Papers for Tuesday, Jan 24 2023

PODIUM is a compact spacecraft navigation unit, currently being designed to provide interplanetary missions with autonomous position and velocity estimations. The unit will make use of Pulsar X-ray observations to measure the distance and distance rate from the host spacecraft to the Solar System Barycenter. Such measurements will then be used by the onboard orbit determination function to estimate the complete orbital elements of the spacecraft. The design aims at 6 kg of mass and 20 W of power, in a volume of 150 mm by 240 mm by 600 mm. PODIUM is designed to minimize the impact on the mission operational and accommodation constraints. The architecture is based on a grazing incidence X-ray telescope with focal distance limited to 50 cm. The effective area shall be in the range 25 to 50 cm2 for photon energies in the range 0.2-10 keV, requiring nesting of several mirrors in the Wolter-1 geometry. Grazing incidence angles will be very small, below 2 deg. The current target FOV is 0.25 deg. The pulsars photon arrivals are detected with a single pixel Silicon Drift Detector (SDD) sensor with timing accuracy below 1usec. The unit has no gimbaling to meet the applicable power, size and mass requirements. Instead, the host spacecraft shall slew and point to allow pulsar observation. The avionics architecture is based on a radiation hardened LEON4 processor, to allow a synchronous propagation task and measurement generation and orbit determination step in an asynchronous task. PODIUM will enable higher autonomy and lower cost for interplanetary missions. L2 space observatories and planetary flybys are the current reference use cases. Onboard autonomous state estimation can reduce the ground support effort required for navigation and orbit correction/maintenance computation, and reduce the turnaround time, thus enabling more accurate maneuvers, reducing the orbit maintenance mass budget.

We present the characterization of the CCD system developed for the ADFOSC instrument on the 3.6m Devasthal Optical Telescope (DOT). We describe various experiments performed to tune the CCD controller parameters to obtain optimum performance in single and four-port readout modes. Different methodologies employed for characterizing the performance parameters of the CCD, including bias stability, noise, defects, linearity, and gain, are described here. The CCD has grade-0 characteristics at temperatures close to its nominal operating temperature of $-120^\circ$C. The overall system is linear with a regression coefficient of 0.9999, readout noise of 6 electrons, and a gain value close to unity. We demonstrate a method to calculate the dark signal using the gradient in the bias frames at lower temperatures. Using the optimized setting, we verify the performance of the CCD detector system on-sky using the ADFOSC instrument mounted on the 3.6m DOT. Some science targets were observed to evaluate the detector's performance in both imaging and spectroscopic modes.

Improvements in the number of confirmed planets and the precision of observations imply a need to better understand subtle effects that may bias interpretations of exoplanet observations. One such effect is the distortion of a short period planet by its host star, affecting its derived density. We extend the work of Burton et al., Correia, and others, using a gravitational potential formulation to a sample of nearly 200 planets with periods less than 3 days. We find five planets exhibiting density variations of >10% and as many as 20 planets with deviations >5%. We derive an analytic approximation for this deviation as a function of the orbital period, transit depth, and mass ratio between the planet and host star, allowing for rapid determination of such tidal effects. We find that current density error bars are typically larger than tidal deviations but that reducing the uncertainty on transit depth and radial velocity (RV) amplitude by a factor of 3 causes tidal effects to dominate density errors (>50%) in >40% of planets in our sample, implying that in the near future upgraded observational precision will cause shape deviations to become a bottleneck with regards to analysis of exoplanet compositions. These two parameters are found to dominate uncertainties compared to errors on stellar mass and radius. We identify a group of eight planets (including WASP-19 b, HAT-P-7 b, and WASP-12 b) for which current density uncertainties are as much as 4x smaller than the potential shift due to tides, implying a possible 4{\sigma} bias on their density estimates.

We present the chemical composition of 206 red giant branch stars members of the Small Magellanic Cloud (SMC) using optical, high-resolution spectra collected with the multi-object spectrograph FLAMES-GIRAFFE at the ESO Very Large Telescope. This sample includes stars in three fields located in different positions within the parent galaxy. We analysed the main groups of elements, namely light- (Na), alpha- (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Fe, Ni, Cu) and s-process elements (Zr, Ba, La). The metallicity distribution of the sample displays a main peak around [Fe/H] ~ -1 dex and a weak metal-poor tail. However, the three fields display [Fe/H] distributions different with each other, in particular a difference of 0.2 dex is found between the mean metallicities of the two most internal fields.The fraction of metal-poor stars increases significantly (from ~1 to ~20%) from the innermost fields to the most external one, likely reflecting an age gradient in the SMC. Also, we found a hint of possible chemically/kinematic distinct substructures. The SMC stars have abundance ratios clearly distinct with respect to the Milky Way stars, in particular for the elements produced by massive stars (like Na, $\alpha$ and most iron-peak elements) that have abundance ratios systematically lower than those measured in our Galaxy. This points out that the massive stars contributed less to the chemical enrichment of the SMC with respect to the Milky Way, according to the low star formation rate expected for this galaxy. Finally, we identified small systematic differences in the abundances of some elements (Na, Ti, V and Zr) in the two innermost fields, suggesting that the chemical enrichment history in the SMC has been not uniform.

We report kinematic and thermal signatures associated with the directly imaged protoplanet candidate in the Elias 2-24 disc. Using the DSHARP ALMA observations of the $^{12}$CO J=2-1 line, we show that the disc kinematics are perturbed, with a detached CO emission spot at the location of the planet candidate and traces of spiral wakes, and also that the observed CO emission intensities require local heating. While the foreground extinction hides the velocity channels associated with the planet, preventing a planet mass estimate, the level of gas heating implied by the CO emission indicates the presence of a warm, embedded giant planet. Comparison with models show this could either be a $\gtrsim 5$M$_\mathrm{Jup}$, or a lower mass ( $\gtrsim 2$M$_\mathrm{Jup}$) but accreting proto-planet.

Robust age estimates of red giant stars are now possible thanks to the precise inference of their mass based on asteroseismic constraints. However, there are cases where such age estimates can be highly precise yet very inaccurate. An example is giants that have undergone mass loss or mass transfer events that have significantly altered their mass. In this context, stars with "apparent" ages significantly higher than the age of the Universe are candidates as stripped stars, or stars that have lost more mass than expected, most likely via interaction with a companion star, or because of the poorly understood mass-loss mechanism along the red-giant branch. In this work we identify examples of such objects among red giants observed by $\textit{Kepler}$, both at low ([Fe/H] $ \lesssim -0.5$) and solar metallicity. By modelling their structure and pulsation spectra, we find a consistent picture confirming that these are indeed low-mass objects consisting of a He core of $\approx 0.5 \, M_\odot$ and an envelope of $\approx 0.1 - 0.2 \, M_\odot$. Moreover, we find that these stars are characterised by a rather extreme coupling ($q \gtrsim 0.4$) between the pressure-mode and gravity-mode cavities, i.e. much higher than the typical value for red clump stars, providing thus a direct seismic signature of their peculiar structure. The complex pulsation spectra of these objects, if observed with sufficient frequency resolution, hold detailed information about the structural properties of likely products of mass stripping, hence can potentially shed light on their formation mechanism. On the other hand, our tests highlight the difficulties associated with measuring reliably the large frequency separation, especially in shorter datasets, with impact on the reliability of the inferred masses and ages of low-mass Red Clump stars with e.g. K2 or TESS data.

We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events co-located on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from $\sim$220 pc cm$^{-3}$ to $\sim$1700 pc cm$^{-3}$, and include sources having exhibited as few as two bursts to as many as twelve. We report a statistically significant difference in both the DM and extragalactic DM (eDM) distributions between repeating and apparently nonrepeating sources, with repeaters having lower mean DM and eDM, and we discuss the implications. We find no clear bimodality between the repetition rates of repeaters and upper limits on repetition from apparently nonrepeating sources after correcting for sensitivity and exposure effects, although some active repeating sources stand out as anomalous. We measure the repeater fraction and find that it tends to an equilibrium of $2.6_{-2.6}^{+2.9}$% over our exposure thus far. We also report on 14 more sources which are promising repeating FRB candidates and which merit follow-up observations for confirmation.

We present new strong-lensing (SL) mass reconstruction of the six Hubble Frontier Fields (HFF) clusters with the MAximum-entropy ReconStruction (${\tt MARS}$) algorithm. ${\tt MARS}$ is a new free-form inversion method, which suppresses spurious small-scale fluctuations while achieving excellent convergence in positions of multiple images. For each HFF cluster, we obtain a model-independent mass distribution from the compilation of the self-consistent SL data in the literature. With $100-200$ multiple images per cluster, we reconstruct solutions with small scatters of multiple images in both source (~0".01) and image planes (~0."05), which are lower than the previous results by an order of magnitude. An outstanding case is the MACS J0416.1-2403 mass reconstruction, which is based on the largest high-quality SL dataset where all 236 multiple images/knots have spectroscopic redshifts. Although our solution is smooth on a large scale, it reveals group/galaxy-scale peaks where the substructures are required by the data. We find that in general, these mass peaks are in excellent spatial agreement with the member galaxies, although {\tt MARS} never uses the galaxy distributions as priors. Our study corroborates the flexibility and accuracy of the$ {\tt MARS}$ algorithm and demonstrates that ${\tt MARS}$ is a powerful tool in the JWST era, when $2-3$ times larger number of multiple image candidates become available for SL mass reconstruction, and self-consistency within the dataset becomes a critical issue.

Thin disk accretion is often modeled in highly dynamical settings using the two-dimensional equations of viscous hydrodynamics, with viscosity representing unresolved turbulence. These equations are supposed to arise after vertical integration of the full three-dimensional equations of hydrodynamics, under the assumption of a geometrically thin disk with mirror symmetry about the midplane. But in the dynamical context, vertical dynamics are neglected by incorrectly assuming instantaneous vertical hydrostatic equilibrium. The resulting errors in the local disk height couple to the horizontal dynamics through some viscosity prescriptions and gravitational softening models. Furthermore, the viscous terms in the horizontal equations are only complete if they are inserted after vertical integration, as if the system is actually two-dimensional. Since turbulence breaks mirror symmetry, it is more physically correct to insert a turbulence model at the three-dimensional level, and impose mirror symmetry only on average. Thus, some viscous terms are usually missing. We revisit the vertical integration procedure, restricting to the regime of a Newtonian, non-self-gravitating disk. We obtain six evolution equations with only horizontal dependence, which determine the local vertical position and velocity of the disk surface, in addition to the usual fluid variables. This "2.5-dimensional" formulation opens the door to efficiently study vertical oscillations of thin disks in dynamical settings, and to improve the treatment of unresolved turbulence. As a demonstration, by including viscous stress at the three-dimensional level, we recover missing viscous terms which involve the vertical variables. We also propose a resummation of the vertically integrated gravitational force, which has a strikingly similar form to a gravitational softening model advocated for in protoplanetary disk studies.

Motivated by the recent observation by NICER of a type I X-ray burst from SAX J1808.4-3658 with a distinct "pause" feature during its rise (Bult et al. 2019), we show that bursts which ignite in a helium layer underneath a hydrogen-rich shell naturally give rise to such pauses, as long as enough energy is produced to eject the outer layers of the envelope by super-Eddington winds. The length of the pause is determined by the extent of the convection generated after ignition, while the rate of change of luminosity following the pause is set by the hydrogen gradient left behind by convection. Using the MESA stellar evolution code, we simulate the accumulation, nuclear burning and convective mixing prior to and throughout the ignition of the burst, followed by the hydrodynamic wind. We show that the results are sensitive to the treatment of convection adopted within the code. In particular, the efficiency of mixing at the H/He interface plays a key role in determining the shape of the lightcurve. The data from SAX J1808.4-3658 favors strong mixing scenarios. Multidimensional simulations will be needed to properly model the interaction between convection and nuclear burning during these bursts, which will then enable a new way to use X-ray burst lightcurves to study neutron star surfaces.

EX Lup is a low-mass pre-main sequence star that occasionally shows accretion-related outbursts. Here, we present JWST/MIRI medium resolution spectroscopy obtained for EX Lup fourteen years after its powerful outburst. EX Lup is now in quiescence and displays a Class II spectrum. We detect a forest of emission lines from molecules previously identified in infrared spectra of classical T Tauri disks: H2O, OH, H2, HCN, C2H2, and CO2. The detection of organic molecules demonstrates that they are back after disappearing during the large outburst. Spectral lines from water and OH are for the first time de-blended and will provide a much improved characterization of their distribution and density in the inner disk. The spectrum also shows broad emission bands from warm, sub-micron size amorphous silicate grains at 10 and 18 um. During the outburst, in 2008, crystalline forsterite grains were annealed in the inner disk within 1 au, but their spectral signatures in the 10 um silicate band later disappeared. With JWST we re-discovered these crystals via their 19.0, 20.0, and 23.5 um emission, whose strength implies that the particles are at ~3 au from the star. This suggests that crystalline grains formed in 2008 were transported outwards and now approach the water snowline, where they may be incorporated into planetesimals. Containing several key tracers of planetesimal and planet formation, EX Lup is an ideal laboratory to study the effects of variable luminosity on the planet-forming material and may provide explanation for the observed high crystalline fraction in solar system comets.

Context. Thanks to the high-precision photometry from space missions such as Kepler and TESS, tidal perturbations and tilting of pulsations have been detected in more than a dozen binary systems. However, only two of these were g-mode pulsators. Aims. We aim to detect tidally perturbed g modes in additional binary systems and characterise them observationally. Methods. We perform a custom data reduction of the available Kepler and TESS photometry of a well-studied sample of 35 binary systems with gamma Doradus pulsators. For each target, we model the binary signal using a sum of 100 sine waves, with frequencies at orbital harmonics, and measure significant pulsation frequencies by iteratively prewhitening the residual light curve. Pulsations are labelled as tidally perturbed g modes if they are part of both period-spacing patterns and orbital-frequency-spaced multiplets. After visual inspection and confirmation, the properties of these targets and g modes are characterised. Results. We detect tidally perturbed g-mode pulsations for five short-period binaries that are circularised and (almost) synchronously rotating: KIC3228863, KIC3341457, KIC4947528, KIC9108579, and KIC12785282. Tidally perturbed g modes that occur within the same star and have the same mode identification (k,m), are found to have near-identical relative amplitude and phase modulations, which are within their respective 1-sigma uncertainties also identical for the Kepler and TESS photometric passbands. By contrast, pulsations with different mode identification (k,m) are found to exhibit different modulations. Moreover, the observed amplitude and phase modulations are correlated, indicating that the binary tides primarily distort g-mode amplitudes on the stellar surface. The phase modulations are then primarily a geometric effect of the integration of the stellar flux over the visible stellar surface. (abbreviated)

Protoclusters of galaxies have been found in the last quarter century. However, most of them have been found through the overdensity of star-forming galaxies, and there had been no known structures identified by multiple spectroscopically confirmed quiescent galaxies at $z>2.5$. In this letter, we report the discovery of an overdense structure of massive quiescent galaxies with the spectroscopic redshift $z=2.77$ in the COSMOS field, QO-1000. We first photometrically identify this structure as a $4.2\sigma$ overdensity with 14 quiescent galaxies in $7\times4\ {\rm pMpc^2}$ from the COSMOS2020 catalog. We then securely confirm the spectroscopic redshifts of 4 quiescent galaxies by detecting multiple Balmer absorption lines with Keck/MOSFIRE. All the spectroscopically confirmed members are massive ($\log{(M_\star/M_\odot)}>11.0$) and located in a narrow redshift range ($2.76<z<2.79$). Moreover, three of them are in the $1\times1\ {\rm pMpc^2}$ in the transverse direction at the same redshift ($z=2.760-2.763$). Such a concentration of four spectroscopically confirmed quiescent galaxies implies that QO-1000 is $>68$ times denser than in the general field. In addition, we confirm that they form a red sequence in the $J-K_s$ color. This structure's halo mass is estimated as $\log{(M_{\rm halo}/M_\odot)}>13.2$ from their stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with $\log{(M_{\rm halo}/M_\odot)}\geq14.8$ at $z=0$. These results suggest that QO-1000 is a more mature protocluster than the other known protoclusters. It is likely in a transition phase between the star-forming protoclusters and the quenched galaxy clusters.

White dwarfs are excellent research laboratories as they reach temperatures, pressures, and magnetic fields that are unattainable on Earth. To better understand how these three physical parameters interact with each other and with other stellar features, we determined the magnetic field strength for a total of 804 hydrogen-rich white dwarfs of which 287 are not in the literature. We fitted the spectra observed with the Sloan Digital Sky Survey using atmospheric models that consider the Zeeman effect due to the magnetic field at each point in the stellar disk. Comparing magnetic and non-magnetic WDs, the literature already shows that the magnetic ones have on average higher mass than the non-magnetic. In addition to that, magnetic fields are more common in cooler WDs than in hotter WDs. In consonance, we found that those with higher magnetic field strengths tend to have higher masses, and lower temperatures, for which models indicate the crystallization process has already started. This reinforces the hypothesis that the field is being generated and/or amplified in the cooling process of the white dwarf. Our sample constitutes the largest number of white dwarfs with determined magnetic fields to date.

The discovery of gravitational waves from merging binary black holes has generated considerable interest in examining whether these black holes could have a primordial origin. If a significant number of black holes have to be produced in the early universe, the primordial scalar power spectrum should have an enhanced amplitude on small scales, when compared to the COBE normalized values on the larger scales that is strongly constrained by the anisotropies in the cosmic microwave background. In the inflationary scenario driven by a single, canonical scalar field, such power spectra can be achieved in models that permit a brief period of ultra slow roll inflation during which the first slow roll parameter decreases exponentially. In this review, we shall consider a handful of such inflationary models as well as a reconstructed scenario and examine the extent of formation of primordial black holes and the generation of secondary gravitational waves in these cases. We shall also discuss the strength and shape of the scalar bispectrum and the associated non-Gaussianity parameter that arise in such situations. We shall conclude with an outlook wherein we discuss the wider implications of the increased strengths of the non-Gaussianities on smaller scales.

The origin of cosmic rays above the knee in the spectrum is an unsolved problem. We present a wind model in which interstellar gas flows along a non-rotating, expanding flux tube with a changing speed and cross-sectional area. Cosmic rays from Galactic sources, such as supernova remnants, which are coupled to the plasma via Alfv\'{e}n waves, provide the main pressure source for driving this outflow. These cosmic rays are then subject to diffusive shock reacceleration at the Galactic wind termination shock, which is located at a distance $\sim200\,{\rm kpc}$. Some of the highest-energy reaccelerated particles propagate upstream against the wind and can contribute to the PeV-EeV range of the spectrum. We analyze the conditions under which efficient reacceleration can occur and find that rigidities $\sim$ 10-40 PV can be obtained and that the termination shock may account for half of the proton spectrum measured in IceCube/IceTop experiment. The highest-energy particles that escape downstream from our termination shock, and similar shocks surrounding most galaxies, can be further accelerated by intergalactic shock fronts.

High-resolution spectra of the LBV candidate Schulte 12 in the Cyg OB2 association were obtained at the 6-meter BTA telescope with the NES echelle spectrograph on the arbitrary dates in 2001-2022. Variability of the emission profile of H$\alpha$ and absorptions of HeI, SiII with time was found. Based on the radial velocity measurements at 10 observation dates, radial velocity variability with an amplitude of $\Delta$Vr$\approx$8 km/s relative to the average value of the heliocentric velocity Vr=$-15.6\pm2.6$ km/s was revealed. This indicates the presence of a companion in the system. Based on the reliable intensity measurements of a sample of DIBs, color excess E(B-V)=1.74$\pm0.03^{m}$ was determined. This results in the interstellar extinction value Av$\approx 5.6^m$ that is only about half of the total extinction. Taking current Schulte 12 parameters, including Gaia~EDR3 parallax, we estimated its absolute magnitude as Mv$\approx -9.2^m$ and luminosity log$(L/L_{\odot})\approx$5.5, which does not exceed the Humphreys-Davidson limit.

Strong coronal magnetic field, when present, manifests itself as bright microwave sources at high frequencies produced by gyroresonant (GR) emission mechanism in thermal coronal plasma. The highest frequency at which this emission is observed is proportional to the absolute value of the strongest coronal magnetic field on the line of sight. Although no coronal magnetic field larger than roughly 2,000 G was expected, recently the field at least twice larger has been reported. Here, we report a search for and statistical study of such strong coronal magnetic fields using high-frequency GR emission. A historic record of spatially resolved microwave observations at high frequencies, 17 and 34 GHz, is available from Nobeyama RadioHeliograph for more than 20 years (1995-2018). Here we employ this data set to identify sources of bright GR emission at 34 GHz and perform a statistical analysis of the identified GR cases to quantify the strongest coronal magnetic fields during two solar cycles. We found that although active regions with the strong magnetic field are relatively rare (less than 1% of all active regions), they appear regularly on the Sun. These active regions are associated with prominent manifestations of solar activity.

There is a robust polyatomic chemistry in diffuse, partially-molecular interstellar gas that is readily accessible in absorption at radio/mm/sub-mm wavelengths. Accurate column densities are derived owing to the weak internal excitation, so relative molecular abundances are well known with respect to each other but not with respect to H2. Here we consider the use of proxies for hydrogen column densities N(H2) and N(H) = N(HI)+2N(H2) based on measurements of HCO+ absorption and CO emission and absorption, and we compare these with results obtained by others when observing HI, H2 and CO toward stars and AGN. We consider the use of HCO+ as a proxy for H2 and show that the assumption of a relative abundance N(H2) = N(HCO+)/3x10^{-9} gives the same view of the atomic-molecular hydrogen transition that is seen in UV absorption toward stars. CO on the other hand shows differences between the radio and optical regimes because emission is always detected when N(\hcop) > 6x10^{11}\pcc or N(H2) > 2x10^20\pcc. Wide variations in the integrated CO {J=1-0} brightness W_CO and N(CO)/N(H2) imply equivalent variations in the CO-H2 conversion factor even while the ensemble mean is near the usual Galactic values. Gas/reddening ratios found in absorption toward stars, N(H)/E(B-V) = 6.2x10^21 H \pcc/mag overall or 6.8x10^21 H \pcc/mag for sightlines at E(B-V) <= 0.08 mag lacking H2 are well below the Galactic mean measured at low reddening and high Galactic latitude, 8.3x10^21 H \pcc/mag.

Advection is believed to be the dominant cooling mechanism in optically thin advection-dominated accretion flows (ADAF's). When outflow is considered, however, the first impression is that advection should be of opposite sign in the inflow and the outflow, due to the opposite direction of radial motion. Then how is the energy balance achieved simultaneously? We investigate the problem in this paper, analysing the profiles of different components of advection with self-similar solutions of ADAF's in spherical coordinates ($r\theta\phi$). We find that for $n < 3\gamma/2-1$, where $n$ is the density index in $\rho \propto r^{-n}$ and $\gamma$ is the heat capacity ratio, the radial advection is a heating mechanism in the inflow and a cooling mechanism in the outflow. It becomes 0 for $n = 3\gamma/2-1$, and turns to a cooling mechanism in the inflow and a heating mechanism in the outflow for $n > 3\gamma/2-1$. The energy conservation is only achieved when the latitudinal ($\theta$-direction) advection is considered, which takes an appropriate value to maintain energy balance, so that the overall effect of advection, no matter the parameter choices, is always a cooling mechanism that cancels out the viscous heating everywhere. For the extreme case of $n=3/2$, latitudinal motion stops, viscous heating is balanced solely by radial advection, and no outflow is developed.

We present an algorithm to extend subhalo merger trees in a low-resolution dark-matter-only simulation by conditionally matching them to those in a high-resolution simulation. The algorithm is general and can be applied to simulation data with different resolutions using different target variables. We instantiate the algorithm by a case in which trees from ELUCID, a constrained simulation of $(500h^{-1}{\rm Mpc})^3$ volume of the local universe, are extended by matching trees from TNGDark, a simulation with much higher resolution. Our tests show that the extended trees are statistically equivalent to the high-resolution trees in the joint distribution of subhalo quantities and in important summary statistics relevant to modeling galaxy formation and evolution in halos. The extended trees preserve certain information of individual systems in the target simulation, including properties of resolved satellite subhalos, and shapes and orientations of their host halos. With the extension, subhalo merger trees in a cosmological scale simulation are extrapolated to a mass resolution comparable to that in a higher-resolution simulation carried out in a smaller volume, which can be used as the input for (sub)halo-based models of galaxy formation. The source code of the algorithm, and halo merger trees extended to a mass resolution of $\sim 2 \times 10^8 h^{-1}M_\odot$ in the entire ELUCID simulation, are available.

The Vera Rubin Observatory will provide an unprecedented set of time-dependent observations of the sky. The planned Legacy Survey of Space and Time (LSST) operating for 10 years will provide dense lightcurves for thousands of active galactic nuclei (AGN) in Deep Drilling Fields (DDFs) and less dense lightcurves for millions of AGN. We model the prospects for measuring time delays for emission lines with respect to the continuum, using these data. We model the artificial lightcurves using Timmer-Koenig algorithm, we use the exemplary cadence to sample them, we supplement lightcurves with the expected contamination by the strong emission lines (Hbeta, Mg II and CIV as well as with Fe II pseudo-continuum and the starlight). We choose the suitable photometric bands appropriate for the redshift and compare the assumed line time delay with the recovered time delay for 100 statistical realizations of the light curves. We show that time delays for emission lines can be well measured from the Main Survey for the bright tail of the quasar distribution (about 15% of all sources) with the accuracy within 1 sigma error, for DDFs results for fainter quasars are also reliable when all 10 years of data are used. There are also some prospects to measure the time delays for the faintest quasars at the smallest redshifts from the first two years of data, and eventually even from the first season. The entire quasar population will allow obtaining results of apparently high accuracy but in our simulations, we see a systematic offset between the assumed and recovered time delay depending on the redshift and source luminosity which will not disappear even in the case of large statistics. Such a problem might affect the slope of the radius-luminosity relation and cosmological applications of quasars if simulations correcting for such effects are not performed.

Dark matter sub-halos that pass near or through a thin tidal star stream locally increase its velocity dispersion. Subsequent orbital evolution further increases the velocity dispersion and stream width, lowering the surface density of a stream. The kinematic properties of streams are measured in cosmological Milky Way-like halo simulations. The distance along a stream is a proxy for the time a star has spent in the stream, although there are a range of ages at any distance. Power law fits to the velocity dispersion with angular distance for the average of the streams in the 10-60 kpc range finds sigma_theta=6 phi^{0.25} km/s, sigma_phi=8 phi^{0.39} km/s, and sigma_r=10 phi^{0.44} km/s for |phi|< 34 degrees, for stars within theta=+/-5 degrees of the stream equator. The errors of the coefficients are about 10% for these streams, with comparable systematic errors depending on exactly which streams are selected and the stream width and length fitted. The stream velocity dispersions close to the clusters generally increase with the sub-halo numbers.

PICO bubble chambers have exceptional sensitivity to inelastic dark matter-nucleus interactions due to a combination of their extended nuclear recoil energy detection window from a few keV to $O$(100 keV) or more and the use of iodine as a heavy target. Inelastic dark matter-nucleus scattering is interesting for studying the properties of dark matter, where many theoretical scenarios have been developed. This study reports the results of a search for dark matter inelastic scattering with the PICO-60 bubble chambers. The analysis reported here comprises physics runs from PICO-60 bubble chambers using CF$_{3}$I and C$_{3}$F$_{8}$. The CF$_{3}$I run consisted of 36.8 kg of CF$_{3}$I reaching an exposure of 3415 kg-day operating at thermodynamic thresholds between 7 and 20 keV. The C$_{3}$F$_{8}$ runs consisted of 52 kg of C$_{3}$F$_{8}$ reaching exposures of 1404 kg-day and 1167 kg-day running at thermodynamic thresholds of 2.45 keV and 3.29 keV, respectively. The analysis disfavors various scenarios, in a wide region of parameter space, that provide a feasible explanation of the signal observed by DAMA, assuming an inelastic interaction, considering that the PICO CF$_{3}$I bubble chamber used iodine as the target material.

We study the formation and early evolution of star clusters that have a wide range of masses and background cloud mass surface densities, $\Sigma_{\rm cloud}$, which help set the initial sizes, densities, and velocity dispersions of the natal gas clumps. Initial clump masses of 300, $3,000$ and $30,000$ $M_\odot$ are considered, from which star clusters are born with an assumed 50% overall star formation efficiency and with 50% primordial binarity. This formation is gradual, i.e., with a range of star formation efficiencies per free-fall time from 1% to 100%, so that the formation time can range from 0.7 Myr for low-mass, high-$\Sigma_{\rm cloud}$ clumps to $\sim30$ Myr for high-mass, low-$\Sigma_{\rm cloud}$ clumps. Within this framework of the Turbulent Clump model, for a given $\Sigma_{\rm cloud}$, clumps of higher mass are of lower initial volume density, but their dynamical evolution leads to higher bound fractions and causes them to form much higher density cluster cores and maintain these densities for longer periods. This results in systematic differences in the evolution of binary properties, degrees of mass segregation and rates of creation of dynamically ejected runaways. We discuss the implications of these results for observed star clusters and stellar populations.

The back-reaction of the perturbed thermal equilibrium in the solar corona on compressive perturbations, also known as the effect of wave-induced thermal misbalance, is known to result in thermal instabilities chiefly responsible for the formation of fine thermal structuring of the corona. We study the role of the magnetic field and field-aligned thermal conduction in triggering instabilities of slow magnetoacoustic and entropy waves in quiescent and hot active region loops, caused by thermal misbalance. Effects of the magnetic field are accounted for by including it in the parametrisation of a guessed coronal heating function, and the finite plasma parameter $\beta$, in terms of the first-order thin flux tube approximation. Thermal conduction tends to stabilise both slow and entropy modes, broadening the interval of plausible coronal heating functions allowing for the existence of a thermodynamically stable corona. This effect is most pronounced for hot loops. In contrast to entropy waves, the stability of which is found to be insensitive to the possible dependence of the coronal heating function on the magnetic field, slow waves remain stable only for certain functional forms of this dependence, opening up perspectives for its seismological diagnostics in future.

Various interactions affect the population of close-in planets. Among them, the tidal and magnetic interactions drive orbital decay and star-planet angular momentum exchange, leading to stellar spin-up. As a result of the above processes, a planet may initiate the mass transfer to the host star once it encounters the Roche limit. Another mechanism providing substantial mass loss is associated with the atmospheric escape caused by photoevaporation followed by orbital expansion, which is thought to be important for hot Neptunes and super-Earths. Thus, the fraction of the initial number of hot Jupiters may transform into lower-mass planets through the Roche-lobe overflow (RLO) phase and continue secular evolution under the effect of photoevaporation. In the present paper, we compile the latest prescriptions for tidal and magnetic migration and mass-loss rates to explore the dynamics of hot Jupiter systems. We study how the implemented interactions shape the orbital architecture of Jovian planets and whether their impact is enough to reproduce the observational sample. Our models suggest that the tidal interaction is able to generate the upper boundary of the hot Jupiter population in the mass-separation diagram. To recreate the sub-Jovian desert, we need to make additional assumptions regarding the RLO phase or the influence of the protoplanetary disc's inner edge on the initial planetary location. According to our estimates, 12-15% of hot Jupiters around solar-mass stars have been engulfed or become lower-mass planets. 0.20-0.25% of the present-day giant planet population undergoes decay intense enough to be detected with modern facilities.

Strangeon star model has passed various observational tests, such as the massive pulsars and the tidal deformability during binary mergers. Pulsar glitch, as a useful probe for studying the interior structure of pulsars, has also been studied in strangeon star model in our previous papers, including the recovery coefficient, the waiting time of glitches and glitch activity. In this paper, the recovery process of a glitch is described in the strangeon star model, based on the starquake picture established in Paper I. After the starquake, the inner motion of the stellar matter would reduce the tangential pressure in the cracked places at the equatorial plane. The recovery (increase) of the tangential pressure would be achieved by a viscous flow towards the cracked places at equatorial plane, which leads to the exponential recovery of the spin frequency. A uniform viscous flow can reproduce the single exponential decay observed in some glitches, and the viscous time-scale $\tau$ and the depth $h$ of the cracking place below the surface can be fitted by the recovery data. It is found that $h$ increases with glitch size $\Delta\nu/\nu$, which is expected in the glitch scenario of strangeon stars. The magnitude of the recovery predicted in this recovery model is also consistent with that derived from observations. The single exponential decay reproduced by a uniform viscous flow can be generalized to two or more exponentials by the multi-component of viscous flows.

Much excitement surrounds the intense mass loss that seems to take place in some massive stars immediately before core collapse. However, occurring too late, it has a negligible impact on the star's evolution or the final yields, which are influenced instead by the longer-term, quasi-steady mass loss taking place during H and He burning. Late-time observations of core-collapse supernovae interacting with the progenitor wind are one means to constrain this secular mass loss. Here, we present radiative transfer calculations for a Type II SN with and without this interaction power, focusing on the phase between 350 and 1000d after explosion. Without interaction power, the ejecta are powered through radioactive decay whose exponential decline produces an ever-fading SN. Instead, with a constant interaction power of $10^{40}$ erg s$^{-1}$ (representative of an SN II ramming into a steady-state $10^{-6} M_\odot$ yr$^{-1}$ wind), the spectrum morphs from decay powered at 350d, with narrow lines forming in the inner metal-rich ejecta, to interaction powered at 1000d, with broad boxy lines forming in the outer H-rich ejecta. Intermediate times are characterized by a hybrid and complex spectrum made of overlapping narrow and broad lines. While interaction boosts primarily the flux in the ultraviolet, which remains largely unobserved today, a knee in the $R$-band light curve or a $U$-band boost are clear signatures of interaction at late times. The model predictions compare favorably with a number of Type II supernovae including SN 2004et or SN 2017eaw at 500-1000d after explosion.

The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH4:H2O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K.We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C2H6, C3H8, C2H2, CH3OH, CO, CO2, and probably also H2CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects.

We present radio observations of the symbiotic recurrent nova V3890 Sagitarii following the 2019 August eruption obtained with the MeerKAT radio telescope at 1.28 GHz and Karl G. Janksy Very Large Array (VLA) at 1.26 to 5 GHz. The radio light curves span from day 1 to 540 days after eruption and are dominated by synchrotron emission produced by the expanding nova ejecta interacting with the dense wind from an evolved companion in the binary system. The radio emission is detected early on (day 6) and increases rapidly to a peak on day 15. The radio luminosity increases due to a decrease in the opacity of the circumstellar material in front of the shocked material and fades as the density of the surrounding medium decreases and the velocity of the shock decelerates. Modelling the light curve provides an estimated mass-loss rate of $M_{\textrm {wind}} \approx 10^{-8} {\textrm {M}}_\odot~{\textrm {yr}}^{-1}$ from the red giant star and ejecta mass in the range of $M_{\textrm {ej}}=10^{-5}-10^{-6}~{\textrm {M}}_\odot$from the surface of the white dwarf. V3890 Sgr likely hosts a massive white dwarf similar to other symbiotic recurrent novae, thus considered a candidate for supernovae type Ia (SNe Ia) progenitor. However, its radio flux densities compared to upper limits for SNe Ia have ruled it out as a progenitor for SN 2011fe.

Icy grain mantles are the main reservoir of the volatile elements that link chemical processes in dark, interstellar clouds with the formation of planets and composition of their atmospheres. The initial ice composition is set in the cold, dense parts of molecular clouds, prior to the onset of star formation. With the exquisite sensitivity of JWST, this critical stage of ice evolution is now accessible for detailed study. Here we show the first results of the Early Release Science program "Ice Age" that reveal the rich composition of these dense cloud ices. Weak ices, including, $^{13}$CO$_2$, OCN$^-$, $^{13}$CO, OCS, and COMs functional groups are now detected along two pre-stellar lines of sight. The $^{12}$CO$_2$ ice profile indicates modest growth of the icy grains. Column densities of the major and minor ice species indicate that ices contribute between 2 and 19% of the bulk budgets of the key C, O, N, and S elements. Our results suggest that the formation of simple and complex molecules could begin early in a water-ice rich environment.

Precise interstellar dust extinction laws are important to infer the intrinsic properties of reddened objects and correctly interpret observations. In this work, we attempt to measure the optical--infrared extinction laws of the Large and Small Magellanic Clouds (LMC and SMC) by using red supergiant (RSG) stars and classical Cepheids as extinction tracers. The spectroscopic RSG samples are constructed based on the APOGEE spectral parameters, Gaia astrometric data, and multi-band photometry. We establish the effective temperature--intrinsic color relations for RSG stars and determine the color excess ratio (CER) E(lambda-GRP)/E(GBP-GRP) for LMC and SMC. We use classical Cepheids to derive base relative extinction A_GRP/E(GBP-GRP). The results are 1.589+-0.014 and 1.412+-0.041 for LMC and SMC. By combining CERs with A_GRP /E(GBP-GRP), the optical--infrared extinction coefficients A_lambda/A_GRP are determined for 16 bands. We adjust the parameters of Rv-dependent extinction laws and obtain the average extinction law of LMC and SMC as Rv=3.40+-0.07 and Rv=2.53+-0.10, which are consistent with Gordon et al. (2003). In the optical bands, the adjusted Rv extinction curves agree with the observations with deviations less than 3%.

Structure formation in the Universe has been well-studied within the Eulerian and Lagrangian perturbation theories, where the latter performs substantially better in comparison with N-body simulations. Standing out is the celebrated Zel'dovich approximation for dust matter. In this work, we recall the description of gravitational noncollisional systems and extend both the Eulerian and Lagrangian approaches by including, possibly anisotropic, velocity dispersion. A simple case with plane symmetry is then studied with an exact, nonperturbative approach, and various approximations of the derived model are then compared numerically. A striking result is that linearized Lagrangian solutions outperform models based on Burgers' equation in the multi-stream regime in comparison with the exact solution. These results are finally extended to a 3D case without symmetries, and master equations are derived for the evolution of all parts of the perturbations.

The quest for atmospheric spectral signatures that may witness biological activity in exoplanets is focused on rocky planets. The best targets for future, challenging spectroscopic observations will be selected among potentially habitable planets. Surface habitability can be quantified and explored with climate and atmospheric models according to temperature-based criteria. The conceptual, modellistic, technological and interpretative complexity of the problem requires to develop flexible climate and atmospheric models suited for a comprehensive exploration of observationally unconstrained parameters, and to simulate and interpret definitely non-terrestrial conditions. We present a summary and preliminary results on the work we are performing on multi-parametric explorations of the habitability and observational properties of rocky planets.

4U 1957+11 is a black hole candidate system that has been in a soft X-ray spectral state since its discovery. We present analyses of recent joint NICER and NuSTAR spectra, which are extremely well-described by a highly inclined disk accreting into a near maximally spinning black hole. Owing to the broad X-ray coverage of NuSTAR the fitted spin and inclination are strongly constrained for our hypothesized disk models. The faintest spectra are observed out to 20 keV, even though their hard tail components are almost absent when described with a simple corona. The hard tail increases with luminosity, but shows clear two track behavior with one track having appreciably stronger tails. The disk spectrum color-correction factor is anti-correlated with the strength of the hard tail (e.g., as measured by the Compton $y$ parameter). Although the spin and inclination parameters are strongly constrained for our chosen model, the mass and distance are degenerate parameters. We use our spectral fits, along with a theoretical prior on color-correction, an observational prior on likely fractional Eddington luminosity, and an observational prior on distance obtained from Gaia studies, to present mass and distance contours for this system. The most likely parameters, given our presumed disk model, suggest a 4.6 $\mathrm{M_\odot}$ black hole at 7.8 kpc observed at luminosities ranging from $\approx 1.7\%$--$9\%$ of Eddington. This would place 4U 1957+11 as one of the few actively accreting sources within the `mass gap' of ${\approx} 2$--$5\,\mathrm{M_\odot}$ where there are few known massive neutron stars or low mass black holes. Higher mass and distance, however, remain viable.

Magnetohydrodynamic (MHD) and photoevaporative winds are thought to play an important role in the evolution and dispersal of planet-forming disks. Here, we analyze high-resolution ($\Delta v \sim$ 7 kms$^{-1}$) optical spectra from a sample of 115 T Tauri stars in the $\sim 5-10$ Myr Upper Sco association and focus on the [O I]$\lambda$6300 and H$\alpha$ lines to trace disk winds and accretion, respectively. Our sample covers a large range in spectral type and we divide it into Warm (G0-M3) and Cool (later than M3) to facilitate comparison with younger regions. We detect the [O I]$\lambda$6300 line in 45 out of 87 upper sco sources with protoplanetary disks and 32 out of 45 are accreting based on H$\alpha$ profiles and equivalent widths. All [O I] $\lambda$6300 Upper Sco profiles have a low-velocity (centroid $< -30$ kms$^{-1}$, LVC) emission and most (36/45) can be fit by a single Gaussian (SC). The SC distribution of centroid velocities and FWHMs is consistent with MHD disk winds. We also find that the Upper Sco sample follows the same accretion luminosity$-$LVC [O I]$\lambda$6300 luminosity relation and the same anti-correlation between SC FWHM and WISE W3-W4 spectral index as the younger samples. These results indicate that accretion and disk winds coevolve and that, as inner disks clear out, wind emission arises further away from the star. Finally, our large spectral range coverage reveals that Cool stars have larger FWHMs normalized by stellar mass than Warm stars indicating that [O I]$\lambda$6300 emission arises closer in towards lower mass/lower luminosity stars.

We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} < 23$), while the other shows signs of moderate absorption ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy distribution (SED) modelling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV X-ray luminosities of ${\sim}10^{\text{44--45}}\,\mathrm{erg\ s^{-1}}$) and star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes (SMBHs) in the high-redshift universe.

From TESS photometry, 493 mid- to late-B stars with high frequencies (Maia variables) have been identified. The distribution of projected rotational velocities shows that the rotation rates of Maia variables are no different from those of SPB stars. Moreover, many Maia stars pulsate with frequencies exceeding 60 c/d. Rapid rotation is ruled out as a possible factor in understanding the Maia variables. There is clearly a serious problem with current pulsational models. Not only are the models unable to account for the Maia stars, but they also fail to account for the fact that SPB and gamma Dor variables form one continuous instability strip from the cool end of the delta Sct region to the hot end of the beta Cep instability strip. Likewise, there is continuity between the distributions of delta Sct, Maia, and beta Cep variables. In fact, Maia stars seem to be an extension of delta Sct stars to the mid-B type. These observations suggest an interplay between multiple driving mechanisms rather than separate dominant mechanisms for each variability group.

The existence of excess absorption in the X-ray spectra of GRBs is well known, but the primary location of the absorbing material is still uncertain. To gain more knowledge about this, we have performed a time-resolved analysis of the X-ray spectra of 199 GRBs observed by the \textit{Swift} X-ray telescope, searching for evidence of a decreasing column density ($N_{\mathrm{H,intr}}$) that would indicate that the GRBs are ionizing matter in their surroundings. We structured the analysis as Bayesian inference and used an absorbed power-law as our baseline model. We also explored alternative spectral models in cases where decreasing absorption was inferred. The analysis reveals seven GRBs that show signs of a decrease in $N_{\mathrm{H,intr}}$, but we note that alternative models for the spectral evolution cannot be ruled out. We conclude that the excess absorption in the vast majority of GRBs must originate on large scales of the host galaxies and/or in the intergalactic medium. Our results also imply that an evolving column density is unlikely to affect the spectral analysis of the early X-ray spectra of GRBs. In line with this, we show that estimating the total $N_{\mathrm{H,intr}}$ from early {\it Swift} data in Window Timing mode reveals the same increasing trend with redshift as previous results based on data taken at later times, but with tighter constraints.

We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from ALMA band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with SNR$>5.2$ in the cube smoothed with 300 km s$^{-1}$ FWHM Gaussian filter. All four sources have near-infrared (NIR) counterparts within 1 arcsec. We perform ultraviolet to far-infrared spectral energy distribution (SED) modeling to derive the photometric redshift and physical properties. Based on photometric redshift, we reveal that two of them are CO(2-1) at a redshift of 1.113 and 1.146, and one is CO(3-2) at $z=2.124$. The three sources are massive galaxies with a stellar mass $\gtrsim10^{10.5}M_\odot$, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at $z\sim1-2$, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress the star formation.

[...] The aim of this paper is to study the precision and theoretical biases in the age determinations of halo stars adopting both asteroseismic and classic observational constraints. [...] We adopt the well-tested SCEPtER pipeline, covering evolutionary phases up to the red giant branch (RGB). The fitting grids contain stars with mass in the range of [0.7; 1.0] $M_{\odot}$ and metallicity [Fe/H] from -2.5 to -0.5. We investigate several scenarios characterised by different adopted observational uncertainties. We also assess the impact of systematic discrepancies between the recovery grid models and target stars by computing several synthetic grids of stellar models with perturbed input physics. In our reference scenario, we recover ages for stars in the main sequence (MS) or subgiant branch (SGB) with a typical 10\%--20\% precision, while we recover those of RGB stars with a precision of about 60\%. However, adopting tighter constraints on asteroseismic parameters, the age precision in RGB improved to 20\%, while few modifications occur in the other analysed evolutionary phases. A systematic discrepancies between grid models and target stars shows that a mismatch in the mixing-length parameter value leads to significant bias in the age estimations for MS stars (about 10\%), but this bias is smaller for SGB and RGB stars. Neglecting the microscopic diffusion effect in the recovery grid leads to a typical 40\% bias in age estimates for stars on the MS. Finally, we applied the technique to stars in globular clusters. We find a precision in age estimates of around 20\% for MS stars and up to 40\% for RGB stars, greater than those obtained with classical methods. We demonstrate the method on stars of the cluster M4, obtaining a cluster age of $11.9 \pm 1.5$ Gyr and a mass at the turn-of off $0.86 \pm 0.04$ $M_{\odot}$, which are in good agreement with literature results.

Recently, intense emission from nebular C III] and C IV emission lines have been observed in galaxies in the epoch of reionization ($z>6$) and have been proposed as the prime way of measuring their redshift and studying their stellar populations. These galaxies might represent the best examples of cosmic reionizers, as suggested by recent low-z observations of Lyman Continuum emitting galaxies, but it is hard to directly study the production and escape of ionizing photons at such high redshifts. The ESO spectroscopic public survey VANDELS offers the unique opportunity to find rare examples of such galaxies at cosmic noon ($z\sim 3$), thanks to the ultra deep observations available. We have selected a sample of 39 galaxies showing C IV emission, whose origin (after a careful comparison to photoionization models) can be ascribed to star formation and not to AGN. By using a multi-wavelength approach, we determine their physical properties including metallicity and ionization parameter and compare them to the properties of the parent population to understand what are the ingredients that could characterize the analogs of the cosmic reionizers. We find that C IV emitters are galaxies with high photons production efficiency and there are strong indications that they might have also large escape fraction: given the visibility of C IV in the epoch of reionization this could become the best tool to pinpoint the cosmic reioinzers.

Primordial black holes (PBH) may form from large cosmological perturbations, produced during inflation when the inflaton's velocity is sufficiently slowed down. This usually requires very flat regions in the inflationary potential. In this paper we investigate another possibility, namely that the inflaton climbs up its potential. When it turns back, its velocity crosses zero, which triggers a short phase of ``uphill inflation'' during which cosmological perturbations grow at a very fast rate. This naturally occurs in double-well potentials if the width of the well is close to the Planck scale. We include the effect of quantum diffusion in this scenario, which plays a crucial role, by means of the stochastic-$\delta N$ formalism. We find that ultra-light black holes are produced with very high abundances, which do not depend on the energy scale at which uphill inflation occurs, and which suffer from substantially less fine tuning than in alternative PBH-production models. They are such that PBHs later drive a phase of PBH domination.

The discovery of the first two macroscopic interstellar objects (ISOs) passing through the Solar System has opened entirely new perspectives in planetary science. The exploration of these objects offers a qualitatively new insight into the processes related to the origin, structure and evolution of planetary systems throughout the Galaxy. Knowledge about these phenomena will greatly advance if current and future sky surveys discover more ISOs. On the other hand, the surveys require better characterization of this population in order to improve their discovery algorithms. However, despite their scientific significance, there is still no comprehensive orbital model of ISOs in the Solar System and computationally efficient algorithm for generating their synthetic representations that would respond to these increasing needs. Currently available method for generating synthetic populations cannot fully take into account important phenomena, such as gravitational focusing and the shielding effect of the Sun. On the other hand, this method is also computationally far too demanding to be used for systematic exploration of the ISO population. This paper presents an analytical method for determining the distributions of the orbital elements of ISOs, as well as computationally efficient algorithm for generating their synthetic populations, based on the multivariate inverse transform sampling method. The developed method is several orders of magnitudes more efficient than the available method, depending on the size of the synthetic population. A Python implementation of the method is freely available and can be used to generate synthetic populations of ISOs with user-defined input parameters.

The Hubble tension refers to the discrepancy in the value of the Hubble constant $H_0$ inferred from the cosmic microwave background and the supernovae observations. In order to alleviate this tension, we propose a modification to the standard $\Lambda$CDM model by replacing the cosmological constant $\Lambda$ with a dynamical scalar field in the framework of Horndeski gravity, which drives the late time accelerated expanding phase of the Universe. With a combination of the $G_4$ and $G_5$ terms of the Horndeski Lagrangian, we show that, it is possible to construct viable scenarios for alleviating the Hubble tension which are free from gradient and ghost instabilities and the superluminal propagation of the scalar and tensor perturbations. Working with two different classes of scalar field potentials and with appropriate choices of model parameters, we exhibit that one can obtain a large enough value of $H_0$, so as to be consistent with the late Universe observations. Since these modifications are extremely small at early times, the corresponding deviations from the $\Lambda$CDM cosmology are completely negligible at high redshifts.

$Context.$ Core-collapse supernovae (CCSNe) are expected to emit gravitational wave signals that could be detected by current and future generation interferometers within the Milky Way and nearby galaxies. The stochastic nature of the signal arising from CCSNe requires alternative detection methods to matched filtering. $Aims.$ We aim to show the potential of machine learning (ML) for multi-label classification of different CCSNe simulated signals and noise transients using real data. We compared the performance of 1D and 2D convolutional neural networks (CNNs) on single and multiple detector data. For the first time, we tested multi-label classification also with long short-term memory (LSTM) networks. $Methods.$ We applied a search and classification procedure for CCSNe signals, using an event trigger generator, the Wavelet Detection Filter (WDF), coupled with ML. We used time series and time-frequency representations of the data as inputs to the ML models. To compute classification accuracies, we simultaneously injected, at detectable distance of 1\,kpc, CCSN waveforms, obtained from recent hydrodynamical simulations of neutrino-driven core-collapse, onto interferometer noise from the O2 LIGO and Virgo science run. $Results.$ We compared the performance of the three models on single detector data. We then merged the output of the models for single detector classification of noise and astrophysical transients, obtaining overall accuracies for LIGO ($\sim99\%$) and ($\sim80\%$) for Virgo. We extended our analysis to the multi-detector case using triggers coincident among the three ITFs and achieved an accuracy of $\sim98\%$.

We present a dedicated experimental study of microscopic mechanisms controlling radiolysis and sputtering of astrophysical ices due to their bombardment by cosmic ray ions. Such ions are slowed down due to inelastic collisions with bound electrons, resulting in ionization and excitation of ice molecules. In experiments on CO ice irradiation, we show that the relative contribution of these two mechanisms of energy loss to molecule destruction and sputtering can be probed by selecting ion energies near the peak of the electronic stopping power. We have observed a significant asymmetry, both in the destruction cross section and the sputtering yield, for pairs of ion energies corresponding to same values of the stopping power on either side of the peak. This implies that the stopping power does not solely control these processes, as usually assumed in the literature. Our results suggest that electronic excitations represent a significantly more efficient channel for radiolysis and, possibly, also for sputtering of CO ice. We also show that the charge state of incident ions as well as the rate for CO$^+$ production in the ice have negligible effect on these processes.

We discuss a novel window to probe the origin of our universe via the mass functions of primordial black holes (PBHs). The mass functions of PBHs are simply estimated using the conventional Press-Schechter formalism for different paradigms of cosmic origin, including inflationary $\Lambda$CDM and bounce cosmology. The standard inflationary $\Lambda$CDM model cannot generate an appreciable number of massive PBHs; however, non-trivial inflation models with blue-tilted power spectra at small scales and matter bounce cosmology provide formation mechanisms for heavy PBHs, which in turn, may seed the observed supermassive black holes (SMBHs). Fitting the observed mass functions of SMBHs in the local universe, we derive for the first time constraints on the PBH current density fraction $f_{\mathrm{PBH}}$ and the characteristic mass $M_{\star}$ for different paradigms of cosmic origin, with the prior assumption that all local SMBHs stem from PBHs. We demonstrate that this newly proposed procedure, relying on astronomical measurements that utilize deep-field scans of SMBHs at high redshift, can in principle be used to constrain models of cosmic origin.

In this work we test Wasserstein distance in conjunction with persistent homology, as a tool for discriminating large scale structures of simulated universes with different values of $\sigma_8$ cosmological parameter (present root-mean-square matter fluctuation averaged over a sphere of radius 8 Mpc comoving). The Wasserstein distance (a.k.a. the pair-matching distance) was proposed to measure the difference between two networks in terms of persistent homology. The advantage of this approach consists in its non-parametric way of probing the topology of the Cosmic web, in contrast to graph-theoretical approach depending on linking length. By treating the halos of the Cosmic Web as points in a point cloud we calculate persistent homologies, build persistence (birth-death) diagrams and evaluate Wasserstein distance between them. The latter showed itself as a convenient tool to compare simulated Cosmic webs. We show that one can discern two Cosmic webs (simulated or real) with different $\sigma_8$ parameter. It turns out that Wasserstein distance's discrimination ability depends on redshift $z$, as well as on the dimensionality of considered homology features. We find that the highest discriminating power this tool obtains at $z=2$ snapshots, among the considered $z=2$, $1$, and $0.1$ ones.

We investigate the long-term optical variability of the Be/X-ray binary GRO J2058+42 and the possible connection with periods of enhanced X-ray activity. We performed an optical spectroscopic and photometric analysis on data collected during about 18 years. We also present the first optical polarimetric observations of this source. The long-term optical light curves in the $BVRI$ bands and the evolution of the H$\alpha$ equivalent width display a sinusoidal pattern with maxima and minima that repeat every $\sim$9.5 years. The amplitude of this variability increases as the wavelength increases. The H$\alpha$ equivalent width varied from about $-0.3$ to $-15$ \AA. We found a significant decrease in the polarization degree during the low optical state. The optical maxima occur near periods of enhanced X-ray activity and are followed by a drop in the optical emission. Unlike many other Be/X-ray binaries, GRO 2058+42 does not display $V/R$ variability. The long-term optical variability agrees with the standard model of a Be/X-ray binary, where the circumstellar disk of the Be star grows and dissipates on timescales of 9--10 years. We find that the dissipation of the disk started after a major X-ray outburst. However, the stability of the H$\alpha$ line shape as a double-peak profile and the lack of asymmetries suggest the absence of a warped disk and argue against the presence of a highly distorted disk during major X-ray outbursts.

We perform a search for stellar-mass black hole candidates in the spatial regions with increased probability of their occurrence, isolated based on the evolutionary scenarios for compact objects originating in disrupted binaries. We analyze the sources located in these regions with available spectral or photometric data, as well as measured proper motions and distances. Nine objects that exhibit characteristics corresponding to theoretical predictions for isolated black holes are marked for further study as black hole candidates.

To show an internal signature of gravitational lensing, two different temporal sections of a single gamma-ray burst (GRB) must be statistically similar. Here two straightforward gravitational lensing tests are defined and applied: a light-curve similarity test and a hardness similarity test. Gravitational millilensing has been claimed to be detected within several individual GRBs that contain two emission episodes separated by a time delay. However, our analyses indicate that none of those claims clearly satisfy both tests. The hardness similarity test performed on GRB 950830 and GRB 090717A found that the ratio between the second and the first emission episodes in each energy channel differed from the same ratio averaged over all detected energy channels at above the 90 percent confidence level. Also, a light curve similarity test performed on GRB 950830, GRB 090717A, and GRB 200716C separately, found that it is unlikely that the two emission episodes in each GRB were drawn from a single parent emission episode for that GRB, with differences at the 3.0 sigma, 8.3 sigma, and 8.3 sigma confidence levels respectively.

Context. Late O-type stars at luminosities $\log L/L_\odot \lesssim 5.2$ show weak winds with mass-loss rates lower than 10$^{-8} M_\odot$ yr$^{-1}$. This implies that their photospheric layers are not strongly affected by the stellar wind. Aims. A hybrid non-local thermodynamic equilibrium (non-LTE) approach is tested for analyses of late O-type stars. A sample of 20 mostly sharp-lined Galactic O stars of spectral types O8 to O9.7 and luminosity classes V and IV, previously studied in the literature using full non-LTE model atmospheres, is investigated. Methods. Hydrostatic plane-parallel atmospheric structures and synthetic spectra computed with Kurucz's Atlas12 code together with non-LTE line-formation codes Detail and Surface, which account for the effects of turbulent pressure on the atmosphere, were employed. High-resolution spectra were analysed to derive atmospheric parameters and elemental abundances. Fundamental stellar parameters were derived by considering stellar evolution tracks and Gaia EDR3 parallaxes. Interstellar reddening was characterised by fitting spectral energy distributions from the UV to the mid-IR. Results. A high precision and accuracy is achieved for all derived parameters for 16 sample stars. Turbulent pressure effects turn out have significant effects. Effective temperatures are determined to 1-3% uncertainty levels, surface gravities to 0.05 to 0.10 dex, masses to better than 8%, radii to better than 10%, and luminosities to better than 20% uncertainty typically. Abundances for C, N, O, Ne, Mg, Al, Si are derived with uncertainties of 0.05 to 0.10 dex and for helium within 0.03 to 0.05 dex (1$\sigma$ standard deviations) in general. Distances to the Lac OB1b association and to the open clusters NGC 2244, IC 1805, NGC 457, and IC 1396 are determined as a byproduct.

The Baade-Wesselink (BW) method of distance determination of Cepheids is used to calibrate the distance scale. Various versions of this method are mainly based on interferometry and/or the surface-brightness color relation (SBCR). We quantify the impact of the SBCR, its slope, and its zeropoint on the projection factor. This quantity is used to convert the pulsation velocity into the radial velocity in the BW method. We also study the impact of extinction and of a potential circumstellar environment on the projection factor. We analyzed HARPS-N spectra of eta Aql to derive its radial velocity curve using different methods. We then applied the inverse BW method using various SBCRs in the literature in order to derive the BW projection factor. We find that the choice of the SBCR is critical: a scatter of about 8% is found in the projection factor for different SBCRs in the literature. The uncertainty on the coefficients of the SBCR affects the statistical precision of the projection factor only little (1-2\%). Confirming previous studies, we find that the method with which the radial velocity curve is derived is also critical, with a potential difference on the projection factor of 9%. An increase of 0.1 in E(B-V) translates into a decrease in the projection factor of 3%. A 0.1 magnitude effect of a circumstellar envelope (CSE) in the visible domain is rather small on the projection factor, about 1.5%. However, we find that a 0.1 mag infrared excess in the K band due to a CSE can increase the projection factor by about 6%. The impact of the surface-brightness color relation on the BW projection factor is found to be critical. Efforts should be devoted in the future to improve the SBCR of Cepheids empirically, but also theoretically, taking their CSE into account as well.

We present JWST NIRSpec spectroscopy for 11 galaxy candidates with photometric redshifts of $z\simeq9-13$ and $M_{\rm\,UV} \in[-21,-18]$ newly identified in NIRCam images in the Cosmic Evolution Early Release Science (CEERS) Survey. We confirm emission line redshifts for 7 galaxies at $z=7.762-8.998$ using spectra at $\sim1-5\mu$m either with the NIRSpec prism or its three medium resolution gratings. For $z\simeq9$ photometric candidates, we achieve a high confirmation rate of $\simeq$90\%, which validates the classical dropout selection from NIRCam photometry. No robust emission lines are identified in three galaxy candidates at $z>10$, where the strong [OIII] and H$\beta$ lines would be redshifted beyond the wavelength range observed by NIRSpec, and the Lyman-$\alpha$ continuum break is not detected with the current sensitivity. Compared with HST-selected bright galaxies ($M_{\rm\,UV}\simeq-22$) that are similarly spectroscopically confirmed at $z\gtrsim8$, these NIRCam-selected galaxies are characterized by lower star formation rates (SFR$\simeq4\,M_{\odot}$~yr$^{-1}$) and lower stellar masses ($\simeq10^{8}\,M_{\odot}$), but with higher [OIII]+H$\beta$ equivalent widths ($\simeq$1100$\r{A}$), and elevated production efficiency of ionizing photons ($\log(\xi_{\rm\,ion}/{\rm\,Hz\,erg}^{-1})\simeq25.8$) induced by young stellar populations ($<10$~Myrs) accounting for $\simeq20\%$ of the galaxy mass, highlighting the key contribution of faint galaxies to cosmic reionization. Taking advantage of the homogeneous selection and sensitivity, we also investigate metallicity and ISM conditions with empirical calibrations using the [OIII]/H$\beta$ ratio. We find that galaxies at $z\sim8-9$ have higher SFRs and lower metallicities than galaxies at similar stellar masses at $z\sim2-6$, which is generally consistent with the current galaxy formation and evolution models.

Upcoming deep galaxy surveys with JWST will probe galaxy evolution during the epoch of reionisation (EoR, $5\leq z\leq10$) over relatively compact areas (e.g. $\sim$ 300\,arcmin$^2$ for the JADES GTO survey). It is therefore imperative that we understand the degree of survey variance, to evaluate how representative the galaxy populations in these studies will be. We use the First Light And Reionisation Epoch Simulations (FLARES) to measure the galaxy bias of various tracers over an unprecedentedly large range in overdensity for a hydrodynamic simulation, and use these relations to assess the impact of bias and clustering on survey variance in the EoR. Star formation is highly biased relative to the underlying dark matter distribution, with the mean ratio of the stellar to dark matter density varying by a factor of 100 between regions of low and high matter overdensity (smoothed on a scale of 14\,$h^{-1}$cMpc). This is reflected in the galaxy distribution -- the most massive galaxies are found solely in regions of high overdensity. As a consequence of the above, galaxies in the EoR are highly clustered, which can lead to large variance in survey number counts. For mean number counts $N\lesssim 100$ (1000), in a unit redshift slice of angular area 300\,arcmin$^2$ (1.4\,deg$^2$), the 2-sigma range in $N$ is roughly a factor of four (two). We present relations between the expected variance and survey area for different survey geometries; these relations will be of use to observers wishing to understand the impact of survey variance on their results.

Precision CCD uvbyCaHbeta photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005-0.020 mag level to V~17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial-velocity information. From single-star members, offsets in the sense (M67 - NGC 752) are Delta E(b-y) = -0.005 +/-0.001 (sem) mag from 327 F/G dwarfs and Delta [Fe/H] = 0.062 +/- 0.006 (sem) dex from the combined m1 and hk indices of 249 F dwarfs, leading to E(b-y) = 0.021 +/- 0.004 (sem), and [Fe/H] = +0.030 +/- 0.016 (sem) for M67, assuming [Fe/H]{Hyades} = +0.12. With probable binaries eliminated using c1,(b-y) indices, 83 members with relative parallax errors < 0.02 generate (m-M)_0 = 8.220 +/- 0.005 (sem) for NGC 752 and an isochronal age of 1.45 +/- 0.05 Gyr. Using the same parallax restriction for 312 stars, M67 has (m-M) = 9.77 +/- 0.02 (sem), leading to an age tied solely to the luminosity of the subgiant branch of 3.70 +/- 0.03 Gyr. The turnoff color spread implies +/- 0.1 Gyr, but the turnoff morphology defines a younger age/higher mass for the stars, consistent with recent binary analysis and broad-band photometry indicating possible missing physics in the isochrones. Anomalous stars positioned blueward of the turnoff are discussed.

In the vicinity of black holes, the influence of strong gravity, plasma physics, and emission processes govern the behavior of the system. Since observations such as those carried out by the EHT are not yet able to unambiguously constrain models for astrophysical and gravitational properties, it is imperative to explore the accretion models, particle distribution function, and description of the spacetime geometry. Our current understanding of these properties is often based on the assumption that the spacetime is well-described by by the Kerr solution to general relativity, combined with basic emission and accretion models. We explore alternative models for each property performing general relativistic magnetohydrodynamic and radiative transfer simulations. By choosing a Kerr solution to general relativity and a dilaton solution to Einstein-Maxwell-dilaton-axion gravity as exemplary black hole background spacetimes, we aim to investigate the influence of accretion and emission models on the ability to distinguish black holes in two theories of gravity. We carry out three-dimensional general relativistic magnetohydrodynamics simulations of both black holes, matched at their innermost stable circular orbit, in two distinct accretion scenarios. Using general-relativistic radiative transfer calculations, we model the thermal synchrotron emission and in the next step apply a non-thermal electron distribution function, exploring representative parameters to compare with multiwavelength observations. We further consider Kerr and dilaton black holes matched at their unstable circular photon orbits, as well as their event horizons. From multiwavelength emission and spectral index analysis, we find that accretion model and spacetime have only a small impact on the spectra compared to the choice of emission model.

Flaring episodes in blazars represent one of the most violent processes observed in extra-galactic objects. Studies of such events shed light on the energetics of the physical processes occurring in the innermost regions of blazars, which cannot otherwise be resolved by any current instruments. In this work, we present some of the largest and most rapid flares captured in the optical band in the blazars 3C 279, OJ 49, S4 0954+658, TXS 1156+295 and PG 1553+113. The source flux was observed to increase by nearly ten times within a timescale of a few weeks. We applied several methods of time series analysis and symmetry analysis. Moreover, we also performed searches for periodicity in the light curves of 3C 279, OJ 49 and PG 1553+113 using the Lomb-Scargle method and found plausible indications of quasi-periodic oscillations (QPOs). In particular, the 33- and 22-day periods found in 3C 279, i.e. a 3:2 ratio, are intriguing. These violent events might originate from magnetohydrodynamical instabilities near the base of the jets, triggered by processes modulated by the magnetic field of the accretion disc. We present a qualitative treatment as the possible explanation for the observed large amplitude flux changes in both the source-intrinsic and source-extrinsic scenarios.

We present a first look at the MRS observations of the nucleus of the spiral galaxy M83, taken with MIRI onboard JWST. The observations show a rich set of emission features from the ionized and warm molecular gas, as well as traces of the dust properties in this highly star forming environment. To begin dissecting the complex processes taking place in this part of the galaxy, we divide the nucleus observations into four different regions. We find that the strength of the emission features appears to strongly vary in all four regions, with the south-east region displaying the weakest features tracing both the dust continuum and ISM properties. Comparison between the cold molecular gas traced by the $^{12}$CO (1-0) transition with ALMA and the H$_2$ 0-0 S(1) transition showed a similar spatial distribution throughout the nucleus. This is in contrast to the distribution of the much warmer H$_2$ emission from the S(7) transition found to be concentrated mainly around the optical nucleus. We modeled the H$_2$ excitation using the rotational emission lines and estimate a total molecular gas mass accounting for the warm H$_2$ component of M($>$50 K)$_{\rm H_{2}}$ = 59.33 ($\pm 4.75$) $\times$ 10$^{6}$ M$_{\odot}$. We compared this value to the total molecular gas mass inferred by probing the cold H$_2$ gas through the $^{12}$CO (1-0) emission, M(CO)$_{\rm H_{2}}$ = 14.99 $\times$ 10$^{6}$ M$_{\odot}$. Our findings indicate that $\sim$75\% of the total molecular gas mass in the core of M83 is contained in the warm H$_2$ component. We also identify [OIV]25.89 $\mu$m and [FeII]25.99 $\mu$m emission (indicative of shocks) in all four nuclear regions with the strongest emission originating from the north-west section. We propose that the diffuse [FeII]25.99 $\mu$m emission is an indication of the combined effects of both the collective supernova explosions and the starbursts themselves.

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa 4 within the SPIRou Legacy Survey large programme, based on data collected with SPIRou at the Canada-France-Hawaii Telescope and the TESS space probe between October 2021 and January 2022. We applied Zeeman-Doppler Imaging to our spectropolarimetric and photometric data to recover a surface brightness distribution compatible with TESS photometry, as well as the large-scale magnetic topology of the star. As expected from the difference in wavelength between near-infrared and optical data, the recovered surface brightness distribution is less contrasted than the previously published one based on ESPaDOnS data, but still features mid-latitude dark and bright spots. The large-scale magnetic field is consistent in shape and strength with the one derived previously, with a poloidal component resembling a 2.2 kG dipole and a toroidal component reaching 1.4 kG and encircling the star at the equator. Our new data confirm that the surface differential rotation of LkCa 4 is about 10 times weaker than that of the Sun, and significantly different from zero. Using our brightness reconstruction and Gaussian Process Regression, we were able to filter the radial velocity activity jitter down to a precision of 0.45 and 0.38 km $\rm s^{-1}$ (from an amplitude of 6.10 km $\rm s^{-1}$), respectively, yielding again no evidence for a close-in massive planet orbiting the star.

We use the state-of-the-art data on cosmic chronometers (CCH) and the Pantheon+ compilation of supernovae of Type Ia (SNIa) to test the constancy of the SNIa absolute magnitude, $M$, and the robustness of the cosmological principle (CP) at $z\lesssim 2$ with a model-agnostic approach. We do so by reconstructing $M(z)$ and the curvature parameter $\Omega_{k}(z)$ using Gaussian Processes. Moreover, we use CCH in combination with radial and angular data on baryon acoustic oscillations (BAO) from various galaxy surveys (6dFGS, BOSS, eBOSS, WiggleZ, DES Y3) to measure the sound horizon at the baryon-drag epoch, $r_d$, from each BAO data point and check their consistency. Given the precision allowed by the CCH data, we find that $M(z)$, $\Omega_k(z)$ and $r_d(z)$ are fully compatible (at $<68\%$ C.L.) with constant values. This justifies our final analyses, in which we put constraints on these constant parameters under the validity of the CP, the metric description of gravity and standard physics in the vicinity of the stellar objects, but otherwise in a model-independent way. If we exclude the SNIa contained in the host galaxies employed by SH0ES, our results read $M=(-19.314^{+0.086}_{-0.108})$ mag, $r_d=(142.3\pm 5.3)$ Mpc and $\Omega_k=-0.07^{+0.12}_{-0.15}$ ($68\%$ C.L.). These values have been obtained without using any information from the main data sets involved in the $H_0$ tension, namely, the cosmic microwave background and the first two rungs of the cosmic distance ladder. If, instead, we also consider the SNIa in the host galaxies, calibrated with Cepheids, we measure $M=(-19.252^{+0.024}_{-0.036})$ mag, $r_d=(141.9^{+5.6}_{-4.9})$ Mpc and $\Omega_k=-0.10^{+0.12}_{-0.15}$.

We present a new method to predict the line-of-sight column density (NH) values of active galactic nuclei (AGN) based on mid-infrared (MIR), soft, and hard X-ray data. We developed a multiple linear regression machine learning algorithm trained with WISE colors, Swift-BAT count rates, soft X-ray hardness ratios, and an MIR-soft X-ray flux ratio. Our algorithm was trained off 451 AGN from the Swift-BAT sample with known NH and has the ability to accurately predict NH values for AGN of all levels of obscuration, as evidenced by its Spearman correlation coefficient value of 0.86 and its 75% classification accuracy. This is significant as few other methods can be reliably applied to AGN with Log(NH <) 22.5. It was determined that the two soft X-ray hardness ratios and the MIR-soft X-ray flux ratio were the largest contributors towards accurate NH determination. This algorithm will contribute significantly to finding Compton-thick (CT-) AGN (NH >= 10^24 cm^-2), thus enabling us to determine the true intrinsic fraction of CT-AGN in the local universe and their contribution to the Cosmic X-ray Background.

We present a Bayesian analysis of data from the FIELDS instrument on board the Parker Solar Probe (PSP) spacecraft with the aim of constraining low frequency ($\lesssim$ 6 MHz) sky in preparation for several upcoming lunar-based experiments. We utilize data recorded during PSP's ``coning roll'' maneuvers, in which the axis of the spacecraft is pointed 45$^{\circ}$ off of the Sun. The spacecraft then rotates about a line between the Sun and the spacecraft with a period of 24 minutes. We reduce the data into two formats: roll-averaged, in which the spectra are averaged over the roll, and phase-binned, in which the spectra are binned according to the phase of the roll. We construct a forward model of the FIELDS observations that includes numerical simulations of the antenna beam, an analytic emissivity function of the galaxy, and estimates of the absorption due to free electrons. Fitting 5 parameters, we find that the roll-averaged data can be fit well by this model and we obtain posterior parameter constraints that are in general agreement with previous estimates. The model is not, however, able to fit the phase-binned data well, likely due to limitations such as the lack of non-smooth emission structure at both small and large scales, enforced symmetry between the northern and southern galactic hemispheres, and large uncertainties in the free electron density. This suggests that significant improvement in the low frequency sky model is needed in order to fully and accurately represent the sky at frequencies below 6 MHz.

We trace the evolution of the edge-on spiral galaxy NGC 3501, making use of its stellar populations extracted from deep integral-field spectroscopy MUSE observations. We present stellar kinematic and population maps, as well as the star formation history, of the south-western half of the galaxy. The derived maps of the stellar line-of-sight velocity and velocity dispersion are quite regular, show disc-like rotation, and no other structural component of the galaxy. However, maps of the stellar populations exhibit structures in the mass-weighted and light-weighted age, total metallicity and [Mg/Fe] abundance. These maps indicate that NGC 3501 is a young galaxy, consisting mostly of stars with ages between 2 to 8 Gyr. Also, they show a thicker more extended structure that is metal-poor and $\alpha$-rich, and another inner metal-rich and $\alpha$-poor one with smaller radial extension. While previous studies revealed that NGC 3501 shows only one morphological disc component in its vertical structure, we divided the galaxy into two regions: an inner metal-rich midplane and a metal-poor thicker envelope. Comparing the star formation history of the inner thinner metal-rich disc and the thicker metal-poor disc, we see that the metal-rich component evolved more steadily, while the metal-poor one experienced several bursts of star formation. We propose this spiral galaxy is being observed in an early evolutionary phase, with a thicker disc already in place and an inner thin disc in an early formation stage. So we are probably witnessing the birth of a future massive thin disc, continuously growing embedded in a preexisting thicker disc.

The J-PAS survey will observe ~1/3 of the northern sky with a set of 56 narrow-band filters using the dedicated 2.55 m JST telescope at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera, in order to demonstrate the scientific potential of J-PAS, two small surveys were performed with the single-CCD Pathfinder camera: miniJPAS (~1 deg2 along the Extended Groth Strip), and J-NEP (~0.3 deg2 around the JWST North Ecliptic Pole Time Domain Field), including all 56 J-PAS filters as well as u, g, r, and i. J-NEP is ~0.5-1.0 magnitudes deeper than miniJPAS, providing photometry for 24,618 r-band detected sources and photometric redshifts (photo-z) for the 6,662 sources with r<23. In this paper we describe the photometry and photo-z of J-NEP and demonstrate a new method for the removal of systematic offsets in the photometry based on the median colours of galaxies, dubbed "galaxy locus recalibration". This method does not require spectroscopic observations except in a few reference pointings and, unlike previous methods, is applicable to the whole J-PAS survey. We use a spectroscopic sample of 787 galaxies to test the photo-z performance for J-NEP and in comparison to miniJPAS. We find that the deeper J-NEP observations result in a factor ~1.5-2 decrease in sigma_NMAD (a robust estimate of the standard deviation of the photo-z error) and the outlier rate relative to miniJPAS for r>21.5 sources, but no improvement in brighter ones. We find the same relation between sigma_NMAD and odds in J-NEP and miniJPAS, suggesting sigma_NMAD can be predicted for any set of J-PAS sources from their odds distribution alone, with no need for additional spectroscopy to calibrate the relation. We explore the causes for photo-z outliers and find that colour-space degeneracy at low S/N, photometry artifacts, source blending, and exotic spectra are the most important factors.

Aims. We study the properties of low-mass stars recently formed in the field of the NGC 376 cluster in the Small Magellanic Cloud (SMC). Methods. Using photometric observations acquired with the Hubble Space Telescope (HST) in the V, I and Halpha bands, we identify 244 candidate pre-main sequence (PMS) stars showing Halpha excess emission at the 5 sigma level and with Halpha equivalent width of 20 \r{A} or more. We derive physical parameters for all PMS stars, including masses, ages, and mass accretion rates. We compare the effective mass accretion rate of stars in NGC 376 to that of objects in the NGC 346 cluster, which features similar metallicity but higher total mass and gas density. Results. We find a median age of 28 Myr for this population (with 25 and 75 percentiles at about 20 and 40 Myr, respectively), in excellent agreement with previous studies of massive stars in the same field. The PMS stars are rather uniformly distributed across the field, whereas massive stars are more clustered. The spatial distribution of PMS objects is compatible with them having formed in the centre of the cluster and then migrated outwards. We find that in NGC 376 the mass accretion rate is systematically lower than in NGC 346 for stars of the same mass and age. This indicates that, besides metallicity, there are other environmental factors affecting the rate of mass accretion onto PMS stars. Our observations suggest that the gas density in the star-forming region might play a role.

The optical depth to reionization, $\tau$, is the least constrained parameter of the cosmological $\Lambda$CDM model. To date, its most precise value is inferred from large-scale polarized CMB power spectra from the $\textit{Planck}$ High-Frequency Instrument (HFI). These maps are known to contain significant contamination by residual non-Gaussian systematic effects, which are hard to model analytically. Therefore, robust constraints on $\tau$ are currently obtained through an empirical cross-spectrum likelihood built from simulations. In this paper, we present a likelihood-free inference of $\tau$ from polarized $\textit{Planck}$ HFI maps which, for the first time, is fully based on neural networks (NNs). NNs have the advantage of not requiring an analytical description of the data and can be trained on state-of-the-art simulations, combining information from multiple channels. By using Gaussian sky simulations and $\textit{Planck}$ $\texttt{SRoll2}$ simulations, including CMB, noise, and residual instrumental systematic effects, we train, test and validate NN models considering different setups. We infer the value of $\tau$ directly from $Q$ and $U$ maps at $\sim 4^\circ$ pixel resolution, without computing power spectra. On $\textit{Planck}$ data, we obtain $\tau_{\rm NN}=0.0579\pm 0.0082$, compatible with current $EE$ cross-spectrum results but with a $\sim30\%$ larger uncertainty, which can be assigned to the inherent non-optimality of our estimator and to the retraining procedure applied to avoid biases. While this paper does not improve on current cosmological constraints on $\tau$, our analysis represents a first robust application of NN-based inference on real data and highlights its potential as a promising tool for complementary analysis of near-future CMB experiments, also in view of the ongoing challenge to achieve a detection of primordial gravitational waves.

Almost 100 compact binary mergers have been detected via gravitational waves by the LIGO-Virgo-KAGRA collaboration in the past few years providing us with a significant amount of new information on black holes and neutron stars. In addition to observations, numerical simulations using newly developed modern codes in the field of gravitational wave physics will guide us to understand the nature of single and binary degenerate systems and highly energetic astrophysical processes. We here present a set of new fully general relativistic hydrodynamic simulations of high-mass binary neutron star systems performed with the publicly available Einstein Toolkit and LORENE codes. We considered systems with a total baryonic mass between 2.8 $M_\odot$ and 4.0 $M_\odot$ and we adopted the SLy equation of state. For all models we analyzed the gravitational wave signal and we report potential indicators of the systems undergoing rapid collapse into a black hole that may be observed by future-planned detectors such as the Einstein Telescope and the Cosmic Explorer. We also extracted the properties of the post-merger black hole, the disk and ejecta masses and their dependence on the binary parameters. We also compare our numerical results with recent analytical fits presented in the literature and we also provide parameter-dependent semi-analytical relations between the total mass and mass ratio of the systems and the resulting black hole masses and spins, coalescence time scale, mass loss, and gravitational wave energy.

The Standard Model Higgs becomes tachyonic at high energy scales according to current measurements. This unstable regime of the Higgs potential can be realized in the early Universe during high scale inflation, potentially with catastrophic consequences. This letter highlights a crucial inherent feature of such configurations that has so far remained ignored: Higgs particle production out of vacuum induced by the rapidly evolving Higgs field, which gets exponentially enhanced due to the tachyonic instability. Such explosive particle production can rapidly drain energy away from the Higgs field, sustaining a significant density of Higgs particles even during inflation, and could initiate a qualitatively different form of preheating in parts of the post-inflationary Universe. Any study of the Higgs field in its tachyonic phase, either during or after inflation, must therefore take this substantial particle energy density into account, which could significantly affect the subsequent evolution of such systems. This could carry important implications for high scale inflation, post-inflationary preheating, observable signals in the cosmic microwave background, gravitational waves, and primordial black holes, as well as deeper concepts ranging from eternal inflation to the metastability of the electroweak vacuum.

The IceCube collaboration has observed the first steady-state point source of high-energy neutrinos, coming from the active galaxy NGC 1068. If neutrinos interacted strongly enough with dark matter, the emitted neutrinos would have been impeded by the dense spike of dark matter surrounding the supermassive black hole at the galactic center, which powers the emission. We derive a stringent upper limit on the scattering cross section between neutrinos and dark matter based on the observed events and theoretical models of the dark matter spike. The bound can be stronger than that obtained by the single IceCube neutrino event from the blazar TXS 0506+056 for some spike models.

The dense environment of neutron stars makes them an excellent target for probing dark matter interactions with the Standard Model. We study neutron star heating from capture of inelastic dark matter, which can evade direct detection constraints. We investigate kinematics of the inelastic scattering process between quasirelativistic dark matter particles and ultrarelativistic targets in neutron stars, and derive analytical expressions for the maximal mass gap allowed for the scattering to occur. We implement them into a fully relativistic formalism for calculating the capture rate and apply it to various scenarios of inelastic dark matter. The projected constraints from neutron stars can systematically surpass those from terrestrial searches, including direct detection and collider experiments. Neutron stars can also be sensitive to the parameter space of inelastic self-interacting dark matter. Our results indicate that extreme astrophysical environments, such as neutron stars, are an important target for searching dark matter.

Lightsail spacecraft, propelled to relativistic velocities via photon pressure using high power density laser radiation, offer a potentially new route to space exploration within and beyond the solar system, extending to interstellar distances. Such missions will require meter-scale lightsails of submicron thickness, posing substantial challenges for materials science and engineering. We analyze the structural and photonic design of flexible lightsails, developing a mesh-based multiphysics simulator based on linear elastic theory, treating the lightsail as a flexible membrane rather than a rigid body. We find that flexible lightsail membranes can be spin stabilized to prevent shape collapse during acceleration, and that certain lightsail shapes and designs offer beam-riding stability despite the deformations caused by photon pressure and thermal expansion. Excitingly, nanophotonic lightsails based on planar silicon nitride membranes patterned with suitably designed optical metagratings exhibit both mechanically and dynamically stable propulsion along the pump laser axis. These advances suggest that laser-driven acceleration of membrane-like lightsails to the relativistic speeds needed to access interstellar distances is conceptually feasible, and that fabrication of such lightsails may be within the reach of modern microfabrication technology.

The Energy Conserving semi-implicit method (ECsim), presented by Lapenta in 2017, is a Particle in Cell (PIC) algorithm for the simulation of plasmas. Energy conservation is achieved within a semi-implicit formulation that does not require any non-linear solver. A mass matrix is introduced to express linearly the particle-field coupling. With the mass matrix the algorithm preserves energy conservation to machine precision. The construction of the mass matrix is the central nature of the method and also the main cost of the computational cycle. We analyze here three methods that modify the construction of the mass matrix. First, we consider how the sub-cycling of the particle motion modifies the mass matrix. Second, we introduce a form of smoothing that reduces the noise while retaining exact energy conservation. Finally, we discuss an approximation of the mass matrix that transform the ECsim scheme to the implicit moment method.

Axion dark matter (DM) is studied on the formation of supermassive black holes (SMBHs) at high $z$. It is shown that the attractive self interaction of this DM may solve the tension between the high angular momentum and the early time formation of SMBH. This fact may serve to specify a model among various axion models whose masses are ranging over very broad scales.

Gravitational waves from merging compact objects provides the opportunity to explore the properties of black holes and neutron stars in the strong regime of gravity. It is therefore of interest to explore the theoretical model that accurately describes them. Using the coset construction, we build a worldline Effective Field Theory that is derived from symmetry principles, does not involve additional degrees of freedom, and describes the most general compact object allowed in an effective Einstein-Maxwell vierbein theory. Such extended object can be described by its mass, spin, charge and size effects: tides, polarization and dissipation. By recognizing the symmetry breaking pattern, we derive all the covariant building blocks and constraints to build up the relevant invariant operators in the action to all orders. The developed theory elucidates the description of compact objects as an Effective Field Theory.

The vacuum stability problem is usually studied assuming that the universe is located in the desired electroweak-breaking vacuum. This may not be the case, however, as seen by checking the evolution history of the early universe. The transition to the stable desired vacuum may not be possible, or the desired vacuum could be meta-stable and long-lived but the universe may already be in an undesired global vacuum from an early stage. We reveal that these situations exist even in the simplest singlet extension of the Standard Model, propose a general procedure to identify them, and divide the parameter space according to different cases. We find that checking cosmological history can provide a more stringent, reasonable and sometimes computationally cheaper limit of vacuum stability on new physics models than the traditional

The discrepancy between the value of Hubble constant measured by CMB observations and local low-redshift based observations has proposed many solutions which require the existence of Physics beyond Standard Model (SM). One of the interesting solutions is based on considering the strong self-interaction between Standard Model (SM) neutrinos through an additional scalar/vector mediator. Interestingly, the strong self-interaction between SM neutrinos also play an important role in obtaining KeV-sterile neutrino as a viable Dark Matter (DM) candidate through the famous Dodelson-Widrow mechanism. In this work, we have tried to find the synergy between the parameter space of active-sterile neutrino mixing vs mass of sterile neutrino allowed by Hubble tension solution and the requirement of getting KeV-sterile neutrino as DM candidate. Interestingly, we get a large amount of parameter space that is consistent with both the requirements and also free from X-Ray constraints. Finally, we have embedded this scenario in a consistent supersymmetric model of particle physics. With in this framework, we have shown that the value of sterile neutrino mass, SM neutrino mass and the required mixing angle can be naturally obtained by considering the supersymmetry breaking scale to be around O(10) TeV. Thus, it would give an interesting testing ground for supersymmetry as well as signatures of Warm Dark Matter (WDM).

We explain that black holes are the most efficient capacitors of quantum information. It is thereby expected that all sufficiently advanced civilizations ultimately employ black holes in their quantum computers. The accompanying Hawking radiation is democratic in particle species. Due to this, the alien quantum computers will radiate in ordinary particles such as neutrinos and photons within the range of potential sensitivity of our detectors. This offers a new avenue for SETI, including the civilizations entirely composed of hidden particles species interacting with our world exclusively through gravity.