Papers for Tuesday, Dec 20 2022

An important task within the broader goal of Space Situational Awareness (SSA) is to observe changes in the orbits of satellites, where the data spans thousands of objects over long time scales (decades). The Two-Line Element (TLE) data provided by the North American Aerospace Defense Command is the most comprehensive and widely-available dataset cataloguing the orbits of satellites. This makes it a highly-attractive data source on which to perform this observation. However, when attempting to infer changes in satellite behaviour from TLE data, there are a number of potential pitfalls. These mostly relate to specific features of the TLE data which are not always clearly documented in the data sources or popular software packages for manipulating them. These quirks produce a particularly hazardous data type for researchers from adjacent disciplines (such as anomaly detection or machine learning). We highlight these features of TLE data and the resulting pitfalls in order to save future researchers from being trapped. A seperate, significant, issue is that existing contributions to manoeuvre detection from TLE data evaluate their algorithms on different satellites, making comparison between these methods difficult. Moreover, the ground-truth in these datasets is often poor quality, sometimes being based on subjective human assessment. We therefore release and describe in-depth an open, curated, benchmark dataset containing TLE data for 15 satellites alongside high-quality ground-truth manoeuvre timestamps.

We develop a comprehensive theoretical model for Lyman-alpha emission, from the scale of individual Lyman-alpha emitters (LAEs) to Lyman-alpha halos (LAHs), Lyman-alpha blobs (LABs), and Lyman-alpha filaments (LAFs) of the diffuse cosmic web itself. To do so, we post-process the high-resolution TNG50 cosmological magnetohydrodynamical simulation with a Monte Carlo radiative transfer method to capture the resonant scattering process of Lyman-alpha photons. We build an emission model incorporating recombinations and collisions in diffuse gas, including radiative effects from nearby AGN, as well as emission sourced by stellar populations. Our treatment includes a physically motivated dust model, which we empirically calibrate to the observed LAE luminosity function. We then focus on the observability, and physical origin, of the $z=2$ Lyman-alpha cosmic web, studying the dominant emission mechanisms and spatial origins. We find that diffuse Lyman-alpha filaments are, in fact, illuminated by photons which originate, not from the intergalactic medium itself, but from within galaxies and their gaseous halos. In our model, this emission is primarily sourced by intermediate mass halos ($10^{10} - 10^{11}\,$M$_{\odot}$), principally due to collisional excitations in their circumgalactic media as well as central, young stellar populations. Observationally, we make predictions for the abundance, area, linear size, and embedded halo/emitter populations within filaments. Adopting an isophotal surface brightness threshold of $10^{-20}\,$erg$\,$s$^{-1}\,$cm$^{-2}\,$arcsec$^{-2}$, we predict a volume abundance of Lyman-alpha filaments of ${\sim}10^{-3}$ cMpc$^{-3}\,$ for lengths above $400\,$pkpc. Given sufficiently large survey footprints, detection of the Lyman-alpha cosmic web is within reach of modern integral field spectrographs, including MUSE, VIRUS, and KCWI.

High spatial resolution observations of CO isotopologue line emission in protoplanetary disks at mid-inclinations (${\approx}$30-75{\deg}) allow us to characterize the gas structure in detail, including radial and vertical substructures, emission surface heights and their dependencies on source characteristics, and disk temperature profiles. By combining observations of a suite of CO isotopologues, we can map the 2D (r, z) disk structure from the disk upper atmosphere, as traced by CO, to near the midplane, as probed by less abundant isotopologues. Here, we present high angular resolution (${\lesssim}$0."1 to ${\approx}$0."2; ${\approx}$15-30 au) observations of CO, $^{13}$CO, and C$^{18}$O in either or both J=2-1 and J=3-2 lines in the transition disks around DM Tau, Sz 91, LkCa 15, and HD 34282. We derived line emission surfaces in CO for all disks and in $^{13}$CO for the DM Tau and LkCa 15 disks. With these observations, we do not resolve the vertical structure of C$^{18}$O in any disk, which is instead consistent with C$^{18}$O emission originating from the midplane. Both the J=2-1 and J=3-2 lines show similar heights. Using the derived emission surfaces, we computed radial and vertical gas temperature distributions for each disk, including empirical temperature models for the DM Tau and LkCa 15 disks. After combining our sample with literature sources, we find that $^{13}$CO line emitting heights are also tentatively linked with source characteristics, e.g., stellar host mass, gas temperature, disk size, and show steeper trends than seen in CO emission surfaces.

The putative ubiquity of massive black holes (MBH) at the center of galaxies, and the hierarchical progress of structure formation along the cosmic history, together necessarily imply the existence of a large population of cosmic MBH binaries. Such systems are understood to be the loudest sources of gravitational waves at mHz frequencies, the regime that will be probed by the next Laser Interferometer Space Antenna (LISA). It has been proposed that the rate at which MBHs pair and then bind to form binaries is critically dependent upon the feedback exerted by the MBHs on the surrounding gaseous environment. Using the publicly available code GIZMO, we perform a suite of simulations aimed at studying the dynamics of a MBH pair embedded in a gaseous disk on 100 pc scale. By means of dedicated modules, we follow the dynamics of MBHs in the presence of different spin-dependent radiative feedback models, and compare the results to a benchmark case with no feedback at all. Our main finding is that feedback causes the secondary MBH to shrink its orbit at a reduced pace, when compared to models where feedback is absent. Moreover, such slower inspiral occurs on eccentric orbits, as feedback has the net effect of hampering the circularization process. Though idealized in many aspects, our study highlights and quantifies the importance of including spin-dependent feedback recipes in hydrodynamic simulations of MBH pairs, and ultimately in assessing the cosmological coalescence rate of such systems in view of their detection through gravitational waves.

We present the first spatially resolved measurements of galaxy properties in the JWST ERO SMACS0723 field. We perform a comprehensive analysis of five $5<z<9$ galaxies with spectroscopic redshifts from NIRSpec observations. We perform spatially resolved SED fitting with BAGPIPES, using NIRCam imaging in 6 bands spanning the wavelength range $0.8-5\mu$m. We produce maps of the inferred physical properties by using a novel approach in the study of high redshift galaxies. This method allows us to study the internal structure and assembly of the first generations of galaxies. We find clear gradients both in the empirical colour maps, as well as in most of the estimated physical parameters. We find regions of considerably different specific star formation rates across each galaxy, which points to very bursty star-formation happening on small scales, not galaxy-wide. The integrated light is dominated by these bursty regions, which exhibit strong line emission detected by NIRSpec and also inferred from the broad-band NIRCam images, with the equivalent width of [OIII]+H$\beta$ reaching up to $\sim3000-4000$\AA rest-frame in these regions. Studying these galaxies in an integrated approach yields extremely young inferred ages of the stellar population ($<$10 Myr), which outshine older stellar populations that are only distinguishable in the spatially resolved maps. This leads to inferring $\sim0.5-1$ dex lower stellar masses by using aperture photometry, when compared to resolved analyses. Such systematics would have strong implications in the shape and evolution of the stellar mass function at these early times, particularly while samples are limited to small numbers of the brightest candidates. Furthermore, the evolved stellar populations revealed in this study imply an extended process of early galaxy formation that could otherwise be hidden behind the light of the most recently formed stars.

Through adaptive optics (AO) imaging with the SOUL+LUCI instrument at the Large Binocular Telescope we were able to resolve, for the first time, individual stars in the gas-rich galaxy DDO68 C. This system was already suggested to be interacting with the extremely metal poor dwarf DDO68, but its nature has remained elusive so far because of the presence of a bright foreground star close to its line of sight, that hampers a detailed study of its stellar population and distance. In our study, we turned this interloper star into an opportunity to have a deeper insight on DDO68 C, using it as a guide star for the AO correction. Although the new data do not allow for a direct distance measurement through the red giant branch tip method, the combined analysis of the resolved-star color-magnitude diagram, of archival GALEX FUV and NUV photometry, and of H$\alpha$ data provides a self-consistent picture in which DDO68 C is at the same $\sim$13 Mpc distance as its candidate companion DDO68. These results indicate that DDO68 is a unique case of a low mass dwarf, less massive than the Magellanic Clouds, interacting with three satellites (DDO68 C and two previously confirmed accreting systems), providing useful constraints on cosmological models and a potential explanation for its anomalous extremely low metallicity.

Direct D-H exchange in radicals is investigated in a quasi-uniform flow employing chirped pulse mm-wave spectroscopy. Inspired by the H-atom catalyzed isomerization of C3H2 reported in our previous study, D atom reactions with the propargyl (C3H3) radical and its photoproducts were investigated. We observed very efficient D atom enrichment in the photoproducts through an analogous process of D addition/H elimination to C3H2 isomers occurring at 40K or below. Cyclic C3HD is the only deuterated isomer observed, consistent with the expected addition/elimination yielding the lowest energy product. The other expected addition/elimination product, deuterated propargyl, is not directly detected, although its presence is inferred by the observations in the latter part of the flow. There, in the high-density region of the flow, we observed both isotopomers of singly deuterated propyne attributed to stabilization of the H + C3H2D or D + C3H3 adducts. The implications of these observations for the deuterium fractionation of hydrocarbon radicals in astrochemical environments is discussed with the support of a monodeuterated chemical kinetic model.

In this paper, we consider the chain of resonances in the Kepler-80 system and evaluate the impact that the additional member of the resonant chain discovered by Shallue & Vanderburg (2018) has on the dynamics of the system and the physical parameters that can be recovered by a fit to the transit timing variations (TTVs). Ultimately, we calculate the mass of Kepler-80 g to be $0.8 \pm 0.3 M_\oplus$ when assuming all planets have zero eccentricity, and $1.0 \pm 0.3 \ M_{\oplus}$ when relaxing that assumption. We show that the outer five planets are in successive three-body mean-motion resonances (MMRs). We assess the current state of two-body MMRs in the system and find that the planets do not appear to be in two-body MMRs. We find that while the existence of the additional member of the resonant chain does not significantly alter the character of the Kepler-80 three-body MMRs, it can alter the physical parameters derived from the TTVs, suggesting caution should be applied when drawing conclusions from TTVs for potentially incomplete systems. We also compare our results to those of MacDonald et al. (2021), who perform a similar analysis on the same system with a different method. Although the results of this work and MacDonald et al. (2021) show that different fit methodologies and underlying assumptions can result in different measured orbital parameters, the most secure conclusion is that which holds true across all lines of analysis: Kepler-80 contains a chain of planets in three-body MMRs but not in two-body MMRs.

We present a multiwavelength study of stellar flares on primarily G-type stars using overlapping time domain surveys in the near ultraviolet (NUV) and optical regimes. The NUV (GALEX) and optical (Kepler) wavelength domains are important for understanding energy fractionations in stellar flares, and for constraining the associated incident radiation on a planetary atmosphere. We follow up on the NUV flare detections presented in Brasseur et al. 2019, using coincident Kepler long (1557 flares) and short (2 flares) cadence light curves. We find no evidence of optical flares at these times, and place limits on the flare energy ratio between the two wavebands. We find that the energy ratio is correlated with GALEX band energy, and extends over a range of about three orders of magnitude in the ratio of the upper limit of Kepler band flare energy to NUV flare energy at the same time for each flare. The two flares with Kepler short cadence data indicate that the true Kepler band energy may be much lower than the long cadence based upper limit. A similar trend appears for the bulk flare energy properties of non-simultaneously observed flares on the same stars. We provide updated models to describe the flare spectral energy distribution from the NUV through the optical including continua and emission lines to improve upon blackbody-only models. The spread of observed energy ratios is much larger than encompassed by these models and suggests new physics is at work. These results call for better understanding of NUV flare physics and provide a cautionary tale about using only optical flare measurements to infer the UV irradiation of close-in planets.

The High Latitude Spectroscopic Survey (HLSS) is the reference baseline spectroscopic survey for NASA's Nancy Grace Roman space telescope, measuring redshifts of $\sim 10$M H$\alpha$ emission line galaxies over a $2000$ deg$^2$ footprint at $z=1-2$. In this work, we use a realistic Roman galaxy mock catalogue to explore optimal modeling of the measured power spectrum. We consider two methods for modelling the redshift-space distortions (one with the canonical Kaiser squashing term $M_A$, and another with a window function on $\beta$ that selects out the coherent radial infall pairwise velocities $M_B$), two models for the nonlinear impact of baryons that smears the BAO signal (one with a fixed ratio between the smearing scales in the perpendicular $k_*^\perp$ and parallel $k_*^\parallel$ and another where these smearing scales are kept as a free parameters, P$_{dw}(k|k_*)$ and P$_{dw}(k|\Sigma_\perp,\Sigma_\parallel)$), and two analytical nonlinear growth corrections (one employing the halo model $F_{HM}$ and another formulated from simulated galaxy clustering of a semi-analytical model $F_{SAM}$). We find that the best model is P$_{dw}(k|\Sigma_\perp,\Sigma_\parallel)*M_B$, which leads to unbiased measurements of cosmological parameters. We expect the tools that we have developed to be useful in probing dark energy and testing gravity using Roman in an accurate and robust manner.

Expansion of wind-blown bubbles or HII regions lead to formation of shocks in the interstellar medium, which compress surrounding gas into dense layers. We made spatially and velocity-resolved observations of the RCW~120 PDR and nearby molecular gas with CO(6-5) and 13CO(6-5) lines and distinguished a bright CO-emitting layer, which we related with the dense shocked molecular gas moving away from the ionizing star due to expansion of HII region. Simulating gas density and temperature, as well as brightness of several CO and C+ emission lines from the PDR, we found reasonable agreement with the observed values. Analysing gas kinematics, we revealed the large-scale shocked PDR and also several dense environments of embedded protostars and outflows. We observe the shocked layer as the most regular structure in the CO(6-5) map and in the velocity space, when the gas around YSOs is dispersed by the outflows.

We test the merger-induced dual active galactic nuclei (dAGN) paradigm using a sample of 35 radio galaxy pairs from the SDSS Stripe 82 field. Using Keck optical spectroscopy, we confirm 21 pairs have consistent redshifts, constituting kinematic pairs; the remaining 14 pairs are line-of-sight projections. We classify the optical spectral signatures via emission line ratios, equivalent widths, and excess of radio power above star-formation predicted outputs. We find 6 galaxies are classified as LINERs and 7 are AGN/starburst composites. Most of the LINERs are retired galaxies, while the composites likely have AGN contribution. All of the kinematic pairs exhibit radio power more than 10$\times$ above the level expected from just star-formation, suggestive of a radio AGN contribution. We also analyze high-resolution (0.3") imaging at 6 GHz from the NSF's Karl G. Jansky Very Large Array for 17 of the kinematic pairs. We find 6 pairs (2 new, 4 previously known) host two separate radio cores, confirming their status as dAGNs. The remaining 11 pairs contain single AGNs, with most exhibiting prominent jets/lobes overlapping their companion. Our final census indicates a dAGN duty cycle slightly higher than predictions of purely stochastic fueling, although a larger sample (potentially culled from VLASS) is needed to fully address the dAGN fraction. We conclude that while dAGNs in the Stripe 82 field are rare, the merger process plays some role in their triggering and it facilitates low to moderate levels of accretion.

The Baryonic Tully-Fisher Relation (BTFR) has applications in galaxy evolution as a testbed for the galaxy-halo connection and in observational cosmology as a redshift-independent secondary distance indicator. We use the 31,000+ galaxy ALFALFA sample -- which provides redshifts, velocity widths, and HI content for a large number of gas-bearing galaxies in the local universe -- to fit and test an extensive local universe BTFR. This BTFR is designed to be as inclusive of ALFALFA and comparable samples as possible. Velocity widths measured via an automated method and $M_{b}$ proxies extracted from survey data can be uniformly and efficiently measured for other samples, giving this analysis broad applicability. We also investigate the role of sample demographics in determining the best-fit relation. We find that the best-fit relations are changed significantly by changes to the sample mass range and to second order, mass sampling, gas fraction, different stellar mass and velocity width measurements. We use a subset of ALFALFA with demographics that reflect the full sample to measure a robust BTFR slope of $3.30\pm0.06$. We apply this relation and estimate source distances, finding general agreement with flow-model distances as well as average distance uncertainties of $\sim0.17$ dex for the full ALFALFA sample. We demonstrate the utility of these distance estimates by applying them to a sample of sources in the Virgo vicinity, recovering signatures of infall consistent with previous work.

Crystal lattice structure is present in stellar compact objects, such as white dwarf stars and in the crust of neutron stars. These structures can be described by a body-centered cubic crystal, which is formed by ions due to Coulombian interactions in presence of stellar electron plasma. The electron-electron interaction is currently described in the electrodynamics context by a quantum homogeneous plasma. Particularly, we investigate the changes in the medium Equations of State (EoS), improving results presented in the literature. The main purpose of this work is to analyse the distribution of electrons in the stellar medium considering their interaction with ions in the crystal lattice. The electric field produced by the presence of crystal lattice is obtained using linear response theory in the context of finite temperature field theory. The screening and distribution of electrons are corrected by an arbitrary number of neighbor ions, which is a novelty in the literature and significantly impact the EoS. Numerical results are presented for a completely degenerate electron plasma and for different species of ions that make up the lattice. These EoS can be applied to determine the structure of the aforementioned compact stellar objects.

This work presents an analytical perturbation method to study the dynamics of an orbiting object subject to the term $J_2$ from the gravitational potential of the main celestial body. This is done using a power series expansion in the perturbation constant $J_2$ on all the variables of the system, and a time regularization based on the argument of latitude of the orbit. This enables the generation of analytic solutions without the need to control the perturbed frequency of the system. The resultant approach allows to approximate the dynamics of the system in osculating elements for orbits at any eccentricity, and to obtain the approximate analytical transformation from osculating to mean elements in these orbits. This includes near circular, elliptic, parabolic and hyperbolic orbits at any inclination. Several examples of application are presented to show the accuracy of the perturbation approach and their related transformations.

The optical morphology of galaxies is strongly related to galactic environment, with the fraction of early-type galaxies increasing with local galaxy density. In this work we present the first analysis of the galaxy morphology-density relation in a cosmological hydrodynamical simulation. We use a convolutional neural network, trained on observed galaxies, to perform visual morphological classification of galaxies with stellar masses $M_\ast > 10^{10} \, \mathrm{M}_\odot$ in the EAGLE simulation into elliptical, lenticular and late-type (spiral/irregular) classes. We find that EAGLE reproduces both the galaxy morphology-density and morphology-mass relations. Using the simulations, we find three key processes that result in the observed morphology-density relation: (i) transformation of disc-dominated galaxies from late-type (spiral) to lenticular galaxies through gas stripping in high-density environments, (ii) formation of lenticular galaxies by merger-induced black hole feedback in low-density environments, and (iii) an increasing fraction of high-mass galaxies, which are more often elliptical galaxies, at higher galactic densities.

The neutral hydrogen (HI) intensity mapping (IM) survey is regarded as a promising approach for cosmic large-scale structure (LSS) studies. A major issue for the HI IM survey is to remove the bright foreground contamination. A key to successfully remove the bright foreground is to well control or eliminate the instrumental effects. In this work, we consider the instrumental effect of polarization leakage and use the U-Net approach, a deep learning-based foreground removal technique, to eliminate the polarization leakage effect.In this method, the principal component analysis (PCA) foreground subtraction is used as a preprocessing step for the U-Net foreground subtraction. Our results show that the additional U-Net processing could either remove the foreground residual after the conservative PCA subtraction or compensate for the signal loss caused by the aggressive PCA preprocessing. Finally, we test the robustness of the U-Net foreground subtraction technique and show that it is still reliable in the case of existing constraint error on HI fluctuation amplitude.

Io's intense volcanic activity results in one of the most colorful surfaces in the solar system. Ultraviolet and visible-wavelength observations of Io are critical to uncovering the chemistry behind its volcanic hues. Here, we present global, spatially resolved UV-visible spectra of Io from the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST), which bridge the gap between previous highly resolved imagery and disk-integrated spectroscopy, to provide an unprecedented combination of spatial and spectral detail. We use this comprehensive dataset to investigate spectral endmembers, map observed spectral features associated with SO$_2$ frost and other sulfur species, and explore possible compositions in the context of Io surface processes. In agreement with past observations, our results are consistent with extensive equatorial SO$_2$ frost deposits that are stable over multi-decade timescales, widespread sulfur-rich plains surrounding the SO$_2$ deposits, and the enrichment of Pele's pyroclastic ring and the high-latitude regions in metastable short-chain sulfur allotropes.

A shock wave propagating perpendicularly to an ambient magnetic field accelerates particles considerably faster than in the parallel propagation regime. However, the perpendicular acceleration stops after the shock overruns a circular particle orbit. At the same time, it may continue in flows resulting from supersonically colliding plasmas bound by a pair of perpendicular shocks. Although the double-shock acceleration mechanism, which we consider in detail, is not advantageous for thermal particles, pre-energized particles may avoid the premature end of acceleration. We argue that if their gyroradius exceeds the dominant turbulence scale between the shocks, these particles might traverse the intershock space repeatedly before being carried away by the shocked plasma. Moreover, entering the space between the shocks of similar velocities $u_{1}\approx u_{2}\approx c$, such particles start bouncing between the shocks at a fixed angle $\approx 35.3^{\circ}$ to the shock surface. Their drift along the shock fronts is slow, $V_{d}\sim\left|u_{2}-u_{1}\right|\ll c$, so that it will take $N\sim Lc/\left|u_{2}-u_{1}\right|d\gg1$ bounces before they escape the accelerator (here, $L$ is the size of the shocks and $d$ is the gap between them). Since these particles more than ten-fold their energy per cycle (two consecutive bounces), we invoke other possible losses that can limit the acceleration. They include drifts due to rippled shocks, the nonparallel mutual orientation of the upstream magnetic fields, and radiative losses.

The orientation of the jet axis to the line of sight of the observer plays a major role in explaining the phenomena observed from blazars and radio galaxies. In the gamma-ray band, only a handful of radio galaxies have been identified, all being located in the nearby Universe (z<0.5). Here we report the identification of 4FGL J1435.5+2021, associated with TXS 1433+205, as a Fanaroff-Riley type II (FR II) radio galaxy at a considerably higher redshift of z=0.748, thereby making it the most distant gamma-ray detected radio galaxy known as of now. The Very Large Array Sky Survey data at 3 GHz resolves the source morphology into a bright core, a jet and two hotspots, with a total end-to-end projected length between lobe extremities of ~170 kpc. The optical and radio properties of this enigmatic object suggest it to be a high-excitation FR II radio galaxy. The multi-wavelength behaviour of TXS 1433+205 is found to be similar to other gamma-ray detected FR II sources but is at the high luminosity end. We suggest that the ongoing and upcoming high-resolution radio surveys will lead to the identification of many more high-redshift radio galaxies in the gamma-ray sky, thus allowing comprehensive studies of misaligned relativistic jets.

Coronal loop oscillations are common phenomena in the solar corona, which are often classified as decaying and decayless oscillations. Using the high-resolution observation measured by the Extreme Ultraviolet Imager (EUI) onboard the Solar Orbiter, we statistical investigate small-scale transverse oscillations with short periods (<200 s) of coronal loops in an active region, i.e., NOAA 12965. A total of 111 coronal loops are identified in EUI 174 A images, and they all reveal transverse oscillations without any significant decaying, regarding as decayless oscillations. Oscillatory periods are measured from about 11 s to 185 s, with a median period of 40 s. Thus, they are also termed as short-period oscillations. The corresponding loop lengths are measured from about 10.5 Mm to 30.2 Mm, and a strong dependence of oscillatory periods on loop lengths is established, indicating that the short-period oscillations are standing kink-mode waves in nature. Based on the coronal seismology, kink speeds are measured to about 330-1910 km/s, and magnetic field strengths in coronal loops are estimated to about 4.1-25.2 G, while the energy flux carried by decayless kink oscillations lies in the range from roughly 7 W m^(-2) to 9220 W m^(-2). Our estimations suggest that the wave energy carried by short-period decayless kink oscillations can not support the coronal heating in the active region.

Recent exoplanet surveys revealed that for solar-type stars, close-in Super-Earths are ubiquitous and many of them are in multi-planet systems. These systems are more compact than the Solar System's terrestrial planets. However, there have been few theoretical studies on the formation of such planets around low-mass stars. In the standard model, the final stage of terrestrial planet formation is the giant impact stage, where protoplanets gravitationally scatter and collide with each other and then evolve into a stable planetary system. We investigate the effect of the stellar mass on the architecture of planetary systems formed by giant impacts. We perform {\it N}-body simulations around stars with masses of 0.1--2 times the solar mass. Using the isolation mass of protoplanets, we distribute the initial protoplanets in 0.05--0.15 au from the central star and follow the evolution for 200 million orbital periods of the innermost protoplanet. We find that for a given protoplanet system, the mass of planets increases as the stellar mass decreases, while the number of planets decreases. The eccentricity and inclination of orbits and the orbital separation of adjacent planets increase with decreasing the stellar mass. This is because as the stellar mass decreases, the relative strength of planetary scattering becomes more effective. We also discuss the properties of planets formed in the habitable zone using the minimum-mass extrasolar nebula model.

X-ray flares are generally believed to be produced by the reactivation of the central engine, and may have the same energy dissipation mechanism as the prompt emission of gamma-ray bursts (GRBs). X-ray flares can therefore provide important clues to understanding the nature of the central engines of GRBs. In this work, we study for the first time the physical connection between differential size and return distributions of X-ray flares of GRBs with known redshifts. We find that the differential distributions of duration, energy, and waiting time can be well fitted by a power-law function. In particular, the distributions for the differences of durations, energies, and waiting times at different times (i.e., the return distributions) well follow a $q$-Gaussian form. The $q$ values in the $q$-Gaussian distributions keep nearly steady for different temporal interval scales, implying a scale-invariant structure of GRB X-ray flares. Moreover, we verify that the $q$ parameters are related to the power-law indices $\alpha$ of the differential size distributions, characterized as $q=(\alpha+2)/\alpha$. These statistical features can be well explained within the physical framework of a self-organizing criticality system.

We often find spectral signatures of chromospheric cold plasma ejections accompanied by flares in a wide range of spatial scales in the solar and stellar atmospheres. However, the relationship between physical quantities (such as mass, kinetic energy, and velocity) of cold ejecta and flare energy has not been investigated in a unified manner for the entire range of flare energies to date. This study analyzed the spectra of cold plasma ejections associated with small-scale flares and solar flares (energy $10^{25}-10^{29}\,\mathrm{erg}$) to supply smaller energy samples. We performed H$\alpha$ imaging spectroscopy observation by the Solar Dynamics Doppler Imager on the Solar Magnetic Activity Research Telescope (SMART/SDDI). We determined the physical quantities of the ejecta by cloud model fitting to the H$\alpha$ spectrum. We determined flare energy by differential emission measure analysis using Atmospheric Imaging Assembly onboard Solar Dynamics Observatory (SDO/AIA) for small-scale flares and by estimating the bolometric energy for large-scale flares. As a result, we found that the ejection mass $M$ and the total flare energy $E_{\mathrm{tot}}$ follow a relation of $M\propto E_{\mathrm{tot}}^{2/3}$. We show that the scaling law derived from a simple physical model explains the solar and stellar observations with a coronal magnetic field strength as a free parameter. We also found that the kinetic energy and velocity of the ejecta correlate with the flare energy. These results suggest a common mechanism driven by magnetic fields to cause cold plasma ejections with flares on the Sun and stars.

Accurate knowledge of the morphology of halos and its evolution are key constraints on the galaxy formation model as well as a determinant parameter of the strong-lensing phenomenon. Using the cosmological hydrodynamic simulation, the Evolution and Assembly of GaLaxies and their Environments (EAGLE), we aim to provide a comprehensive analysis of the evolution of the morphology of galaxy halos and of their mass distributions with a focus on the snapshot at redshift $z=0.5$. We developed an iterative strategy involving a principal component analysis (PCA) to investigate the properties of the EAGLE halos and the differences in alignment between the various components. The mass distributions of the dark-matter (DM), gas, and star halos are characterised by a half-mass radius, a concentration parameter and (projected) axis ratios. We present statistics of the shape parameters of 336\,540 halos from the EAGLE RefL0025N0376 simulation and describe their evolution from redshift $z=15$ to $z=0$. We measured the three-dimensional and two-dimensional projected shape parameters for the DM, the gas, and the star components as well as for all particles. At $z=0.5$, the minor axis of gas aligns with the minor axis of DM for massive halos ($M>10^{12}$ M$_\odot$), but this alignment is poorer for less massive halos. The DM halos axis ratios $b/a$ and $c/a$ have median values of $0.82 \pm 0.11$ and $0.64 \pm 0.12$, respectively. The sphericity of gas in halos w/ and w/o stars appears to be negatively correlated to the total mass, while the sphericity of DM is insensitive to it. The measured projected axis ratios, $b_p/a_p$, of star halos at $z=0.5$ have a median value of $0.80 \pm 0.07$, which is in good agreement with ground-based and space-based measurements within 1 $\sigma$. For DM halos, we measure a value of $0.85 \pm 0.06$.

The existence of neutron stars was not confirmed until the discovery of pulsars at radio wavelengths in late 1960s. Since then, these highly compact and magnetized objects have been observed across the electromagnetic spectrum, and widely studied. However, lots of the studies related to neutron stars require precise determination of their distances and proper motions. This thesis focuses on high-precision astrometry of neutron stars using the data from the Very Long Baseline Array (VLBA) and the Gaia space telescope operating, respectively, at radio and optical frequencies. The neutron stars studied in the thesis include the extremely magnetized magnetars, the fast-spinning millisecond pulsars, the gravitational-wave-emitting double neutron stars and neutron star X-ray binaries. As a major accomplishment, this thesis presents the novel analysis and the results of the MSPSRpi project -- the largest astrometric survey of millisecond pulsars, then point out the abundant implications of the astrometric results. Additionally, the release of the astrometric results is bound to facilitate the detection of an ultra-low-frequency gravitational-wave background. Methodologically, this thesis applied advanced VLBI techniques to pulsar astrometry using the original data reduction pipeline psrvlbireduce, which leads to the first two significant magnetar parallaxes, and paves the way for studying magnetar formation channels with their velocity distribution. The astrometry Bayesian inference package sterne, developed during the PhD program, serves as a versatile and powerful tool for the inference of astrometric parameters.

We report the detection of several quasi-periodicities around 0.6--2.5 days in the optical emission of the blazar S4 0954+658. The source was observed by the Transiting Exoplanet Survey Satellite (TESS) in six sectors and it showed these features in all but one of them, with a QPO of 1.52 days apparently present in portions of four of them. We used the generalized Lomb-Scargle periodogram method to search for significant signals and we confirmed them using a weighted wavelet transform for time-frequency domain analyses. We discuss several possible explanations for these rapid quasi-periodic variations and suggest that an origin in the innermost part of the accretion disk is most likely. Within this framework, we provide estimates for the mass of the black hole at the core of this blazar.

The ubiquity of sulfur ions within the Jovian magnetosphere has led to suggestions that the implantation of these ions into the surface of Europa may lead to the formation of SO2. However, previous studies on the implantation of sulfur ions into H2O ice (the dominant species on the Europan surface) have failed to detect SO2 formation. Other studies concerned with similar implantations into CO2 ice, which is also known to exist on Europa, have offered seemingly conflicting results. In this letter, we describe the results of a study on the implantation of 290 keV S+ ions into condensed CO2 at 20 and 70 K. Our results demonstrate that SO2 is observed after implantation at 20 K, but not at the Europa-relevant temperature of 70 K. We conclude that this process is likely not a reasonable mechanism for SO2 formation on Europa, and that other mechanisms should be explored instead.

Though S0 galaxies are usually thought to be `red and dead', they often demonstrate weak star formation organised in ring structures and located in their outer disks. We try to clarify the nature of this phenomenon and its difference from star formation in spiral galaxies. The moderate-luminosity nearby S0 galaxy, UGC 4599, is studied here. By applying long-slit spectroscopy at the Russian 6m telescope, we have measured stellar kinematics for the main body of the galaxy and strong emission-line flux ratios in the ring. After inspecting the gas excitation in the ring using line ratio diagrams and having shown that it is ionized by young stars, we have determined the gas oxygen abundance by using conventional strong-line calibration methods. We have inspected the gas kinematics in the ring with Fabry-Perot interferometer data obtained at the William Herschel Telescope. The pattern and properties of the brightest star formation regions are studied with the tunable filter MaNGaL at the 2.5m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute (CMO SAI MSU). The gas metallicity in the ring is certainly subsolar, [O/H]$=-0.4 \pm 0.1$~dex, that is different from the majority of the outer starforming rings in S0s studied by us which have typically nearly solar metallicity. The total stellar component of the galaxy which is old in the center is less massive than its extended gaseous disk. We conclude that probably the ring and the outer disk of UGC~4599 are a result of gas accretion from a cosmological filament.

The source-frequency phase-referencing (SFPR) technique has been demonstrated to have great advantages for mm-VLBI observations. By implementing simultaneous multi-frequency receiving systems on the next generation Event Horizon Telescope (ngEHT) antennas, it is feasible to carry out a frequency phase transfer (FPT) which could calibrate the non-dispersive propagation errors and significantly increase the phase coherence in the visibility data. Such increase offers an efficient approach for weak source or structure detection. SFPR also makes it possible for high precision astrometry, including the core-shift measurements up to sub-mm wavelengths for Sgr A* and M87* etc. We also briefly discuss the technical and scheduling considerations for future SFPR observations with the ngEHT.

We report the flux and spectral variability of PG 1553+113 on intra-night (IDV) to short-term timescales using BVRI data collected over 91 nights from 28 February to 8 November 2019 employing ten optical telescopes: three in Bulgaria, two each in India and Serbia, and one each in Greece, Georgia, and Latvia. We monitored the blazar quasi-simultaneously for 16 nights in the V and R bands and 8 nights in the V, R, I bands and examined the light curves (LCs) for intra-day flux and colour variations using two powerful tests: the power-enhanced F-test and the nested ANOVA test. The source was found to be significantly (> 99%) variable in 4 nights out of 27 in R-band, 1 out of 16 in V-band, and 1 out of 6 nights in I-band. No temporal variations in the colours were observed on IDV timescale. During the course of these observations the total variation in R-band was 0.89 mag observed. We also investigated the spectral energy distribution (SED) using B, V, R, and I band data. We found optical spectral indices in the range of 0.878+-0.029 to 1.106+-0.065 by fitting a power law to these SEDs of PG 1553+113. We found that the source follows a bluer-when-brighter trend on IDV timescales. We discuss possible physical causes of the observed spectral variability.

Stellar coronal mass ejections (CMEs) are a growing research field, especially during the past decade. The large number of so far detected exoplanets raises the open question for the CME activity of stars, as CMEs may strongly affect exoplanetary atmospheres. In addition, as CMEs contribute to stellar mass- and angular momentum loss and are therefore relevant for stellar evolution, there is need for a better characterization of this phenomenon. In this article we review the different methodologies used up to now to attempt the detection of stellar CMEs. We discuss the limitations of the different methodologies and conclude with possible future perspectives of this research field.

Since the discovery of the accelerated expansion of the present Universe, significant theoretical developments have been made in the area of modified gravity. In the meantime, cosmological observations have been providing more high-quality data, allowing us to explore gravity on cosmological scales. To bridge the recent theoretical developments and observations, we present an overview of a variety of modified theories of gravity and the cosmological observables in the cosmic microwave background and large-scale structure, supplemented with a summary of predictions for cosmological observables derived from cosmological perturbations and sophisticated numerical studies. We specifically consider scalar-tensor theories in the Horndeski and DHOST family, massive gravity/bigravity, vector-tensor theories, metric-affine gravity, and cuscuton/minimally-modified gravity, and discuss the current status of those theories with emphasis on their physical motivations, validity, appealing features, the level of maturity, and calculability. We conclude that the Horndeski theory is one of the most well-developed theories of modified gravity, although several remaining issues are left for future observations. The paper aims to help to develop strategies for testing gravity with ongoing and forthcoming cosmological observations.

The visual perception of the natural night sky in many places of the world is strongly disturbed by anthropogenic light. Part of this artificial light is scattered in the atmosphere and propagates towards the observer, adding to the natural brightness and producing a light polluted sky. However, atmospheric scattering is not the only mechanism contributing to increase the visual skyglow. The rich and diverse biological media forming the human eye also scatter light very efficiently and contribute, in some cases to a big extent, to the total sky brightness detected by the retinal photoreceptors. In this paper we quantify this effect and assess its relevance when the eye pupil is illuminated by light sources within the visual field. Our results show that intraocular scattering constitutes a significant part of the perceived sky brightness at short distances from streetlights. These results provide quantitative support to the everyday experience that substantial gains in naked-eye star limiting magnitudes can be achieved by blocking the direct light from the lamps that reaches the eye pupil.

Inaccurate limb-darkening models can be a significant source of error in the analysis of the light curves for transiting exoplanet and eclipsing binary star systems. To test the accuracy of published limb-darkening models, I have compared limb-darkening profiles predicted by stellar atmosphere models to the limb-darkening profiles measured from high-quality light curves of 43 FGK-type stars in transiting exoplanet systems observed by the Kepler and TESS missions. The comparison is done using the parameters $h^{\prime}_1 = I_{\lambda}(\frac{2}{3})$ and $h^{\prime}_2 = h^{\prime}_1 - I_{\lambda}(\frac{1}{3})$, where $I_{\lambda}(\mu)$ is the specific intensity emitted in the direction $\mu$, the cosine of the angle between the line of sight and the surface normal vector. These parameters are straightforward to interpret and insensitive to the details of how they are computed. I find that most (but not all) tabulations of limb-darkening data agree well with the observed values of $h^{\prime}_1$ and $h^{\prime}_2$. There is a small but significant offset $\Delta h^{\prime}_1 \approx 0.006$ compared to the observed values that can be ascribed to the effect of a mean vertical magnetic field strength $\approx 100$\,G that is expected in the photospheres of these inactive solar-type stars but that is not accounted for by typical stellar model atmospheres. The implications of these results for the precision of planetary radii measured by the PLATO mission are discussed briefly.

We study partial tidal disruption and present a quantitative analysis of the orbital dynamics of the remnant self-bound core. We perform smoothed particle hydrodynamical simulations to show that partial disruption of a star due to the tidal field of a black hole leads to a jump in the specific orbital energy and angular momentum of the core. It directly leads to deviation in the core's trajectory apart from getting a boost in its velocity. Our analysis shows that the variations in the specific orbital energy and angular momentum are higher when the pericentre distance is lower. We conclude that higher mass asymmetry of the two tidal tails increases the magnitude of the trajectory deviations. Our study reveals that observable deviations are only possible when mass ratio $q \lesssim 10^3 $, which indicates the range of intermediate-mass black holes.

In this paper, we place the Milky Way (MW) in the context of similar-looking galaxies in terms of their star-formation and chemical evolution histories. We select a sample of 138 Milky-Way analogues (MWAs) from the SDSS-IV/MaNGA survey based on their masses, Hubble types, and bulge-to-total ratios. To compare their chemical properties to the detailed spatially-resolved information available for the MW, we use a semi-analytic spectral fitting approach, which fits a self-consistent chemical-evolution and star-formation model directly to the MaNGA spectra. We model the galaxies' inner and outer regions assuming that some of the material lost in stellar winds falls inwards. We also incorporate chemical enrichment from type II and Ia supernovae to follow the alpha-element abundance at different metallicities and locations. We find some MWAs where the stellar properties closely reproduce the distribution of age, metallicity, and alpha enhancement at both small and large radii in the MW. In these systems, the match is driven by the longer timescale for star formation in the outer parts, and the inflow of enriched material to the central parts. However, other MWAs have very different histories. These divide into two categories: self-similar galaxies where the inner and outer parts evolve identically; and centrally-quenched galaxies where there is very little evidence of late-time central star formation driven by material accreted from the outer regions. We find that, although selected to be comparable, there are subtle morphological differences between galaxies in these different classes, and that the centrally-quenched galaxies formed their stars systematically earlier.

We investigate early dark energy models in the context of the lensing anomaly by considering two different Cosmic Microwave Background (CMB) datasets: a complete Planck, and a second one primarily based on SPTPol and Planck temperature ($l<1000$). We contrast the effects of allowing the phenomenological lensing amplitude ($\Al$) to be different from unity. We find that the fraction of early dark energy, while not immediately affected by the lensing anomaly, can induce mild deviations, through correlations with the parameters $H_0$ and $S_8$. {We extend the analysis also by marginalizing the Newtonian lensing potential, finding a $\gtrsim 1\sigma$ deviation, when allowing for an amplitude rescaling and scale-dependence. Modeling the rescaling of the theory lensing potential and the acoustic smoothing of the CMB spectra, we find that only to a moderate level the anomaly can be addressed by modifying the lensing signal itself and that an additional $\Al \sim 1.1$ at $\sim 2\sigma$ significance should be addressed by pre-recombination physics. Finally, we also comment on the lensing anomaly in a non-flat ($\Omega_{\rm k} \neq 0$) scenario, finding that the late-time flatness of the universe is robust and not correlated with the additional smoothing in the CMB spectra.

Polycyclic aromatic hydrocarbons (PAHs) play a critical role in the reprocessing of stellar radiation and in balancing the heating and cooling processes in the interstellar medium (ISM), but appear to be destroyed in HII regions. However, the mechanisms driving their destruction are still not completely understood. Using PHANGS-JWST and PHANGS-MUSE observations, we investigate how the PAH fraction changes in about 1500 HII regions across four nearby star-forming galaxies (NGC 628, NGC 1365, NGC 7496, IC 5332). We find a strong anti-correlation between the PAH fraction and the ionization parameter (the ratio between the ionizing photon flux and the hydrogen density) of HII regions. This relation becomes steeper for more luminous HII regions. The metallicity of HII regions has only a minor impact on these results in our galaxy sample. We find that the PAH fraction decreases with the H$\alpha$ equivalent width - a proxy for the age of the HII regions - although this trend is much weaker than the one identified using the ionization parameter. Our results are consistent with a scenario where hydrogen-ionizing UV radiation is the dominant source of PAH destruction in star-forming regions.

Photometric reverberation mapping can detect the radial extent of the accretion disc (AD) in Active Galactic Nuclei by measuring the time delays between light curves observed in different continuum bands. Quantifying the constraints on the efficiency and accuracy of the delay measurements is important for recovering the AD size-luminosity relation, and potentially using quasars as standard candles. We have explored the possibility of determining the AD size of quasars using next-generation Big Data surveys. We focus on the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory, which will observe several thousand quasars with the Deep Drilling Fields and up to 10 million quasars for the main survey in six broadband filter during its 10-year operational lifetime. We have developed extensive simulations that take into account the characteristics of the LSST survey and the intrinsic properties of the quasars. The simulations are used to characterise the light curves from which AD sizes are determined using various algorithms. We find that the time delays can be recovered with an accuracy of 5 and 15% for light curves with a time sampling of 2 and 5 days, respectively. The results depend strongly on the redshift of the source and the relative contribution of the emission lines to the bandpasses. Assuming an optically thick and geometrically thin AD, the recovered time-delay spectrum is consistent with black hole masses derived with 30% uncertainty.

Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ring-like structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ~0.3" (30pc) resolution new JWST/MIRI imaging with archival ALMA CO(2-1) mapping of the central ~5kpc of the nearby barred spiral galaxy NGC1365, to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two well-known bright bar lanes that surround a smooth dynamically cold gas disk (R_gal ~ 475pc) reminiscent of non-star-forming disks in early type galaxies and likely fed by gas inflow triggered by stellar feedback in the lanes. The lanes host a large number of JWST-identified massive young star clusters. We find some evidence for temporal star formation evolution along the ring. The complex kinematics in the gas lanes reveal strong streaming motions and may be consistent with convergence of gas streamlines expected there. Indeed, the extreme line-widths are found to be the result of inter-`cloud' motion between gas peaks; ScousePy decomposition reveals multiple components with line widths of <sigma_CO,scouse> ~ 19km/s and surface densities of <Sigma_H2,scouse> ~ 800M_sun/pc^2, similar to the properties observed throughout the rest of the central molecular gas structure. Tailored hydro-dynamical simulations exhibit many of the observed properties and imply that the observed structures are transient and highly time-variable. From our study of NGC1365, we conclude that it is predominantly the high gas inflow triggered by the bar that is setting the star formation in its CMZ.

Recently gamma-ray bursts (GRBs) have been detected at very high-energy (VHE) gamma-rays by imaging atmospheric Cherenkov telescopes, and a two-component jet model has often been invoked to explain multi-wavelength data. In this work, multi-wavelength afterglow emission from an extremely bright gamma-ray burst, GRB 221009A, is examined. The isotropic-equivalent gamma-ray energy of this event is among the largest, which suggests that similarly to previous VHE GRBs, the jet opening angle is so small that the collimation-corrected gamma-ray energy is nominal. Afterglow emission from such a narrow jet decays too rapidly, especially if the jet propagates into uniform circumburst material. In the two-component jet model, another wide jet component with a smaller Lorentz factor dominates late-time afterglow emission, and we show that multi-wavelength data of GRB 221009A can be explained by narrow and wide jets with opening angles similar to those employed for other VHE GRBs. We also discuss how model degeneracies can be disentangled with observations.

Classification is valuable and necessary in spectral analysis, especially for data-driven mining. Along with the rapid development of spectral surveys, a variety of classification techniques have been successfully applied to astronomical data processing. However, it is difficult to select an appropriate classification method in practical scenarios due to the different algorithmic ideas and data characteristics. Here, we present the second work in the data mining series - a review of spectral classification techniques. This work also consists of three parts: a systematic overview of current literature, experimental analyses of commonly used classification algorithms and source codes used in this paper. Firstly, we carefully investigate the current classification methods in astronomical literature and organize these methods into ten types based on their algorithmic ideas. For each type of algorithm, the analysis is organized from the following three perspectives. (1) their current applications and usage frequencies in spectral classification are summarized; (2) their basic ideas are introduced and preliminarily analysed; (3) the advantages and caveats of each type of algorithm are discussed. Secondly, the classification performance of different algorithms on the unified data sets is analysed. Experimental data are selected from the LAMOST survey and SDSS survey. Six groups of spectral data sets are designed from data characteristics, data qualities and data volumes to examine the performance of these algorithms. Then the scores of nine basic algorithms are shown and discussed in the experimental analysis. Finally, nine basic algorithms source codes written in python and manuals for usage and improvement are provided.

Among the most central open questions on the initial mass function (IMF) of stars is the impact of the environment on the shape of the core mass function (CMF) and thus potentially on the IMF. The ALMA-IMF Large Program aims to investigate the variations of the core distributions with cloud characteristics, as diagnostic observables of the formation process and evolution. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has been recently found to be top-heavy with respect to the Salpeter slope. W43-MM2&MM3 is a useful test case for environmental studies because it harbors a rich cluster containing a statistically significant number of cores, previously characterized in paper III. We applied a multiscale decomposition technique on the ALMA 1.3 mm and 3 mm continuum images to define six subregions. For each subregion we characterize the high column density probability distribution function, n-PDF, shape of the cloud gas using the 1.3 mm image. Using the core catalog, we investigate correlations between the CMF, n-PDF and core mass segregation. We classify the subregions into different stages of evolution, from quiescent to burst to post-burst, based on the surface number density of cores, number of outflows, and UCHii presence. The high-mass end of the subregion CMFs vary from being close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst). Moreover, the second tail of the n-PDF varies from steep, to flat like observed for the high mass star-forming clouds. We found that subregions with flat second n-PDF tails display top-heavy CMFs. The CMF may evolve from Salpeter to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises the question of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, a hypothesis that remains to be tested.

We report evidence from eclipse timing that two otherwise apparently normal cataclysmic variables have experienced abrupt changes in their orbital periods. The orbital period of HS 2325+8205 increased by 22.15 msec (1.3 x 10-6 of the orbital period) around 1 February 2011 and the orbital period of EP Dra increased by 4.51 msec (7.2 x 10-7 of the orbital period) around 7 December 2001. In neither case was there any apparent change in the subsequent behaviour of the system. These changes are currently unexplained.

Accurate estimation of brightness of (3200) Phaethon up to lower phase angles are essential for planning of the on-board camera of the DESTINY$^{+}$ mission. We have carried out intensive observations of Phaethon in the optical wavelength ($g$, $r$, and $i$) with the TriCCS camera on the Seimei 3.8 m telescope in October and November, 2021. We derived the absolute magnitude $H_\mathrm{V}$ and the slope parameter $G$ of Phaethon as $H_\mathrm{V}=14.23\pm0.02$ and $G=0.040\pm0.008$ from multiple photometric observations including lower phase angles down to $\sim$9$^{\circ}$ with the $H$-$G$ model. Using the $H_\mathrm{V}$ value and the geometric albedo of Phaethon derived in previous polarimetric studies, we estimated that the Phaethon's diameter is within a range of 5.22 to 6.74 km, which is consistent with radar and occultation observations. With the linear model, we derived $H_\mathrm{V}=14.65\pm0.02$, which corresponds to a diameter range of 4.30 to 5.56 km. Our simultaneous tricolor lightcurves of Phaethon indicate that no rotational spectral variations larger than 0.018 and 0.020 mag in the g-r and r-i colors, possibly related to inhomogeneity of the surface material and/or structure, are seen at the 2021 apparition.

As a complement to the HyGAL Stratospheric Observatory for Infrared Astronomy Legacy Program, we report the results of a ground-based absorption line survey of simple molecules in diffuse and translucent Galactic clouds. Using the Institut de Radioastronomie Millim\'etrique (IRAM) 30 m telescope, we surveyed molecular lines in the 2 mm and 3 mm wavelength ranges toward 15 millimeter continuum sources. These sources, which are all massive star-forming regions located mainly in the first and second quadrants of the Milky Way, form the subset of the HyGAL sample that can be observed by the IRAM 30 m telescope. We detected HCO$^+$ absorption lines toward 14 sightlines, toward which we identified 78 foreground cloud components, as well as lines from HCN, HNC, C$_2$H, and c-C$_3$H$_2$ toward most sightlines. In addition, CS and H$_2$S absorption lines are found toward at least half of the continuum sources. Static Meudon photodissociation region (PDR) isobaric models that consider ultraviolet-dominated chemistry were unable to reproduce the column densities of all seven molecular species by just a factor of a few, except for H$_2$S. The inclusion of other formation routes driven by turbulent dissipation could possibly explain the observed high column densities of these species in diffuse clouds. There is a tentative trend for H$_2$S and CS abundances relative to H$_2$ to be larger in diffuse clouds ($X$(H$_2$S) and $X$(CS) $\sim 10^{-8} - 10^{-7}$) than in translucent clouds ($X$(H$_2$S) and $X$(CS) $\sim 10^{-9} - 10^{-8}$) toward a small sample; however, a larger sample is required in order to confirm this trend. The derived H$_2$S column densities are higher than the values predicted from the isobaric PDR models, suggesting that chemical desorption of H$_2$S from sulfur-containing ice mantles may play a role in increasing the H$_2$S abundance.

The gas metallicity distributions across individual galaxies and across galaxy samples can teach us much about how galaxies evolve. Massive galaxies typically possess negative metallicity gradients, and mass and metallicity are tightly correlated on local scales over wide range of galaxy masses; however, the precise origins of such trends remain elusive. Here, we employ data from SDSS-IV MaNGA to explore how gas metallicity depends on local stellar mass density and on galactocentric radius within individual galaxies. We also consider how the strengths of these dependencies vary across the galaxy mass-size plane. We find that radius is more predictive of local metallicity than stellar mass density in extended lower mass galaxies, while we find density and radius to be almost equally predictive in higher-mass and more compact galaxies. Consistent with previous work, we find a mild connection between metallicity gradients and large-scale environment; however, this is insufficient to explain variations in gas metallicity behaviour across the mass-size plane. We argue our results to be consistent with a scenario in which extended galaxies have experienced smooth gas accretion histories, producing negative metallicity gradients over time. We further argue that more compact and more massive systems have experienced increased merging activity that disrupts this process, leading to flatter metallicity gradients and more dominant density-metallicity correlations within individual galaxies.

We present TXPipe, a modular, automated and reproducible pipeline for generating data vectors in cosmology analyses. The pipeline is developed within the Rubin Observatory Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC), and designed for cosmology analyses using LSST data. In this paper, we present the pipeline for the so-called 3$\times$2pt analysis - a combination of three two-point functions that measure the auto- and cross-correlation between galaxy density and shapes. We perform the analysis both in real and harmonic space using TXPipe and other LSST-DESC tools. We validate the pipeline using Gaussian simulations and show that the pipeline accurately measures data vectors and recovers the input cosmology to the accuracy level required for the first year of LSST data. We also apply the pipeline to a realistic mock galaxy sample extracted from the CosmoDC2 simulation suite Korytov et al. (2019). TXPipe establishes a baseline framework that can be built upon as the LSST survey proceeds. Furthermore, the pipeline is designed to be easily extended to science probes beyond the 3$\times$2pt analysis.

UltraLight Dark Matter (ULDM) is an axion-like dark matter candidate with an extremely small particle mass. ULDM halos consist of a spherically symmetric solitonic core and an NFW-like skirt. We simulate halo creation via soliton mergers and use these results to explore the core-halo mass relation. We calculate the eigenstates of the merged halos and use these to isolate the solitonic core and calculate its relative contribution to the halo mass. We compare this approach to using a fitting function to isolate the core and find a difference in masses up to 30%. We analyze three families of simulations: equal-mass mergers, unequal-mass mergers, and halos with a two-step merger history. Setting the halo mass to the initial mass in the simulation does not yield a consistent core-halo relationship. Excluding material "ejected" by the collision yields a core-halo relationship with a slope of 1/3 for simultaneous mergers and roughly 0.4 for two-step mergers. Our findings suggest there is no universal core-halo mass relationship for ULDM and shed light on the differing results for the core-halo relationship previously reported in the literature.

We report the discovery of a compact group of galaxies, CGG-z5, at z~5.2 in the EGS field covered by the JWST/CEERS survey. CGG-z5 was selected as the highest overdensity of galaxies at z>2 in recent JWST public surveys and consists of six candidate members lying within a projected area of 1.5''x3'' (10x20 kpc$^2$). All group members are HST/F435W and HST/F606W dropouts while securely detected in the JWST/NIRCam bands, yielding a narrow range of robust photometric redshifts 5.0<z<5.3. The most massive galaxy in the group has stellar mass log$(M_{*}/M_{\odot})\approx9.8$ while the rest are low mass satellites (log$(M_{*}/M_{\odot})\approx8.4-9.2$). While several group members were already detected in HST and IRAC bands, the low stellar masses and the compactness of the structure required the sensitivity and resolution of JWST for its identification. To assess the nature and evolutionary path of CGG-z5 we searched for similar compact structures in the EAGLE simulation and followed their evolution with time. We find that all the identified structures merge into a single galaxy by z=3 and form a massive galaxy (log$(M_{*}/M_{\odot})>11$) at z~1. This implies that CGG-z5 could be a ``proto-massive galaxy" captured during a short-lived phase of massive galaxy formation.

Here, we study the distribution of Fundamental-mode Cepheids in the Magellanic Cloud as a function of their positions and ages using the data from the OGLE~IV survey. Age of the Cepheids are determined through well known period - age relations for the LMC and SMC Cepheids which are used to understand the star formation scenario in the Magellanic Cloud. The age distributions of the Cepheids in LMC and SMC show peak around $155^{+45}_{-35}$ Myr and $224^{+51}_{-42}$ Myr, respectively. This indicates that a major star formation event took place in the Magellanic Cloud at about 200\,Myr ago. It is believed that this event might have been triggered by a close encounter between the two components of the Magellanic Cloud or due to a possible tidal interaction between the Magellanic Cloud and Milky Way galaxy during one of its pericentric passages round the Milky Way. Cepheids are found to be asymmetrically distributed in both the LMC and SMC. A high-density clumpy structure is found to be located towards eastern side of the LMC and south-west direction of the SMC from their respective galactic centres.

As Open clusters are excellent sources to probe the structural details of the Galactic disk, we used physical parameters available for more than 6000 open clusters like age, distance, reddening, and kinematic information to understand the Galactic disk morphology. We map the spiral structure of the Galaxy and found that most of the clusters leave the spiral arms after about 10-20 Myr and fill the inter-arm regions as they age. We determine the spiral pattern rotation speed of the Galaxy Omega as 26.5+/-1.5 km/s/kpc, which is found to be constant within last 80 Myr, and the corotation radius Rc as 1.08 solar radius. Based on the distribution of clusters younger than 700 Myr, we found a Solar offset of -17.0+/-0.9 pc, and estimated the scale height 91.7+/-1.9 pc from the Galactic plane and 89.6+/-2.6 from the reddening plane. The interstellar extinction is found varying in a sinusoidal manner with the Galactic longitude and maximum and minimum Galactic absorption occurring in the longitudinal direction of 59+/-10 deg and 239+/-10 deg, respectively. This study allows us to investigate the properties of the Galactic disk, spiral arms, and reddening distributions and we could reveal a layer of interstellar material with varying thickness along the Galactic longitude that is inclined with respect to the formal Galactic plane.

We study variable stars in the field of the open cluster NGC 381 using photometric data observed over 27 nights and identify a total of 57 variable stars out of which five are member stars. The variable stars are classified based on their periods, amplitudes, light curve shapes, and locations in the H-R diagram. We found a rich variety of variable stars in the cluster. We identified a total of 10 eclipsing binaries out of which 2 are Algol type (EA) while 8 are W UMa type (EW) binaries. The estimated ages of these EW binaries are greater than 0.6 Gyr which is in agreement with the formation time constraint of > 0.6 Gyr on short-period eclipsing binaries. The estimation of the physical parameters of the three EW type binaries is done using PHOEBE model-fitting software. The pulsating variable stars include one each from {\delta} Scuti and {\gamma} Dor variability class. We determined the pulsation modes of pulsating variables with the help of the FAMIAS package. We obtained 15 rotational variables stars comprising four dwarf stars identified on the basis log(g) versus log(Tef f ) diagram. These dwarf stars are found to have generally larger periods than the remaining rotational variables.

The precise mechanism that forms jets and large-scale vortices on the giant planets is unknown. An inverse cascade has been suggested. Alternatively, energy may be directly injected by small-scale convection. Our aim is to clarify whether an inverse cascade feeds zonal jets and large-scale eddies in a system of rapidly rotating, deep, geostrophic spherical-shell convection. We analyze the nonlinear scale-to-scale transfer of kinetic energy in such simulations as a function of the azimuthal wave number, m. We find that the main driving of the jets is associated with upscale transfer directly from the small convective scales to the jets. This transfer is very nonlocal in spectral space, bypassing large-scale structures. The jet formation is thus not driven by an inverse cascade. Instead, it is due to a direct driving by Reynolds stresses from small-scale convective flows. Initial correlations are caused by the effect of uniform background rotation and shell geometry on the flows. While the jet growth suppresses convection, it increases the correlation of the convective flows, which further amplifies the jet growth until it is balanced by viscous dissipation. To a much smaller extent, energy is transferred upscale to large-scale vortices directly from the convective scales, mostly outside the tangent cylinder. There, large-scale vortices are not driven by an inverse cascade either. Inside the tangent cylinder, the transfer to large-scale vortices is weaker, but more local in spectral space, leaving open the possibility of an inverse cascade as a driver of large-scale vortices. In addition, large-scale vortices receive kinetic energy from the jets via forward transfer. We therefore suggest a jet instability as an alternative formation mechanism of largescale vortices. Finally, we find that the jet kinetic energy scales as $\ell^{-5}$, the same as for the zonostrophic regime.

The total luminosity and spectral shape of the non-thermal emission produced by cosmic rays depends on their interstellar environment, a dependence that gives rise to correlations between galaxies' bulk properties -- star formation rate, stellar mass, and others -- and their non-thermal spectra. Understanding the physical mechanisms of cosmic ray transport, loss, and emission is key to understanding these correlations. Here, in the first paper of the series, we present a new method to compute the non-thermal spectra of star-forming galaxies, and describe an open-source software package -- COsmic-ray, Neutrino, Gamma-ray and Radio Non-Thermal Spectra (CONGRuENTS) -- that implements it. As a crucial innovation, our method requires as input only a galaxy's effective radius, star formation rate, stellar mass, and redshift, all quantities that are readily available for large samples of galaxies and do not require expensive, spatially resolved gas measurements. From these inputs we derive individual, galaxy-by-galaxy models for the background gas and radiation field through which cosmic rays propagate, from which we compute steady state cosmic ray spectra for hadronic and leptonic particles in both the galactic disc and halo by solving the full kinetic equation. We invoke modern models for cosmic ray transport and include all significant emission and loss mechanisms. In this paper we describe the model and validate it against non-thermal emission measured in nearby star-forming galaxies that span four orders of magnitude in star formation rate.

This study investigates and compares brightness and area of coronal bright points (CBPs) inside and outside of coronal holes (CHs) using the single-dish Band 6 observations by the Atacama Large Millimeter/submillimeter Array (ALMA), combined with extreme-ultraviolet (EUV) 193 $\overset{\circ}{\mathrm{A}}$ filtergrams obtained by the Atmospheric Imaging Assembly (AIA) and magnetograms obtained by the Helioseismic and Magnetic Imager (HMI), both on board Solar Dynamics Observatory (SDO). The CH boundaries were extracted from the SDO/AIA images using the Collection of Analysis Tools for Coronal Holes (CATCH) and CBPs were identified in the SDO/AIA, SDO/HMI, and ALMA data. Measurements of brightness and areas in both ALMA and SDO/AIA images were conducted for CBPs within CHs and quiet Sun regions outside CHs. A statistical analysis of the measured physical properties resulted in a lower average CBP brightness in both ALMA and SDO/AIA data for CBPs within the CHs. Depending on the CBP sample size, the difference in intensity for the SDO/AIA data, and brightness temperature for the ALMA data, between the CBPs inside and outside CHs ranged from between 2$\sigma$ and 4.5$\sigma$, showing a statistically significant difference between those two CBP groups. For CBP areas, CBPs within the CH boundaries showed smaller areas on average, with the observed difference between the two CBP groups between 1$\sigma$ and 2$\sigma$ for the SDO/AIA data, and up to 3.5$\sigma$ for the ALMA data, indicating that CBP areas are also significantly different. Given the measured properties, we conclude that the CBPs inside CHs tend to be less bright on average, but also smaller in comparison to those outside of CHs. This conclusion might point to the specific physical conditions and properties of the local CH region around a CBP limiting the maximum achievable intensity (temperature) and size of a CBP.

In this paper we present CALSAGOS: Clustering ALgorithmS Applied to Galaxies in Overdense Systems which is a PYTHON package developed to select cluster members and to search, find, and identify substructures. CALSAGOS is based on clustering algorithms and was developed to be used in spectroscopic and photometric samples. To test the performance of CALSAGOS we use the S-PLUS's mock catalogues and we found an error of 1\% - 6\% on member selection depending on the function that is used. Besides, CALSAGOS has a $F_1$-score of 0.8, a precision of 85\% and a completeness of 100\% in the identification of substructures in the outer regions of galaxy clusters ($r > r_{200}$). The $F_1$-score, precision and completeness of CALSAGOS fall to 0.5, 75\% and 40\% when we consider all substructure identifications (inner and outer) due to the function that searches, finds, and identifies the substructures works in 2D and cannot resolve the substructures projected over others.

The current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), comprised of major installations such as the MAGIC telescopes, H.E.S.S. and VERITAS, is classified as the 3$^{\mathrm{rd}}$ generation of suchs instruments. These telescopes use multipixel cameras composed of thousands of photomultiplier tubes (PMTs). The total light throughput of such instruments depends, besides the PMT photon detection efficiency (PDE), on the mirror dish reflectivity, and the light absorption by the camera window. The supremacy of PMTs is currently being challenged by photon sensors rapidly spreading in popularity, the silicon photomultipliers (SiPMs), that are becoming a valid alternative thanks to their high PDE, low operating voltage and flexibility in installation. In this report, we investigate the performance of an existing 3$^{\mathrm{rd}}$-generation IACT array (taking as an example MAGIC) in which PMTs would be replaced with SiPMs, with minimal further hardware intervention. This would mean that other systems of the telescope responsible for the light collection, in particular the optics, would remain the same, and only the electronic to steer the different photodetectors would be modified. We find an increase of sensitivity up to a factor of 2 for energies below 200~GeV. Interestingly, we also find that the stronger sensitivity of SiPMs in the red part of the spectrum, a source of background for IACTs, does not affect this conclusion.

The ESO Public Survey Southern H-ATLAS Regions Ks-band Survey (SHARKS) comprises 300 square degrees of deep imaging at 2.2 microns (the Ks band) with the VISTA InfraRed CAMera (VIRCAM) at the 4-metre Visible and Infrared Survey Telescope for Astronomy (VISTA). The first data release of the survey, comprising 5% of the data, was published via the ESO database on 31 January 2022. We describe the strategy and status of the first data release and present the data products. We discuss briefly different scientific areas being explored with the SHARKS data and conclude with an outline of planned data releases.

We examine the acoustic and magnetic energy generation and propagation in beta Hydri (G2 IV). The underlying motivation for this work is based on the solar, stellar, and galactic relevance of beta Hydri (a star in the Southern hemisphere), which is readily understood as a prime example and proxy of the future Sun - thus allowing assessments and analyses of the secular decay of solar activity. Regarding the magnetic energy generation, we consider longitudinal flux tube waves. We also assess acoustic waves. For the acoustic wave energy flux, the difference between the results obtained for beta Hydri and the Sun is significantly smaller than typically attained for main-sequence stars, which is largely due to the gravity-dependence of the acoustic energy generation. Furthermore, we study the height-dependent behavior of the magnetic energy flux for different magnetic filling factors corresponding to different flux tube spreadings. Finally, we comment on possible directions of future research.

Broadband receiver data need colour corrections applying to correct for the different source spectra across their wide bandwidths. The full integration over a receiver bandpass may be computationally expensive and redundant when repeated many times. Colour corrections can be applied, however, using a simple quadratic fit based on the full integration instead. Here we describe fastcc and interpcc, quick Python and IDL codes that return, respectively, colour correction coefficients for different power-law spectral indices and modified black bodies for various Cosmic Microwave Background related experiments. The codes are publicly available, and can be easily extended to support additional telescopes.

This work presents a mission concept for in-orbit particle collection for sampling and exploration missions towards Near-Earth asteroids. Ejecta is generated via a small kinetic impactor and two possible collection strategies are investigated: collecting the particle along the anti-solar direction, exploiting the dynamical features of the L$_2$ Lagrangian point or collecting them while the spacecraft orbits the asteroid and before they re-impact onto the asteroid surface. Combining the dynamics of the particles in the Circular Restricted Three-Body Problem perturbed by Solar Radiation Pressure with models for the ejecta generation, we identify possible target asteroids as a function of their physical properties, by evaluating the potential for particle collection.

The nearby bright M-dwarf star L~98-59 has three terrestrial-sized planets. One challenge remaining in characterizing atmospheres around such planets is that it is not known a priori whether they possess any atmospheres. Here we report the study of the atmospheres of L~98-59~c and L~98-59~d using the near-infrared spectral data from the G141 grism of HST/WFC3. We can reject the hypothesis of a clear atmosphere dominated by hydrogen and helium at a confidence level of $\sim$ 3~sigma for both planets. Thus they may have a primary hydrogen-dominated atmosphere with an opaque cloud layer, or have lost their primary hydrogen-dominated atmosphere and re-established a secondary thin atmosphere, or have no atmosphere at all. We cannot distinguish between these scenarios for the two planets using the current HST data. Future observations with JWST would be capable of confirming the existence of atmospheres around L~98-59~c and d and determining their compositions.

(704) Interamnia is one of the largest asteroids that locates in the outer main-belt region, which may contain a large amount of water ice underneath its surface. We observe this asteroid using 8.2 m Subaru telescope at mid-infrared wavebands, and utilize thermophysical model for realistic surface layers (RSTPM) to analyze mid-infrared data from Subaru along with those of IRAS, AKARI and WISE/NEOWISE. We optimize the method to convert the WISE magnitude to thermal infrared flux with temperature dependent color corrections, which can provide significant references for main-belt asteroids at a large heliocentric distance with low surface temperature. We derive best-fitting thermal parameters of Interamnia - a mean regolith grain size of $190_{-180}^{+460}~\rm \mu m$, with a roughness of $0.30_{-0.17}^{+0.35}$ and RMS slope of $27_{-9}^{+13}$ degrees, thereby producing thermal inertia ranging from 9 to $92~\rm Jm^{-2}s^{-1/2}K^{-1}$ due to seasonal temperature variation. The geometric albedo and effective diameter are evaluated to be $0.0472_{-0.0031}^{+0.0033}$ and $339_{-11}^{+12}~\rm km$, respectively, being indicative of a bulk density of $1.86\pm0.63~\rm g/cm^3$. The low thermal inertia is consistent with typical B/C-type asteroids with $D\geq100$ km. The tiny regolith grain size suggests the presence of a fine regolith on the surface of Interamnia. Moreover, the seasonal and diurnal temperature distribution indicates that thermal features between southern and northern hemisphere appear to be very different. Finally, we present an estimation of volume fraction of water ice of $9\%\sim66\%$ from the published grain density and porosity of carbonaceous chondrites.

The inheritance of material across the star and planet formation process is traced by deuterium fractionation. We report here the first detection of doubly deuterated methanol towards pre-stellar cores. We study the deuterium fractionation of methanol, CH$_{3}$OH, towards two starless and two pre-stellar cores. We derive a D/H ratio of 0.8-1.9$\%$ with CH$_{2}$DOH in pre-stellar cores H-MM1 and L694-2, consistent with measurements in more evolved Class 0/I objects and comet 67P/Churyumov-Gerasimenko, suggesting a direct chemical link arising in the pre-stellar stage. Furthermore, the column density ratios of CHD$_{2}$OH/CH$_{2}$DOH are $\sim$50-80$\%$, consistently high as that towards Class 0/I objects, indicating an efficient formation mechanism of CHD$_{2}$OH, possibly through H atom additions to D$_{2}$CO. The CH$_{2}$DOH/CH$_{3}$OH and CHD$_{2}$OH/CH$_{3}$OH column density ratios in the two pre-stellar cores are larger than that in the two starless cores B68 and L1521E, representing an evolutionary trend of methanol deuteration in early-stage cores.

Nearly all intragroup (IGL) and intracluster light (ICL) comes from stars that are not bound to any single galaxy but were formed in galaxies and later unbound from them. In this review we focus on the physical properties - phase space properties, metallicity and age distribution - of the ICL and IGL components of the groups and clusters in the local universe, within 100 Mpc distance. Kinematic information on these very low surface brightness structures mostly comes from discrete tracers such as planetary nebulae and globular clusters, showing highly unrelaxed velocity distributions. Cosmological hydrodynamical simulations provide key predictions for the dynamical state of IGL and ICL and find that most IC stars are dissolved from galaxies that subsequently merge with the central galaxy. The increase of the measured velocity dispersion with radius in the outer halos of bright galaxies is a physical feature that makes it possible to identify IGL and ICL components. In the local groups and clusters, IGL and ICL are located in the dense regions of these structures. Their light fractions relative to the total luminosity of the satellite galaxies in a given group or cluster are between a few to ten percent, significantly lower than the average values in more evolved, more distant clusters. IGL and ICL in the Leo I and M49 groups, and the Virgo cluster core around M87, has been found to arise from mostly old (>~10 Gyr) metal-poor ([Fe/H]<-1.0) stars of low-mass progenitor galaxies. New imaging facilities such as LSST, Euclid, and the `big eyes' on the sky - ELT and JWST with their advanced instrumentation-promise to greatly increase our knowledge of the progenitors of the IGL and ICL stars, their ages, metal content, masses and evolution, thereby increasing our understanding of this enigmatic component.

This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) -- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status of the instrumentation. We also present results of a transition observation, which offers unique measurements on several novel aspects. We estimate the RFI suppression required for such a radio astronomy instrumentation at the Moon distances from Earth to be of the order of 80 dB. We analyse a method of separating Earth- and satellite-originated radio frequency interference (RFI). It is found that the RFI level at frequencies lower than a few MHz is smaller than the receiver noise floor.

Using Fisher information matrices, we forecast the uncertainties $\sigma_M$ on the measurement of a "Planet X" at heliocentric distance $d_X$ via its tidal gravitational field's action on the known planets. Using planetary measurements currently in hand, including ranging from the Juno, Cassini, and Mars-orbiting spacecraft, we forecast a median uncertainty (over all possible sky positions) of $\sigma_M=0.22M_\oplus (d_x/400\,\textrm{AU})^3.$ A definitive $(5\sigma)$ detection of a $5M_\oplus$ Planet X at $d_X=400$ AU should be possible over the full sky but over only 5% of the sky at $d_X=800$ AU. The gravity of an undiscovered Earth- or Mars-mass object should be detectable over 90% of the sky to a distance of 260 or 120 AU, respectively. Upcoming Mars ranging improves these limits only slightly. We also investigate the power of high-precision astrometry of $\approx8000$ Jovian Trojans over the 2023--2035 period from the upcoming Legacy Survey of Space and Time (LSST). We find that the dominant systematic errors in optical Trojan astrometry (photocenter motion, non-gravitational forces, and differential chromatic refraction) can be solved internally with minimal loss of information. The Trojan data allow useful cross-checks with Juno/Cassini/Mars ranging, but do not significantly improve the best-achievable $\sigma_M$ values until they are $\gtrsim10\times$ more accurate than expected from LSST. The ultimate limiting factor in searches for a Planet X tidal field is confusion with the tidal field created by the fluctuating quadrupole moment of the Kuiper Belt as its members orbit. This background will not, however, become the dominant source of Planet X uncertainty until the data get substantially better than they are today.

Recently, Halpern et al. discovered an oscillation with a period of 464 s in the cataclysmic variable 1RXS J230645.0+550816. I conducted extensive photometric observations of this object to clarify the coherence of this oscillation and to measure the oscillation period with high precision. Observations were obtained over 22 nights in 2018 and 2019. The total duration of observations was 110 hr. The oscillation was revealed in each long night of observations and was coherent throughout all my observations covering 15 months. Due to the large coverage of observations, I determined the oscillation period with high precision, which was 464.45600+\-0.00010 s. The oscillation semi-amplitude was large and showed changes from 41.8+\-1.5 mmag in 2018 to 48.6+\-1.8 mmag in 2019. The oscillation pulse profile was symmetrical with a noticeably wider minimum compared to the maximum and showed no noticeable changes during 2018 and 2019. The high precision of the oscillation period allowed me to derive an oscillation ephemeris with a long validity of 70 years. This ephemeris can be used for future studies of oscillation period changes. Although short-period X-ray oscillations have not yet been detected in 1RXS J230645.0+550816, the intermediate polar nature of this object is very probable due to the high degree of coherence of the 464-s oscillation.

An important stage in the evolution of massive binaries is the formation of a compact object in the system. It is believed that in some cases a momentum kick is imparted to the newly born object, changing the orbital parameters of the binary, such as eccentricity and orbital period, and even acquiring an asynchronous orbit between its components. In this situation, tides play a central role in the evolution of these binaries. In this work we aim to study how the orbital parameters of a massive binary change after the formation of a compact object when the stellar spin of the non-degenerate companion is not aligned with the orbital angular momentum. We used MESA, which we modified to be able to evolve binaries with different values of the inclination between the orbital planes before and just after the formation of the compact object. These modifications to the equations solved by the MESA code are extended to the case of non-solid body rotation. We find that the impact of having different initial inclinations is mostly present in the evolution towards an equilibrium state that is independent of the inclination. If the binary separation is small enough such that the interaction happens when the star is burning hydrogen in its core, this state is reached before the beginning of a mass-transfer phase, while for a wider binary not all conditions characterizing the equilibrium are met. These findings show that including the inclination in the equations of tidal evolution to a binary after a kick is imparted onto a newly born compact object changes the evolution of some parameters, such as the eccentricity and the spin period of the star, depending on how large this inclination is. Moreover, these results can be used to match the properties of observed X-ray binaries to estimate the strength of the momentum kick.

We show that the common envelope jets supernova (CEJSN) r-process scenario is compatible with very recent observationally determined properties of the stars in the ultra faint dwarf (UFD) galaxy Reticulum II that are strongly enhanced in r-process elements. These new results, like efficient mixing of the r-process elements in the Reticulum II galaxy, have some implications on the CEJSN r-process scenario for UFD galaxies. In particular, the energetic jets efficiently mix with the common envelope ejecta and then with the entire interstellar medium of Reticulum II. The compatibility that we find between the scenario and new observations suggests that the CEJSN r-process scenario supplies a non-negligible fraction of the r-process elements.

We present new evolutionary models of primordial very massive stars, with initial masses ranging from $100\,\mathrm{{M}_{\odot}}$ to $1000\,\mathrm{{M}_{\odot}}$, that extend from the main sequence until the onset of dynamical instability caused by the creation of electron-positron pairs during core C, Ne, or O burning, depending on the star's mass and metallicity. Mass loss accounts for radiation-driven winds as well as pulsation-driven mass-loss on the main sequence and during the red supergiant phase. After examining the evolutionary properties, we focus on the final outcome of the models and associated compact remnants. Stars that avoid the pair-instability supernova channel, should produce black holes with masses ranging from $\approx 40\, \mathrm{{M}_{\odot}}$ to $\approx 1000\,\mathrm{{M}_{\odot}}$. In particular, stars with initial masses of about $100\,\mathrm{{M}_{\odot}}$ could leave black holes of $\simeq 85-90\, \mathrm{{M}_{\odot}}$, values consistent with the estimated primary black hole mass of the GW190521 merger event. Overall, these results may contribute to explain future data from next-generation gravitational-wave detectors, such as the Einstein Telescope and Cosmic Explorer, which will have access to as-yet unexplored BH mass range of $\approx 10^2-10^4\,\mathrm{{M}_{\odot}}$ in the early universe.

To understand the mechanism behind high-$z$ Ly${\alpha}$ nebulae, we simulate the scattering of Ly${\alpha}$ in a $\rm H\,I$ halo about a central Ly${\alpha}$ source. For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total $\rm H\,I$ column densities, $\rm H\,I$ spatial concentrations, and central source galaxies (e.g., with Ly${\alpha}$ line widths corresponding to those typical of AGN or star-forming galaxies). We compute the spatial-frequency diffusion and the polarization of the Ly${\alpha}$ photons scattered by atomic hydrogen. Our scattering-only model reproduces the typical size of Ly${\alpha}$ nebulae ($\sim 100\,$kpc) at total column densities $N_{\rm HI} \geq 10^{20} \rm cm^{-2}$ and predicts a range of positive, flat, and negative polarization radial gradients. We also find two general classes of Ly${\alpha}$ nebula morphologies: with and without bright cores. Cores are seen when $N_{\rm HI}$ is low, i.e., when the central source is directly visible, and are associated with a polarization jump, a steep increase in the polarization radial profile just outside the halo center. Of all the parameters tested in our smooth or clumpy medium model, $N_{\rm HI}$ dominates the trends. The radial behaviors of the Ly${\alpha}$ surface brightness, spectral line shape, and polarization in the clumpy model with covering factor $f_c \gtrsim 5$ approach those of the smooth model at the same $N_{\rm HI}$. A clumpy medium with high $N_{\rm HI}$ and low $f_c \lesssim 2$ generates Ly${\alpha}$ features via scattering that the smooth model cannot: a bright core, symmetric line profile, and polarization jump.

We compare embedded young massive star clusters (YMCs) to (sub-)millimeter line observations tracing the excitation and dissociation of molecular gas in the starburst ring of NGC 1365. This galaxy hosts one of the strongest nuclear starbursts and richest populations of YMCs within 20 Mpc. Here we combine near-/mid-IR PHANGS-JWST imaging with new ALMA multi-J CO (1-0, 2-1 and 4-3) and [CI](1-0) mapping, which we use to trace CO excitation via R42 = I_CO(4-3)/I_CO(2-1) and R21 = I_CO(2-1)/I_CO(1-0) and dissociation via RCICO = I_[CI](1-0)/I_CO(2-1) at 330 pc resolution. We find that the gas flowing into the starburst ring from northeast to southwest appears strongly affected by stellar feedback, showing decreased excitation (lower R42) and increased signatures of dissociation (higher RCICO) in the downstream regions. There, radiative transfer modeling suggests that the molecular gas density decreases and temperature and [CI/CO] abundance ratio increase. We compare R42 and RCICO with local conditions across the regions and find that both correlate with near-IR 2 um emission tracing the YMCs and with both PAH (11.3 um) and dust continuum (21 um) emission. In general, RCICO exhibits ~ 0.1 dex tighter correlations than R42, suggesting CI to be a more sensitive tracer of changing physical conditions in the NGC 1365 starburst than CO (4-3). Our results are consistent with a scenario where gas flows into the two arm regions along the bar, becomes condensed/shocked, forms YMCs, and then these YMCs heat and dissociate the gas.

We present new neutral atomic carbon [CI](3P1-3P0) mapping observations within the inner ~7 kpc and ~4 kpc of the disks of NGC3627 and NGC4321 at a spatial resolution of 190 pc and 270 pc, respectively, using the ALMA Atacama Compact Array (ACA). We combine these with the CO(2-1) data from PHANGS-ALMA, and literature [CI] and CO data for two other starburst and/or active galactic nucleus (AGN) galaxies (NGC1808, NGC7469), to study: a) the spatial distributions of CI and CO emission; b) the observed line ratio RCICO = I_[CI](1-0)/I_CO(2-1) as a function of various galactic properties; and c) the abundance ratio of [CI/CO]. We find excellent spatial correspondence between CI and CO emission and nearly uniform RCICO ~0.1 across the majority of the star-forming disks of NGC3627 and NGC4321. However, RCICO strongly varies from ~0.05 at the centre of NGC4321 to >0.2-0.5 in NGC1808's starburst centre and NGC7469's centre with an X-ray AGN. Meanwhile, RCICO does not obviously vary with $U$, similar to the prediction of PDR models. We also find a mildly decreasing RCICO with an increasing metallicity over 0.7-0.85 solar metallicity, consistent with the literature. Assuming various typical ISM conditions representing GMCs, active star-forming regions and strong starbursting environments, we calculate the LTE radiative transfer and estimate the [CI/CO] abundance ratio to be ~0.1 across the disks of NGC3627 and NGC4321, similar to previous large-scale findings in Galactic studies. However, this abundance ratio likely has a substantial increase to ~1 and >1-5 in NGC1808's starburst and NGC7469's strong AGN environments, respectively, in line with the expectations for cosmic-ray dominated region (CRDR) and X-ray dominated region (XDR) chemistry. Finally, we do not find a robust evidence for a generally CO-dark, CI-bright gas in the disk areas we probed. (abbreviated)

Feedback and outflows in galaxies that are associated with a quasar phase are expected to be pivotal in quenching the most massive galaxies. However, observations targeting the molecular outflow phase, which dominates both the mass and momentum and removes the immediate fuel for star formation, are limited in high-z QSO hosts. Massive quiescent galaxies found at z ~ 4 are predicted to have already quenched star formation by z ~ 5 and undergone their most intense growth at z > 6. Here, we present two ALMA detections of molecular outflows, traced by blue-shifted absorption of the OH 119 micron doublet, from a sample of three z > 6 infrared luminous QSO hosts: J2310+1855 and P183+05. OH 119 micron is also detected in emission in P183+05, and tentatively in the third source: P036+03. Using similar assumptions as for high-z Dusty Star-Forming Galaxy outflows, we find that our QSOs drive molecular outflows with comparable mass outflow rates, and that are comparably energetic except for J2310+1855's significantly lower outflow energy flux. We do not find evidence, nor require additional input from the central AGN to drive the molecular outflow in J2310+1855 but can not rule out an AGN contribution in P183+05 if a significant AGN contribution to L_FIR is assumed and/or if the outflow covering fraction is high (> 53%), which evidence from the literature suggests is unlikely in these sources. Differences observed in the blue-shifted absorption spectral properties may instead be caused by the QSO hosts' more compact dust continuum, limiting observations to lower altitude and more central regions of the outflow.

We present a study of the internal structure of 82 star clusters located at the outer regions of the Large Magellanic Cloud and the Small Magellanic Cloud using data of the VISCACHA Survey. Through the construction of the minimum spanning tree, which analyzes the relative position of stars within a given cluster, it was possible to characterize the internal structure and explore the fractal or subclustered distribution for each cluster. We computed the parameters m (which is the average length of the connected segments normalized by the area), s (which is the mean points separation in units of cluster radius), and Q (the ratio of these components). These parameters are useful to distinguish between radial, homogeneous, and substructured distributions of stars. The dependence of these parameters with the different characteristics of the clusters, such as their ages and spatial distribution, was also studied. We found that most of the studied clusters present a homogeneous stellar distribution or a distribution with a radial concentration. Our results are consistent with the models, suggesting that more dynamically evolved clusters seem to have larger Q values, confirming previous results from numerical simulations. There also seems to be a correlation between the internal structure of the clusters and their galactocentric distances, in the sense that for both galaxies, the more distant clusters have larger Q values. We also paid particular attention to the effects of contamination by non-member field stars and its consequences finding that field star decontamination is crucial for these kinds of studies.

We present the first analysis of photometric observations of the supernova (SN) impostor AT 2016blu located in the galaxy NGC 4559. This transient source was discovered by the Lick Observatory Supernova Search in January 2012 and has continued its eruptive variability since then. Photometry of AT 2016blu reveals at least 19 outbursts in 2012-2022. AT 2016blu's outbursts show irregular variability with multiple closely spaced peaks of varying brightness. While the individual outbursts have irregular light curves, concentrations of these peaks seem to repeat with a period of roughly 110-115 d. Based on this period, the next outburst of AT 2016blu should occur around February 2023. AT 2016blu shares some similarities with SN 2000ch in NGC 3432, where it has been proposed that brightening episodes are caused by violent encounters at periastron in a binary system containing a luminous blue variable (LBV). We propose that AT 2016blu outbursts are also driven by binary interactions that intensify around times of periastron in an eccentric system. The intrinsic variability of the LBV-like primary star may cause different intensity and duration of binary interaction at each periastron passage. The binary interaction of AT 2016blu also resembles the periastron encounters of $\eta$ Carinae leading up to its Great Eruption and the erratic pre-SN eruptions of SN 2009ip. This similarity suggests that AT 2016blu might also be headed for a catastrophe, making it a target of great interest.

Neutron star equations of state with strong phase transitions may support twin stars, hybrid and hadronic stars with the same mass but different tidal deformabilities. The presence of twin stars in the population of merging neutron stars produces distinctive gaps in the joint distribution of binary tidal deformabilities and chirp masses. We analyze a simulated population of binary neutron star mergers recovered with a network of next-generation (XG) ground-based gravitational-wave detectors to determine how many observations are needed to infer, or rule out, the existence of twin stars. Using a hierarchical inference framework based on a simple parametric twin-star model, we find that a single week of XG observations may suffice to detect a tidal deformability difference of several hundred between twins and measure the mass scale at which twins occur to within a few percent. For less pronounced twins, XG observations will place a stringent upper bound on the tidal deformability difference.

Cosmic voids, the underdense regions in the Universe, are impacted by dark energy and massive neutrinos. In this work, relying on the DEMNUni suite of cosmological simulations, we explore the void size function in cosmologies with both dynamical dark energy and massive neutrinos. We investigate the impact of different choices of dark matter tracers on the void size function and study its sensitivity to the joint effect of modifying the dark energy equation of state and the sum of neutrino masses. We show that dark energy and massive neutrinos produce separable effects on the void size function. This statistic therefore allows us to distinguish among a wide range of combinations of dark energy equations of state and total neutrino masses, and its exploitation in forthcoming large galaxy surveys will be extremely useful in breaking degeneracies among these cosmological parameters.

Traditional estimators of the galaxy power spectrum and bispectrum are sensitive to the survey geometry. They yield spectra that differ from the true underlying signal since they are convolved with the window function of the survey. For the current and future generations of experiments, this bias is statistically significant on large scales. It is thus imperative that the effect of the window function on the summary statistics of the galaxy distribution is accurately modelled. Moreover, this operation must be computationally efficient in order to allow sampling posterior probabilities while performing Bayesian estimation of the cosmological parameters. In order to satisfy these requirements, we built a deep neural network model that emulates the convolution with the window function, and we show that it provides fast and accurate predictions. We trained (tested) the network using a suite of 2000 (200) cosmological models within the cold dark matter scenario, and demonstrate that its performance is agnostic to the precise values of the cosmological parameters. In all cases, the deep neural network provides models for the power spectra and the bispectrum that are accurate to better than 0.1 per cent on a timescale of 10 $\mu$s.

The time step criterion plays a crucial role in direct N-body codes. If not chosen carefully, it will cause a secular drift in the energy error. Shared, adaptive time step criteria commonly adopt the minimum pairwise time step, which suffers from discontinuities in the time evolution of the time step. This has a large impact on the functioning of time step symmetrisation algorithms. We provide new demonstrations of previous findings that a smooth and weighted average over all pairwise time steps in the N-body system, improves the level of energy conservation. Furthermore, we compare the performance of 27 different time step criteria, by considering 3 methods for weighting time steps and 9 symmetrisation methods. We present performance tests for strongly chaotic few-body systems, including unstable triples, giant planets in a resonant chain, and the current Solar System. We find that the harmonic symmetrisation methods (methods A3 and B3 in our notation) are the most robust, in the sense that the symmetrised time step remains close to the time step function. Furthermore, based on our Solar System experiment, we find that our new weighting method based on direct pairwise averaging (method W2 in our notation), is slightly preferred over the other methods.

The history of the Universe and the forces that shaped it are encoded in maps of the cosmos. From understanding these maps, we gain insights into nature that are inaccessible by other means. Unfortunately, the connection between fundamental physics and cosmic observables is often left to experts (and/or computers), making the general lessons from data obscure to many particle theorists. Fortunately, the same basic principles that govern the interactions of particles, like locality and causality, also control the evolution of the Universe as a whole and the manifestation of new physics in data. By focusing on these principles, we can understand more intuitively how the next generation of cosmic surveys will inform our understanding of fundamental physics. In these lectures, we will explore this relationship between theory and data through three examples: light relics ($N_{\rm eff}$) and the cosmic microwave background (CMB), neutrino mass and gravitational lensing of the CMB, and primordial non-Gaussianity and the distribution of galaxies. We will discuss both the theoretical underpinnings of these signals and the real-world obstacles to making the measurements.

We outline the ``dark siren'' galaxy catalog method for cosmological inference using gravitational wave (GW) standard sirens, clarifying some common misconceptions in the implementation of this method. When a confident transient electromagnetic counterpart to a GW event is unavailable, the identification of a unique host galaxy is in general challenging. Instead, as originally proposed by Schutz (1986), one can consult a galaxy catalog and implement a dark siren statistical approach incorporating all potential host galaxies within the localization volume. Trott & Hunterer 2021 recently claimed that this approach results in a biased estimate of the Hubble constant, $H_0$, when implemented on mock data, even if optimistic assumptions are made. We demonstrate explicitly that, as previously shown by multiple independent groups, the dark siren statistical method leads to an unbiased posterior when the method is applied to the data correctly. We highlight common sources of error possible to make in the generation of mock data and implementation of the statistical framework, including the mismodeling of selection effects and inconsistent implementations of the Bayesian framework, which can lead to a spurious bias.

We consider the effects of strong gravitational lensing by galaxy-scale deflectors on the observations of high-energy (E$\gg$GeV) neutrinos (HEN). For HEN at cosmological distances, the optical depth for multiple imaging is $\sim 10^{-3}$, implying that while we do not expect any multiply imaged HEN with present samples, next-generation experiments should be able to detect the first such event. We then present the distribution of expected time delays to aid in the identification of such events, in combination with directional and energy information. In order to assist in the evaluation of HEN production mechanisms, we illustrate how lensing affects the observed number counts for a variety of intrinsic luminosity functions of the source population. Finally, we see that the lensing effects on the cosmic neutrino background flux calculation would be negligible by taking kpc-scale jets as an example.

Right-handed neutrinos (RHNs) provide a natural portal to a dark sector accommodating dark matter (DM). In this work, we consider that the dark sector is connected to the standard model only via RHNs and ask how DM can be produced from RHNs. Our framework concentrates on a rather simple and generic interaction that couples RHNs to a pair of dark particles. Depending on whether RHNs are light or heavy in comparison to the dark sector and also on whether one or both of them are in the freeze-in/out regime, there are many distinct scenarios resulting in rather different results. We conduct a comprehensive and systematic study of all possible scenarios in this paper. For illustration, we apply our generic results to the type-I seesaw model with the dark sector extension, addressing whether and when DM in this model can be in the freeze-in or freeze-out regime. Some observational consequences in this framework are also discussed.

In this letter, the Grey-Disk and the Core-Corona models are combined in a scenario that aims to explain different unexpected features observed in the interactions of the highest energy particles in the Earth's atmosphere. In particular, the observed distributions of $X_{\rm max}$ and $N_\mu$ are explained, assuming that the ultra-high-energy cosmic ray spectrum is dominated by protons produced by a few extra-galactic sources with different injection spectra and maximum energy cutoffs. The compliance of this heterodox scenario with other relevant observations as the instep region in the energy spectrum, the event-by-event correlations between $X_{\rm max}$ and the detected signal at the ground and the absence of detection, so far, of UHE neutrinos or photons, are also briefly discussed. If confirmed, such a scenario would dramatically change the present understanding of the UHECR primary composition and, thus, the characteristics of their sources.

Wilsonian effective theories exploit hierarchies of scale to simplify the description of low-energy behaviour and play as central a role for gravity as for the rest of physics. They are useful both when hierarchies of scale are explicit in a gravitating system and more generally for understanding precisely what controls the size of quantum corrections in gravitational systems. But effective descriptions are also relevant for open systems (e.g. fluid mechanics as a long-distance description of statistical systems) for which the `integrating out' of unobserved low-energy degrees of freedom complicate a straightforward application of Wilsonian methods. Observations performed only on one side of an apparent horizon provide examples where open system descriptions also arise in gravitational physics. This chapter describes some early adaptations of Open Effective Theories (i.e. techniques for exploiting hierarchies of scale in open systems) in gravitational settings. Besides allowing the description of new types of phenomena (such as decoherence) these techniques also have an additional benefit: they sometimes can be used to resum perturbative expansions at late times and thereby to obtain controlled predictions in a regime where perturbative predictions otherwise generically fail.

In this work, we compute the structure and composition of the inner crust of a neutron star in the presence of a strong magnetic field, such as it can be found in magnetars. To determine the geometry and characteristics of the crust inhomogeneities, we consider the compressible liquid drop model, where surface and Coulomb terms are included in the variational equations, and we compare our results with previous calculations based on more approximate treatments. For the equation of state (EoS), we consider two non-linear relativistic mean-field models with different slopes of the symmetry energy, and we show that the extension of the inhomogeneous region inside the star core due to the magnetic field strongly depends on the behavior of the symmetry energy in the crustal EoS. Finally, we argue that the extended spinodal instability observed in previous calculations can be related to the presence of small amplitude density fluctuations in the magnetar outer core, rather than to a thicker solid crust. The compressible liquid drop model formalism, while in overall agreement with the previous calculations, leads to a systematic suppression of the metastable solutions, thus allowing a more precise estimation of the crust-core transition density and pressure, and therefore a better estimation of the crustal radius.

LLR measures the distance between observatories on Earth and retro-reflectors on Moon since 1969. In this paper, we study the possible violation of the equality of passive and active gravitational mass ($m_{a}/m_{p}$), for Aluminium (Al) and Iron (Fe), using LLR data. Our new limit of $3.9\cdot10^{-14}$ is about 100 times better than that of Bartlett and Van Buren [1986] reflecting the benefit of the many years of LLR data.

We consider a model of baryogenesis based on adding lepton number-violating quadratic mass terms to the inflaton potential of a non-minimally coupled inflation model. The $L$-violating mass terms generate a lepton asymmetry in a complex inflaton field via the mass term Affleck-Dine mechanism, which is transferred to the Standard Model (SM) sector when the inflaton decays to right-handed (RH) neutrinos. The model is minimal in that it requires only the SM sector, RH neutrinos, and a non-minimally coupled inflaton sector. We find that baryon isocurvature fluctuations can be observable in metric inflation but are negligible in Palatini inflation. The model is compatible with reheating temperatures that may be detectable in the observable primordial gravitational waves predicted by metric inflation.

Despite being created through a fundamentally quantum-mechanical process, cosmological structures have not yet revealed any sign of genuine quantum correlations. Among the obstructions to the direct detection of quantum signatures in cosmology, environmental-induced decoherence is arguably one of the most inevitable. Yet, we discover a mechanism of quantum recoherence for the adiabatic perturbations when they couple to an entropic sector. After a transient phase of decoherence, a turning point is reached, recoherence proceeds and adiabatic perturbations exhibit a large amount of self-coherence at late-time. This result is also understood by means of a non-Markovian master equation, which reduces to Wilsonian effective-field theory in the unitary limit. This allows us to critically assess the validity of open-quantum-system methods in cosmology and to highlight that re(de)coherence from linear interactions has no flat-space analogue.

Asymptotically safe quantum gravity is an approach to quantum gravity that achieves formulates a standard quantum field theory for the metric. Therefore, even the deep quantum gravity regime, that is expected to determine the true structure of the core of black holes, is described by a spacetime metric. The essence of asymptotic safety lies in a new symmetry of the theory -- quantum scale symmetry -- which characterizes the short-distance regime of quantum gravity. It implies the absence of physical scales. Therefore, the Newton coupling, which corresponds to a scale, namely the Planck length, must vanish asymptotically in the short-distance regime. This implies a weakening of the gravitational interaction, from which a resolution of classical spacetime singularities can be expected. In practise, properties of black holes in asymptotically safe quantum gravity cannot yet be derived from first principles, but are constructed using a heuristic procedure known as Renormalization Group improvement. The resulting asymptotic-safety inspired black holes have been constructed both for vanishing and for nonvanishing spin parameter. They are characterized by (i) the absence of curvature singularities, (ii) a more compact event horizon and photon sphere, (iii) a second (inner) horizon even at vanishing spin and (iv) a cold remnant as a possible final product of the Hawking evaporation. Observations can start to constrain the quantum-gravity scale that can be treated as a free parameter in asymptotic-safety inspired black holes. For slowly-spinning black holes, constraints from the EHT and X-ray observations can only constrain quantum-gravity scales far above the Planck length. In the limit of near-critical spin, asymptotic-safety inspired black holes may ``light up" in a way the ngEHT may be sensitive to, even for a quantum-gravity scale equalling the Planck length.

The plunge-merger stage of the binary-black-hole (BBH) coalescence, when the bodies' velocities reach a large fraction of the speed of light and the gravitational-wave (GW) luminosity peaks, provides a unique opportunity to probe gravity in the dynamical and nonlinear regime. How much do the predictions of general relativity differ from the ones in other theories of gravity for this stage of the binary evolution? To address this question, we develop a parametrized waveform model, within the effective-one-body formalism, that allows for deviations from general relativity in the plunge-merger-ringdown stage. As first step, we focus on nonprecessing-spin, quasicircular BBHs. In comparison to previous works, for each GW mode, our model can modify, with respect to general-relativistic predictions, the instant at which the amplitude peaks, the instantaneous frequency at this time instant, and the value of the peak amplitude. We use this waveform model to explore several questions considering both synthetic-data injections and two GW signals. In particular, we find that deviations from the peak GW amplitude and instantaneous frequency can be constrained to about 20$\%$ with GW150914. Alarmingly, we find that GW200129_065458 shows a strong violation of general relativity. We interpret this result as a false violation, either due to waveform systematics (mismodeling of spin precession) or due to data-quality issues depending on one's interpretation of this event. This illustrates the use of parametrized waveform models as tools to investigate systematic errors in plain general relativity. The results with GW200129_065458 also vividly demonstrate the importance of waveform systematics and of glitch mitigation procedures when interpreting tests of general relativity with current GW observations.