Papers for Tuesday, Oct 26 2021

Forthcoming time-domain surveys, such as the Rubin Observatory Legacy Survey of Space and Time, will vastly increase samples of supernovae (SNe) and other optical transients, requiring new data-driven techniques to analyse their photometric light curves. Here, we present the "Python for Intelligent Supernova-COsmology Light-curve Analysis" (PISCOLA), an open source data-driven light-curve fitter using Gaussian Processes that can estimate rest-frame light curves of transients without the need for an underlying light-curve template. We test PISCOLA on large-scale simulations of type Ia SNe (SNe Ia) to validate its performance, and show it successfully retrieves rest-frame peak magnitudes for average survey cadences of up to 7 days. We also compare to the existing SN Ia light-curve fitter SALT2 on real data, and find only small (but significant) disagreements for different light-curve parameters. As a proof-of-concept of an application of PISCOLA, we decomposed and analysed the PISCOLA rest-frame light-curves of SNe Ia from the Pantheon SN Ia sample with Non-Negative Matrix Factorization. Our new parametrization provides a similar performance to existing light-curve fitters such as SALT2. We further derived a SN Ia colour law from PISCOLA fits over $\sim$3500 to 7000\AA, and find agreement with the SALT2 colour law and with reddening laws with total-to-selective extinction ratio $R_V \lesssim 3.1$.

The paper investigates the influence of accretion heating and turbulent heat conduction on the equilibrium of protoplanetary disks, extending the 2D axis-symmetric passive disk model of Flock (Flock et al. 2016, ApJ 827, 144). The model includes dust sublimation and radiative transfer with the flux-limited diffusion approximation, and predicts the density and temperature profiles as well as the dust to gas ratio of the disk. It is shown that the accretion heating can have a large impact: For accretion rates above 5*10^(-8) M_solar /yr a zone forms behind the silicate condensation front with sufficiently high temperature to sublimate the dust and form a gaseous cavity. Assuming a Prandtl number ~ 0.7, it is furthermore shown that the turbulent heat conduction cannot be neglected in the evaluation of the temperature profile. While the inner rim position is not affected by viscous heating, the dead zone edge shifts radially outward for higher accretion rates.

Observed magnitudes of many quasars with redshifts exceeding $z=5$ correspond to luminosities $L_{\rm bol} > 10^{14}\,L_\odot$. The standard mechanism of quasar energy release by accretion suggests that masses of superluminous quasars should exceed $10^{10}\,M_\odot$. On the other hand, the age of these objects in the standard cosmological model is below one billion years, which is too short to explain their formation in the early Universe. Many quasars are known to be gravitationally lensed; showing multiple images of the same object. In the case of remote quasars with no multiple images, it is still possible that they are also gravitationally lensed by foreground objects of intermediate masses, such as globular clusters or dwarf galaxies. Such mesolensing would result in essential amplification of quasar brightnesses, subject to geometrical configuration between the lens and the lensed object. Here we estimate the fraction of quasars whose brightness might have been amplified by gravitational lensing.

We present new simulations of the formation of the Magellanic Stream based on an updated first-passage interaction history for the Magellanic Clouds, including both the Galactic and Magellanic Coronae and a live dark matter halo for the Milky Way. This new interaction history is needed because previously successful orbits need updating to account for the Magellanic Corona and the loosely bound nature of the Magellanic Group. These orbits involve two tidal interactions over the last 3.5 Gyrs and reproduce the Stream's position and appearance on the sky, mass distribution, and velocity profile. Most importantly, our simulated Stream is only $\sim$20 kpc away from the Sun at its closest point, whereas previous first-infall models predicted a distance of $100-200$ kpc. This dramatic paradigm shift in the Stream's 3D position would have several important implications. First, estimates of the observed neutral and ionized masses would be reduced by a factor of $\sim$5. Second, the stellar component of the Stream is also predicted to be $<$20 kpc away. Third, the enhanced interactions with the MW's hot corona at this small distance would substantially shorten the Stream's lifetime. Finally, the MW's UV radiation field would be much stronger, potentially explaining the H$\alpha$ emission observed along most of the Stream. Our prediction of a 20 kpc Stream could be tested by searching for UV absorption lines towards distant MW halo stars projected onto the Stream.

Most stars host convection zones in which heat is transported directly by fluid motion. Parameterizations like mixing length theory adequately describe convective flows in the bulk of these regions, but the behavior of convective boundaries is not well understood. Here we present 3D numerical simulations which exhibit penetration zones: regions where the entire luminosity could be carried by radiation, but where the temperature gradient is approximately adiabatic and convection is present. To parameterize this effect, we define the "penetration parameter" $\mathcal{P}$ which compares how far the radiative gradient deviates from the adiabatic gradient on either side of the Schwarzschild convective boundary. Following Roxburgh (1989) and Zahn (1991), we construct an energy-based theoretical model in which the extent of penetration is controlled by $\mathcal{P}$. We test this theory using 3D numerical simulations which employ a simplified Boussinesq model of stellar convection. We find significant convective penetration in all simulations. Our simple theory describes the simulations well. Penetration zones can take thousands of overturn times to develop, so long simulations or accelerated evolutionary techniques are required. In stellar contexts, we expect $\mathcal{P} \approx 1$ and in this regime our results suggest that convection zones may extend beyond the Schwarzschild boundary by up to $\sim$20-30\% of a mixing length. We present a MESA stellar model of the Sun which employs our parameterization of convective penetration as a proof of concept. We discuss prospects for extending these results to more realistic stellar contexts.

In this paper we investigate the robustness of age measurements, age spreads, and stellar models in young pre-main sequence stars. For this effort, we study a young cluster, $\lambda$ Orionis, within the Orion star-forming complex. We use Gaia data to derive a sample of 357 targets with spectroscopic temperatures from spectral types or from the automated spectroscopic pipeline in APOGEE Net. After accounting for systematic offsets between the spectral type and APOGEE temperature systems, the derived properties of stars on both systems are consistent. The complex ISM, with variable local extinction, motivates a star-by-star dereddening approach. We use a spectral energy distribution (SED) fitting method calibrated on open clusters for the Class III stars. For the Class II population, we use a Gaia G-RP dereddening method, minimizing systematics from disks, accretion, and other physics associated with youth. The cluster age is systematically different in models incorporating the structural impact of starspots or magnetic fields than in nonmagnetic models. Our mean ages range from 2-3 Myr (nonmagnetic models) to 3.9$\pm$0.2 Myr in the SPOTS model (f=0.34). We find star-by-star dereddening methods distinguishing between pre-MS classes provide a smaller age spread than techniques using a uniform extinction, and infer a minimum age spread of 0.19 dex and a typical age spread of 0.35 dex after modelling age distributions convolved with observed errors. This suggests that the $\lambda$ Ori cluster may have a long star formation timescale and that spotted stellar models significantly change age estimates for young clusters.

We review the current scenario of long-duration Gamma-ray burst (LGRB) progenitors, and in addition, present models of massive stars for a mass range of $10\text{--}150 \, \mathrm{M}_\odot$ with $\Delta \mathrm{M}=10 \, \mathrm{M}_\odot$ and rotation rate $v/v_{\rm{crit}}=0$ to $0.6$ with a velocity resolution $\Delta v/v_{\rm{crit}} =0.1$. We further discuss possible metallicity and rotation rate distribution from our models that might be preferable for the creation of successful LGRB candidates given the observed LGRB rates and their metallicity evolution. In the current understanding, LGRBs are associated with Type-Ic supernovae (SNe). To establish LGRB-SN correlation, we discuss three observational paths: (i) space-time coincidence, (ii) evidence from photometric light curves of LGRB afterglows and SN Type-Ic, (iii) spectroscopic study of both LGRB afterglow and SN. Superluminous SNe are also believed to have the same origin as LGRBs. Therefore, we discuss constraints on the progenitor parameters that can possibly dissociate these two events from a theoretical perspective. We further discuss the scenario of single star versus binary star as a more probable pathway to create LGRBs. Given the limited parameter space in the mass, mass ratio and separation between the two components in a binary, binary channel is less likely to create LGRBs to match the observed LGRB rate. Despite effectively-single massive stars are fewer in number compared to interacting binaries, their chemically homogeneous evolution (CHE) might be the major channel for LGRB production.

G0.253+0.016, commonly referred to as "the Brick" and located within the Central Molecular Zone, is one of the densest ($\approx10^{3-4}$ cm$^{-3}$) molecular clouds in the Galaxy to lack signatures of widespread star formation. We set out to constrain the origins of an arc-shaped molecular line emission feature located within the cloud. We determine that the arc, centred on $\{l_{0},b_{0}\}=\{0.248^{\circ}, 0.18^{\circ}\}$, has a radius of $1.3$ pc and kinematics indicative of the presence of a shell expanding at $5.2^{+2.7}_{-1.9}$ km s$^{-1}$. Extended radio continuum emission fills the arc cavity and recombination line emission peaks at a similar velocity to the arc, implying that the molecular and ionised gas are physically related. The inferred Lyman continuum photon rate is $N_{\rm LyC}=10^{46.0}-10^{47.9}$ photons s$^{-1}$, consistent with a star of spectral type B1-O8.5, corresponding to a mass of $\approx12-20$ M$_{\odot}$. We explore two scenarios for the origin of the arc: i) a partial shell swept up by the wind of an interloper high-mass star; ii) a partial shell swept up by stellar feedback resulting from in-situ star formation. We favour the latter scenario, finding reasonable (factor of a few) agreement between its morphology, dynamics, and energetics and those predicted for an expanding bubble driven by the wind from a high-mass star. The immediate implication is that G0.253+0.016 may not be as quiescent as is commonly accepted. We speculate that the cloud may have produced a $\lesssim10^{3}$ M$_{\odot}$ star cluster $\gtrsim0.4$ Myr ago, and demonstrate that the high-extinction and stellar crowding observed towards G0.253+0.016 may help to obscure such a star cluster from detection.

Feedback from active galactic nuclei (AGN) has become established as a fundamental process in the evolution of the most massive galaxies. Its impact on Milky Way (MW)-mass systems, however, remains comparatively unexplored. In this work, we use the Auriga simulations to probe the impact of AGN feedback on the dynamical and structural properties of galaxies, focussing on the bar, bulge, and disc. We analyse three galaxies -- two strongly and one very weakly barred -- using three setups: (i) the fiducial Auriga model, which includes both radio and quasar mode feedback, (ii) a setup with no radio mode, and (iii) one with neither the radio nor the quasar mode. When removing the radio mode, gas in the circumgalactic medium cools more efficiently and subsequently settles in an extended disc, with little effect on the inner disc. Contrary to previous studies, we find that although the removal of the quasar mode results in more massive central components, these are in the form of compact discs, rather than spheroidal bulges. Therefore, galaxies without quasar mode feedback are more baryon-dominated and thus prone to forming stronger and shorter bars, which reveals an anti-correlation between the ejective nature of AGN feedback and bar strength. Hence, we report that the effect of AGN feedback (i.e. ejective or preventive) can significantly alter the dynamical properties of MW-like galaxies. Therefore, the observed dynamical and structural properties of MW-mass galaxies can be used as additional constraints for calibrating the efficiency of AGN feedback models.

With Gaia parallaxes it is possible to study the stellar populations associated with individual Galactic supernova remnants (SNR) to estimate the mass of the exploding star. Here we analyze the luminous stars near the Vela pulsar and SNR to find that its progenitor was probably (>90%) low mass (8.1-10.3Msun). The presence of the O star gamma2 Vel a little over 100 pc from Vela is the primary ambiguity, as including it in the analysis volume significantly increases the probability (to 5%) of higher mass (>20Msun) progenitors. However, to be a high mass star associated with gamma2 Vel's star cluster at birth, the progenitor would have to a runaway star from an unbound binary with an unusually high velocity. The primary impediment to analyzing large numbers of Galactic SNRs in this manner is the lack of accurate distances. This can likely be solved by searching for absorption lines from the SNR in stars as a function of distance, a method which yielded a distance to Vela in agreement with the direct pulsar parallax. If Vela was a 10Msun supernova in an external galaxy, the 50 pc search region used in extragalactic studies would contain only ~10% of the stars formed in a 50~pc region around the progenitor at birth and ~90% of the stars in the search region would have been elsewhere.

Upon entering the tidal sphere of a supermassive black hole, a star is ripped apart by tides and transformed into a stream of debris. The ultimate fate of that debris, and the properties of the bright flare that is produced and observed, depends on a number of parameters, including the energy of the center of mass of the original star. Here we present the results of a set of smoothed particle hydrodynamics simulations in which a $1~M_\odot $, $\gamma = 5/3$ polytrope is disrupted by a $10^6 ~M_\odot$ supermassive black hole. Each simulation has a pericenter distance of $r_{\rm p} = r_{\rm t}$ (i.e., $\beta \equiv r_{\rm t}/r_{\rm p} = 1$ with $r_{\rm t}$ the tidal radius), and we vary the eccentricity $e$ of the stellar orbit from $e = 0.8$ up to $e = 1.20$ and study the nature of the fallback of debris onto the black hole and the long-term fate of the unbound material. For simulations with eccentricities $e \lesssim 0.98$, the fallback curve has a distinct, three-peak structure that is induced by self-gravity. For simulations with eccentricities $e \gtrsim 1.06$, the core of the disrupted star reforms following its initial disruption. Our results have implications for, e.g., tidal disruption events produced by supermassive black hole binaries.

We present the discovery of an exceptional dimming event in a cool supergiant star in the Local Volume spiral M51. The star, dubbed M51-DS1, was found as part of a Hubble Space Telescope (HST) search for failed supernovae. The supergiant, which is plausibly associated with a very young ($\lesssim6$ Myr) stellar population, showed clear variability (amplitude $\Delta F814W\approx0.7$ mag) in numerous HST images obtained between 1995 and 2016, before suddenly dimming by $>2$ mag in $F814W$ sometime between late 2017 and mid-2019. In follow-up data from 2021, the star rebrightened, ruling out a failed supernova. Prior to its near-disappearance, the star was luminous and red ($M_{F814W}\lesssim-7.6$ mag, $F606W-F814W=1.9$ - $2.2$ mag). Modelling of the pre-dimming spectral energy distribution of the star favors a highly reddened, very luminous ($\log[L/L_{\odot}] = 5.4$ - $5.7$) star with $T_{\mathrm{eff}}\approx3700$ - $4700$ K, indicative of a cool yellow- or post-red supergiant with an initial mass of $\approx26$ - $40$ $M_{\odot}$. However, the local interstellar extinction and circumstellar extinction are uncertain, and could be lower: the near-IR colors are consistent with a red supergiant, which would be cooler ($T_{\mathrm{eff}}\lesssim3700$ K) and slightly less luminous ($\log[L/L_{\odot}] = 5.2$ - $5.3$), giving an inferred initial mass of $\approx19$ - $22$ $M_{\odot}$. In either case, the dimming may be explained by a rare episode of enhanced mass loss that temporarily obscures the star, potentially a more extreme counterpart to the 2019 - 2020 "Great Dimming" of Betelgeuse. Given the emerging evidence that massive evolved stars commonly exhibit variability that can mimic a disappearing star, our work highlights a substantial challenge in identifying true failed supernovae.

We propose that chirally asymmetric plasma can be produced in the gap regions of the magnetospheres of pulsars and black holes. We show that, in the case of supermassive black holes situated in active galactic nuclei, the chiral charge density and the chiral chemical potential are very small and unlikely to have any observable effects. In contrast, the chiral asymmetry produced in the magnetospheres of magnetars can be substantial. It can trigger the chiral plasma instability that, in turn, can lead to observable phenomena in magnetars. In particular, the instability should trigger circularly polarized electromagnetic radiation in a wide window of frequencies, spanning from radio to near-infrared. As such, the produced chiral charge has the potential to affect some features of fast radio bursts.

The high number of objects in the LEO is a risk that collisions between sub-orbital or escape velocity objects with an orbiting object of satellites occur when two satellites collide while orbiting the earth. One of the approaches to avoid collisions is a robotic configuration of satellite constellations. Satellite constellations should not be confused with satellite clusters, which are groups of satellites moving in close proximity to each other in nearly identical orbits; nor with satellite series or satellite programs, which are generations of satellites launched successively; nor with satellite fleets, which are groups of satellites from the same manufacturer or operator that operate an independent system. CfEOS constellations designed for geospatial applications and Earth observation. Unlike a single satellite, a constellation can provide permanent global or near-global coverage anywhere on Earth. CfEOS constellations are configured in sets of complementary orbital planes and connect to ground stations located around the globe. This paper describes the GNC analysis, the orbit propagation and robotic systems configuration for Collision-free Earth observation satellites (CfEOS) constellations.

We propose for the first time that KIC 12602250 is a low-amplitude radial double-mode $\delta$ Scuti star with amplitude modulation. The detailed frequency analysis is given for the light curve of KIC 12602250 which is delivered from the Kepler mission. The Fourier analysis of the long cadence data (i.e. Q0 - Q17, spanning 1471 days) reveals that the variations of the light curve are dominated by the strongest mode with frequency F0 = 11.6141 $\rm{d^{-1}}$, suggesting that KIC 12602250 is a $\delta$ Scuti star. The other independent mode F1 = 14.9741 $\rm{d^{-1}}$ is newly detected. The amplitude of the light variations of \target is $\sim$ 0.06 mag, which indicates that this is a low-amplitude $\delta$ Scuti star, but the ratio of F0/F1 is estimated as 0.7756 which is typical of HADS, and a slow amplitude growth is detected in F1 and $f_{3}$, which could be due to stellar evolution, suggesting that KIC 12602250 could be a post main sequence $\delta$ Scuti which is crossing the instability strip for the first time.

We present $\texttt{Abacus}$, a fast and accurate cosmological $N$-body code based on a new method for calculating the gravitational potential from a static multipole mesh. The method analytically separates the near- and far-field forces, reducing the former to direct $1/r^2$ summation and the latter to a discrete convolution over multipoles. The method achieves 70 million particle updates per second per node of the Summit supercomputer, while maintaining a median fractional force error of $10^{-5}$. We express the simulation time step as an event-driven "pipeline", incorporating asynchronous events such as completion of co-processor work, Input/Output, and network communication. $\texttt{Abacus}$ has been used to produce the largest suite of $N$-body simulations to date, the $\texttt{AbacusSummit}$ suite of 60 trillion particles (Maksimova et al., 2021), incorporating on-the-fly halo finding. $\texttt{Abacus}$ enables the production of mock catalogs of the volume and resolution required by the coming generation of cosmological surveys.

We present the public data release of the AbacusSummit cosmological $N$-body simulation suite, produced with the $\texttt{Abacus}$ $N$-body code on the Summit supercomputer of the Oak Ridge Leadership Computing Facility. $\texttt{Abacus}$ achieves $\mathcal{O}\left(10^{-5}\right)$ median fractional force error at superlative speeds, calculating 70M particle updates per second per node at early times, and 45M particle updates per second per node at late times. The simulation suite totals roughly 60 trillion particles, the core of which is a set of 139 simulations with particle mass $2\times10^{9}\,h^{-1}\mathrm{M}_\odot$ in box size $2\,h^{-1}\mathrm{Gpc}$. The suite spans 97 cosmological models, including Planck 2018, previous flagship simulation cosmologies, and a linear derivative and cosmic emulator grid. A sub-suite of 1883 boxes of size $500\,h^{-1}\mathrm{Mpc}$ is available for covariance estimation. AbacusSummit data products span 33 epochs from $z=8$ to $0.1$ and include lightcones, full particle snapshots, halo catalogs, and particle subsets sampled consistently across redshift. AbacusSummit is the largest high-accuracy cosmological $N$-body data set produced to date.

We describe a new method (\textsc{CompaSO}) for identifying groups of particles in cosmological $N$-body simulations. \textsc{CompaSO} builds upon existing spherical overdensity (SO) algorithms by taking into consideration the tidal radius around a smaller halo before competitively assigning halo membership to the particles. In this way, the \textsc{CompaSO} finder allows for more effective deblending of haloes in close proximity as well as the formation of new haloes on the outskirts of larger ones. This halo-finding algorithm is used in the \textsc{AbacusSummit} suite of $N$-body simulations, designed to meet the cosmological simulation requirements of the Dark Energy Spectroscopic Instrument (DESI) survey. \textsc{CompaSO} is developed as a highly efficient on-the-fly group finder, which is crucial for enabling good load-balancing between the GPU and CPU and the creation of high-resolution merger trees. In this paper, we describe the halo-finding procedure and its particular implementation in \Abacus{Abacus}, accompanying it with a qualitative analysis of the finder. {We test the robustness of the \textsc{CompaSO} catalogues before and after applying the cleaning method described in an accompanying paper and demonstrate its effectiveness by comparing it with other validation techniques.} We then visualise the haloes and their density profiles, finding that they are well fit by the NFW formalism. Finally, we compare other properties such as radius-mass relationships and two-point correlation functions with that of another widely used halo finder, \textsc{ROCKSTAR}.

Tracking the formation and evolution of dark matter haloes is a critical aspect of any analysis of cosmological $N$-body simulations. In particular, the mass assembly of a halo and its progenitors, encapsulated in the form of its merger tree, serves as a fundamental input for constructing semi-analytic models of galaxy formation and, more generally, for building mock catalogues that emulate galaxy surveys. We present an algorithm for constructing halo merger trees from AbacusSummit, the largest suite of cosmological $N$-body simulations performed to date consisting of nearly 60 trillion particles, and which has been designed to meet the Cosmological Simulation Requirements of the Dark Energy Spectroscopic Instrument (DESI) survey. Our method tracks the cores of haloes to determine associations between objects across multiple timeslices, yielding lists of halo progenitors and descendants for the several tens of billions of haloes identified across the entire suite. We present an application of these merger trees as a means to enhance the fidelity of AbacusSummit halo catalogues by flagging and "merging" haloes deemed to exhibit non-monotonic past merger histories. We show that this cleaning technique identifies portions of the halo population that have been deblended due to choices made by the halo finder, but which could have feasibly been part of larger aggregate systems. We demonstrate that by cleaning halo catalogues in this post-processing step, we remove potentially unphysical features in the default halo catalogues, leaving behind a more robust halo population that can be used to create highly-accurate mock galaxy realisations from AbacusSummit.

We introduce the AbacusHOD model and present two applications of AbacusHOD and the AbacusSummit simulations to observations. AbacusHOD is an HOD framework written in Python that is particle-based, multi-tracer, highly generalized, and highly efficient. It is designed specifically with multi-tracer/cosmology analyses for next generation large-scale structure surveys in mind, and takes advantage of the volume and precision offered by the new state-of-the-art AbacusSummit cosmological simulations. The model is also highly customizable and should be broadly applicable to any upcoming surveys and a diverse range of cosmological analyses. In this paper, we demonstrate the capabilities of the AbacusHOD framework through two example applications. The first example demonstrates the high efficiency and the large HOD extension feature set through an analysis full-shape redshift-space clustering of BOSS galaxies at intermediate to small scales (<30Mpc/h), assessing the necessity of introducing secondary galaxy biases (assembly bias). We find strong evidence for using halo environment instead of concentration to trace secondary galaxy bias, a result which also leads to a moderate reduction to the "lensing is low" tension. The second example demonstrates the multi-tracer capabilities of the AbacusHOD package through an analysis of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) cross-correlation measurements between three different galaxy tracers, LRGs, ELGs, and QSOs. We expect the AbacusHOD framework, in combination with the AbacusSummit simulation suite, to play an important role in a simulation-based analysis of the up-coming Dark Energy Spectroscopic Instrument (DESI) datasets.

We describe a method for generating halo catalogues on the light cone using the \Abacus{AbacusSummit} suite of $N$-body simulations. The main application of these catalogues is the construction of realistic mock galaxy catalogues and weak lensing maps on the sky. Our algorithm associates the haloes from a set of coarsely-spaced snapshots with their positions at the time of light-cone crossing by matching halo particles to on-the-fly light cone particles. It then records the halo and particle information into an easily accessible product, which we call the \Abacus{AbacusSummit} halo light cone catalogues. Our recommended use of this product is in the halo mass regime of $M_{\rm halo} > 2.1 \times 10^{11} \ M_\odot/h$ for the \texttt{base} resolution simulations, i.e. haloes containing at least 100 particles, where the interpolated halo properties are most reliable. To test the validity of the obtained catalogues, we perform various visual inspections and consistency checks. In particular, we construct galaxy mock catalogues of emission-line galaxies (ELGs) at $z \sim 1$ by adopting a modified version of the \Abacus{AbacusHOD} script, which builds on the standard halo occupation distribution (HOD) method by including various extensions. We find that the multipoles of the auto-correlation function are consistent with the predictions from the full-box snapshot, implicitly validating our algorithm. In addition, we compute and output CMB convergence maps and find that the auto- and cross-power spectrum agrees with the theoretical prediction at the subpercent level. Halo light cone catalogues for 25 \texttt{base} and 2 \texttt{huge} simulations at the fiducial cosmology is available at DOI:\href{https://www.doi.org/10.13139/OLCF/1825069}{10.13139/OLCF/1825069}

We study the linear growth and nonlinear saturation of the "acoustic Resonant Drag Instability" (RDI) when the dust grains, which drive the instability, have a wide, continuous spectrum of different sizes. This physics is generally applicable to dusty winds driven by radiation pressure, such as occurs around red-giant stars, star-forming regions, or active galactic nuclei. Depending on the physical size of the grains compared to the wavelength of the radiation field that drives the wind, two qualitatively different regimes emerge. In the case of grains that are larger than the radiation's wavelength -- termed the constant-drift regime -- the grain's equilibrium drift velocity through the gas is approximately independent of grain size, leading to strong correlations between differently sized grains that persist well into the saturated nonlinear turbulence. For grains that are smaller than the radiation's wavelength -- termed the non-constant-drift regime -- the linear instability grows more slowly than the single-grain-size RDI and only the larger grains exhibit RDI-like behavior in the saturated state. A detailed study of grain clumping and grain-grain collisions shows that outflows in the constant-drift regime may be effective sites for grain growth through collisions, with large collision rates but low collision velocities.

Polarization offers a unique view in the physical processes of astrophysical jets. We report on optical circular polarization observations of two famous blazars, namely 3C 279 and PKS 1510-089, at high linearly polarized states. This is the first time PKS 1510-089 is observed in optical circular polarization. While only upper limits can be extracted from our observing campaign, the non-detection of optical circular polarization allows us to provide meaningful constraints on their magnetic field strength and jet composition. We find that high-energy emission models requiring high magnetic field strength and a low positron fraction can be excluded.

We use Cloudy photoionisation models to predict the flux profiles for optical/IR emissions lines that trace the footprint of X-ray gas in NGC 4151, such as [Fe X] 6375A and [Si X] 1.43um. These are a subset of coronal lines, from ions with ionisation potential $\geq$ that of O VII, i.e., 138eV. The footprint lines are formed in gas over the same range in ionisation state as the H and He-like of O and Ne ions, which are also the source of X-ray emission-lines. The footprint lines can be detected with optical and IR telescopes, such as Hubble Space Telescope/STIS and James Webb Space Telescope/NIRSpec, and, therefore, can potentially be used to measure the kinematics of the extended X-ray emission gas. As a test case, we use the footprints to quantify the properties of the X-ray outflow in the Seyfert 1 galaxy NGC 4151. To confirm the accuracy of our method, we compare our model predictions to the measured flux from archival STIS spectra and previous ground-based studies, and the results are in good agreement. We also use our X-ray footprint method to predict the mass profile for the X-ray emission-line gas in NGC 4151 and derive a total spatially-integrated X-ray mass of $7.8 \times 10^{5}~M_{sun}$, in comparison to $5.4 \times 10^{5}~M_{sun}$ measured from the Chandra X-ray analysis. Our results indicate that high-ionisation footprint emission lines in the optical and near-infrared can be used to accurately trace the kinematics and physical conditions of AGN ionised, X-ray emission line gas.

We find that low-mass halo stars on radial orbits that are located within 2 kpc of the Sun have at least two distinct components; the velocity and photometrically determined metallicity distributions of these components cannot be explained by a single radial merger event (RME). The first component has [Fe/H] ~ -1.6, accounts for one third of halo stars near the Sun, and is consistent with the Virgo Radial Merger (VRM); it has previously been shown that the VRM was accreted into the Milky Way halo within the past few Gyr. The second component likely includes stars with more than one origin, but about half of these stars could be consistent with a second, early, massive contribution to the halo with [Fe/H] ~ -1.0 and low energy, as has been proposed for the origin of the "Gaia Sausage" and "Gaia-Enceladus" halo stars. These stars which comprise the "Gaia Sausage" velocity structure are a combination of VRM and other stars on radial orbits.

The spin, $\lambda$, of dark matter (DM) halos in cosmological simulations follows a log normal distribution and has little correlation with galaxy observables. As such, there is currently no way to infer the $\lambda$ parameter of individual halos hosting observed galaxies. We present here a first attempt to measure $\lambda$ starting from the dynamically distinct stellar components identified in high-resolution cosmological simulations with Galactic Structure Finder. In a subsample of NIHAO galaxies, we find tight correlations between the total angular momentum (AM) of the DM halos, $J_h$, and the azimuthal AM, $J_z$, of the stellar components of the form: log($J_h$)=$\alpha$+$\beta\cdot$log($J_z$). The stellar halos have the tightest relation with $\alpha=9.50\pm0.42$ and $\beta=0.46\pm0.04$. The other tight relation is with the disks: $\alpha=6.15\pm0.92$ and $\beta=0.68\pm0.07$. We used Gaia DR2 and APOGEE to generate a combined kinematics-abundance space, where the Galaxy's thin and thick stellar disks stars can be neatly separated and their rotational velocity profiles, $v_{\phi}(R)$, can be computed. For both disks, $v_{\phi}(R)$ decreases with radius with $\sim$2 km s$^{-1}$ kpc$^{-1}$ for $R\gtrsim5$ kpc, resulting in $v_{\phi,thin}\backsimeq221$ km s$^{-1}$ and $v_{\phi,thick}\backsimeq188$ km s$^{-1}$ at $R_{\odot}$. These velocity profiles together with the Galaxy mass model of Cautun et al. (2020) result in the AM for the two disks: $J_{z,thin}=(3.26\pm0.43)\times10^{13}$ and $J_{z,thick}=(1.20\pm0.30)\times10^{13}$ M$_{\odot}$ kpc km s$^{-1}$, where the DM halo is assumed to have a contracted NFW profile. Adopting the correlation found in simulations, the spin estimate of the Galaxy's DM halo is $\lambda_{MW}=0.061^{+0.022}_{-0.016}$. If the DM halo has a NFW profile instead, the spin becomes $\lambda_{MW}=0.088^{+0.024}_{-0.020}$, making the Galaxy a more extreme outlier.

We present here the updated calibration of The Nuclear Spectroscopic Telescope ARray NuSTAR, which was performed using data on the Crab accumulated over the last 9 years in orbit. The basis for this new calibration contains over 250ks of focused Crab (imaged through the optics) and over 500ks of stray-light Crab (not imaged through optics). We measured an epoch averaged Crab spectrum of the stray-light Crab data and define a canonical Crab spectrum of Gamma = 2.103 +- 0.001 and N = 9.69 +- 0.02 keV-1 cm-2 s-1 at 1 keV, which we use as our calibration standard. The new calibration, released in the CALDB update 20211020, provides significant updates to: 1) the detector absorption component, 2) the detector response function, and 3) the effective area vignetting function. The calibration improves agreement between FPMA and FPMB across detectors with a standard deviation of 1.7% for repeat observations between off-axis angles of 1-4 arcmin, and the measured flux has increased by 5-15%, with 5% below 1 arcmin off-axis angle, 10% between 1-2 arcmin, and 15 above 4arcmin.

The morphology and kinematics of the molecular interstellar medium are controlled by processes such as turbulence, gravity, stellar feedback, and Galactic shear. Using a sample of 15149 young stellar objects (YSOs) with Gaia Data Release 2 (DR2) astrometric measurements, we study morphology and kinematic structure of their associated molecular gas. We identify 150 YSO associations with distance $d \lesssim 3 \;\rm kpc$. The YSO associations are oriented parallel to the disk midplane, with a median angle of 30$^{\circ}$, and they have a median aspect ratio of 1.97. Along the Galactic longitude direction, the velocity dispersion is related to the separation by $\sigma_{v_l} = 0.58{\;}(r_l/{\rm pc})^{0.66\pm0.05}({\rm km\ s^{-1}})$, along the Galactic latitude direction, $\sigma_{v_b} = 0.54 {\;} (r_b/{\rm pc})^{0.64\pm0.04}({\rm km\ s^{-1}})$, and overall $\sigma_{v,{\rm 2D}} = 0.74 {\;} (r/{\rm pc})^{0.67\pm0.05}({\rm km\ s^{-1}})$. The slope is on the stepper side, yet consistent with previous measurements. The energy dissipation rate of turbulence $\dot{\epsilon} = \sigma_{v,{\rm 3D}}^3 /L$ decreases with the Galactocentric distance $r_{\rm gal}$ by $\dot{\epsilon} = 1.77\times10^{-4}e^{-0.45 \; (r_{\rm gal}/ {\rm kpc})}{\;}({\rm erg\ g^{-1}\ s^{-1}})$ for clouds with $40\; {\rm pc}<r < 130 \;\rm pc$, which corresponds to a gradient of 0.2 $\rm dex \; kpc^{-1}$. This decrease can be explained if turbulence is driven by cloud collisions, as the clouds located in the inner Galaxy have higher chances to accrete smaller clouds. Although the density structures of the complexes are anisotropic, the turbulence is consistent with being isotropic. Thus, the clouds are long-lived, stationary structures shaped by the Galactic motion where turbulence is maintained by a continuous injection.

Galaxy clusters are good targets for examining our understanding of cosmology. Apart from numerical simulations and gravitational lensing, X-ray observation is the most common and conventional way to analyze the gravitational structures of galaxy clusters. Therefore, it is valuable to have simple analytical relations that can connect the observed distribution of the hot, X-ray emitting gas to the structure of the dark matter in the clusters as derived from simulations. In this article, we apply a simple framework that can analytically connect the hot gas empirical parameters with the standard parameters in the cosmological cold dark matter model. We have theoretically derived two important analytic relations, $r_s \approx \sqrt{3}r_c$ and $\rho_s \approx 9\beta kT/8 \pi Gm_gr_c^2$, which can easily relate the dark matter properties in galaxy clusters with the hot gas properties. This can give a consistent picture describing gravitational astrophysics for galaxy clusters by the hot gas and cold dark matter models.

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track ($\mu>1$) in the observed radio and X-ray luminosity relations ($L_{\rm R}\propto L_{\rm X}^{\mu}$), but the thin disk component may not be able to explain the standard track ($\mu\approx 0.6$) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.

We firstly derive the stellar population properties: age and metallicity for $\sim$ 43,000 low redshift galaxies in the seventh data release (DR7) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, which have no spectroscopic observations in the Sloan Digital Sky Survey(SDSS). We employ a fitting procedure based on the small-scale features of galaxy spectra so as to avoid possible biases from the uncertain flux calibration of the LAMOST spectroscopy. We show that our algorithm can successfully recover the average age and metallicity of the stellar populations of galaxies down to signal-to-noise$\geq$5 through testing on both mock galaxies and real galaxies comprising LAMOST and their SDSS counterparts. We provide a catalogue of the age and metallicity for $\sim$ 43,000 LAMOST galaxies online. As a demonstration of the scientific application of this catalogue, we present the Holmberg effect on both age and metallicity of a sample of galaxies in galaxy pairs.

Using the photometric data of several sky surveys, we reanalyzed the c-type RR Lyrae star BE Dor (MACHO 5.4644.8, OGLE-LMC-RRLYR-06002), which was discovered to show cyclic period changes. The O-C diagram and pulsation period obtained from Fourier analysis show that there are significant period modulations in BE Dor. However, different from previous viewpoint, the changes are quasi-periodic and abrupt. Therefore, the light-travel time effect caused by the companion motion cannot explain the changes. Noting a same subtype star KIC 9453114 with similar phenomena has a high macroturbulent velocity, and the degree of O-C changes seem to be positively correlated with these velocities, we consider that the mechanism leading to period modulation should be caused by the interaction between turbulent convection and magnetic field activity in the ionization zone, i.e., Stothers model. This model may not explain the general Blazhko effect, but should explain such phenomena as period modulations in BE Dor and those other c-type RR Lyrae stars.

The detection and parametrization of molecular clumps is the first step in studying them. We propose a method based on Local Density Clustering algorithm while physical parameters of those clumps are measured using the Multiple Gaussian Model algorithm. One advantage of applying the Local Density Clustering to the clump detection and segmentation, is the high accuracy under different signal-to-noise levels. The Multiple Gaussian Model is able to deal with overlapping clumps whose parameters can be derived reliably. Using simulation and synthetic data, we have verified that the proposed algorithm could characterize the morphology and flux of molecular clumps accurately. The total flux recovery rate in $^{13}\rm CO$ (J=1-0) line of M16 is measured as 90.2\%. The detection rate and the completeness limit are 81.7\% and 20 K km s$ ^{-1} $ in $^{13}\rm CO$ (J=1-0) line of M16, respectively.

Context. The populations of small bodies of the Solar System (asteroids, comets, Kuiper Belt objects) are used to constrain the origin and evolution of the Solar System. Both their orbital distribution and composition distribution are required to track the dynamical pathway from their regions of formation to their current locations. Aims. We aim at increasing the sample of Solar System objects (SSOs) that have multi-filter photometry and compositional taxonomy. Methods. We search for moving objects in the SkyMapper Southern Survey. We use the predicted SSO positions to extract photometry and astrometry from the SkyMapper frames. We then apply a suite of filters to clean the catalog for false-positive detections. We finally use the near-simultaneous photometry to assign a taxonomic class to objects. Results. We release a catalog of 880,528 individual observations, consisting of 205,515 known and unique SSOs. The catalog completeness is estimated to be about 97% down to V=18 mag and the purity to be above 95% for known SSOs. The near-simultaneous photometry provides either three, two, or a single color that we use to classify 117,356 SSOs with a scheme consistent with the widely used Bus-DeMeo taxonomy. Conclusions. The present catalog contributes significantly to the sample of asteroids with known surface properties (about 40% of main-belt asteroids down to an absolute magnitude of 16). We will release more observations of SSOs with future SkyMapper data releases.

We calculated morphological parameters for 70821 galaxies from VIPERS (spectroscopic galaxy survey performed on VIMOS spectroscope at VLT). These parameters includes Gini, M20, Concentration, Asymmetry and Smoothness. Results correlate with the distribution of these parameters for other simulated and observed samples. We also studied dependence of these parameters with Sersic power index of radial distribution of surface brightness of galaxy image. Our aim was to find a clear separation of VIPERS galaxies on elliptical and spiral. This is necessary for testing the method of Sersic index (ns) calculation in statmorph program. To find such bimodality we use B-V color index from VIPERS database. To perform the error analysis of morphological parameters we simulated galaxy images with random background of different magnitude and estimated the errors as dispersion of the parameters. We also found asymptotic values of errors of morphological parameters by increasing the numbers of mock images. To analyse the possible variation of each morphological parameter during the convolution of close galactic images, we have simulated them to research. In the result of this investigation we have analysed the dependence of the every morphological parameter from CAS and Gini/M20 statistics from the distance between galactic centers. The differences between our results for VIPERS and Gini-M20 distribution for PanStarrs galaxies at z<0.5 could be explained it by cosmological evolution of galaxies. We found out that in modern Universe there are much more elliptical galaxies than at z>0.5 which corresponds to VIPERS sample. Also we concluded that galaxy mergers were more frequent in the early Universe.

Radio relics are giant ($\sim$Mpc) synchrotron sources that are believed to be produced by the (re)acceleration of cosmic-ray electrons (CRe) by shocks in the intracluster medium. In this numerical study, we focus on the possibility that some radio relics may arise when electrons undergo diffusive shock acceleration at multiple shocks in the outskirts of merging galaxy clusters. This multi-shock (MS) scenario appears viable to produce CRe that emit visible synchrotron emission. We show that electrons that have been shocked multiple times develop an energy spectrum that significantly differs from the power-law spectrum expected in the case of a single shock scenario. As a consequence, the radio emission generated by CRe that shocked multiple times is higher than the emission produced by CRe that are shocked only once. In the case explored in this paper, the radio emission produced in the two scenarios differ by one order of magnitude. In particular in the MS scenario, the simulated relic follows a KGJP spectral shape, consistent with observation. Furthermore, the produced radio emission is large enough to be detectable with current radio telescopes (e.g. LOFAR, JVLA).

St 2-22 is a relatively poorly-studied S-type symbiotic system that belongs to a small group of jet-producing systems as a result of disc-accretion onto a white dwarf fed by its red giant companion.\\ The goal of this paper is to analyse the nature and derive the basic parameters of St 2-22, and to follow the jet evolution.\\ Photometric monitoring through over 16 yrs and high-quality spectroscopic data enabled us to shed new light on its nature. The high-resolution SALT spectra and $V I_C$ photometry obtained during and between the last two outbursts have been used to search for periodic changes, to derive spectroscopic orbits of both system components, and to study the outburst and jet evolution.\\ We present the orbital and stellar parameters of the system components. The orbital period is P$_{orb} = 918 \pm6^d$. The double-line spectroscopic orbits indicate the mass ratio $q = M_{g} M_{h}^{-1} = 3.50 \pm0.53$, and the components masses $M_{g} \sin^3{i} \sim 2.35$ M$_{sun}$, and $M_{h} \sin^3{i} \sim 0.67$ M$_{sun}$. The orbit shows significant eccentricity, $e = 0.16 \pm0.07$. The orbital inclination is close to 70 degrees. During outbursts, accelerating and decelerating jets are observed with changes of their radial velocity component in a range from $\sim 1500$ up to nearly $1800$ km s$^{-1}$. St 2-22 turned out to be a classical symbiotic system very similar to the precursor of the group -- Z And.

We present EOS, a procedure for determining the Outgoing Longwave Radiation (OLR) and top-of-atmosphere (TOA) albedo for a wide range of conditions expected to be present in the atmospheres of rocky planets with temperate conditions. EOS is based on HELIOS and HELIOS-K, which are novel and publicly available atmospheric radiative transfer (RT) codes optimized for fast calculations with GPU processors. These codes were originally developed for the study of giant planets. In this paper we present an adaptation for applications to terrestrial-type, habitable planets, adding specific physical recipes for the gas opacity and vertical structure of the atmosphere. To test the reliability of the procedure we assessed the impact of changing line opacity profile, continuum opacity model, atmospheric lapse rate and tropopause position prescriptions on the OLR and the TOA albedo. The results obtained with EOS are in line with those of other RT codes running on traditional CPU processors, while being at least one order of magnitude faster. The adoption of OLR and TOA albedo data generated with EOS in a zonal and seasonal climate model correctly reproduce the fluxes of the present-day Earth measured by the CERES spacecraft. The results of this study disclose the possibility to incorporate fast RT calculations in climate models aimed at characterizing the atmospheres of habitable exoplanets.

We have measured the gas temperature in the IC 63 photodissociation region (PDR) using the S(1) and S(5) pure rotation lines of molecular hydrogen with SOFIA/EXES. We divide the PDR into three regions for analysis based on the illumination from $\gamma$ Cas: "sunny," "ridge" and "shady." Constructing rotation diagrams for the different regions, we obtain temperatures of T$_{ex}$=$562^{+52}_{-43}$ K towards the "ridge" and T$_{ex}$=$495^{+28}_{-25}$ K in the "shady" side. The H$_2$ emission was not detected on the "sunny" side of the ridge, likely due to the photo-dissociation of H$_2$ in this gas. Our temperature values are lower than the value of T$_{ex}$=685$\pm$68 K using the S(1), S(3), and S(5) pure rotation lines, derived by Thi et al. (2009) using lower spatial-resolution ISO-SWS data at a different location of the IC 63 PDR. This difference indicates that the PDR is inhomogeneous and illustrates the need for high-resolution mapping of such regions to fully understand their physics. The detection of a temperature gradient correlated with the extinction into the cloud, points to the ability of using H$_2$ pure rotational line spectroscopy to map the gas temperature on small scales. We used a PDR model to estimate the FUV radiation and corresponding gas densities in IC 63. Our results shows the capability of SOFIA/EXES to resolve and provide detailed information on the temperature in such regions.

Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs), but identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer (EIS) observations of sigmoidal active region 10977. We analyze the coronal plasma composition in the active region and its evolution as the sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and the sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical active region coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. The Hence, plasma composition observations of active region 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.

The separate-universe approach provides an effective description of cosmological perturbations at large scales, where the universe can be described by an ensemble of independent, locally homogeneous and isotropic patches. By reducing the phase space to homogeneous and isotropic degrees of freedom, it greatly simplifies the analysis of large-scale fluctuations. It is also a prerequisite for the stochastic-inflation formalism. In this work, we formulate the separate-universe approach in the Hamiltonian formalism, which allows us to analyse the full phase-space structure of the perturbations. Such a phase-space description is indeed required in dynamical regimes which do not benefit from a background attractor, as well as to investigate quantum properties of cosmological perturbations. We find that the separate-universe approach always succeeds in reproducing the same phase-space dynamics for homogeneous and isotropic degrees of freedom as the full cosmological perturbation theory, provided that the wavelength of the modes under consideration are larger than some lower bound that we derive. We also compare the separate-universe approach and cosmological perturbation theory at the level of the gauge-matching procedure, where the agreement is not always guaranteed and requires specific matching prescriptions that we present.

Gravitational-wave observations of binary neutron star mergers and their electromagnetic counterparts provide an independent measurement of the Hubble constant, $H_0$, through the standard-sirens approach. Current methods of determining $H_0$, such as measurements from the early universe and the local distance ladder, are in tension with one another. If gravitational waves are to break this tension a thorough understanding of systematic uncertainty for gravitational-wave observations is required. To accurately estimate the properties of gravitational-wave signals measured by LIGO and Virgo, we need to understand the characteristics of the detectors noise. Non-gaussian transients in the detector data and rapid changes in the instrument, known as non-stationary noise, can both add a systematic uncertainty to inferred results. We investigate how non-stationary noise affects the estimation of the luminosity distance of the source, and therefore of $H_0$. Using a population of 200 simulated binary neutron star signals, we show that non-stationary noise can bias the estimation of the luminosity distance by up to 2.4\%. However, only $\sim$15\% of binary neutron star signals would be affected around their merger time with non-stationary noise at a similar level to that seen in the first half of LIGO-Virgo's third observing run. Comparing the expected bias to other systematic uncertainties, we argue that non-stationary noise in the current generation of detectors will not be a limiting factor in resolving the tension on $H_0$ using standard sirens. Although, evaluating non-stationarity in gravitational-wave data will be crucial to obtain accurate estimates of $H_0$.

Context. A region at the inner edge of the main asteroid belt is populated by the Hungaria asteroids. Among these objects, the Hungaria family is formed as the result of a catastrophic disruption of (434) Hungaria asteroid hundred million years ago. Due to the Yarkovsky effect, the fragments depending on their direction of rotation are slowly drifting inward or outward from the actual place of collision. Due to this slow drift these bodies could approach the locations of the various mean-motion resonances (MMRs) of outer type with Mars. Aims. We aim to study the actual dynamical structure of Hungaria asteroids that is primarily shaped by various MMRs of outer type with Mars. Moreover, we also seek connections between the orbital characteristics of Hungaria asteroids and their absolute magnitude. Methods. To map the resonant structure and dynamics of asteroids belonging to the Hungaria group, we use the method FAIR (as FAst Identification of mean motion Resonances), which can detect MMRs without the a priori knowledge of the critical argument. We also compile stability maps of the regions around the MMRs by using the maximal variations in the asteroids' eccentricities, semi-major axes, and inclinations. We numerically integrate the orbits of all asteroids belonging to the Hungaria group available in the JPL Horizon database together with the Solar System planets for one and ten million years. Results. Having studied the resonant structure of the Hungaria group, we find that several asteroids are involved in various MMRs with Mars. We identify both short and long-term MMRs. Besides, we also find a relationship between the absolute magnitude of asteroids and the MMR in which they are involved.

Circumstellar dust is formed and evolved within the envelope of evolved stars, including Asymptotic Giant Branch (AGB) and Red Supergiant (RSG). The extinction of stellar light by circumstellar dust is vital for interpreting RSG/AGB observations and determining high-mass RSG progenitors of core-collapse supernovae. Nevertheless, circumstellar dust properties are not well understood. Modern understanding of dust evolution suggests that intense stellar radiation can radically change the dust properties across the circumstellar envelope through the RAdiative Torque Disruption (RATD) mechanism. In this paper, we study the impacts of RATD on the grain size distribution (GSD) of circumstellar dust and model its effects on photometric observations of $\alpha$ Orionis (Betelgeuse). Due to the RATD effects, large grains presumably formed in the dust formation zone are disrupted into smaller species of size $a < 0.5\,\rm\mu m$. Using the GSD constrained by the RATD effect, we model the visual extinction of background stars and Betelgeuse. We find that the extinction decreases at near-UV, optical, and infrared wavelengths while increasing at far-UV wavelengths. The resulting flux well reproduces the observation from the near-UV to near-IR range, suggesting the scenario of driving stellar winds by smaller grains $a \lesssim 0.1\,\rm\mu m$. Our results can be used to explain dust extinction and photometric observations toward other RSG/AGB stars.

Considering the relatively high precision that will be reached by future observatories, it has recently become clear that one dimensional (1D) atmospheric models, in which the atmospheric temperature and composition of a planet are considered to vary only in the vertical, will be unable to represent exoplanetary transmission spectra with a sufficient accuracy. This is particularly true for warm to (ultra-) hot exoplanets because the atmosphere is unable to redistribute all the energy deposited on the dayside, creating a strong thermal and often compositional dichotomy on the planet. This situation is exacerbated by transmission spectroscopy, which probes the terminator region. This is the most heterogeneous region of the atmosphere. However, if being able to compute transmission spectra from 3D atmospheric structures (from a global climate model, e.g.) is necessary to predict realistic observables, it is too computationally expensive to be used in a data inversion framework. For this reason, there is a need for a medium-complexity 2D approach that captures the most salient features of the 3D model in a sufficiently fast implementation. With this in mind, we present a new open-source documented version of Pytmosph3R that handles the computation of transmission spectra for atmospheres with up to three spatial dimensions and can account for time variability. Taking the example of an ultra hot Jupiter, we illustrate how the changing orientation of the planet during the transit can allow us to probe the horizontal variations in the atmosphere. We further implement our algorithm in TauREx to allow the community to perform 2D retrievals. We describe our extensive cross-validation benchmarks and discuss the accuracy and numerical performance of each model.

Multimessenger astronomy is arguably the branch of the astroparticle physics field that has seen the most significant developments in recent years. In this manuscript, we will review the state-of-the-art, the recent observations, and the prospects and challenges for the near future. We will give special emphasis to the observation carried out with neutrino telescopes.

Exoplanet and brown dwarf atmospheres commonly show signs of disequilibrium chemistry. In the James Webb Space Telescope era high resolution spectra of directly imaged exoplanets will allow the characterization of their atmospheres in more detail, and allow systematic tests for the presence of chemical species that deviate from thermochemical equilibrium in these atmospheres. Constraining the presence of disequilibrium chemistry in these atmospheres as a function of parameters such as their effective temperature and surface gravity will allow us to place better constrains in the physics governing these atmospheres. This paper is part of a series of works presenting the Sonora grid of atmosphere models (Marley et al 2021, Morley et al in prep.). In this paper we present a grid of cloud-free, solar metallicity atmospheres for brown dwarfs and wide separation giant planets with key molecular species such as CH4, H2O, CO and NH3 in disequilibrium. Our grid covers atmospheres with Teff~[500 K,1300 K], logg~[3.0,5.5] (cgs) and an eddy diffusion parameter of logKzz=2, 4 and 7 (cgs). We study the effect of different parameters within the grid on the temperature and composition profiles of our atmospheres. We discuss their effect on the near-infrared colors of our model atmospheres and the detectability of CH4, H2O, CO and NH3 using the JWST. We compare our models against existing MKO and Spitzer observations of brown dwarfs and verify the importance of disequilibrium chemistry for T dwarf atmospheres. Finally, we discuss how our models can help constrain the vertical structure and chemical composition of these atmospheres.

With the increasing sensitivity of gravitational-wave detectors, we expect to observe multiple binary neutron-star systems through gravitational waves in the near future. The combined analysis of these gravitational-wave signals offers the possibility to constrain the neutron-star radius and the equation of state of dense nuclear matter with unprecedented accuracy. However, it is crucial to ensure that uncertainties inherent in the gravitational-wave models will not lead to systematic biases when information from multiple detections are combined. To quantify waveform systematics, we perform an extensive simulation campaign of binary neutron-star sources and analyse them with a set of four different waveform models. Based on our analysis with about 38 simulations, we find that statistical uncertainties in the neutron-star radius decrease to $\pm 250\rm m$ ($2\%$ at $90\%$ credible interval) but that systematic differences between currently employed waveform models can be twice as large. Hence, it will be essential to ensure that systematic biases will not become dominant in inferences of the neutron-star equation of state when capitalizing on future developments.

Thermal phase curves of exoplanet atmospheres have revealed temperature maps as a function of planetary longitude, often by sinusoidal decomposition of the phase curve. We construct a framework for describing two-dimensional temperature maps of exoplanets with mathematical basis functions derived for a fluid layer on a rotating, heated sphere with drag/friction, which are generalizations of spherical harmonics. These basis functions naturally produce physically-motivated temperature maps for exoplanets with few free parameters. We investigate best practices for applying this framework to temperature maps of hot Jupiters by splitting the problem into two parts: (1) we constrain the temperature map as a function of latitude by tuning the basis functions to reproduce general circulation model (GCM) outputs, since disk-integrated phase curve observations do not constrain this dimension; and (2) we infer the temperature maps of real hot Jupiters using original reductions of several Spitzer phase curves, which directly constrain the temperature variations with longitude. The resulting phase curves can be described with only three free parameters per bandpass -- an efficiency improvement over the usual five or so used to describe sinusoidal decompositions of phase curves. Upon obtaining the hemispherically averaged dayside and nightside temperatures, the standard approach would be to use zero-dimensional box models to infer the Bond albedo and redistribution efficiency. We elucidate the limitation of these box models by demonstrating that negative Bond albedos may be obtained due to a choice of boundary condition on the nightside temperature. We propose generalized definitions for the Bond albedo and heat redistribution efficiency for use with two-dimensional (2D) temperature maps. Open-source software called kelp is provided to efficiently compute these phase curves.

Owing to recent advances in radial-velocity instrumentation and observation techniques, the detection of Earth-mass planets around Sun-like stars may soon be primarily limited by intrinsic stellar variability. Several processes contribute to this variability, including starspots, pulsations, and granulation. Although many previous studies have focused on techniques to mitigate signals from pulsations and other types of magnetic activity, granulation noise has to date only been partially addressed by empirically-motivated observation strategies and magnetohydrodynamic simulations. To address this deficit, we present the GRanulation And Spectrum Simulator ($\texttt{GRASS}$), a new tool designed to create time-series synthetic spectra with granulation-driven variability from spatially- and temporally-resolved observations of solar absorption lines. In this work, we present $\texttt{GRASS}$, detail its methodology, and validate its model against disk-integrated solar observations. As a first-of-its-kind empirical model for spectral variability due to granulation in a star with perfectly known center-of-mass radial-velocity behavior, $\texttt{GRASS}$ is an important tool for testing new methods of disentangling granular line-shape changes from true Doppler shifts.

We investigate which physical properties are most predictive of the position of local star forming galaxies on the BPT diagrams, by means of different Machine Learning (ML) algorithms. Exploiting the large statistics from the Sloan Digital Sky Survey (SDSS), we define a framework in which the deviation of star-forming galaxies from their median sequence can be described in terms of the relative variations in a variety of observational parameters. We train artificial neural networks (ANN) and random forest (RF) trees to predict whether galaxies are offset above or below the sequence (via classification), and to estimate the exact magnitude of the offset itself (via regression). We find, with high significance, that parameters associated to variations in the nitrogen-over-oxygen abundance ratio (N/O) are the most predictive for the [N II]-BPT diagram, whereas properties related to star formation (like variations in SFR or EW(H$\alpha$)) perform better in the [S II]-BPT diagram. We interpret the former as a reflection of the N/O-O/H relationship for local galaxies, while the latter as primarily tracing the variation in the effective size of the S$^{+}$ emitting region, which directly impacts the [S II] emission lines. This analysis paves the way to assess to what extent the physics shaping local BPT diagrams is also responsible for the offsets seen in high redshift galaxies or, instead, whether a different framework or even different mechanisms need to be invoked.

Context. The numerical modeling of the generation and transfer of polarized radiation is a key task in solar and stellar physics research and has led to a relevant class of discrete problems that can be reframed as linear systems. In order to solve such problems, it is common to rely on efficient stationary iterative methods. However, the convergence properties of these methods are problem-dependent, and a rigorous investigation of their convergence conditions, when applied to transfer problems of polarized radiation, is still lacking. Aims. After summarizing the most widely employed iterative methods used in the numerical transfer of polarized radiation, this article aims to clarify how the convergence of these methods depends on different design elements, such as the choice of the formal solver, the discretization of the problem, or the use of damping factors. The main goal is to highlight advantages and disadvantages of the different iterative methods in terms of stability and rate of convergence. Methods. We first introduce an algebraic formulation of the radiative transfer problem. This formulation allows us to explicitly assemble the iteration matrices arising from different stationary iterative methods, compute their spectral radii and derive their convergence rates, and test the impact of different discretization settings, problem parameters, and damping factors. Conclusions. The general methodology used in this article, based on a fully algebraic formulation of linear transfer problems of polarized radiation, provides useful estimates of the convergence rates of various iterative schemes. Additionally, it can lead to novel solution approaches as well as analyses for a wider range of settings, including the unpolarized case.

Glycinamide is considered to be one of the possible precursors of the simplest amino acid glycine. Its only rotational spectrum reported so far has been in the cm-wave region. The aim of this work is to extend its laboratory spectrum into the mm wave region to support its searches in the ISM. Glycinamide was synthesised chemically and was studied with broadband rotational spectroscopy in the 90-329 GHz region. Tunneling across a low energy barrier between two symmetry equivalent configurations of the molecule resulted in splitting of each vibrational state and many perturbations in associated rotational energy levels, requiring careful coupled state fits for each vibrational doublet. We searched for emission of glycinamide in the imaging spectral line survey ReMoCA performed with ALMA toward Sgr B2(N). We report the first analysis of the mm-wave rotational spectrum of glycinamide, resulting in fitting to experimental measurement accuracy of over 1200 transition frequencies for the ground state tunneling doublet, of many lines for tunneling doublets for two singly excited vibrational states, and determination of precise vibrational separation in each doublet. We did not detect emission from glycinamide in the hot core Sgr B2(N1S). We found that glycinamide is at least seven times less abundant than aminoacetonitrile and 1.8 times less abundant than urea in this source. A comparison with results of astrochemical kinetics models for species related to glycinamide suggests that its abundance may be at least one order of magnitude below the upper limit obtained toward Sgr B2(N1S). This means that glycinamide emission in this source likely lies well below the spectral confusion limit in the frequency range covered by the ReMoCA survey. Targetting sources with a lower level of spectral confusion, such as the Galactic Center shocked region G+0.693-0.027, may be a promising avenue. [abridged]

Atomic gas in the diffuse interstellar medium (ISM) is organized in filamentary structures. These structures usually host cold and dense molecular clumps. The Galactic magnetic field is considered to play an important role in the formation of these clumps. Our goal is to explore the role of the magnetic field in the HI - H$_{2}$ transition process. We targeted a filamentary cloud where gas transitions from atomic to molecular. This cloud is located at the edges of an expanding structure, known as the North Celestial Pole Loop (NCPL). We probed the magnetic field properties of the cloud with optical polarization observations. We performed multi-wavelength spectroscopic observations of different species in order to probe the gas phase properties of the cloud. We identified two distinct sub-regions within the cloud. One of the regions hosts purely atomic gas, while the other is dominated by molecular gas although most of it is CO-dark. The estimated plane-of-the-sky magnetic field strength between the two regions remains constant within uncertainties and lies in the range 20 ~ 30$~\mu$G. The total magnetic field strength does not scale with density which implies that gas is compressed along the field lines. We also found that turbulence is sub-Alfv\'enic. The HI velocity gradients are in general perpendicular to the mean magnetic field orientation, except for the region close to the CO clump where they tend to become parallel. The latter is likely related to gas undergoing gravitational infall. The magnetic field morphology of the target cloud is parallel to the HI column density structure of the cloud in the atomic region, while it tends to become perpendicular to the HI structure in the molecular region. If this is verified in more cases it has important consequences for the ISM magnetic field modeling with HI data.

In the fuzzy dark matter (FDM) model, gravitationally collapsed objects always consist of a solitonic core located within a virialised halo. Although various numerical simulations have confirmed that the collapsed structure can be described by a cored NFW like density profile, there is still disagreement about the relation between the core mass and the halo mass. To fully understand this relation, we have assembled a large sample of cored haloes based on both idealised soliton mergers and cosmological simulations with various box sizes. We find that there exists a sizeable dispersion in the core-halo mass relation that increases with halo mass, indicating that the FDM model allows cores and haloes to coexist in diverse configurations. We provide a new empirical equation for a core halo mass relation with uncertainties that can encompass all previously found relations in the dispersion, and emphasise that any observational constraints on the particle mass using a tight one-to-one core-halo mass relation should suffer from an additional uncertainty on the order of 50 % for halo masses $ \ge 10^9 (8 \times 10^{-23} eV/ (mc^2))^{3/2} M_\odot$. We suggest that tidal stripping may be one of the effects contributing to the scatter in the relation.

Weak gravitational lensing is a powerful statistical tool for probing the growth of cosmic structure and measuring cosmological parameters. However, as shown by studies such as M\'enard et al. (2010), dust in the circumgalactic region of haloes dims and reddens background sources. In a weak lensing analysis, this selects against sources behind overdense regions; since there is more structure in overdense regions, we will underestimate the amplitude of density perturbations $\sigma_8$ if we do not correct for the effects of circumgalactic dust. To model the dust distribution we employ the halo model. Assuming a fiducial dust mass profile based on measurements from M\'enard et al. (2010), we compute the ratio $Z$ of the systematic error to the statistical error for a survey similar to the Nancy Grace Roman Space Telescope reference survey (2000 deg$^2$ area, single-filter effective source density 30 galaxies arcmin$^{-2}$). For a waveband centered at $1580$ nm ($H$-band), we find that $Z_{H} = 0.47$. For a similar survey with waveband centered at $620$ nm ($r$-band), we also computed $Z_{r} = 3.6$. Within our fiducial dust model, since $Z_{r} > 1$, the systematic effect of dust will be significant on weak lensing image surveys. We also computed the dust bias on the amplitude of the power spectrum, $\sigma_{8}$, and found it to be for each waveband $\Delta \sigma_8/\sigma_8 = -3.9\times 10^{-4}$ ($H$ band) or $-2.9\times 10^{-3}$ ($r$ band) if all other parameters are held fixed (the forecast Roman statistical-only error $\sigma(\sigma_8)/\sigma_8$ is $9\times 10^{-4}$).

During the last years and decades several individual studies and large-scale spectroscopic surveys significantly improved our knowledge of the Galactic metallicity distribution based on open clusters. The availability of Gaia data provided a further step forward in our knowledge. However, still some open issues remain, for example the influence of radial migration on the interpretation of the observed gradients. We used spectroscopic metallicities from individual studies and from the APOGEE survey to compile a sample of 136 open clusters, with a membership verification based on Gaia DR2. Additionally, we present photometric metallicity estimates of 14 open clusters in a somewhat outer Galactic region. Eight age groups allow us to study the evolution of the metallicity gradient in detail, showing within the errors an almost constant gradient of about $-$0.06 dex/kpc. Furthermore, using the derived gradients and an analysis of the individual objects, we estimate a mean migration rate of 1 kpc/Gyr for objects up to about 2 Gyr. Here, the change of the guiding radius is clearly the main contributor. For older and dynamically hotter objects up to 6 Gyr we infer a lower migration rate of up to 0.5 kpc/Gyr. The influence of epicyclic excursions increases with age and contributes already about 1 kpc to the total migration distance after 6 Gyr. A comparison of our results with available models shows good agreement. However, there is still a lack of a suitable coverage of older objects, future studies are still needed to provide a better sampling in this respect.

One of the problems for the cyclic Universe will be its compatibility with a vast population of indestructible black holes that accumulate from cycle to cycle. The article considers a simple iterative model of the evolution of black holes in a cyclic Universe, independent of specific cosmological theories. The model has two free parameters that determine the iterative decrease in the number of black holes and the increase in their individual mass. It is shown that this model, with wide variations in the parameters, explains the observed number of supermassive black holes at the centers of galaxies, as well as the relationships between different classes of black holes. The mechanism of accumulation of relict black holes during repeated pulsations of the Universe may be responsible for the black hole population detected by LIGO observations and probably responsible for the dark matter phenomenon. The number of black holes of intermediate masses corresponds to the number of globular clusters and dwarf satellite galaxies. These results argue for models of the oscillating Universe, and at the same time impose substantial requirements on them. Models of a pulsating Universe should be characterized by a high level of relict gravitational radiation generated at the time of maximum compression of the Universe and mass mergers of black holes, as well as solve the problem of the existence of the largest black hole that is formed during this merger. It has been hypothesized that some neutron stars can survive from past cycles of the Universe and contribute to dark matter. These relict neutron stars will have a set of features by which they can be distinguished from neutron stars born in the current cycle of the birth of the Universe. The observational signs of relict neutron stars and the possibility of their search in different wavelength ranges are discussed.

Relativistic jets can interact with the ambient gas distribution of the host galaxy, before breaking out to larger scales. In the past decade several studies have simulated jet-driven outflows to understand how they affect the nearby environment, and over what spatial and temporal scales such interactions occur. The simulations are able to capture the interaction of the jets with the turbulent clumpy interstellar medium and the resultant energetics of the gas. In this review we summarise the results of such recent studies and discuss their implications on the evolution of the dynamics of the gas distribution and the star formation rate.

We present a toy model for radio emission in HMXBs with strongly magnetized neutron stars (NS) where a wind-collision region is formed by the NS outflow and the stellar wind of the massive companion. Radio emission is expected from the synchrotron radiation of shock-accelerated electrons and the free-free emission of the stellar wind. We found that the predicted relation between the GHz luminosity ($L_R$) and the accretion X-ray luminosity ($L_X$) can be written as $L_R \propto L_X^b$ for most parameters. No correlation with X-rays is expected ($b=0$) when the thermal emission of the stellar wind dominates in radio. We typically find a steep correlation ($b=12/7$) for sub-Eddington X-ray luminosities and a more shallow one ($b=2(p-1)/7$) for super-Eddington X-ray luminosities, where $p$ is the power-law index of accelerated electrons. The maximum predicted radio luminosity is independent of the NS properties, while it depends on the stellar wind momentum, binary separation distance, and the minimum electron Lorentz factor. Using a Bayesian approach we modelled the radio observations of \sj that cover a wide range of mass accretion rates. Our results support a shock origin for the radio detections at sub-Eddington X-ray luminosities. However, no physically meaningful parameters could be found for the super-Eddington phase of the outburst, suggesting a different origin. Future observations with more sensitive instruments might reveal a large number of HMXBs with strongly magnetized NSs in radio, allowing determination of the slope in the $L_R-L_X$ relation, and putting the wind-collision scenario into test.

The actual knowledge of the structure and future evolution of our universe is based on the use of cosmological models, which can be tested through the so-called 'probes', namely astrophysical phenomena, objects or structures with peculiar properties that can help to discriminate among different cosmological models. Among all the existing probes, of particular importance are the Supernovae Ia (SNe Ia) and the Gamma Ray Bursts (GRBs): the former are considered among the best standard candles so far discovered but suffer from the fact that can be observed until redshift $z=2.26$, while the latter are promising standardizable candles which have been observed up to $z=9.4$, surpassing even the farthest quasar known to date, which is at $z=7.64$. The standard candles can be used to test the cosmological models and to give the expected values of cosmological parameters, in particular the Hubble constant value. The Hubble constant is affected by the so-called \say{Hubble constant tension}, a discrepancy in more than 4 $\sigma$ between its value measured with local probes and its value measured through the cosmological probes. The increase in the number of observed SNe Ia, as well as the future standardization of GRBs through their correlations, will surely be of help in alleviating the Hubble constant tension and in explaining the structure of the universe at higher redshifts. A promising class of GRBs for future standardization is represented by the GRBs associated with Supernovae Ib/c, since these present features similar to the SNe Ia class and obey a tight correlation between their luminosity at the end of the plateau emission in X-rays and the time at the end of the plateau in the rest-frame.

Irradiation of the accretion disc causes reflection signatures in the observed X-ray spectrum, encoding important information about the disc structure and density. A Type I X-ray burst will strongly irradiate the accretion disc and alter its properties. Previous numerical simulations predicted the evolution of the accretion disc due to an X-ray burst. Here, we process time-averaged simulation data of six time intervals to track changes in the reflection spectrum from the burst onset to just past its peak. We divide the reflecting region of the disc within $r\lesssim50$ km into 6-7 radial zones for every time interval and compute the reflection spectra for each zone. We integrate these reflection spectra to obtain a total reflection spectrum per time interval. The burst ionizes and heats the disc, which gradually weakens all emission lines. Compton scattering and bremsstrahlung rates increase in the disc during the burst rise, and the soft excess at $<$3 keV rises from $\approx4$% to $\approx38$% of the total emission at the burst peak. A soft excess is expected to be ubiquitous in the reflection spectra of X-ray bursts. Structural disc changes such as inflation because of heating or drainage of the inner disc due to Poynting-Robertson drag affect the strength of the soft excess. Further studies on the dependence of the reflection spectrum characteristics to changes in the accretion disc during an X-ray burst may lead to probes of the disc geometry.

Ultra-hot Jupiters have dayside temperatures at which most molecules are expected to thermally dissociate. The dissociation of water vapour results in the production of the hydroxyl radical (OH). While OH absorption is easily observed in near-infrared spectra of M dwarfs, which have similar effective temperatures as ultra-hot Jupiters, it is often not considered when studying the atmospheres of ultra-hot Jupiters. We use high-resolution spectroscopic observations of a transit of WASP-76b obtained using CARMENES to study the presence of OH. After validating the OH line list, we generate model transit spectra of WASP-76b with petitRADTRANS. The data are corrected for stellar and telluric contamination and cross-correlated with the model spectra. After combining all cross-correlation functions from the transit, a detection map is constructed. Constraints on the planet properties from the OH absorption are obtained from a Markov chain Monte Carlo analysis. OH is detected in the atmosphere of WASP-76b with a peak signal-to-noise ratio of 6.1. From the retrieval we obtain $K_p=232 \pm 12$ km/s and a blueshift of $-13.2 \pm 1.6$ km/s, which are offset from the expected velocities. Considering the fast spin rotation of the planet, the blueshift is best explained with the signal predominantly originating from the evening terminator and the presence of a strong dayside-to-nightside wind. The increased $K_p$ over its expected value (196.5 km/s) is, however, a bit puzzling. The signal is found to be broad, with a full width at half maximum of $16.8^{+4.6}_{-4.0}$ km/s. The retrieval results in a weak constraint on the mean temperature of 2700-3700 K at the pressure range of the OH signal. We show that OH is readily observable in the transit spectra of ultra-hot Jupiters. Studying this molecule can provide insights into the molecular dissociation processes in the atmospheres of such planets.

Recently, microquasar jets have aroused the interest of many researchers focusing on the astrophysical plasma outflows and various jet ejections. In this work, we concentrate on the investigation of electromagnetic radiation and particle emissions from the jets of stellar black hole binary systems characterized by their hadronic content in their jets. Such emissions are reliably described within the context of the relativistic magneto-hydrodynamics. Our model calculations are based on the Fermi acceleration mechanism through which the primary particles (mainly protons) of the jet are accelerated. As a result, a small portion of thermal protons of the jet acquire relativistic energies, through shock-waves generated into the jet plasma. From the inelastic collisions of fast (non-thermal) protons with the thermal (cold) ones, secondary charged and neutral particles (pions, kaons, muons, $\eta$-particles, etc.) are created as well as electromagnetic radiation from the radio wavelength band, to X-rays and even to very high energy $\gamma$-ray emission. One of our main goals is, through the appropriate solution of the transport equation and taking into account the various mechanisms that cause energy losses to the particles, to study the secondary particle distributions within hadronic astrophysical jets. After testing our method on the Galactic MQs SS 433 and Cyg X-1, as a concrete extragalactic binary system, we examine the LMC X-1 located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy. It is worth mentioning that, for the companion O star (and its extended nebula structure) of the LMC X-1 system, new observations using spectroscopic data from VLT/UVES have been published few years ago.

Bearing in mind our previous study on asymptotic behavior of null geodesics near future null infinity, we analyze the behavior of geometrical quantities such as a certain extrinsic curvature and Riemann tensor in the Bondi coordinates. In the sense of asymptotics, the condition for an $r$-constant hypersurface to be a photon surface is shown to be controlled by a key quantity that determines the fate of photons initially emitted in angular directions. As a consequence, in four dimensions, such a non-expanding photon surface can be realized even near future null infinity in the presence of enormous energy flux for a short period of time. By contrast, in higher-dimensional cases, no such a photon surface can exist. This result also implies that the dynamically transversely trapping surface, which is proposed as an extension of a photon surface, can have an arbitrarily large radius in four dimensions.

Turbulent magnetic field fluctuations observed in the solar wind often maintain a constant magnitude condition accompanied by spherically polarized velocity fluctuations; these signatures are characteristic of large-amplitude Alfv\'{e}n waves. Nonlinear energy transfer in Alfv\'{e}nic turbulence is typically considered in the small-amplitude limit where the constant magnitude condition may be neglected; in contrast, nonlinear energy transfer in the large-amplitude limit remains relatively unstudied. We develop a method to analyze finite-amplitude turbulence through studying fluctuations as constant magnitude rotations in the stationary wave (de Hoffmann-Teller) frame, which reveals that signatures of finite-amplitude effects exist deep into the MHD range. While the dominant fluctuations are consistent with spherically-polarized large-amplitude Alfv\'{e}n waves, the subdominant mode is relatively compressible. Signatures of nonlinear interaction between the finite-amplitude spherically polarized mode with the subdominant population reveal highly aligned transverse components. In theoretical models of Alfv\'{e}nic turbulence, alignment is thought to reduce nonlinearity; our observations require that alignment is sufficient to either reduce shear nonlinearity such that non-Alfv\'{e}nic interactions may be responsible for energy transfer in spherically polarized states, or that counter-propagating fluctuations maintain anomalous coherence, which is a predicted signature of reflection-driven turbulence.

For more than 60 years, the predominant SETI search paradigm has entailed the observation of stars in an effort to detect alien electromagnetic signals that deliberately target Earth. However, this strategy is fraught with challenges when examined from ETs perspective. Astronomical, physiological, psychological, and intellectual problems are enumerated. Consequently, ET is likely to attempt a different strategy in order to best establish communications. It will send physical AI robotic probes that would be linked together by a vast interstellar network of communications nodes. This strategy would solve most or all problems associated with interstellar signaling.

We investigate a mechanism for the production of self-interacting dark matter based on WIMP-like messenger state decays into dark matter and dark radiation occurring after recombination. Such a transition leads to a mild relaxation of the Hubble tension, and at the same time may resolve the small-scale structure problems of the $\Lambda$CDM. We illustrate this mechanism in the Higgs portal dark matter model, which we find to be a promising route.

Context. Numerical solutions to transfer problems of polarized radiation in solar and stellar atmospheres commonly rely on stationary iterative methods, which often perform poorly when applied to large problems. In recent times, stationary iterative methods have been replaced by state-of-the-art preconditioned Krylov iterative methods for many applications. However, a general description and a convergence analysis of Krylov methods in the polarized radiative transfer context are still lacking. Aims. We describe the practical application of preconditioned Krylov methods to linear transfer problems of polarized radiation, possibly in a matrix-free context. The main aim is to clarify the advantages and drawbacks of various Krylov accelerators with respect to stationary iterative methods. Methods. We report the convergence rate and the run time of various Krylov-accelerated techniques combined with different formal solvers when applied to a 1D benchmark transfer problem of polarized radiation. In particular, we analyze the GMRES, BICGSTAB, and CGS Krylov methods, preconditioned with Jacobi, or (S)SOR. Results. Krylov methods accelerate the convergence, reduce the run time, and improve the robustness of standard stationary iterative methods. Jacobi-preconditioned Krylov methods outperform SOR-preconditioned stationary iterations in all respects. In particular, the Jacobi-GMRES method offers the best overall performance for the problem setting in use. Conclusions. Krylov methods can be more challenging to implement than stationary iterative methods. However, an algebraic formulation of the radiative transfer problem allows one to apply and study Krylov acceleration strategies with little effort. Furthermore, many available numerical libraries implement matrix-free Krylov routines, enabling an almost effortless transition to Krylov methods.

Context. Several numerical problems require the interpolation of discrete data that present various types of discontinuities. The radiative transfer is a typical example of such a problem. This calls for high-order well-behaved techniques to interpolate both smooth and discontinuous data. Aims. The final aim is to propose new techniques suitable for applications in the context of numerical radiative transfer. Methods. We have proposed and tested two different techniques. Essentially non-oscillatory (ENO) techniques generate several candidate interpolations based on different substencils. The smoothest candidate interpolation is determined from a measure for the local smoothness, thereby enabling the essential non-oscillatory property. Weighted ENO (WENO) techniques use a convex combination of all candidate substencils to obtain high-order accuracy in smooth regions while keeping the essentially non-oscillatory property. In particular, we have outlined and tested a novel well-performing fourth-order WENO interpolation technique for both uniform and nonuniform grids. Results. Numerical tests prove that the fourth-order WENO interpolation guarantees fourth-order accuracy in smooth regions of the interpolated functions. In the presence of discontinuities, the fourth-order WENO interpolation enables the non-oscillatory property, avoiding oscillations. Unlike B\'ezier and monotonic high-order Hermite interpolations, it does not degenerate to a linear interpolation near smooth extrema of the interpolated function. Conclusions. The novel fourth-order WENO interpolation guarantees high accuracy in smooth regions, while effectively handling discontinuities. This interpolation technique might be particularly suitable for several problems, including a number of radiative transfer applications such as multidimensional problems, multigrid methods, and formal solutions.

Neutrino oscillations and mean-field effects considerably enrich the phenomenology of neutrino evolution in the early Universe. Taking into account these effects, most notably the neutrino self-interaction mean-field contribution, we revisit the problem of the evolution of primordial neutrino asymmetries including for the first time the complete expression for collisions, which describe scattering and annihilations with electron/positrons and reactions among (anti)neutrinos. We show that a generalisation of the adiabatic transfer of averaged oscillations (ATAO) scheme, a numerical method previously developed without neutrino degeneracy and based on the large separation of time scales in this problem, is sufficient to reach the same accuracy as the full quantum kinetic equation integration, but is notably faster. This approximation highlights the physics of synchronous oscillations at play in the evolution of neutrino chemical potentials, especially in the particular case with only two-neutrino mixing. In particular, it allows to understand what controls the beginning and the amplitude of oscillations, but also why there is a subsequent regime of collective oscillations with larger frequencies. We also find that it is very important to use the full collision term instead of relying on damping-like approximations, in order not to overestimate how collisions reduce these synchronous oscillations. Finally we study qualitatively how mixing parameters affect the final neutrino configuration, and in particular we show that the CP-violating Dirac phase cannot substantially affect the final $N_{\rm eff}$ nor the final electronic (anti)-neutrino spectrum, and thus should not affect cosmological observables.

Symmergent gravity is the $R+R^2$ gravity theory which emerges in a way restoring gauge symmetries broken explicitly by the ultraviolet cutoff in effective field theories. To test symmergent gravity we construct novel black hole solutions in four dimensions, and study their shadow in the vacuum as well as plasma medium. Our detailed analyses show that the horizon radius, Hawking temperature, Bekenstein-Hawking entropy, shadow angular radius, and photon deflection angle are sensitive probes of the symmergent gravity and particle spectrum of the underlying quantum field theory.

The chameleon model is a modified gravity theory that introduces an additional scalar field that couples to matter through a conformal coupling. This `chameleon field' possesses a screening mechanism through a nonlinear self-interaction term which allows the field to affect cosmological observables in diffuse environments whilst still being consistent with current local experimental constraints. Due to the self-interaction term the equations of motion of the field are nonlinear and therefore difficult to solve analytically. The analytic solutions that do exist in the literature are either approximate solutions and or only apply to highly symmetric systems. In this work we introduce the software package SELCIE (https://github.com/C-Briddon/SELCIE.git). This package equips the user with tools to construct an arbitrary system of mass distributions and then to calculate the corresponding solution to the chameleon field equation. It accomplishes this by using the finite element method and either the Picard or Newton nonlinear solving methods. We compared the results produced by SELCIE with analytic results from the literature including discrete and continuous density distributions. We found strong (sub-percentage) agreement between the solutions calculated by SELCIE and the analytic solutions.