Papers for Friday, May 20 2022

We take advantage of exquisitely deep optical imaging data from HST/ACS in the F475W ($g_{F475W}$) and F606W ($V_{F606W}$) bands, to study the properties of the globular cluster (GC) population in the intermediate mass lenticular galaxy PGC 087327, in the Hydra I galaxy cluster. We inspect the photometric (magnitudes and color) and morphometric (compactness, elongation, etc.) properties of sources lying in an area of $\sim19\times19$ kpc centered on PGC 087327, and compare them with four neighbouring fields over the same HST/ACS mosaic. This allowed us to identify a list of GC candidates and to inspect their properties using a background decontamination method. Relative to the four comparison fields, PGC 087327 shows a robust overdensity of GCs, $N_{GC}=82\pm9$. At the estimated magnitude of the galaxy, this number implies a specific frequency of $S_N=1.8\pm0.7$. In spite of the short wavelength interval available with the $g_{F475W}$ and $V_{F606W}$ passbands, the color distribution shows a clear bimodality with a blue peak at $\langle g_{F475W}{-}V_{F606W} \rangle =0.47\pm0.05$ mag and a red peak at $\langle g_{F475W}{-}V_{F606W}\rangle =0.62\pm0.03$ mag. We also observe the typical steeper slope of the radial distribution of red GCs relative to blue ones. Thanks to the unique depth of the available data, we characterize the GC luminosity function (GCLF) well beyond the expected GCLF turn-over. We find $g^{TOM}_{F475W} = 26.54\pm0.10$ mag and $V^{TOM}_{F606W} = 26.08 \pm 0.09$ mag, which after calibration yields a distance of $D_{GCLF} = 56.7 \pm 4.3(statistical) \pm 5.2(systematic)$ Mpc.

Very massive stars (VMS) dominate the physics of young clusters due to their ionising radiation and extreme stellar winds. It is these winds that determine their lifepaths until expiration. Observations in the Arches cluster show that VMS all have similar temperatures. The VLT-Flames Tarantula survey analysed VMS in the 30 Dor region of the LMC also finding a narrow range of temperatures, albeit at higher values - likely a metallicity effect. Using MESA, we study the main-sequence evolution of VMS with a new mass-loss recipe that switches from optically-thin O-star winds to optically-thick Wolf-Rayet type winds through the model-independent transition mass-loss rate of Vink & Gr\"afener. We examine the temperature evolution of VMS with mass loss that scales with the luminosity-over-mass (L/M) ratio and the Eddington parameter ($\Gamma_{\rm e}$), assessing the relevance of the surface hydrogen (H) abundance which sets the number of free electrons. We present grids of VMS models at Galactic and LMC metallicity and compare our temperature predictions with empirical results. Models with a steep $\Gamma_{\rm e}$-dependence evolve horizontally in the Hertzsprung-Russel (HR) diagram at nearly constant luminosities, requiring a delicate and unlikely balance between envelope inflation and enhanced mass loss over the entire VMS mass range. By contrast, models with a steep L/M-dependent mass loss are shown to evolve vertically in the HR-diagram at nearly constant Teff, naturally reproducing the narrow range of observed temperatures, as well as the correct trend with metallicity. This distinct behavior of a steeply dropping luminosity is a self-regulatory mechanism that keeps temperatures constant during evolution in the HR-diagram.

Precision analysis of galaxy-galaxy strong gravitational lensing images provides a unique way of characterizing small-scale dark matter halos, and could allow us to uncover the fundamental properties of dark matter's constituents. In recent years, gravitational imaging techniques made it possible to detect a few heavy subhalos. However, gravitational lenses contain numerous subhalos and line-of-sight halos, whose subtle imprint is extremely difficult to detect individually. Existing methods for marginalizing over this large population of sub-threshold perturbers in order to infer population-level parameters are typically computationally expensive, or require compressing observations into hand-crafted summary statistics, such as a power spectrum of residuals. In this work we present the first analysis pipeline to combine parametric lensing models and a recently-developed neural simulation-based inference technique called truncated marginal neural ratio estimation (TMNRE) to constrain the warm dark matter halo mass function cutoff scale directly from multiple lensing images. Through a proof-of-concept application to simulated data, we show that our approach enables empirically testable inference of the dark matter cutoff mass through marginalization over a large population of realistic perturbers that would be undetectable on their own, and over lens and source parameters uncertainties. To obtain our results, we combine the signal contained in a set of images with Hubble Space Telescope resolution. Our results suggest that TMNRE can be a powerful approach to put tight constraints on the mass of warm dark matter in the multi-keV regime, which will be relevant both for existing lensing data and in the large sample of lenses that will be delivered by near-future telescopes.

MAXI J1348-630 is a low mass X-ray binary discovered in 2019 during a bright outburst. During this event, the system sampled both hard and soft states following the standard evolution. We present multi-epoch optical and near-infrared spectroscopy obtained with X-shooter at the Very Large Telescope. Our dataset includes spectra taken during the brightest phases of the outburst as well as the decay towards quiescence. We study the evolution of the main emission lines, paying special attention to the presence of features commonly associated with accretion disc winds, such as blue-shifted absorptions, broad emission line wings and flat-top profiles. We find broad emission line wings in H-alpha during the hard-to-soft transition and blue-shifted absorption troughs at ~-500 km/s in H-beta, HeI-5876, H-alpha and Pa-beta during the bright soft-intermediate state. In addition, flat-top profiles are seen throughout the outburst. We interpret these observables as signatures of a cold (i.e. optical to infrared) accretion disc wind present in the system. We discuss the properties of the wind and compare them with those seen in other X-ray transients. In particular, the wind velocity that we observe is low when compared to those of other systems, which might be a direct consequence of the relatively low binary inclination, as suggested by several observables. This study strengthen the hypothesis that cold winds are a common feature in low mass X-ray binaries and that they can also be detected in low inclination objects via high-quality optical and infrared spectroscopy.

We report the discovery of Tucana B, an isolated ultra-faint dwarf galaxy at a distance of D=1.4 Mpc. Tucana B was found during a search for ultra-faint satellite companions to the known dwarfs in the outskirts of the Local Group, although its sky position and distance indicate the nearest galaxy to be $\sim$500 kpc distant. Deep ground-based imaging resolves Tucana B into stars, and it displays a sparse red giant branch consistent with an old, metal poor stellar population analogous to that seen in the ultra-faint dwarf galaxies of the Milky Way, albeit at fainter apparent magnitudes. Tucana B has a half-light radius of 80$\pm$35 pc, and an absolute magnitude of $M_V$=$-$6.9$\pm$0.3 mag ($L_V$=5.0$\pm$1.5$\times$10$^4$ $L_{\odot}$), which is again comparable to the Milky Way's ultra-faint satellites. There is no evidence for a population of young stars, either in the optical color magnitude diagram or in GALEX archival ultraviolet imaging. Likewise, archival HI observations indicate that Tucana B has no neutral gas reservoir, although it is in a portion of the sky contaminated with complex HI features associated with the Milky Way. Given its isolation and physical properties, Tucana B may be a definitive example of an ultra-faint dwarf that has been quenched by reionization, providing strong confirmation of a key driver of galaxy formation and evolution at the lowest mass scales. It also signals a new era of ultra-faint dwarf galaxy discovery at the extreme edges of the Local Group.

We present a basic model for the calculation of the luminosity distribution of supernova remnant populations. We construct theoretical Ha and joint [S II] - Ha luminosity functions for supernova remnants by combining prescriptions from a basic evolution model that provides the shock velocity and radius for SNRs of different age and pre-shock density, with shock excitation models that give the gas emissivity for shocks of different physical parameters. We assume a flat age distribution, and we explore the effect of different pre-shock density distributions or different magnetic parameters. We find very good agreement between the shape of the model Ha and the joint [S II] - Ha luminosity functions and those measured from SNR surveys in nearby galaxies.

Despite the rich observational results on interstellar magnetic fields in star-forming regions, it is still unclear how dynamically significant the magnetic fields are at varying physical scales, because direct measurement of the field strength is observationally difficult. The Davis-Chandrasekhar-Fermi (DCF) method has been the most commonly used method to estimate the magnetic field strength from polarization data. It is based on the assumption that gas turbulent motion is the driving source of field distortion via linear Alfv\'en waves. In this work, using MHD simulations of star-forming clouds, we test the validity of the assumption underlying the DCF method by examining its accuracy in the real 3D space. Our results suggest that the DCF relation between turbulent kinetic energy and magnetic energy fluctuation should be treated as a statistical result instead of a local property. We then develop and investigate several modifications to the original DCF method using synthetic observations, and propose new recipes to improve the accuracy of DCF-derived magnetic field strength. We further note that the biggest uncertainty in the DCF analysis may come from the linewidth measurement instead of the polarization observation, especially since the line-of-sight gas velocity can be used to estimate the gas volume density, another critical parameter in the DCF method.

The evolution of the Kelvin-Helmholtz Instability (KHI) is widely used to assess the performance of numerical methods. We employ this instability to test both the smoothed particle hydrodynamics (SPH) and the meshless finite mass (MFM) implementation in OpenGadget3. We quantify the accuracy of SPH and MFM in reproducing the linear growth of the KHI with different numerical and physical set-ups. Among them, we consider: $i)$ numerical induced viscosity, and $ii)$ physically motivated, Braginskii viscosity, and compare their effect on the growth of the KHI. We find that the changes of the inferred numerical viscosity when varying nuisance parameters such as the set-up or the number of neighbours in our SPH code are comparable to the differences obtained when using different hydrodynamical solvers, i.e. MFM. SPH reproduces the expected reduction of the growth rate in the presence of physical viscosity and recovers well the threshold level of physical viscosity needed to fully suppress the instability. In the case of galaxy clusters with a virial temperature of $3\times10^7$ K, this level corresponds to a suppression factor of $\approx10^{-3}$ of the classical Braginskii value. The intrinsic, numerical viscosity of our SPH implementation in such an environment is inferred to be at least an order of magnitude smaller (i.e. $\approx10^ {-4}$), re-ensuring that modern SPH methods are suitable to study the effect of physical viscosity in galaxy clusters.

The outer Galaxy is an environment with metallicity lower than the Solar one and, because of this, the formation and survival of molecules in star-forming regions located in the inner and outer Galaxy is expected to be different. To gain understanding on how chemistry changes throughout the Milky Way, it is crucial to observe outer Galaxy star-forming regions to constrain models adapted for lower metallicity environments. The project "chemical complexity in star-forming regions of the outer Galaxy" (CHEMOUT) aims to address this problem observing a sample of 35 high-mass star-forming cores at Galactocentric distances up to ~23 kpc with the IRAM 30m telescope in various 3mm and 2mm bands. In this work we analyse observations of methanol (CH3OH), one of the simplest complex organic molecules crucial for organic chemistry in star-forming regions, and of two chemically related species, HCO and formaldehyde (H2CO), towards 15 out of the 35 targets of the CHEMOUT sample. In fact, only targets previously detected in both HCO and H2CO, both precursors of methanol, were considered. We detected CH3OH in all 15 targets. Using a Local Thermodynamic Equilibrium approach, we derive CH3OH excitation temperatures in the range 7 - 16 K and line widths smaller than 4 km/s, consistent with emission from a cold and quiescent envelope. The CH3OH fractional abundances w.r.t. H2 range between ~0.6 x 10^{-9} and ~7.4 x 10^{-9}. These values are comparable to those found in star-forming regions in the inner and local Galaxy. Our results have important implications in the organic, and possibly pre-biotic, chemistry occurring in the outermost star-forming regions of the Galaxy, and can help setting the frontiers of the Galactic habitable zone.

While beta Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the beta Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new IRTF/SpeX spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 micron forsterite emission feature and recover a 23 micron forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies' composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to beta Pic's planetary architecture, we find that the dust population exterior to the orbits of beta Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3-5 micron dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally-processed closer to the star but more Fe-poor and primordial farther from the star.

We present the discovery and multi-wavelength characterization of SRGA J181414.6-225604, a Galactic hard X-ray transient discovered during the ongoing SRG/ART-XC sky survey. Using data from the Palomar Gattini-IR survey, we identify a spatially and temporally coincident variable infrared (IR) source, IRAS 18111-2257, and classify it as a very late-type (M7-M8), long period ($1502 \pm 24$ days) and luminous ($M_K\approx -9.9 \pm 0.2$) O-rich Mira donor star located at a distance of $\approx 14.6^{+2.9}_{-2.3}$ kpc. Combining multi-color photometric data over the last $\approx 25$ years, we show that the IR counterpart underwent a recent (starting $\approx 800$ days before the X-ray flare) enhanced mass loss (reaching $\approx 2.1 \times 10^{-5}$ M$_\odot$ yr$^{-1}$) episode resulting in an expanding dust shell obscuring the underlying star. Multi-epoch follow-up from Swift, NICER and NuSTAR reveal a $\approx 200$ day long X-ray outburst reaching a peak luminosity of $L_X \approx 2.5 \times 10^{36}$ erg s$^{-1}$, characterized by a heavily absorbed ($N_{\rm H} \approx 6\times 10^{22}$ cm$^{-2}$) X-ray spectrum consistent with an optically thick Comptonized plasma. The X-ray spectral and timing behavior suggest the presence of clumpy wind accretion together with a dense ionized nebula overabundant in silicate material surrounding the compact object. Together, we show that SRGA J181414.6-225604 is a new symbiotic X-ray binary in outburst, triggered by an intense dust formation episode of a highly evolved donor. Our results offer the first direct confirmation for the speculated connection between enhanced late-stage donor mass loss and active lifetimes of the symbiotic X-ray binaries.

The simultaneous detection of gravitational waves and light from the binary neutron star merger GW170817 led to independent measurements of distance and redshift, providing a direct estimate of the Hubble constant $H_0$ that does not rely on a cosmic distance ladder nor assumes a specific cosmological model. By using gravitational waves as ''standard sirens'', this approach holds promise to arbitrate the existing tension between the $H_0$ value inferred from the cosmic microwave background and those obtained from local measurements. However, the known degeneracy in the gravitational-wave analysis between distance and inclination of the source lead to a $H_0$ value from GW170817 that was not precise enough to resolve the existing tension. In this review, we summarize recent works exploiting the viewing-angle dependence of the electromagnetic signal, namely the associated short gamma-ray burst and kilonova, to constrain the system inclination and improve on $H_0$. We outline the key ingredients of the different methods, summarize the results obtained in the aftermath of GW170817 and discuss the possible systematics introduced by each of these methods.

We here present the results from a detailed analysis of nebular abundances of commonly observed ions in the collisional ring galaxy Cartwheel using the Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) dataset. The analysis includes 221 HII regions in the star-forming ring, in addition to 40 relatively fainter H$\alpha$ emitting regions in the spokes, disk and the inner ring. The ionic abundances of He, N, O and Fe are obtained using the direct method (DM) for 9, 20, 20, and 17 ring HII regions, respectively, where the S$^{++}$ temperature-sensitive line is detected. For the rest of the regions, including all the nebulae between the inner and the outer ring, we obtained O abundances using the strong-line method (SLM). The ring regions have a median $12+\log\rm{\frac{O}{H}}$=8.19$\pm$0.15, $\log\rm{\frac{N}{O}}=-$1.57$\pm$0.09 and $\log\rm{\frac{Fe}{O}}=-$2.24$\pm$0.09 using the DM. Within the range of O abundances seen in the Cartwheel, the N/O and Fe/O values decrease proportionately with increasing O, suggesting local enrichment of O without corresponding enrichment of primary N and Fe. The O abundances of the disk HII regions obtained using the SLM show a well-defined radial gradient. The mean O abundance of the ring HII regions is lower by $\sim$0.1 dex as compared to the extrapolation of the radial gradient. The observed trends suggest the preservation of the pre-collisional abundance gradient, displacement of most of the processed elements to the ring, as predicted by the recent simulation by Renaud et al. (2018), and post-collisional infall of metal-poor gas in the ring.

We present evidence, via a large survey of 191 new spectra along with previously-published spectra, of a divide in the 3-$\mu$m spectral properties of the low-albedo asteroid population. One group ("Sharp-types" or ST, with band centers $<$ 3 $\mu$m) has a spectral shape consistent with carbonaceous chondrite meteorites, while the other group ("not-Sharp-types" or NST, with bands centered $>$ 3 $\mu$m) is not represented in the meteorite literature but is as abundant as the STs among large objects. Both groups are present in most low-albedo asteroid taxonomic classes, and except in limited cases taxonomic classifications based on 0.5-2.5-$\mu$m data alone cannot predict whether an asteroid is ST or NST. Statistical tests show the STs and NSTs differ in average band depth, semi-major axis, and perihelion at confidence levels $\ge$98\%, while not showing significant differences in albedo. We also show that many NSTs have a 3-$\mu$m absorption band shape like Comet 67P, and likely represent an important small-body composition throughout the solar system. A simple explanation for the origin of these groups is formation on opposite sides of the ammonia snow line, with the NST group accreting H2O and NH3 and the ST group only accreting H2O, with subsequent thermal and chemical evolution resulting in the minerals seen today. Such an explanation is consistent with recent dynamical modeling of planetesimal formation and delivery, and suggests that much more outer solar system material was delivered to the main asteroid belt than would be thought based on the number of D-class asteroids found today.

We analyze two sectors of TESS photometry of the nova-like cataclysmic variable star V533 Her. We detect a periodicity consistent with the binary orbital period and estimate a revised value of 3.53709(2) hr. We also detect a strong signal near a period of 3.8 h that we associate with positive superhumps. The superhump frequency varies over the TESS observations with the fractional difference between the superhump and orbital periods, $\epsilon$, ranging between $0.055\le \epsilon \le 0.080$. The superhump amplitude is correlated with its frequency such that the amplitude increases as $\epsilon$ decreases. Positive superhumps result from an instability that generates an eccentric accretion disk and $\epsilon$ is a measure of the disk precession rate in the binary rest frame. The observed correlation implies that as the disk precession rate slows, the disk eccentricity increases.

Active galactic nuclei (AGN) feedback has a major impact onto the supermassive black-hole (SMBH) growth, the properties of the host galaxies, and their cosmic evolution. We investigate the effects of different kinetic feedback prescriptions on the observable properties of AGN and their host galaxies at $z>6$ in a suite of zoom-in cosmological simulations. We find that kinetic feedback decreases the column density of the interstellar medium (ISM) in the host galaxy by up to a factor of $\approx10$, especially when the SMBHs reach high accretion rates ($\approx10-30\,\mathrm{M_\odot\,yr^{-1}}$). In particular, kinetic feedback is required to extend the ISM size to $>1$ kpc and match the observed sizes of the gas reservoirs in $z>6$ AGN host galaxies. Moreover, it produces unobscured lines of sight along which the AGN can be detected in the rest-frame UV band with magnitudes consistent with observed values of $z>6$ AGN. The assumed geometry of the outflow plays an important role in shaping the observed properties of high-redshift AGN. We find that a biconical geometry is favored over a spherical one to reproduce the observed properties, but it overestimates the number of multiple AGN systems detectable in X-ray observations. This result suggests that simplistic BH seeding recipes widely employed in cosmological simulations produce too many X-ray detectable multiple AGN at $z=6-7$, thus soliciting the adoption of more physically motivated seeding prescriptions.

We present hydrodynamical simulations to model the accretion flow from a polar circumbinary disc onto a high eccentricity ($e=0.78$) binary star system with near unity mass ratio ($q=0.83$), as a model for binary HD 98800 BaBb. We compare the polar circumbinary disc accretion flow with the previously studied coplanar case. In the coplanar case, the circumbinary disc becomes eccentric and the accretion alternates from being dominant onto one binary member to the other. For the polar disc case involving a highly eccentric binary, we find that the circumbinary disc retains its initially low eccentricity and that the primary star accretion rate is always about the same as the secondary star accretion rate. Recent observations of the binary HD 98800 BaBb, which has a polar circumbinary disc, have been used to determine the value of the $\rm H\alpha$ flux from the brighter component. From this value, we infer that the accretion rate is much lower than for typical T Tauri stars. The eccentric orbit of the outer companion HD 98800 A increases the accretion rate onto HD 98800 B by $\sim 20$ per cent after each periastron passage. Our hydrodynamical simulations are unable to explain such a low accretion rate unless the disc viscosity parameter is very small, $\alpha < 10^{-5}$. Additional observations of this system would be useful to check on this low accretion rate.

Ionized gas probes the influence of massive stars on their environment. The Cygnus X region (d~1.5 kpc) is one of the most massive star forming complexes in our Galaxy, in which the Cyg OB2 association (age of 3-5 Myr and stellar mass $2 \times 10^{4}$ M$_{\odot}$) has a dominant influence. We observe the Cygnus X region at 148 MHz using the Low Frequency Array (LOFAR) and take into account short-spacing information during image deconvolution. Together with data from the Canadian Galactic Plane Survey, we investigate the morphology, distribution, and physical conditions of low-density ionized gas in a $4^{\circ} \times 4^{\circ}$ (100 pc $\times$ 100 pc) region at a resolution of 2' (0.9 pc). The Galactic radio emission in the region analyzed is almost entirely thermal (free-free) at 148 MHz, with emission measures of $10^3 < EM~{\rm[pc~cm^{-6}]} < 10^6$. As filamentary structure is a prominent feature of the emission, we use DisPerSE and FilChap to identify filamentary ridges and characterize their radial ($EM$) profiles. The distribution of radial profiles has a characteristic width of 4.3 pc and a power-law distribution ($\beta = -1.8 \pm 0.1$) in peak $EM$ down to our completeness limit of 4200 pc cm$^{-6}$. The electron densities of the filamentary structure range from $10 < n_e~{\rm[cm^{-3}]} < 400$ with a median value of 35 cm$^{-3}$, remarkably similar to [N II] surveys of ionized gas. Cyg OB2 may ionize at most two-thirds of the total ionized gas and the ionized gas in filaments. More than half of the filamentary structures are likely photoevaporating surfaces flowing into a surrounding diffuse (~5 cm$^{-3}$) medium. However, this is likely not the case for all ionized gas ridges. A characteristic width in the distribution of ionized gas points to the stellar winds of Cyg OB2 creating a fraction of the ionized filaments through swept-up ionized gas or dissipated turbulence.

In the field of gravitational-wave (GW) interferometers, the most severe limitation to the detection of GW signals from astrophysical sources comes from random noise, which reduces the instrument sensitivity and impacts the data quality. For transient searches, the most problematic are transient noise artifacts, known as glitches, happening at a rate around $1 \text{min}^{-1}$. As they can mimic GW signals, there is a need for better modeling and inclusion of glitches in large-scale studies, such as stress testing the searches pipelines and increasing confidence of a detection. In this work, we employ Generative Adversarial Networks (GAN) to learn the underlying distribution of blip glitches and to generate artificial populations. Taking inspiration from the field of image processing, we implement Wasserstein GAN with consistency term penalty for the generation of glitches in time domain. Furthermore, we share the trained weights through the \texttt{gengli}, a user-friendly open-source software package for fast glitch generation and provide practical examples about its usage.

Fast radio burst (FRB) source 20180916B exhibits a 16.33-day periodicity in its burst activity. It is as of yet unclear what proposed mechanism produces the activity, but polarization information is a key diagnostic. Here, we report on the polarization properties of 44 bursts from FRB 20180916B detected between 2018 December and 2021 December by CHIME/FRB, the FRB project on the Canadian Hydrogen Intensity Mapping Experiment the Canadian Hydrogen Intensity Mapping Experiment. In contrast to previous observations, we find significant variations in the Faraday rotation measure (RM) of FRB 20180916B. Over the nine month period 2021 April$-$2021 December we observe an apparent secular increase in $\rm{RM}$ of $\sim 50 \; \rm{rad\, m^{-2}}$ (a fractional change of over $40\%$) that is accompanied by a possible drift of the emitting band to lower frequencies. This interval displays very little variation in the dispersion measure ($\Delta \rm{DM}\lesssim 0.8\; \rm{pc\, cm^{-3}}$) which indicates that the observed RM evolution is likely produced from coherent changes in the Faraday-active medium's magnetic field. Burst-to-burst RM variations appear unrelated to the activity cycle phase. The degree of linear polarization of our burst sample ($\gtrsim 80\%$) is consistent with the negligible depolarization expected for this source in the 400-800 MHz bandpass of CHIME. FRB 20180916B joins other repeating FRBs in displaying substantial RM variations between bursts. This is consistent with the notion that repeater progenitors may be associated with young stellar populations by their preferential occupation of dynamic magnetized environments commonly found in supernova remnants, pulsar wind nebulae or near high mass stellar companions.

We investigate the kinemato-chemical distribution of a sample of Red Giant Branch (RGB) stars from the LAMOST survey crossed matched with Gaia DR2 proper motions, and present the time tagging for the well-known ridge structures (diagonal distributions in the $R, V_{\phi}$ plane) in the range of Galactocentric distance R = 8 to 18 kpc. We detect six long-lived ridge structures, including five ridges apparent in the radial velocity distribution and one ridge apparent in the vertical velocity. Based on an analysis of the evolution of the angular momentum distribution, we find that four ridges are relatively stationary, while another is evolving with time, which is confirmed by the difference analysis at different populations and supporting that there might be two kinds of dynamical origins with possible coupling mechanisms. Furthermore, ridge features are also vividly present in the chemical properties ([Fe/H], [$\alpha$/Fe]), in particular for the mass distribution (M). The comparison between the north and south hemispheres of the Galaxy does not show a clear asymmetry in the phase space location even though the amplitude (e.g., vertical velocity) is asymmetrical. Moreover, we find that diagonal ridge structures may affect the shape of the rotation curve, which is manifested as fluctuations and undulations on top of a smooth profile.

We trace the evolution of research on extreme solar and solar-terrestrial events from the 1859 Carrington event to the rapid development of the last twenty years. Our focus is on the largest observed/inferred/theoretical cases of sunspot groups, flares on the Sun and Sun-like stars, coronal mass ejections, solar proton events, and geomagnetic storms. The reviewed studies are based on modern observations, historical or long-term data including the auroral and cosmogenic radionuclide record, and Kepler observations of Sun-like stars. We compile a table of 100- and 1000-year events based on occurrence frequency distributions for the space weather phenomena listed above. Questions considered include the Sun-like nature of superflare stars and the existence of impactful but unpredictable solar "black swans" and extreme "dragon king" solar phenomena that can involve different physics from that operating in events which are merely large.

Globular clusters (GCs) have been at the heart of many longstanding questions in many sub-fields of astronomy and, as such, systematic identification of GCs in external galaxies has immense impacts. In this study, we take advantage of M87's well-studied GC system to implement supervised machine learning (ML) classification algorithms - specifically random forest and neural networks - to identify GCs from foreground stars and background galaxies using ground-based photometry from the Canada-France-Hawai'i Telescope (CFHT). We compare these two ML classification methods to studies of "human-selected" GCs and find that the best performing random forest model can reselect 61.2% $\pm$ 8.0% of GCs selected from HST data (ACSVCS) and the best performing neural network model reselects 95.0% $\pm$ 3.4%. When compared to human-classified GCs and contaminants selected from CFHT data - independent of our training data - the best performing random forest model can correctly classify 91.0% $\pm$ 1.2% and the best performing neural network model can correctly classify 57.3% $\pm$ 1.1%. ML methods in astronomy have been receiving much interest as Vera C. Rubin Observatory prepares for first light. The observables in this study are selected to be directly comparable to early Rubin Observatory data and the prospects for running ML algorithms on the upcoming dataset yields promising results.

NGC 300 ULX1 is a pulsating ultraluminous X-ray source (PULX) with the longest spin period of $P\simeq31.6\,\rm s$ and a high spin-up rate of $\dot P\simeq5.56\times10^{-7}\,\rm s\,s^{-1}$ that is ever seen in the confirmed PULXs. In this paper, the inferred magnetic field of NGC 300 ULX1 is $\sim3.0\times10^{14}\,\rm G$ using the recent observed parameters after its first detection of pulsations. According to the evolved simulation of the magnetic field and the spin period, it will become a recycled pulsar or a millisecond pulsar under the conditions of the companion mass and the accretion rate limitation. We suggest that NGC 300 ULX1 is an accreting magnetar accounting for its super Eddington luminosity. We also propose that there might be other accreting magnetars in the confirmed PULXs. Such PULXs will be helpful for understanding the magnetar evolution and the millisecond pulsar formation whose magnetic field is stronger than $\sim10^{9}\,\rm G$.

Over the past years, the amount of detected multi-planet systems significantly grew, an important sub-class of which being the compact configurations. A precise knowledge of them is crucial to understand the conditions with which planetary systems form and evolve. However, observations often leave these systems with large uncertainties, notably on the orbital eccentricities. This is especially prominent for systems with low-mass planets detected with Radial Velocities (RV), the amount of which is more and more important in the exoplanet population. It is becoming a common approach to refine these parameters with the help of orbital stability arguments. Such dynamical techniques can be computationally expensive. In this work we use an alternative procedure faster by orders of magnitude than classical N-body integration approaches. We couple a reliable exploration of the parameter space with the precision of the Numerical Analysis of Fundamental Frequencies (NAFF, Laskar 1990) fast chaos indicator. We also propose a general procedure to calibrate the NAFF indicator on any multi-planet system without additional computational cost. This calibration strategy is illustrated on HD 45364, in addition to yet-unpublished measurements obtained with the HARPS and CORALIE high-resolution spectrographs. We validate the calibration approach on HD 202696. We test the performances of this stability-driven approach on two systems with different architectures. First we study HD 37124, a 3-planet system composed of planets in the Jovian regime. Then, we analyse HD 215152, a compact system of four low-mass planets. We demonstrate the potential of the NAFF stability-driven approach to refine the orbital parameters and planetary masses. We stress the importance of undertaking systematic global dynamical analyses on every new multi-planet system discovered.

The backreaction term ${\cal Q}_\CD$ and the averaged spatial Ricci scalar $\average{\CR}$ in the spatially averaged inhomogeneous Universe can be used to combine into effective perfect fluid energy density $\varrho_{\rm eff}^{\CD}$ and pressure $p_{\rm eff}^{\CD}$ that can be regarded as new effective sources for the backreaction effects. In order to model the realistic evolution of backreaction, we adopt the Chevallier-Polarski-Linder(CPL) parameterizations of the equation of state(EoS) of the effective perfect fluid. To deal with observations in the backreaction context, in this paper, we employ two metrics to describe the the late time Universe, one of them is the standard Friedmann-Lema\^{\i}tre-Robertson-Walker(FLRW) metric, and the other is a template metric with an evolving curvature parameter introduced by Larena et. al. in \cite{larena2009testing}. We also fit the CPL backreaction model using type Ia supernova(SN Ia) data and observational Hubble parameter data(OHD) with these two metrics, and find out that parameter tensions between two different data sets are larger when the backreaction model is equipped with the template metric, therefore we conclude that the prescription of the geometrical instantaneous spatially-constant curvature $\kappa_{\CD}$ needs to be modified.

The concept of sphere of influence of a planet is useful in both the context of impact monitoring of asteroids with the Earth and of the design of interplanetary trajectories for spacecrafts. After reviewing the classical results, we propose a new definition for this sphere that depends on the position and velocity of the small body for given values of the Jacobi constant $C$. Here we compare the orbit of the small body obtained in the framework of the circular restricted three-body problem, with orbits obtained by patching two-body solutions. Our definition is based on an optimisation process, minimizing a suitable target function with respect to the assumed radius of the sphere of influence. For different values of $C$ we represent the results in the planar case: we show the values of the selected radius as a function of two angles characterising the orbit. In this case, we also produce a database of radii of the sphere of influence for several initial conditions, allowing an interpolation.

Aims. The present study aims at providing a deeper insight into the power and limitation of an unsupervised classification algorithm (called Fisher-EM) on spectra of galaxies. This algorithm uses a Gaussian mixture in a discriminative latent subspace. To this end, we investigate the capacity of this algorithm to segregate the physical parameters used to generate mock spectra and the influence of the noise on the classification. Methods. With the code CIGALE and different values for nine input parameters characterising the stellar population, we have simulated a sample of 11 475 optical spectra of galaxies containing 496 monochromatic fluxes. The statistical model and the optimum number of clusters is given in Fisher-EM by the integrated completed likelihood (ICL) criterion. We repeated the analyses several times to assess the robustness of the results. Results. Two distinct classifications can be distinguished in the case of the noiseless spectra. The one above 13 clusters disappears when noise is added, while the classification with 12 clusters is very robust against noise down to a signal to noise ratio (SNR) of 3. At SNR=1, the optimum is 5 clusters, but the classification is still compatible with the previous one. The distribution of the parameters used for the simulation shows an excellent discrimination between classes. A higher dispersion both in the spectra within each class and in the parameter distribution, leads us to conclude that despite a much higher ICL, the classification with more than 13 clusters in the noiseless case is not physically relevant. Conclusions. This study yields two conclusions valid at least for the Fisher-EM algorithm. Firstly, the unsupervised classification of spectra of galaxies is both reliable and robust to noise. Secondly, such analyses are able to extract the useful physical information contained in the spectra and to build highly meaningful classifications. In an epoch of data-driven astrophysics, it is important to trust unsupervised machine learning approaches that do not require training samples which are unavoidably biased.

The strong equivalence principle is a cornerstone of general relativity, tested with exquisite accuracy in the Solar system. However, tests in the strong-field regime require a compact object. Currently, PSR J0337+1715 is the unique millisecond pulsar found in a triple stellar system, orbiting two white dwarfs within an area comparable to the orbit of the Earth. This configuration offers the opportunity for a dramatic improvement over previous tests, provided that accurate and regular timing of the pulsar can be achieved. This also requires the development of a new timing model solving numerically the relativistic three-body problem with great accuracy. We report on the analysis of the high-quality dataset gathered on PSR J0337+1715 by the Nan{\c c}ay radiotelescope over the past 8 years. In particular, I will show how we could obtain the most stringent limit to-date on a potential violation of the strong equivalent principle in the strong field regime. I will also introduce preliminary resuts showing that the presence of a small planet in the system may explain a tiny residual signal so far unaccounted for, which if confirmed would make this system exceptionally rich.

Originally proposed as a cosmological probe of the large-scale structure, line intensity mapping (LIM) also offers a unique window into the astrophysics of galaxy evolution. Adding to the astrophysical explorations of LIM technique that have traditionally focused on small, non-linear scales, we present a novel method to study the global star formation law using forthcoming data from large-scale baryonic acoustic oscillation (BAO) intensity mapping. Using the amplitude of the percent-level but scale-dependent bias induced by baryon fraction fluctuations on BAO scales, we show that combining auto- and cross-correlation power spectra of two (or more) LIM signals allows to probe the star formation law power index $\mathcal{N}$. We examine the prospect for mapping H$\alpha$ and [OIII] lines across all scales, especially where imprints of the baryon fraction deviation exist, with space missions like SPHEREx. We show that although SPHEREx may only marginally probe $\mathcal{N}$ by accessing a modest number of large-scale modes in its 200 deg$^2$ deep survey, future infrared all-sky surveys reaching a comparable depth with an improved spectral resolution ($R \gtrsim 400$) are likely to constrain $\mathcal{N}$ to a precision of 10$-$30%, sufficient for distinguishing models with varying feedback assumptions, out to $z\sim4$ using BAO intensity mapping. Leveraging this effect, large, cosmic-variance-limited LIM surveys in the far future can scrutinize the physical connection between galaxy evolution and the large-scale cosmological environment, while performing stringent tests of the standard cosmological model.

K2-139 b is a warm Jupiter with an orbital period of 28.4 d, but only three transits of this system have previously been observed, in the long-cadence mode of K2, limiting the precision with which the orbital period can be determined, and future transits predicted. We report photometric observations of four transits of K2-139 b with ESA's CHaracterising ExOPlanet Satellite (CHEOPS), conducted with the goal of measuring the orbital obliquity via spot-crossing events. We jointly fit these CHEOPS data alongside the three previously-published transits from the K2 mission, considerably increasing the precision of the ephemeris of K2-139 b. The transit times for this system can now be predicted for the next decade with a $1 \sigma$ precision less than 10 minutes, compared to over one hour previously, allowing the efficient scheduling of observations with Ariel. We detect no significant deviation from a linear ephemeris, allowing us to exclude the presence of a massive outer planet orbiting with a period less than 150 d, or a brown dwarf with a period less than one year. We also determine the scaled semi-major axis, the impact parameter, and the stellar limb-darkening with improved precision. This is driven by the shorter cadence of the CHEOPS observations compared to that of K2, and validates the sub-exposure technique used for analysing long-cadence photometry. Finally, we note that the stellar spot configuration has changed from the epoch of the K2 observations; unlike the K2 transits, we detect no evidence of spot-crossing events in the CHEOPS data.

In-orbit background is an unavoidable feature of all space-borne X-ray detectors, and arises both from cosmic sources (diffuse or point-like) and from the interaction of the detectors themselves with the space environment (primary or secondary cosmic rays, geomagnetically trapped particles, activation of spacecraft structures). In this chapter the main background sources are discussed, with their principal effects on the various detector types, and simulation and mitigation strategies are described.

Carbonaceous asteroids, including Ryugu and Bennu, which have been explored by the Hayabusa2 and OSIRIS-REx missions, were probably important carriers of volatiles to the inner Solar System. However, Ryugu has experienced significant volatile loss, possibly from hypervelocity impact heating. Here we present impact experiments at speeds comparable to those expected in the main asteroid belt (3.7 km s-1 and 5.8 km s-1) and with analogue target materials. We find that loss of volatiles from the target material due to impacts is not sufficient to account for the observed volatile depletion of Ryugu. We propose that mutual collisions in the main asteroid belt are unlikely to be solely responsible for the loss of volatiles from Ryugu or its parent body. Instead, we suggest that additional processes, for example associated with the diversity in mechanisms and timing of their formation, are necessary to account for the variable volatile contents of carbonaceous asteroids.

We present the results of a kinematic analysis of red giants and subgiants whose centroids are in the plane of our Galaxy. For this, the positions, parallaxes, proper motions, and radial velocities of these stars from the $Gaia$ EDR3 catalog were used. We applied two approaches to obtain kinematic parameters. The first approach -- solving the equations of the Ogorodnikov--Milne model with respect to 12 kinematic parameters -- is generally accepted, but has a number of disadvantages. The second approach developed by us is to find the components of galactocentric centroid's velocity and their partial derivatives with respect to coordinates directly from differential equations for the stellar velocity field. To calculate the kinematic parameters by the methods mentioned above, same stellar samples were used. From these samples spherical regions with a radius of 1 kpc were selected, the centers of which were located strictly in the Galactic mid-plane at the nodes of the coordinate grid ($x_{gal}$, $y_{gal}$) of a rectangular Galactocentric coordinate system with step 100 pc. The region of the Galaxy under study occupies the coordinate interval $115^\circ < \theta < 245^\circ$, 0 kpc$ < R < $16 kpc, -1 kpc$ < z < $1 kpc. We show the behavior of local kinematic parameters as well as global parameters such as the circular velocity of stars as a function of galactocentric coordinates. For the first time, the components of centroids' spatial velocities and all 9 their kinematic parameters as well as their behavior as a function of galactic coordinates have been derived. The behavior of the $\partial V_R/\partial \theta$ and $\partial V_\theta/\partial \theta$ parameters as a function of galactic coordinates has been derived for the first time.

Shock metamorphism of minerals in meteorites provides insights into the ancient Solar System. Calcite is an abundant aqueous alteration mineral in carbonaceous chondrites. Return samples from the asteroids Ryugu and Bennu are expected to contain calcite-group minerals. Although shock metamorphism in silicates has been well studied, such data for aqueous alteration minerals are limited. Here, we investigated the shock effects in calcite with marble using impact experiments at the Planetary Exploration Research Center of Chiba Institute of Technology. We produced decaying compressive pulses with a smaller projectile than the target. A metal container facilitates recovery of a sample that retains its pre-impact stratigraphy. We estimated the peak pressure distributions in the samples with the iSALE shock physics code. The capability of this method to produce shocked grains that have experienced different degrees of metamorphism from a single experiment is an advantage over conventional uniaxial shock recovery experiments. The shocked samples were investigated by polarizing microscopy and X-ray diffraction analysis. We found that more than half of calcite grains exhibit undulatory extinction when peak pressure exceeds 3 GPa. This shock pressure is one order of magnitude higher than the Hugoniot elastic limit (HEL) of marble, but it is close to the HEL of a calcite crystal, suggesting that the undulatory extinction records dislocation-induced plastic deformation in the crystal. Finally, we propose a strategy to re-construct the maximum depth of calcite grains in a meteorite parent body, if shocked calcite grains are identified in chondrites and/or return samples from Ryugu and Bennu.

We present Pandora, a new software to model, detect, and characterize transits of extrasolar planets with moons in stellar photometric time series. Pandora uses an analytical description of the transit light curve for both the planet and the moon in front of a star with atmospheric limb darkening and it covers all cases of mutual planet-moon eclipses during transit. The orbital motion of the star-planet-moon system is computed with a high accuracy as a nested Keplerian problem. We have optimized Pandora for computational speed to make it suitable for large-scale exomoon searches in the new era of space-based high-accuracy surveys. We demonstrate the usability of Pandora for exomoon searches by first simulating a light curve with four transits of a hypothetical Jupiter with a giant Neptune-sized exomoon in a one-year orbit around a Sun-like star. The 10 min cadence of the data matches that of the upcoming PLATO mission and the noise of 100 parts per million is dominated by photon noise, assuming a photometrically quiet, $m_V = 11$ Sun-like star for practicality. We recovered the simulated system parameters with the UltraNest Bayesian inference package. The run-time of this search is about five hours on a standard computer. Pandora is the first photodynamical open-source exomoon transit detection algorithm, implemented fully in the Python programming language and available for the community to join the search for exomoons.

Abridged. The bright-rimmed cloud IC1396N hosts CO, H$_2$, and Herbig-Haro outflows powered by millimetre compact sources. We aim to characterise the kinematics and physical conditions of the H$_2$ emission features spread over IC1396N, which appear as chains of knots with a jet-like morphology, tracing different H$_2$ outflows, and to obtain further information about (and an identification of) the driving sources. Low-resolution, long-slit near-infrared spectra were acquired with NICS at the TNG, using grisms KB (R~1200), HK and JH (R~500). Several slit pointings and PA were used throughout IC1396N to sample a number of the H$_2$ knots previously detected in deep H$_2$ 2.12 $\mu$m images. The knots exhibit rich ro-vibrational spectra of H$_2$, consistent with shock-excited excitation, from which radial velocities and relevant physical conditions of the IC1396N H$_2$ outflows were derived. These also allowed estimating extinction ranges towards several features. [FeII] emission was only detected towards a few knots, which also display unusually large H$_2$ 1-0 S(3)/S(1) flux ratios. The obtained radial velocities confirm that most of the outflows are close to the plane of the sky. Nearby knots in the same chain often display different radial velocities, both blue-shifted and red-shifted, which we interpret as due to ubiquitous jet precession in the driving sources or the development of oblique shocks. One of the chains (strand A) appears as a set of features trailing a leading bow-shock structure consistent with the results of 3-D magneto-hydrodynamical models. Either side of the leading bow-shock (A15) exhibits a different radial velocity, whose possible explanations are discussed in the paper. Our data cannot confirm whether strands A and B have both been originated by the intermediate mass young stellar object BIMA 2.

Switchbacks -- abrupt reversals of the magnetic field within the solar wind -- have been ubiquitously observed by Parker Solar Probe (PSP). Their origin, whether from processes near the solar surface or within the solar wind itself, remains under debate, and likely has key implications for solar wind heating and acceleration. Here, using three-dimensional expanding box simulations, we examine the properties of switchbacks arising from the evolution of outwards-propagating Alfv\'en waves in the expanding solar wind in detail. Our goal is to provide testable predictions that can be used to differentiate between properties arising from solar surface processes and those from the in-situ evolution of Alfv\'en waves in switchback observations by PSP. We show how the inclusion of the Parker spiral causes magnetic field deflections within switchbacks to become asymmetric, preferentially deflecting in the plane of the Parker spiral and rotating in one direction towards the radial component of the mean field. The direction of the peak of the magnetic field distribution is also shown to be different from the mean field direction due to its highly skewed nature. Compressible properties of switchbacks are also explored, with magnetic-field-strength and density fluctuations being either correlated or anticorrelated depending on the value of $\beta$, agreeing with predictions from theory. We also measure dropouts in magnetic-field strength and density spikes at the boundaries of these synthetic switchbacks, both of which have been observed by PSP. The agreement of these properties with observations provide further support for the Alfv\'en wave model of switchbacks.

Black hole-like objects with mass greater than $10 M_{\odot}$, as discovered by gravitational antennas, can produce long time-scale (several years) gravitational microlensing effects. Considered separately, previous microlensing surveys were insensitive to such events because of their limited duration of 6-7 years. We combined light curves from the EROS-2 and MACHO surveys to the Large Magellanic Cloud (LMC) to create a joint database for 14.1 million stars, covering a total duration of 10.6 years, with fluxes measured through 4 wide passbands. We searched for multi-year microlensing events in this catalog of extended light curves, complemented by 24.1 million light curves observed by only one of the surveys. Our analysis, combined with previous analysis from EROS, shows that compact objects with mass between $10^{-7}$ and $200 M_{\odot}$ can not constitute more than $\sim 20\%$ of the total mass of a standard halo (at $95\%$ CL). We also exclude that $\sim 50\%$ of the halo is made of Black Holes (BH) lighter than $1000 M_{\odot}$.

Switchbacks -- rapid, large deflections of the solar wind's magnetic field -- have generated significant interest as possible signatures of the key mechanisms that heat the corona and accelerate the solar wind. In this context, an important task for theories of switchback formation and evolution is to understand their observable distinguishing features, allowing them to be assessed in detail using spacecraft data. Here, we work towards this goal by studying the influence of the Parker spiral on the evolution of Alfv\'enic switchbacks in an expanding plasma. Using simple analytic arguments based on the physics of one-dimensional spherically polarized (constant-field-magnitude) Alfv\'en waves, we find that, by controlling the wave's obliquity, a Parker spiral strongly impacts switchback properties. Surprisingly, the Parker spiral can significantly enhance switchback formation, despite normalized wave amplitudes growing more slowly in its presence. In addition, switchbacks become strongly asymmetric: large switchbacks preferentially involve magnetic-field rotation in the plane of the Parker spiral (tangential deflections) rather than perpendicular (normal) rotations, and such deflections are strongly "tangentially skewed," meaning switchbacks always involve field rotations in the same direction (towards the positive-radial direction for an outwards mean field). In a companion paper, we show that these properties also occur in turbulent 3-D fields with switchbacks, with various caveats. These results demonstrate that substantial care is needed in assuming that specific features of switchbacks can be used to infer properties of the low corona; asymmetries and nontrivial correlations can develop as switchbacks propagate due to the interplay between expansion and spherically polarized, divergence-free magnetic fields.

This paper provides a new analysis of ROSAT observations of the Coma cluster, to determine the amount of soft X--ray radiation in excess of the contribution from the hot intra--cluster medium. The re--analysis is made possible by a high--resolution study of the hot intra--cluster medium with the XMM-Newton and Planck telescopes out to the cluster's virial radius. The analysis confirms the original findings of a strong excess of soft X--ray radiation, which is likely to be of thermal origin. We find quantitative agreement between the detected soft excess and the physical characteristics of warm--hot intergalactic medium (WHIM) filaments seen in hydrodynamical simulations. We conclude that the most plausible explanation for the soft excess is the presence of $\sim 10$~Mpc--long filaments at $\log T(K)\simeq 6$, with a baryon overdensity $\sim 300$, converging towards the Coma cluster. This interpretation therefore provides support for the identification of the missing low--redshift baryons with WHIM filaments, as predicted by numerical simulations.

We derive astroparticle constraints in different dark matter scenarios alternative to cold dark matter (CDM): thermal relic warm dark matter, WDM; fuzzy dark matter, $\psi$DM; self-interacting dark matter, SIDM; sterile neutrino dark matter, $\nu$DM. Our framework is based on updated determinations of the high-redshift UV luminosity functions for primordial galaxies out to redshift $z\sim 10$, on redshift-dependent halo mass functions in the above DM scenarios from numerical simulations, and on robust constraints on the reionization history of the Universe from recent astrophysical and cosmological datasets. First, we build up an empirical model of cosmic reionization characterized by two parameters, namely the escape fraction $f_{\rm esc}$ of ionizing photons from primordial galaxies, and the limiting UV magnitude $M_{\rm UV}^{\rm lim}$ down to which the extrapolated UV luminosity functions are steeply increasing. Second, we perform standard abundance matching of the UV luminosity function and the halo mass function, obtaining a relationship between UV luminosity and halo mass whose shape depends on an astroparticle quantity $X$ specific of each DM scenario (e.g., WDM particle mass); we exploit such a relation to introduce in the analysis a constraint from primordial galaxy formation, in terms of the threshold halo mass above which primordial galaxies can efficiently form stars. Third, we implement a sequential updating Bayesian MCMC technique to perform joint inference on the three parameters $f_{\rm esc}$, $M_{\rm UV}^{\rm lim}$, $X$, and to compare the outcomes of different DM scenarios on the reionization history. Finally, we highlight the relevance of our astroparticle estimates in predicting the behavior of the high-redshift UV luminosity function at faint, yet unexplored magnitudes, that may be tested with the advent of the James Webb Space Telescope.

I examine recent fitting of luminous supernovae (LSNe) with extra energy sources of magnetar and helium burning and find that in about half of these LSNe the fitting parameters have some problems. In some LSNe the total energy of these two energy sources is larger than the kinetic energy of the ejecta that the fitting yields. In some others LSNe the total energy of the delayed neutrino explosion mechanism and these two extra sources combined is smaller than the kinetic energy that the fitting yields. These difficulties suggest that, like earlier claims that jets power superluminous supernovae (SLSNe), jets also power the less luminous LSNe. A magnetar might also supply energy. However, in most cases jets supply more energy than the magnetar, during the explosion and possibly at late times. I strengthen an earlier claim that jets launched at magnetar birth cannot be ignored. I explain the trend of maximum rise time for a given luminosity of hydrogen deficient core collapse supernovae (CCSNe), in particular LSNe and SLSNe, with a toy model of jets that are active for a long time after explosion.

The origins of the GeV gamma-rays from nearby radio galaxies are unknown. Hadronic emission from magnetically arrested disks (MADs) around central black holes (BHs) is proposed as a possible scenario. Particles are accelerated in the MAD by magnetic reconnection and stochastic turbulence acceleration. We pick out the fifteen brightest radio galaxies in the GeV band from the Fermi 4LAC-DR2 catalog and apply the MAD model. We find that we can explain the data in the GeV bands by the MAD model if the accretion rate is lower than 0.1% of the Eddington rate. For a higher accretion rate, GeV gamma-rays are absorbed by two-photon interaction due to copious low-energy photons. If we assume another proposed prescription of the electron heating rate by magnetic reconnection, the MAD model fails to reproduce the GeV data for the majority of our sample. This indicates that the electron heating rate is crucial. We also apply the MAD model to Sgr A* and find that GeV gamma-rays observed at the Galactic center do not come from the MAD of Sgr A*. We estimate the cosmic ray intensity from Sgr A*, but it is too low to explain the high-energy cosmic ray intensity on Earth.

Studies on small-scale jets' formation, propagation, evolution, and role, such as type I and II spicules, mottles, and fibrils in the lower solar atmosphere's energetic balance, have progressed tremendously thanks to the combination of detailed observations and sophisticated mathematical modelling. This review provides a survey of the current understanding of jets, their formation in the solar lower atmosphere, and their evolution from observational, numerical, and theoretical perspectives. First, we review some results to describe the jet properties, acquired numerically, analytically and through high-spatial and temporal resolution observations. Further on, we discuss the role of hydrodynamic and magnetohydrodynamic instabilities, namely Rayleigh-Taylor and Kelvin-Helmholtz instabilities, in jet evolution and their role in the energy transport through the solar atmosphere in fully and partially ionised plasmas. Finally, we discuss several mechanisms of magnetohydrodynamic wave generation, propagation, and energy transport in the context of small-scale solar jets in detail. This review identifies several gaps in the understanding of small-scale solar jets and some misalignments between the observational studies and knowledge acquired through theoretical studies and numerical modelling. It is to be expected that these gaps will be closed with the advent of high-resolution observational instruments, such as Daniel K. Inouye Solar Telescope, Solar Orbiter, Parker Solar Probe, and Solar CubeSats for Linked Imaging Spectropolarimetry, combined with further theoretical and computational developments.

High energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry and mass loss. The active ~22 Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity to quantify the effects of stellar XUV irradiation on planetary atmospheres as a function of both age and orbital separation. In this paper we present over 5 hours of Far-UV (FUV) observations of AU Mic taken with the Cosmic Origins Spectrograph (COS; 1070-1360 Angstrom) on the Hubble Space Telescope (HST). We provide an itemization of $176$ emission features in the HST/COS FUV spectrum and quantify the flux contributions from formation temperatures ranging from $10^4-10^7$ K. We detect 13 flares in the FUV white-light curve with energies ranging from $10^{29} - 10^{31}$ ergs. The majority of the energy in each of these flares is released from the transition region between the chromosphere and the corona. There is a 100x increase in flux at continuum wavelengths $\lambda < 1100$ Angstrom, in each flare which may be caused by thermal Bremsstrahlung emission. We calculate that the baseline atmospheric mass-loss rate for AU Mic b, is $\sim 10^8$ g s$^{-1}$, although this rate can be as high as $\sim 10^{14}$ g s$^{-1}$ during flares with $L_\textrm{flare} \simeq 10^{33}$ erg s$^{-1}$. Finally, we model the transmission spectra for AU Mic b and c with a new panchromatic spectrum of AU Mic and motivate future JWST observations of these planets.

The existence of $10^9\ {\rm M_\odot}$ supermassive black holes (SMBHs) within the first billion years of the universe remains a puzzle in our conventional understanding of black hole formation and growth. The so-called direct-collapse scenario suggests that the formation of supermassive stars (SMSs) can yield the massive seeds of early SMBHs. This scenario leads to an overly massive BH galaxy (OMBG), whose nuclear black hole's mass is comparable to or even greater than the surrounding stellar mass: a $10^4-10^6~{\rm M_\odot}$ seed black hole is born in a dark matter halo with a mass as low as $10^7-10^8~{\rm M_\odot}$. The black hole to stellar mass ratio is $M_{\rm bh}/M_* \gg 10^{-3}$, well in excess of the typical values at lower redshift. We investigate how long these newborn BHs remain outliers in the $M_{\rm bh}-M_{*}$ relation, by exploring the subsequent evolution of two OMBGs previously identified in the Renaissance simulations. We find that both OMBGs have $M_{\rm bh}/M_* > 1$ during their entire life, from their birth at $z\approx 15$ until they merge with much more massive haloes at $z\approx 8$. We find that the OMBGs are spatially resolvable from their more massive, $10^{11}~{\rm M_\odot}$, neighboring haloes until their mergers are complete at $z\approx 8$. This affords a window for future observations with JWST and sensitive X-ray telescopes to diagnose the direct-collapse scenario, by detecting similar OMBGs and establishing their uniquely high black hole-to-stellar mass ratio.

With the rapid development of asteroseismology thanks to space-based photometry missions such as CoRoT, Kepler, TESS, and in the future, PLATO, and the use of inversion techniques, quasi-model-independent constraints on the stellar properties can be extracted from a given stellar oscillation spectrum. In this context, inversions based on frequency separation ratios, that are less sensitive to surface effects, appear as a promising technique to constrain the properties of stellar convective cores. We developed an inversion based on frequency separation ratios with the goal of damping the surface effects of the oscillation frequencies. Using this new inversion, we defined a new indicator to constrain the boundary mixing properties of convective cores in solar-like oscillators. We verified our inversion technique by conducting tests in a controlled environment, where the stellar mass and radius are known exactly, and conducted an extensive hare and hounds exercise. The inversion is not affected by surface effects. With the construction of an extensive set of models, favoured and forbidden regions can be highlighted in the parameter space. If the ratios are well fitted, the inversion is unsurprisingly not providing additional information. The indicator coupled with the inversion based on frequency separation ratios seems promising at probing the properties of convective cores, especially for F-type stars exhibiting solar-like oscillations.

The coalescence of two neutron stars is accompanied by the emission of gravitational waves, and can also feature electromagnetic counterparts powered by mass ejecta and the formation of a relativistic jet after the merger. Since neutron stars can feature strong magnetic fields, the non-trivial interaction of the neutron star magnetospheres might fuel potentially powerful electromagnetic transients prior to merger. A key process powering those precursor transients is relativistic reconnection in strong current sheets formed between the two stars. In this work, we provide a detailed analysis of how the twisting of the common magnetosphere of the binary leads to an emission of electromagnetic flares, akin to those produced in the solar corona. By means of relativistic force-free electrodynamics simulations, we clarify the role of different magnetic field topologies in the process. We conclude that flaring will always occur for suitable magnetic field alignments, unless one of the neutron stars has a magnetic field significantly weaker than the other.

Context. Phased Array Feeds (PAFs) are multi element receivers in the focal plane of a telescope that make it possible to form simultaneously multiple beams on the sky by combining the complex gains of the individual antenna elements. Recently the Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF receivers and carried out several observing programs including two imaging surveys and a time domain survey. The Apertif imaging surveys use a configuration, where 40 partially overlapping compound beams (CBs) are simultaneously formed on the sky and arranged in an approximately rectangular shape. Aims. This manuscript aims to characterise the response of the 40 Apertif CBs to create frequency-resolved, I, XX and YY polarization empirical beam shapes. The measured CB maps can be used for image deconvolution, primary beam correction and mosaicing of Apertif imaging data. Methods. We use drift scan measurements to measure the response of each of the 40 CBs of Apertif. We derive beam maps for all individual beams in I, XX and YY polarisation in 10 or 18 frequency bins over the same bandwidth as the Apertif imaging surveys. We sample the main lobe of the beams and the side lobes up to a radius of 0.6 degrees from the beam centres. In addition, we derive beam maps for each individual WSRT dish as well. Results. We present the frequency and time dependence of the beam shapes and sizes. We compare the compound beam shapes derived with the drift scan method to beam shapes derived with an independent method using a Gaussian Process Regression comparison between the Apertif continuum images and the NRAO VLA Sky Survey (NVSS) catalogue. We find a good agreement between the beam shapes derived with the two independent methods.

Sub-relativistic materials launched during the merger of binary compact objects and the core-collapse of massive stars acquire velocity structures when expanding in a stratified environment. The remnant (either a spinning magnetized neutron star (NS) or a central black hole) from the compact-object or core-collapse could additionally inject energy into the afterglow via spin-down luminosity or/and by accreting fall-back material, producing a refreshed shock, modifying the dynamics, and leading to rich radiation signatures at distinct timescales and energy bands with contrasting intensities. We derive the synchrotron light curves evolving in a stratified environment when a power-law velocity distribution parametrizes the energy of the shock, and the remnant continuously injects energy into the blastwave. As the most relevant case, we describe the latest multi-wavelength afterglow observations ($\gtrsim 900$ days) of the GW170817/GRB 170817A event via a synchrotron afterglow model with energy injection of a sub-relativistic material. The features of the remnant and the synchrotron emission of the sub-relativistic material are consistent with a spinning magnetized NS and the faster "blue" kilonova afterglow, respectively. Using the multi-band observations of some short-bursts with evidence of kilonova, we provide constraints on the expected afterglow emission.

Asteroids, planets, stars in some open clusters, as well as molecular clouds appear to possess a preferential spin-orbit alignment, pointing to shared processes that tie their rotation at birth to larger parent structures. We present a new mechanism that describes how collections of particles or 'clouds' gain a prograde rotational component when they collapse or contract while subject to an external, central force. The effect is geometric in origin, as relative shear on curved orbits moves their shared center-of-mass slightly inward and toward the external potential during a collapse, exchanging orbital angular momentum into aligned (prograde) rotation. We perform illustrative analytical and N-body calculations to show that this process of prograde spin-up proceeds quadratically in time ($\delta L_\mathrm{rot} \propto t^2$) until the collapse nears completion. The total rotational gain increases with the size of the cloud prior to its collapse: $\delta L_\mathrm{rot}/L_\mathrm{H} \propto (R_\mathrm{cl}/R_\mathrm{H})^5$, and typically with distance to the source of the potential ($L_\mathrm{H}\propto r_0)$. For clouds that form at the interface of shear and self-gravity ($R_\mathrm{cl} \sim R_\mathrm{H}$), prograde spin-up means that even setups with large initial retrograde rotation collapse to form prograde-spinning objects. Being a geometric effect, prograde spin-up persists around any central potential that triggers shear, even those where the shear is strongly retrograde. We highlight an application to the Solar System, where prograde spin-up can explain the frequency of binary objects in the Kuiper belt with prograde rotation.

At least one in five of all planetary nebulae are the product of a common envelope (CE) interaction, where the companion in-spirals into the envelope of an asymptotic giant branch (AGB) star ejecting the nebula and leaving behind a compact binary. In this work we carry out 3D, smoothed particle hydrodynamics simulations of the CE interaction between a 1.7 $M_{\odot}$ thermally pulsating AGB star and a 0.6$M_{\odot}$ companion. The interaction takes place when the giant is on the expanding phase of the seventh thermal pulse and has a radius of 250 $R_{\odot}$. The post-CE orbital separations varies between 20-31 $R_{\odot}$, with the inclusion of recombination energy resulting in wider separations. Based on the observed short in-spiral timescales, we suggest that thermal pulses can trigger CEs, extending the ability of AGB stars to capture companions into CEs, leading to the prediction of a larger population of post-CE binaries. Simulations that include a tabulated equation of state unbind a great deal more gas, likely unbinding the entire envelope on short timescales. The shape of the CE after the in-spiral is more spherical for AGB than RGB stars, and even more so if recombination energy is included. We expect that the planetary nebula formed from this CE will have different features from those observed by Zuo et al. Finally, we make some considerations on the value of the CE efficiency implied by these simulations and discuss the discrepancy between the small post-CE separations typically observed in PN compared to the relatively wider values derived here.

Despite being mostly secluded, dark sector particles may feebly interact with photons via a small mass-dimension 4 millicharge, a mass-dimension 5 magnetic and electric dipole moment, or a mass-dimension 6 anapole moment and charge radius. If sufficiently light, the LHC may produce an intense and collimated beam of these particles in the far forward direction. We study the prospects of searching for such dark sector particles with electromagnetic form factors via their electron scattering signature in the Forward Liquid Argon Experiment (FLArE) detector at the Forward Physics Facility (FPF). We find that FLArE can provide new probes of sub-GeV dark particles with dipole moments and strong sensitivities for millicharged particles in the 100 MeV to 100 GeV region. This complements other search strategies using scintillation signatures or dark matter direct detection and allows for probing strongly interacting dark matter motivated by the EDGES anomaly. Along with the FORMOSA detector, this leads to a very diverse and leading experimental program in the search for millicharged particles in the FPF.

The transport of energetic charged particles (e.g., cosmic rays) in turbulent magnetic fields is usually characterized in terms of the diffusion parallel and perpendicular to a large-scale (or mean) magnetic field. The nonlinear guiding center theory (NLGC) has been a prominent perpendicular diffusion theory. A recent version of this theory, based on random ballistic spreading of magnetic field lines and a backtracking correction (RBD/BC), has shown good agreement with test particle simulations for a two-component magnetic turbulence model. The aim of the present study is to test the generality of the improved theory by applying it to the noisy reduced magnetohydrodynamic (NRMHD) turbulence model, determining perpendicular diffusion coefficients that are compared with those from the field line random walk (FLRW) and unified nonlinear (UNLT) theories and our test particle simulations. The synthetic NRMHD turbulence model creates special conditions for energetic particle transport, with no magnetic fluctuations at higher parallel wavenumbers so there is no resonant parallel scattering if the particle Larmor radius $R_{\rm L}$ is even slightly smaller than the minimum resonant scale. This leads to non-monotonic variation in the parallel mean free path $\lambda_\parallel$ with $R_{\rm L}$. Among the theories considered, only RBD/BC matches simulations within a factor of two over the range of parameters considered. This accuracy is obtained even though the theory depends on $\lambda_\parallel$ and has no explicit dependence on $R_{\rm L}$. In addition, the UNLT theory often provides accurate results and even the FLRW limit provides a very simple and reasonable approximation in many cases.

We propose that the recent observations reported by the different Pulsar Timing Array (PTA) collaborations (i.e.~IPTA, EPTA, PPTA, and NANOGrav) of a common process over several pulsars could correspond to a stochastic gravitational wave background (SGWB) produced by turbulent sources in the early universe, in particular due to the magnetohydrodynamic (MHD) turbulence induced by primordial magnetic fields. I discuss recent results of numerical simulations of MHD turbulence and present an analytical template of the SGWB validated by the simulations. We use this template to constrain the magnetic field parameters using the results reported by the PTA collaborations. Finally, we compare the constraints on the primordial magnetic fields obtained from PTA with those from blazar signals observed by Fermi Large Area Telescope (LAT), from ultra high-energy cosmic rays, and from the cosmic microwave background. We show that a non-helical primordial magnetic field produced at the scale of the quantum chromodynamics phase transition is compatible with such constraints and it could additionally provide with a magnetic field at recombination that would help to alleviate the Hubble tension.

Nuclear weak rates in stellar environments are obtained by shell-model calculations including Gamow-Teller (GT) and spin-dipole transitions, and applied to nuclear weak processes in stars. The important roles of accurate weak rates for the study of astrophysical processes are pointed out. The weak rates in $sd$-shell are used to study the evolution of ONeMg cores in stars with 8-10 M$_{\odot}$. Cooling of the core by nuclear Urca processes, and the heating by double e-captures on $^{20}$Ne are studied. Especially, the e-capture rates for a second-forbidden transition in $^{20}$Ne are evaluated with the multipole expansion method of Walecka and Behrens-B$\ddot{\mbox{u}}$hring, and the final fate of the cores, core-collapse or thermonuclear explosion, are discussed. The weak rates in $pf$-shell are applied to nucleosynthesis of iron-group elements in Type Ia supernovae. The over-production problem of neutron-rich iron isotopes compared with the solar abundances is now reduced to be within a factor of two. The weak rates for nuclear Urca pair with $A$=31 in the island of inversion are evaluated with the effective interaction obtained by the extended Kuo-Krenciglowa method. The transition strengths and e-capture rates in $^{78}$Ni, important for core-collapse processes, are evaluated with the $pf$-$sdg$ shell, and compared with those obtained by the random-phase-approximation and an effective rate formula. $\beta$-decay rates of $N$ =126 isotones are evaluated with both the GT and first-forbidden transitions. The half-lives are found to be shorter than those obtained by standard models. Neutrino-nucleus reaction cross sections on $^{13}$C, $^{16}$O and $^{40}$Ar are obtained with new shell-model Hamiltonians. Implications on nucleosynthesis, neutrino detection, neutrino oscillations and neutrino mass hierarchy are discussed.

Barrow proposed that the area law of the entropy associated with a horizon might receive a "fractal correction" due to quantum gravitational effects -- in place of $S\propto A$, we have instead $S\propto A^{1+\delta/2}$, where $0\leqslant \delta \leqslant 1$ measures the deviation from the standard area law ($\delta=0$). Based on black hole thermodynamics, we argue that the Barrow entropy should run (i.e., energy scale dependent), which is reasonable given that quantum gravitational corrections are expected to be important only in high energy regime. When applied to the Friedmann equation, we demonstrate the possibility that such a running Barrow entropy index could give rise to a dynamical effective dark energy, which is asymptotically positive and vanishing, but negative at the Big Bang. Such a sign switching dark energy could help to alleviate the Hubble tension. Other cosmological implications are discussed.

We consider the search for gamma-rays produced by the annihilation or decay of low-mass dark matter which couples to quarks. In this scenario, most of the photons are produced from the decays of $\pi^0$ or $\eta$ mesons. These decays produce distinctly different photon signatures due to the difference in meson mass. We assess the ability of the future MeV-range observatories to constrain the hadronic final states produced by dark matter annihilation or decay from the shape of the resulting photon spectrum. We then comment on how this information can be used to determine properties of the dark matter coupling to the quark current, based on the approximate symmetries of low-energy QCD.

This work explains how the presence of a Type-IV singularity (a mild singularity) can influence the dynamics of a bouncing universe. In particular, we examine bounce cosmology that appears with a Type-IV singularity in the context of a ghost free Gauss-Bonnet theory of gravity. Depending on the time of occurrence of the Type-IV singularity, three different cases may arise -- when the singularity occurs before the bounce or after the bounce or at the instant of the bounce respectively. However in all of these cases, we find that in the case when the singularity ``globally'' affects the spacetime, the scalar power spectrum becomes red tilted and the tensor-to-scalar ratio is too large to be consistent with the observational data. Based on these findings, we investigate a different bouncing scenario which also appears with a Type-IV singularity, and the singularity affects the spacetime ``locally'' around the time when it occurs. As a result, and unlike to the previous scenario, the perturbation modes in the second bouncing scenario are likely to generate far away from the bounce in the deep contracting phase. This finally results to the simultaneous compatibility of the observable quantities with the Planck data, and ensures the viability of the bounce model where the Type-IV singularity has local effects on the spacetime around the time of the singularity.

In the environment of a hot plasma, as achieved in stellar explosions, capture and photodisintegration reactions proceeding on excited states in the nucleus can considerably contribute to the astrophysical reaction rate. Such reaction rates including the excited-state contribution are obtained from theoretical calculations as the direct experimental determination of these astrophysical rates is currently unfeasible. In the present study, ($\gamma$,p) and ($\gamma$,$\alpha$) reactions in the mass and energy range relevant to the astrophysical $p$ process are considered and the feasibility of measuring them with the ELISSA detector system at the future Variable Energy $\gamma$-ray (VEGA) facility at ELI-NP is investigated. The simulation results reveal that, for the ($\gamma$,p) reaction on twelve targets of $^{29}$Si, $^{56}$Fe, $^{74}$Se, $^{84}$Sr, $^{91}$Zr, $^{96,98}$Ru, $^{102}$Pd, $^{106}$Cd, and $^{115, 117, 119}$Sn, and the ($\gamma$,$\alpha$) reaction on five targets of $^{50}$V, $^{87}$Sr, $^{123,125}$Te, and $^{149}$Sm, the yields of the reaction channels with the transitions to the excited states in the residual nucleus are relevant and even dominant. It is further found that for each considered reaction, the total yields of the charged-particle $X$ may be dominantly contributed from one, two or three ($\gamma$,$X_{i}$) channels within a specific, narrow energy range of the incident $\gamma$-beam. Furthermore, the energy spectra of the ($\gamma$,$X_{i}$) channels with $0\leq i\leq 10$ are simulated for each considered reaction, with the incident $\gamma$-beam energies in the respective energy range as derived before. It becomes evident that measurements of the photon-induced reactions with charged-particle emissions considered in this work are feasible with the VEGA+ELISSA system and will provide knowledge useful for nuclear astrophysics.

We use 2n streams, where n is an integer, of axially symmetric radiation to solve the equation of transfer for a layered medium. This is a generalization of Schuster's classic 2 stream model. As is well known, using only the first 2n Legendre polynomials to describe the angular dependence of radiation reduces the equation of transfer to a first order differential equation in a space of 2n dimensions. It is convenient to characterize the radiation as 2n stream intensities propagating at zenith angles having cosines called the 2n Gauss-Legendre cosines defined to be solutions of equating the Legendre polynomial of degree 2n to zero. We show how to efficiently and accurately solve the equation of transfer with vector and matrix methods analogous to those used to solve Schroedinger's equation of quantum mechanics. To model strong forward scattering, like that of visible light by Earth's clouds, we have introduced a new family of phase functions. These give the maximum possible forward scattering p(p+1) for a phase function constructed from the first 2p Legendre polynomials, where p is an integer. We show illustrative examples of radiative-transfer phenomena calculated with this new method.