primary ratios is the nuclear fragmentation of freshly accelerated particles around sources. In this work, we further study this scenario based on new observations of Galactic diffuse gamma rays by LHAASO and neutrinos by IceCube. We find that the spectra of cosmic ray nuclei, the diffuse ultra-high-energy gamma rays, and the Galactic component of neutrinos can be simultaneously explained, given an average confinement and interaction time of $\sim 0.25$ Myr around sources. These multi-messenger data thus provide evidence of non-negligible grammage of Galactic cosmic rays surrounding sources besides the traditional one during the propagation.

Very recently, several pulsar timing array collaborations, including CPTA, EPTA, and NANOGrav, reported their results from searches for an isotropic stochastic gravitational wave background (SGWB), with each finding positive evidence for SGWB. In this work, we assessed the credibility of interpreting the Hellings-Downs correlated free-spectrum process of EPTA, PPTA, and NANOGrav as either the result of supermassive black hole binary mergers or various stochastic SGWB sources that originated in the early Universe, including first-order phase transitions, cosmic strings, domain walls, and large-amplitude curvature perturbations. Our observations show that the current new datasets do not display a strong preference for any specific SGWB source based on Bayesian analysis.

PSR J0026-1955 was independently discovered by the Murchison Widefield Array (MWA) recently. The pulsar exhibits subpulse drifting, where the radio emission from a pulsar appears to drift in spin phase within the main pulse profile, and nulling, where the emission ceases briefly. The pulsar showcases a curious case of drift rate evolution as it exhibits rapid changes between the drift modes and a gradual evolution in the drift rate within a mode. Here we report new analysis and results from observations of J0026-1955 made with the upgraded Giant Meterwave Radio Telescope (uGMRT) at 300-500 MHz. We identify two distinct subpulse drifting modes: A and B, with mode A sub-categorised into A0, A1, and A2, depending upon the drift rate evolutionary behaviour. Additionally, the pulsar exhibits short and long nulls, with an estimated overall nulling fraction of ~58%, which is lower than the previously reported value. Our results also provide evidence of subpulse memory across nulls and a consistent behaviour where mode A2 is often followed by a null. We investigate the drift rate modulations of J0026-1955 and put forward two different models to explain the observed drifting behaviour. We suggest that either a change in polar gap screening or a slow relaxation in the spark configuration could possibly drive the evolution in drift rates. J0026-1955 belongs to a rare subset of pulsars which exhibit subpulse drifting, nulling, mode changing, and drift rate evolution. It is, therefore, an ideal test bed for carousel models and to uncover the intricacies of pulsar emission physics.

The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2/4/2022, an M-class flare followed by a filament eruption was seen both by the instruments on board the mission and from several observatories in Earth's orbit. The complexity of the observed features is compared with the predictions given by the standard flare model in 3D. We use the observations from a multi-view dataset, which includes EUV imaging to spectroscopy and magnetic field measurements. These data come from IRIS, SDO, Hinode, as well as several instruments on Solar Orbiter. Information given by SDO/HMI and Solar Orbiter PHI/HRT shows that a parasitic polarity emerging underneath the filament is responsible for bringing the flux rope to an unstable state. As the flux rope erupts, Hinode/EIS captures blue-shifted emission in the transition region and coronal lines in the northern leg of the flux rope prior to the flare peak. Solar Orbiter SPICE captures the whole region, complementing the Doppler diagnostics of the filament eruption. Analyses of the formation and evolution of a complex set of flare ribbons and loops show that the parasitic emerging bipole plays an important role in the evolution of the flaring region. While the analysed data are overall consistent with the standard flare model, the present particular magnetic configuration shows that surrounding magnetic activity such as nearby emergence needs to be taken into account to fully understand the processes at work. This filament eruption is the first to be covered from different angles by spectroscopic instruments, and provides an unprecedented diagnostic of the multi-thermal structures present before and during the flare. This dataset of an eruptive event showcases the capabilities of coordinated observations with the Solar Orbiter mission.

We discuss the interpretation of the detected signal by Pulsar Timing Array (PTA) observations as a gravitational wave background (GWB) of cosmological origin. We combine NANOGrav 15-years and EPTA-DR2new data sets and confront them against backgrounds from supermassive black hole binaries (SMBHBs) and cosmological signals from inflation, cosmic (super)strings, first-order phase transitions, Gaussian and non-Gaussian large scalar fluctuations, and audible axions. We find that Gaussian scalar-induced, and to a lesser extent audible axion and cosmic superstring signals, provide a better fit than SMBHBs. These results depend, however, on modelling assumptions, so further data and analysis are needed to reach robust conclusions. Independently of the signal origin, the data strongly constrain the parameter space of cosmological signals, e.g.~setting, at 68\% CL, an upper bound on primordial non-Gaussianity at PTA scales as $|f_{nl}| \lesssim 4.9$, and lower bounds on the mass and decay constant of an audible axion as $m_a \gtrsim 8.0 \cdot 10^{-11}$ meV and $f_a \gtrsim 1.3 \cdot 10^{18}$ GeV.

We present relativistic, radiation magnetohydrodynamic simulations of supercritical neutron star accretion columns in Cartesian geometry, including temperature-dependent, polarization-averaged Rosseland mean opacities accounting for classical electron scattering in a magnetic field. Just as in our previous pure Thomson scattering simulations, vertical oscillations of the accretion shock and horizontally propagating entropy waves (photon bubbles) are present in all our simulations. However, at high magnetic fields $\gtrsim10^{12}$~G, the magnetic opacities produce significant differences in the overall structure and dynamics of the column. At fixed accretion rate, increasing the magnetic field strength results in a shorter accretion column, despite the fact that the overall opacity within the column is larger. Moreover, the vertical oscillation amplitude of the column is reduced. Increasing the accretion rate at high magnetic fields restores the height of the column. However, a new, slower instability takes place at these field strengths because they are in a regime where the opacity increases with temperature. This instability causes both the average height of the column and the oscillation amplitude to substantially increase on a time scale of $\sim10$~ms. We provide physical explanations for these results, and discuss their implications for the observed properties of these columns, including mixed fan-beam/pencil-beam emission patterns caused by the oscillations.

Atmospheric gravity waves (AGWs) are low-frequency, buoyancy-driven waves that are generated by turbulent convection and propagate obliquely throughout the solar atmosphere. Their proposed energy contribution to the lower solar atmosphere and sensitivity to atmospheric parameters (e.g. magnetic fields and radiative damping) highlight their diagnostic potential. We investigate AGWs near a quiet Sun disk center region using multi-wavelength data from the Interferometric BIdimensional Spectrometer (IBIS) and the Solar Dynamics Observatory (SDO). These observations showcase the complex wave behavior present in the entire acoustic-gravity wave spectrum. Using Fourier spectral analysis and local helioseismology techniques on simultaneously observed line core Doppler velocity and intensity fluctuations, we study both the vertical and horizontal properties of AGWs.Propagating AGWs with perpendicular group and phase velocities are detected at the expected temporal and spatial scales throughout the lower solar atmosphere. We also find previously unobserved, varied phase difference distributions among our velocity and intensity diagnostic combinations. Time-distance analysis indicates that AGWs travel with an average group speed of 4.5 kms$^{-1}$, which is only partially described by a simple simulation suggesting that high-frequency AGWs dominate the signal. Analysis of the median magnetic field (4.2 G) suggests that propagating AGWs are not significantly affected by quiet Sun photospheric magnetic fields. Our results illustrate the importance of multi-height observations and the necessity of future work to properly characterize this observed behavior.

This study aims to elucidate the tension in the Hubble constant ($H_0$), a key metric in cosmology representing the universe's expansion rate. Conflicting results from independent measurements such as the Planck satellite mission and the SH0ES collaboration have sparked interest in exploring alternative cosmological models. We extend the analysis by SH0ES to an arbitrary cosmographic model, obtaining a competitive local $H_0$ determination which only assumes the standard flat $\Lambda$CDM model ($73.14 \pm 1.10$ km/s/Mpc), and another which only assumes the FLRW metric ($74.56 \pm 1.61$ km/s/Mpc). The study also stresses the importance of the supernova magnitude calibration ($M_B$) in cosmological inference and highlights the tension in $M_B$ when supernovae are calibrated either by CMB and BAO observations or the first two rungs of the cosmic distance ladder. This discrepancy, independent of the physics involved, suggests that models solely changing the Hubble flow and maintaining a sound horizon distance consistent with CMB, fail to explain the discrepancy between early- and late-time measurements of $H_0$.

We compute the evidence in favour of two models, one based on field-aligned thermal conduction alone and another that includes thermal misbalance as well, in explaining the damping of slow magneto-acoustic waves in hot coronal loops. Our analysis is based on the computation of the marginal likelihood and the Bayes factor for the two damping models. We quantify their merit in explaining the apparent relationship between slow mode periods and damping times, measured with SOHO/SUMER in a set of hot coronal loops. The results indicate evidence in favour of the model with thermal misbalance in the majority of the sample, with a small population of loops for which thermal conduction alone is more plausible. The apparent possibility of two different regimes of slow-wave damping, if due to differences between the loops of host active regions and/or the photospheric dynamics, may help with revealing the coronal heating mechanism.

Poynting flux is the flux of magnetic energy, which is responsible for chromospheric and coronal heating in the solar atmosphere. It is defined as a cross product of electric and magnetic fields, and in ideal MHD conditions it can be expressed in terms of magnetic field and plasma velocity. Poynting flux has been computed for active regions and plages, but estimating it in the quiet Sun (QS) remains challenging due to resolution effects and polarimetric noise. However, with upcoming DKIST capabilities, these estimates will become more feasible than ever before. Here, we study QS Poynting flux in Sunrise/IMaX observations and MURaM simulations. We explore two methods for inferring transverse velocities from observations - FLCT and a neural network based method DeepVel - and show DeepVel to be the more suitable method in the context of small-scale QS flows. We investigate the effect of azimuthal ambiguity on Poynting flux estimates, and we describe a new method for azimuth disambiguation. Finally, we use two methods for obtaining the electric field. The first method relies on idealized Ohm's law, whereas the second is a state-of-the-art inductive electric field inversion method PDFI SS. We compare the resulting Poynting flux values with theoretical estimates for chromospheric and coronal energy losses and find that some of Poynting flux estimates are sufficient to match the losses. Using MURaM simulations, we show that photospheric Poynting fluxes vary significantly with optical depth, and that there is an observational bias that results in underestimated Poynting fluxes due to unaccounted shear term contribution.

We examine the East-West asymmetry of the peak intensity in energetic storm particle (ESP) events using the improved Particle Acceleration and Transport in the Heliosphere (iPATH) model. We find that injection efficiency peaks east of the nose of coronal mass ejection shock where the shock exhibits a quasi-parallel geometry. We show that the peak intensity at the eastern flank is generally larger than that at the western flank and it positively correlates with the injection efficiency. We also examine this asymmetry for heavy ions, which depends sensitively on the ion energy. Comparison between the modelling results with the measurements of ESP events at 1 au shows a reasonable agreement. We suggest that the injection efficiency can be a primary factor leading to the East-West asymmetry of the peak intensity in ESP events. Additionally, the charge-to-mass (Q/A) dependence of the maximum particle energy affects this asymmetry for heavy ions.

We test the possibility that the black holes (BHs) detected by LIGO-Virgo-KAGRA (LVK) may be cosmologically coupled and grow in mass proportionally to the cosmological scale factor to some power $k$, which may also act as the dark energy source. This approach was proposed as an extension of Kerr BHs embedded in cosmological backgrounds and possibly without singularities. In our analysis, we test these cosmologically coupled BHs either with or without connection to dark energy. Assuming that the minimum mass of a BH with stellar progenitor is $2M_\odot$, we estimate the probability that at least one BH among the observed ones had an initial mass below this threshold, thereby falsifying the hypothesis. We consider either the primary $m_1$ or the secondary $m_2$ BHs of 72 confidently detected gravitational wave events and adopt two different approaches. In the first one, we directly derive the probability from the observed events, and we obtain a tension with the $k=3$ scenario at the level of 2.6$\sigma$ and 3.05$\sigma$ for the $m_1$ or $m_2$ cases respectively. In the second approach, we assume the LVK power-law-plus-peak (PLPP) mass distribution, which takes into account the observational bias, and we find tensions at the level of 3.7$\sigma$ and $4.0\sigma$ for the $m_1$ and $m_2$ masses respectively. We show that these bounds can be alleviated by allowing lower $k$ values or faster BHs mergers (i.e., shorter delay times $t_{\rm d}$). In particular the $m_1$-based results in the following 2$\sigma$ upper bounds: $k \leq 2.4$ for the direct approach or $k \leq 1.7$ in the PLLP approach. For $k = 0.5$, a value previously studied in the gravitational wave context, we find no relevant constraints, even increasing the minimum BH mass to $\sim 4 M_\odot$. Finally, we show that future observations should quickly strengthen these bounds.

We present a detailed study on SN2019szu, a Type I superluminous supernova at $z=0.213$, that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry shows a pre-explosion plateau lasting $\sim$ 40 days. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from $\sim$15000\,K to $\sim$20000\,K over the first 70 days, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line even during the rising phase of the light curve, inconsistent with an apparently compact photosphere. We show that this early feature is [O II] $\lambda\lambda$7320,7330. We also see evidence for [O III] $\lambda\lambda$4959, 5007, and [O III] $\lambda$4363 further strengthening this line identification. Comparing with models for nebular emission, we find that the oxygen line fluxes and ratios can be reproduced with $\sim$0.25\,M$_{\odot}$ of oxygen rich material with a density of $\sim10^{-15}\,\rm{g\,cm}^{-3}$. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of $\sim$5500\,$\Angstrom$. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.

Recent discovery of additional mechanism of electroluminescence (EL) in noble gases due to neutral bremsstrahlung (NBrS) effect led to a prediction that NBrS EL should be present in noble liquids as well. A rigorous theory of NBrS EL in noble liquids was developed accordingly in the framework of Cohen-Lekner and Atrazhev approach. In this work, we confirm this prediction: for the first time, visible-range EL has been observed in liquid Ar at electric fields reaching 90~kV/cm, using Gas Electron Multiplier (GEM) and Thick GEM (THGEM) structures. Absolute light yields of the EL were measured and found to be in excellent agreement with the theory, provided that momentum-transfer cross section of electron-atom scattering (instead of energy-transfer one) is used for calculation of NBrS cross section.

Seeley and Wordsworth (2021) showed that in small-domain cloud-resolving simulations the pattern of precipitation transforms in extremely hot climates ($\ge$ 320 K) from quasi-steady to organized episodic deluges, with outbursts of heavy rain alternating with several dry days. They proposed a mechanism for this transition involving increased water vapor absorption of solar radiation leading to net lower-tropospheric radiative heating. This heating inhibits lower-tropospheric convection and decouples the boundary layer from the upper troposphere during the dry phase, allowing lower-tropospheric moist static energy to build until it discharges, resulting in a deluge. We perform cloud-resolving simulations in polar night and show that the same transition occurs, implying that some revision of their mechanism is necessary. We show that episodic deluges can occur even if the lower-tropospheric radiative heating rate is negative, as long as the magnitude of the upper-tropospheric radiative cooling is about twice as large. We find that in the episodic deluge regime the mean precipitation can be inferred from the atmospheric column energy budget and the period can be predicted from the time for radiation and reevaporation to cool the lower atmosphere.

Gravitational wave signals from extreme mass ratio inspirals are a key target for space-based gravitational wave detectors. These systems are typically modeled as a distributionally-forced Teukolsky equation, where the smaller black hole is treated as a Dirac delta distribution. Time-domain solvers often use regularization approaches that approximate the Dirac distribution that often introduce small length scales and are a source of systematic error, especially near the smaller black hole. We describe a multi-domain discontinuous Galerkin method for solving the distributionally-forced Teukolsky equation that describes scalar fields evolving on a Kerr spacetime. To handle the Dirac delta, we expand the solution in spherical harmonics and recast the sourced Teukolsky equation as a first-order, one-dimensional symmetric hyperbolic system. This allows us to derive the method's numerical flux to correctly account for the Dirac delta. As a result, our method achieves global spectral accuracy even at the source's location. To connect the near field to future null infinity, we use the hyperboloidal layer method, allowing us to supply outer boundary conditions and providing direct access to the far-field waveform. We document several numerical experiments where we test our method, including convergence tests against exact solutions, energy luminosities for circular orbits, the scheme's superconvergence properties at future null infinity, and the late-time tail behavior of the scalar field. We also compare two systems that arise from different choices of the first-order reduction variables, finding that certain choices are numerically problematic in practice. The methods developed here may be beneficial when computing gravitational self-force effects, where the regularization procedure has been developed for the spherical harmonic modes and high accuracy is needed at the Dirac delta's location.

By applying auxiliary-field quantum Monte Carlo, we calculate the equation of state (EOS) and B1-B2 phase transition of magnesium oxide (MgO) up to 1 TPa. The results agree with available experimental data at low pressures and are used to benchmark the performance of various exchange-correlation functionals in density functional theory calculations. We determine PBEsol is an optimal choice for the exchange-correlation functional and perform extensive phonon and quantum molecular-dynamics calculations to obtain the thermal EOS. Our results provide a preliminary reference for the EOS and B1-B2 phase boundary of MgO from zero up to 10,500 K.

Particles are accelerated to very high, non-thermal energies during explosive energy-release phenomena in space, solar, and astrophysical plasma environments. While it has been established that magnetic reconnection plays an important role in the dynamics of Earth's magnetosphere, it remains unclear how magnetic reconnection can further explain particle acceleration to non-thermal energies. Here we review recent progress in our understanding of particle acceleration by magnetic reconnection in Earth's magnetosphere. With improved resolutions, recent spacecraft missions have enabled detailed studies of particle acceleration at various structures such as the diffusion region, separatrix, jets, magnetic islands (flux ropes), and dipolarization front. With the guiding-center approximation of particle motion, many studies have discussed the relative importance of the parallel electric field as well as the Fermi and betatron effects. However, in order to fully understand the particle acceleration mechanism and further compare with particle acceleration in solar and astrophysical plasma environments, there is a need for further investigation of, for example, energy partition and the precise role of turbulence.

This paper explores the detection capability of space-borne detectors to the anisotropic stochastic gravitational-wave background (SGWB) without relying on the low-frequency approximation. To assess the detection performance, we calculate the power-law integrated sensitivity (PLIS) curve. Our results demonstrate that a single detector has limited capabilities in detecting multipole moments beyond the monopole ($l=0$), quadrupole ($l=2$), and hexadecapole ($l=4$). However, when multiple detectors are combined, the presence of multiple pointing directions and the separation between detectors significantly enhance the detection capabilities for the other multipole moments. For instance, when considering the dipole ($l=1$), combining TianQin with TianQin II and LISA with TianQin significantly improves the detection sensitivity by 2-3 orders of magnitude, compared with using a single TianQin and a single LISA, respectively.

A gauge-invariant perturbation theory on a generic background spacetime is developing from 2003 and ``zero-mode problem'' for linear metric perturbations was proposed as the essential problem of this theory. In the perturbation theory on the Schwarzschild background spacetime, $l=0,1$ modes correspond to the above ``zero-mode'' and the gauge-invariant treatments of these modes is a famous non-trivial problem in perturbation theories on the Schwarzschild background spacetime. Due to this situation, a gauge-invariant treatment for these $l=0,1$-mode perturbations is proposed. Through this gauge-invariant treatment, the solutions to the linearized Einstein equation for these modes with a generic matter field are derived. In the vacuum case, the linearized version of uniqueness theorem of Kerr spacetime is confirmed in a gauge-invariant manner. In this sense, our proposal is reasonable.

Numerical simulation of strange quark stars (QSs) is challenging due to the strong density discontinuity at the stellar surface. In this paper, we report successful simulations of rapidly rotating QSs and study their oscillation modes in full general relativity. Building on top of the numerical relativity code \texttt{Einstein Toolkit}, we implement a positivity-preserving Riemann solver and a dust-like atmosphere to handle the density discontinuity at the surface. We demonstrate the robustness of our numerical method by performing stable evolutions of rotating QSs close to the Keplerian limit and extracting their oscillation modes. We focus on the quadrupolar $l=|m|=2$ $f$-mode and study whether they can still satisfy the universal relations recently proposed for rotating neutron stars (NSs). We find that two of the three proposed relations can still be satisfied by rotating QSs. For the remaining broken relation, we propose a new relation to unify the NS and QS data by invoking the dimensionless spin parameter $j$. The onsets of secular instabilities for rotating QSs are also studied by analyzing the $f$-mode frequencies. Same as the result found previously for NSs, we find that QSs become unstable to the Chandrasekhar-Friedman-Schutz instability when the angular velocity of the star $\Omega \approx 3.4 \sigma_0$ for sequences of constant central energy density, where $\sigma_0$ is the mode frequency of the corresponding nonrotating configurations. For the viscosity-driven instability, we find that QSs become unstable when $j\approx 0.881$ for both sequences of constant central energy density and constant baryon mass. Such a high value of $j$ cannot be achieved by realistic rotating NSs before reaching the Keplerian limit.

Compact Michelson interferometers are well positioned to replace existing displacement sensors in the readout of seismometers and suspension systems, such as those used in contemporary gravitational-wave detectors. Here, we continue our previous investigation of a customised compact displacement sensor built by SmarAct, which operated on the principle of deep frequency modulation. The focus of this paper is on the linearity of this device. We show the three primary sources of nonlinearity that arise in the sensor -- residual ellipticity, intrinsic distortion of the Lissajous figure, and distortion caused by exceeding the velocity limit imposed by the demodulation algorithm. We verify the theoretical models through an experimental demonstration designed to maximise the nonlinear noise to dominate regions of the readout's power spectrum. We finally simulate the effect that these nonlinearities are likely to have if implemented in the readout of the Advanced LIGO suspensions and show that the noise nonlinearities should not dominate across the key sub-\SI{10}{\Hz} frequency band.

We present a method for fitting monotone curves using cubic B-splines with a monotonicity constraint on the coefficients. We explore different ways of enforcing this constraint and analyze their theoretical and empirical properties. We propose two algorithms for solving the spline fitting problem: one that uses standard optimization techniques and one that trains a Multi-Layer Perceptrons (MLP) generator to approximate the solutions under various settings and perturbations. The generator approach can speed up the fitting process when we need to solve the problem repeatedly, such as when constructing confidence bands using bootstrap. We evaluate our method against several existing methods, some of which do not use the monotonicity constraint, on some monotone curves with varying noise levels. We demonstrate that our method outperforms the other methods, especially in high-noise scenarios. We also apply our method to analyze the polarization-hole phenomenon during star formation in astrophysics. The source code is accessible at \texttt{\url{https://github.com/szcf-weiya/MonotoneSplines.jl}}.

Massive particles produced during inflation leave specific signatures in soft limits of correlation functions of primordial fluctuations. When the Goldstone boson of broken time translations acquires a reduced speed of sound, implying that de Sitter boosts are strongly broken, we introduce a novel discovery channel to detect new physics during inflation, called the cosmological low-speed collider signal. This signal is characterised by a distinctive resonance lying in mildly-soft kinematic configurations of cosmological correlators, indicating the presence of a heavy particle, whose position enables to reconstruct its mass. We show that this resonance can be understood in terms of a non-local single field effective field theory, in which the heavy field becomes effectively non-dynamical. This theory accurately describes the full dynamics of the Goldstone boson and captures all multi-field physical effects distinct from the non-perturbative particle production leading to the conventional cosmological collider signal. As such, this theory provides a systematic and tractable way to study the imprint of massive fields on cosmological correlators. We conduct a thorough study of the low-speed collider phenomenology in the scalar bispectrum, showing that large non-Gaussianities with new shapes can be generated, in particular beyond weak mixing. We also provide a low-speed collider template for future cosmological surveys.

We investigate the possibility that inflation originates from a composite field theory, in terms of an effective chiral Lagrangian involving a dilaton and pions. The walking dynamics of the theory constrain the potential in a specific way, where the anomalous dimensions of operators involving pions play a crucial role. For realistic values of the anomalous dimensions, we find a successful hybrid inflation occurring via the dilaton-inflaton, with the pions acting as waterfall fields. Compositeness consistency strongly constrain the model, predicting a dilaton scale $f_\chi \sim \mathcal{O} (1)$ in unit of the Planck scale, an inflation scale $H_\text{inf} \sim 10^{10}$ GeV, and the pion scale around $10^{14}$ GeV. We further discuss possible phenomenological consequences of this theory.

The nuclear reaction network within the interior of the Sun is an efficient MeV physics factory, and can produce long-lived particles generic to dark sector models. In this work we consider the sensitivity of satellite instruments, primarily the RHESSI Spectrometer, that observe the Quiet Sun in the MeV regime where backgrounds are low. We find that Quiet Sun observations offer a powerful and complementary probe in regions of parameter space where the long-lived particle decay length is longer than the radius of the Sun, and shorter than the distance between the Sun and Earth. We comment on connections to recent model-building work on heavy neutral leptons coupled to neutrinos and high-quality axions from mirror symmetries.

In this paper, we discuss a general method to obtain exact cosmological solutions in modified gravity, to demonstrate the method it is employed to obtain exact cosmological solutions in $f(R,\phi)$ gravity. Here, we show that, given a particular evolution of the Universe, we could obtain different models of gravity that give that evolution, using the same construction. Further, we obtain an exact inflationary solution for Starobinsky action with a negligible cosmological constant. This analysis helps us to have a better understanding of Starobinsky inflation. With our analysis we could refine the parameter values and predictions of Starobinsky inflation. Also, we make an observation that there exist a no-go theorem for a bounce from Starobinsky action in the absence of scalar fields or a cosmological constant.

Wave packets propagating in inhomogeneous media experience a coupling between internal and external degrees of freedom and, as a consequence, follow spin-dependent trajectories. These are known as spin Hall effects, which are well known in optics and condensed matter physics. Similarly, the gravitational spin Hall effect is expected to affect the propagation of gravitational waves on curved spacetimes. In this general-relativistic setup, the curvature of spacetime acts as impurities in a semiconductor or inhomogeneities in an optical medium, leading to a frequency- and polarization-dependent propagation of wave packets. In this letter, we study this effect for strong-field lensed gravitational waves generated in hierarchical triple black hole systems in which a stellar-mass binary merges near a more massive black hole. We calculate how the gravitational spin Hall effect modifies the gravitational waveforms and show its potential for experimental observation. If detected, these effects will bear profound implications for astrophysics and tests of general relativity.

According to the Banados-Silk-West (BSW) process, rotating black holes can act as particle colliders capable of achieving arbitrarily high center-of-mass energy (CME), provided that a specific angular momentum of one of the particles is present. In this discussion, we demonstrate that both Kerr black holes and Schwarzschild black holes could serve as potential sources of high-energy particles in the polar region.

In the cosmos, any two bodies share a gravitational attraction. When in proximity to one another in empty space, their motions can be modeled by Newtonian gravity. Newton found their orbits when the two bodies are infinitely small, the so-called two-body problem. The general situation in which the bodies have varying shapes and sizes, called the full two-body problem, remains open. We find relative equilibria (RE) and their stability for an approximation of the full two-body problem, where each body is restricted to a plane and consists of two point masses connected by a massless rod, a dumbbell. In particular, we find symmetric RE in which the bodies are arranged colinearly, perpendicularly, or trapezoidally. When the masses of the dumbbells are pairwise equal, we find asymmetric RE bifurcating from the symmetric RE. And while we find that only the colinear RE have nonlinear/energetic stability (for sufficiently large radii), we also find that the perpendicular and trapezoid configurations have radial intervals of linear stability. We also provide a geometric restriction on the location of RE for a dumbbell body and any number of planar rigid bodies in planar orbit (an extension of the Conley Perpendicular Bisector Theorem).

The current framework for dark matter searches at beam dump and fixed target experiments relies on four benchmark models, the complex scalar, inelastic scalar, pseudo-Dirac and finally, Majorana DM models. While this approach has so far been successful in the interpretation of the available data, it a priori excludes the possibility that DM is made of spin-1 particles -- a restriction which is neither theoretically nor experimentally justified. In this work we extend the current landscape of sub-GeV DM models to a set of models for spin-1 DM, including a family of simplified models (involving one DM candidate and one mediator -- the dark photon) and an ultraviolet complete model based on a non-abelian gauge group where DM is a spin-1 Strongly Interacting Massive Particle. For each of these models, we calculate the DM relic density, the expected number of signal events at beam dump experiments, the rate of energy injection in the early universe thermal bath and in the Intergalactic Medium, as well as the helicity amplitudes for forward processes subject to the unitary bound. We then compare these predictions with experimental results from Planck, CMB surveys, IGM temperature observations, LSND, MiniBooNE, NA64, and BaBar and with available projections from LDMX and Belle II. Through this comparison, we identify the regions in the parameter space of the models considered in this work where DM is simultaneously thermally produced, compatible with present observations, and within reach at Belle II and LDMX. We find that the simplified models are strongly constrained by current beam dump experiments and the unitarity bound, and will thus be conclusively probed in the first stage of LDMX data taking. We also find that the SIMP model explored in this work predicts the observed DM abundance, is compatible with current observations and within reach at LDMX in a wide region of the parameter space.

In the framework of scalar-tensor gravity, we consider non-flat interacting quintessence cosmology where a scalar field is interacting with dark matter. Such a scalar field can be a standard or a phantom one. We use the Noether Symmetry Approach to obtain general exact solutions for cosmological equations and to select scalar-field self-interaction potentials. It turns out that the found solutions can reproduce the accelerated expansion of the Universe, and are compatible with observational dataset, as the SNeIa Pantheon data, gamma ray bursts Hubble diagram, and direct measurements of the Hubble parameter.

The active galaxy NGC 1068 was recently identified by the IceCube neutrino observatory as the first known steady-state, extragalactic neutrino point source, associated with about 79 events over ten years. We use the IceCube data to place limits on possible neutrino self-interactions mediated by scalar particles with mass between 1 - 10 MeV. We find that a flavor-specific $\nu_{\tau}$ self-interaction is constrained beyond existing published bounds, while a flavor-universal self-interaction is not.