Papers for Tuesday, Sep 05 2023

Gravitational Wave (GW) astronomy has experienced remarkable growth in recent years, driven by advancements in ground-based detectors. While detecting compact binary coalescences (CBCs) has become routine, searching for more complex ones, such as mergers involving eccentric and precessing binaries and sub-solar mass binaries, has presented persistent challenges. These challenges arise from using the standard matched filtering algorithm, whose computational cost increases with the dimensionality and size of the template bank. This urges the pressing need for faster search pipelines to efficiently identify GW signals, leading to the emergence of the hierarchical search strategy. This method looks for potential candidate events using a sparse template bank in the first stage, followed by dense templates around potential events in the second stage. Although the hierarchical search speeds up the standard PyCBC analysis by more than a factor of 20, as demonstrated in a previous work~\cite{kanchan_hierarchical}, assigning statistical significance to detected signals was done in a heuristic way. In this article, we present a robust approach for background estimation in a two-stage hierarchical search. Our method models background triggers from time-shifted triggers in a two-detector network, extrapolating to higher statistic values. Through an extensive injection campaign for a population of simulated signals on real data, we test the effectiveness of our background estimation approach. The results show our method achieves a sensitive volume-time product comparable to the standard two-detector PyCBC search. This equivalence holds for an inverse false alarm rate of 10 years and chirp mass $1.4-10~\text{M}_\odot$, substantially reducing computational cost with a remarkable speed-up of nearly 13 times compared to PyCBC analysis.

We show that magnetar models for ULX behaviour have serious internal inconsistencies. The magnetic fields required to increase the limiting luminosity for radiation pressure above the observed (assumed isotropic) luminosities are completely incompatible with the spin-up rates observed for pulsing ULXs. We note that at least one normal Be-star + neutron star system, with a standard (non-magnetar) field, is observed to become a ULX during a large outburst, and return to its previous Be-star binary state afterwards. We note further that recent polarimetric observations of the well-studied binary Cyg X-3 reveal that it produces strong emission directed away from the observer, in line with theoretical suggestions of its luminosity from evolutionary arguments. We conclude that the most likely explanation for ULX behaviour involves radiation beaming by accretion disc winds. A large fraction of X-ray binaries must pass through a ULX state in the course of their evolution.

Fuzzy dark matter (FDM) has dynamical properties that differ significantly from cold dark matter (CDM). These dynamical differences are strongly manifested on the spatial scale of dwarf spheroidal galaxies (dSphs), which roughly corresponds to the de Broglie wavelength of a canonical mass FDM particle. We study simulations of a dSph satellite which is tidally perturbed by its host galaxy, in order to identify dynamical signatures that are unique to FDM, and to quantify the imprints of such perturbations on an observable stellar tracer population. We find that a perturbed FDM soliton develops a long-standing breathing mode, whereas for CDM such a breathing mode quickly phase-mixes and disappears. We also demonstrate that such signatures become imprinted on the dynamics of a stellar tracer population, making them observable with sufficiently precise astrometric measurements.

Low-mass dwarf galaxies are expected to showcase pristine `cuspy' inner dark matter density profiles compared to their stellar sizes, as they form too few stars to significantly drive dark matter heating through supernovae-driven outflows. Here, we study such simulated faint systems ($10^4 \leq M_{\star} \leq 2\times 10^6 \, M_\mathrm{\odot}$) drawn from high-resolution (3 pc) cosmological simulations from the `Engineering Dwarf Galaxies at the Edge of galaxy formation' (EDGE) project. We confirm that these objects have steep and rising inner dark matter density profiles at $z=0$, little affected by galaxy formation effects. But five dwarf galaxies from the suite showcase a detectable HI reservoir ($M_{\mathrm{HI}}\approx 10^{5}-10^{6} \, M_\mathrm{\odot}$), analogous to the observed population of faint, HI-bearing dwarf galaxies. These reservoirs exhibit episodes of ordered rotation, opening windows for rotation curve analysis. Within actively star-forming dwarfs, stellar feedback easily disrupts the tenuous HI discs ($v_{\phi} \approx 10\, \mathrm{km} \, \mathrm{s}^{-1}$), making rotation short-lived ($\ll 150 \, \mathrm{Myr}$) and more challenging to interpret for dark matter inferences. Contrastingly, we highlight a long-lived ($\geq 500 \, \mathrm{Myr}$) and easy-to-interpret HI rotation curve extending to $\approx 2\, r_{1/2, \text{3D}}$ in a quiescent dwarf, that has not formed new stars since $z=4$. This stable gas disc is supported by an oblate dark matter halo shape that drives high angular momentum gas flows. Our results strongly motivate further searches for HI rotation curves in the observed population of HI-bearing low-mass dwarfs, that provide a key regime to disentangle the respective roles of dark matter microphysics and galaxy formation effects in driving dark matter heating.

The nature of the first Pop III stars is still a mystery and the energy distribution of the first supernovae is completely unexplored. For the first time we account simultaneously for the unknown initial mass function (IMF), stellar mixing, and energy distribution function (EDF) of Pop III stars in the context of a cosmological model for the formation of a MW-analogue. Our data-calibrated semi-analytic model is based on a N-body simulation and follows the formation and evolution of both Pop III and Pop II/I stars in their proper timescales. We discover degeneracies between the adopted Pop III unknowns, in the predicted metallicity and carbonicity distribution functions and the fraction of C-enhanced stars. Nonetheless, we are able to provide the first available constraints on the EDF, $dN/dE_\star \propto E_{\star}^{-\alpha_e}$ with $1\leq \alpha_e \leq2.5$. In addition, the characteristic mass of the Pop III IMF should be $m_{\rm ch}<100\:{\rm M_\odot}$, assuming a mass range consistent with hydrodynamical simulations (0.1-1000$\:{\rm M_\odot}$). Independent of the assumed Pop III properties, we find that all [C/Fe]>+0.7 stars (with [Fe/H]<-2.8) have been enriched by Pop III supernovae at a $>20\%$ level, and all [C/Fe]>+2 stars at a $>95\%$ level. All very metal-poor stars with $\rm [C/Fe]<0$ are predicted to be predominantly enriched by Pop III hypernovae and/or pair instabillity supernovae. To better constrain the primordial EDF, it is absolutely crucial to have a complete and accurate determination of the metallicity distribution function, and the properties of C-enhanced metal-poor stars (frequency and [C/Fe]) in the Galactic halo.

Radio Relics are typically found to be arc-like regions of synchrotron emission in the outskirts of merging clusters. They typically show synchrotron spectra that steepen towards the cluster center, indicating that they are caused by relativistic electrons being accelerated at outwards traveling merger shocks. A number of radio relics break with this ideal picture and show morphologies that are bent the opposite way and spectral index distributions which do not follow expectations from the ideal picture. We propose that these "Wrong Way" Relics can form when an outwards travelling shock wave is bent inwards by an in-falling galaxy cluster or group. We test this in an ultra-high resolution zoom-in simulation of a massive galaxy cluster with an on-the-fly spectral Cosmic Ray model. This allows us to study not only the synchrotron emission at colliding shocks, but also their synchrotron spectra to adress the open question of relics with strongly varying spectral indices over the relic surface.

Our position inside the Galactic disc had prevented us from establishing an accurate rotation curve, until the advent of Gaia, whose third data release (Gaia DR3) made it possible to specify it up to twice the optical radius. We aim to establish a new rotation curve of the Galaxy from the Gaia DR3, by drastically reducing uncertainties and systematics, and with the goal to provide a new estimate of the mass of the Galaxy. We have compared different estimates, established a robust assessment of the systematic uncertainties, and addressed differences in methodologies, particularly regarding distance estimates. This results in a sharply decreasing rotation curve for the Milky Way, the decrease in velocity between 19.5 and 26.5 kpc is approximately 30 km s$^{-1}$. We have identified, for the first time, a Keplerian decline of the rotation curve, starting at $\sim$ 19 kpc and up to $\sim$ 26.5 kpc from the Galaxy center, while a flat rotation curve is rejected with a significance of 3$\sigma$. The total mass is revised downwards to $2.06^{+0.24}_{-0.13}\times 10^{11}\ M_{\odot}$, in agreement with an absence of significant mass increase at radii larger than 19 kpc. The upper limit of the total mass was evaluated by considering the upper values of velocity measurements, which leads to a strict, unsurpassable, limit of $5.4\times 10^{11}\ M_{\odot}$.

About 12 billion years ago, the Universe was first experiencing light again after the dark ages, and galaxies filled the environment with stars, metals and dust. How efficient was this process? How fast did these primordial galaxies form stars and dust? We can answer these questions by tracing the Star Formation Rate Density (SFRD) back to its widely unknown high redshift tail, traditionally observed in the Near-InfraRed (NIR), Optical and UV bands. Thus, the objects with a high amount of dust were missing. We aim to fill this knowledge gap by studying Radio Selected NIR-dark (\textit{RS-NIRdark}) sources, i.e. sources not having a counterpart at UV-to-NIR wavelengths. We widen the sample by Talia et al. (2021) from 197 to 272 objects in the COSMic evolution Survey (COSMOS) field, including also photometrically contaminated sources, previously excluded. Another important step forward consists in the visual inspection of each source in the bands from u* to MIPS-24$\mu$m. According to their "environment" in the different bands, we are able to highlight different cases of study and calibrate an appropriate photometric procedure for the objects affected by confusion issues. We estimate that the contribution of RS-NIRdark to the Cosmic SFRD at 3$<$z$<$5 is $\sim$10--25$\%$ of that based on UV-selected galaxies.

The ultra-luminous X-ray source CXO~J133815.6+043255 is a strong candidate for a bona-fide intermediate mass black hole, residing in the outskirts of NGC~5252. We present 22~GHz radio observations of this source obtained serendipitously in an ongoing high-frequency imaging survey of radio-quiet Active Galactic Nuclei (AGN), and use this new data point to construct the broad-band radio spectral energy distribution (SED). We find that the SED exhibits a spectral slope of $\alpha=-0.66\pm0.02$, consistent with a steep spectrum from optically-thin synchrotron emission from an unresolved jet. We also find that the $L_R / L_X$ ratio is approximately $10^{-3}$, inconsistent with radio-quiet AGN and many ULXs but consistent with low-luminosity AGN (LLAGN) and radio-loud quasars. Together, these observations support the conclusion that CXO~J133815.6+043255 is an intermediate-mass black hole producing a low-mass analog of radio jets seen in classical quasars.

We present the first comprehensive study of a giant, $\approx \! \! 70$ kpc-scale nebula around a radio-quiet quasar at $z<1$. The analysis is based on deep integral field spectroscopy with MUSE of the field of HE$\,$0238$-$1904, a luminous quasar at $z=0.6282$. The nebula emits strongly in $\mathrm{[O \, II]}$, $\rm H \beta$, and $\mathrm{[O \, III]}$, and the quasar resides in an unusually overdense environment for a radio-quiet system. The environment likely consists of two groups which may be merging, and in total have an estimated dynamical mass of $M_{\rm dyn}\approx 4\times 10^{13}$ to $10^{14}\ {\rm M_\odot}$. The nebula exhibits largely quiescent kinematics and irregular morphology. The nebula may arise primarily through interaction-related stripping of circumgalactic and interstellar medium (CGM/ISM) of group members, with some potential contributions from quasar outflows. The simultaneous presence of the giant nebula and a radio-quiet quasar in a rich environment suggests a correlation between such circum-quasar nebulae and environmental effects. This possibility can be tested with larger samples. The upper limits on the electron number density implied by the [O\,II] doublet ratio range from $\log(n_{\rm e, [O \, II]} / \mathrm{cm^{-3}}) < 1.2$ to $2.8$. However, assuming a constant quasar luminosity and negligible projection effects, the densities implied from the measured line ratios between different ions (e.g., [O\,II], [O\,III], and [Ne V]) and photoionization simulations are often 10$-$400 times larger. This large discrepancy can be explained by quasar variability on a timescale of $\approx 10^4{-}10^5$ years.

Machian Gravity (MG) presents a mathematical framework that captures the essence of Mach's principle. It was formulated to address the limitations of general relativity and provide a gravity theory founded on robust logical principles. Unlike the approach of modifying existing theories by introducing extra scalar and vector degrees of freedom to account for observational data, MG offers a more coherent alternative. Previous investigations have revealed MG's potential to explain diverse phenomena, such as galactic velocity patterns, galaxy cluster mass distribution, and cosmic expansion, without requiring additional dark components in the universe. This study applies the MG acceleration law to a wide array of galaxies sourced from the SPARC galactic database. Through meticulous analysis, we have determined the optimal parameters of the Machian gravity model for each individual SPARC galaxy, consequently fitting their distinctive rotational profiles. Similar to the Modified Newtonian Dynamics (MOND), our results suggest the presence of an acceleration scale linked to galaxies, governing their rotational behavior near the outer regions. Importantly, this acceleration scale exhibits variability across different galaxies, albeit typically remaining around the order of $10^{-8} {\rm cm/s^2}$.

In addition to being spectacular objects, Very Massive Stars (VMS) are suspected to have a tremendous impact on their environment and on the whole cosmic evolution. The nucleosynthesis both during their advanced stages and their final explosion may contribute greatly to the overall enrichment of the Universe. Their resulting supernovae are candidates for the most superluminous events and their extreme conditions also lead to very important radiative and mechanical feedback effects, from local to cosmic scale. We explore the impact of rotation and metallicity on the evolution of very massive stars across cosmic times. With the recent implementation of an equation of state in the GENEC stellar evolution code, appropriate for describing the conditions in the central regions of very massive stars in the advanced phases, we present new results on VMS evolution from Population III to solar metallicity. Low metallicity VMS models are highly sensitive to rotation, while the evolution of higher metallicity models is dominated by mass loss effects. The mass loss affects strongly their surface velocity evolution, breaking quickly at high metallicity while reaching the critical velocity for low metallicity models. The comparison to observed VMS in the LMC shows that the mass loss prescriptions used for these models are compatible with observed mass loss rates. In our framework for modelling rotation, our models of VMS need a high initial velocity to reproduce the observed surface velocities. The surface enrichment of these VMS is difficult to explain with only one initial composition, and could suggest multiple populations in the R136 cluster. At a metallicity typical of R136, only our non- or slowly rotating VMS models may produce Pair Instability supernovae. The most massive black holes that can be formed are less massive than about 60 M$_\odot$.

We present a cryogenic configurable slit unit (CSU) for a multi object infrared spectrograph with an effective field of view of 9.1 arcmin x 9.1 arcmin that was completely conceived and designed in the laboratory at TIFR. Several components of the CSU including the controller for the commercially procured piezo-walkers, controlled loop position sensing mechanism using digital slide callipers and a cryogenic test facility for the assembled prototype were also developed in-house. The principle of the CSU involves division of the field of view of the spectrometer into contiguous and parallel spatial bands, each one associated with two opposite sliding metal bars that can be positioned to create a slit needed to make spectroscopic observations of one astronomical object. A three-slit prototype of the newly designed CSU was built and tested extensively at ambient and cryogenic temperatures. The performance of the CSU was found to be as per specifications.

A new parametrization of the phenomenological Hubble parameter is proposed to explore the issue of the cosmological landscape. The constraints on model parameters are derived through the Markov Chain Monte Carlo (MCMC) method by employing a comprehensive union of datasets such as 34 data points from cosmic chronometers (CC), 42 points from baryonic acoustic oscillations (BAO), a recently updated set of 1701 Pantheon$^+$ (P22) data points derived from Type Ia supernovae (SNeIa), and 162 data points from gamma-ray bursts (GRB). The kinematic behavior of the models is also investigated by encompassing the transition from deceleration to acceleration and the evolution of the jerk parameter. From the analysis of the parametric models, it is strongly indicated that the Universe is currently undergoing an accelerated phase. Furthermore, the models are compared by using the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), so that a comparative assessment of model performance can be available.

Understanding the complete nature of Galactic sources that accelerate cosmic rays up to $10^{15}$ eV energy (Galactic PeVatrons) is still an unsolved problem in high-energy astrophysics. Although supernova remnants have long been considered as the best candidates for Galactic PeVatrons, a clear association of SNRs with PeVatrons needs further exploration. Recently, the LHAASO collaboration published its first catalog of 90 very high energy (VHE) gamma-ray sources, and a few of them have no obvious counterparts at other wavelengths. Here, we will present morphology and spectral analysis of one such unassociated source LHAASO J2108+5157 using VERITAS and HAWC data.

The second data release of the LOFAR Two-Metre Sky Survey (LoTSS) covers 27% of the northern sky, with a total area of $\sim 5,700$ deg$^2$. The high angular resolution of LOFAR with Dutch baselines (6 arcsec) allows us to carry out optical identifications of a large fraction of the detected radio sources without further radio followup; however, the process is made more challenging by the many extended radio sources found in LOFAR images as a result of its excellent sensitivity to extended structure. In this paper we present source associations and identifications for sources in the second data release based on optical and near-infrared data, using a combination of a likelihood-ratio cross-match method developed for our first data release, our citizen science project Radio Galaxy Zoo: LOFAR, and new approaches to algorithmic optical identification, together with extensive visual inspection by astronomers. We also present spectroscopic or photometric redshifts for a large fraction of the optical identifications. In total 4,116,934 radio sources lie in the area with good optical data, of which 85% have an optical or infrared identification and 58% have a good redshift estimate. We demonstrate the quality of the dataset by comparing it with earlier optically identified radio surveys. This is by far the largest ever optically identified radio catalogue, and will permit robust statistical studies of star-forming and radio-loud active galaxies.

We present the first systematic search for UV signatures from radio source-driven AGN feedback in Compact Steep Spectrum (CSS) radio galaxies. Owing to their characteristic sub-galactic jets (1-20 kpc projected linear sizes), CSS hosts are excellent laboratories for probing galaxy scale feedback via jet-triggered star formation. The sample consists of 7 powerful CSS galaxies, and 2 galaxies host to radio sources >20 kpc as control, at low to intermediate redshifts (z<0.6). Our new HST images show extended UV continuum emission in 6/7 CSS galaxies; with 5 CSS hosts exhibiting UV knots co-spatial and aligned along the radio-jet axis. Young (<10 Myr), massive (>5 M$_\odot$) stellar populations are likely to be the dominant source of the blue excess emission in radio galaxies at these redshifts. Hence, the radio-aligned UV regions could be attributed to jet-induced starbursts. Lower near-UV SFRs compared to other indicators suggests low scattered AGN light contribution to the observed UV. Dust attenuation of UV emission appears unlikely from high internal extinction correction estimates in most sources. Comparison with evolutionary synthesis models shows that our observations are consistent with recent (~1-8 Myr old) star forming activity likely triggered by current or an earlier episode of radio emission, or by a confined radio source that has frustrated growth due to a dense environment. While follow-up spectroscopic and polarized light observations are needed to constrain the activity-related components in the observed UV, the detection of jet-induced star formation is a confirmation of an important prediction of the jet feedback paradigm.

External irradiation of a neutron star (NS) accretion disc induces Poynting-Robertson (PR) drag, removing angular momentum and increasing the mass accretion rate. Recent simulations show PR drag significantly enhancing the mass accretion rate during Type I X-ray bursts, which could explain X-ray spectral features such as an increase in the persistent emission and a soft excess. However, prograde spin of the NS is expected to weaken PR drag, challenging its importance during bursts. Here, we study the effect of spin on PR drag during X-ray bursts. We run four simulations, with two assuming a non-spinning NS and two using a spin parameter of $a_*=0.2$, corresponding to a rotation frequency of 500 Hz. For each scenario, we simulate the disc evolution subject to an X-ray burst and compare it to the evolution found with no burst. PR drag drains the inner disc region during a burst, moving the inner disc radius outward by $\approx1.6$ km in the $a_*=0$ and by $\approx2.2$ km in the $a_*=0.2$ simulation. The burst enhances the mass accretion rate across the innermost stable circular orbit $\approx7.9$ times when the NS is not spinning and $\approx11.2$ times when it is spinning. The explanation for this seemingly contradictory result is that the disc is closer to the NS when $a_*=0.2$, and the resulting stronger irradiating flux offsets the weakening effect of spin on the PR drag. Hence, PR drag remains a viable explanation for the increased persistent emission and soft excess observed during X-ray bursts in spinning NS systems.

The precessing jet-nozzle scenario previously proposed was applied to model-fit the kinematics of five superluminal components (C19,C20,C21,B5 and B7) of jet-B in blazar 3C345. Based on a specific pattern for the the precessing common trajectory of jet-B, the kinematic properties (including trajectory,coordinates, core separation and apparent velocity) were model-fitted and their flux evolution could be studied. Through model-simulation of their kinematic behavior, the bulk Lorentz factor, viewing angle and Doppler factor were derived as continuous functions of time and the association of their flux evolution with their Doppler-boosting effect was investigated. The 43GHz light-curves of the five superluminal components can be well interpreted in terms of their Doppler effect. The close association of their flux evolution with the Doppler-boosting effect firmly validates our precessing nozzle scenario and supports the traditional point-view that superluminal components are physical entities (traveling shocks or plasmoids) participating relativistic motion toward us at small angles. The model-simulation of kinematic behavior of superluminal components by using our precessing nozzle scenario with specific patterns (helical or ballistic) assumed for the precessing common trajectories yields the model-derived bulk Lorentz factor, apparent velocity, viewing angle and Doppler factor as continuous functions of time, which are most applicable to study the connection of flux evolution with Doppler boosting effect for the superluminal components.

Accretion of material onto a black hole drags any magnetic fields present inwards, increasing their strength. Theory predicts that sufficiently strong magnetic fields can halt the accretion flow, producing a magnetically arrested disk (MAD). We analyze archival multi-wavelength observations of an outburst from the black hole X-ray binary MAXI J1820+070 in 2018. The radio and optical fluxes are delayed by about 8 and 17 days respectively, compared to the X-ray flux. We interpret this as evidence for the formation of a MAD. In this scenario, the magnetic field is amplified by an expanding corona, forming a MAD around the time of the radio peak. The optical delay is then due to thermal viscous instability in the outer disk.

The evidence of the stochastic gravitational-wave background around the nano-hertz frequency range was recently found by worldwide pulsar timing array (PTA) collaborations. One of the cosmological explanations is the gravitational waves induced by enhanced curvature perturbations, but the issue of primordial black hole (PBH) overproduction in this scenario was pointed out in the literature. Motivated by this issue and the $\Omega_\text{GW} \sim f^2$ scaling suggested by the data, we study the gravitational waves induced in a cosmological epoch dominated by a stiff fluid ($w=1$) and find that they can safely explain the PTA data well without PBH overproduction.

White dwarf studies carry significant implications across multiple fields of astrophysics, including exoplanets, supernova explosions, and cosmological investigations. Thus, accurate determinations of their fundamental parameters (Teff and log g) are of utmost importance. While optical surveys have provided measurements for many white dwarfs, there is a lack of studies utilising ultraviolet (UV) data, particularly focusing on the warmer ones that predominantly emit in the UV range. Here, we present the medium-resolution far-UV spectroscopic survey of 311 hydrogen-atmosphere (DA) white dwarfs obtained with Cosmic Origins Spectrograph (COS) onboard Hubble Space Telescope confirming 49 photometric Gaia candidates. We used 3D extinction maps, parallaxes, and atmospheric models to fit the spectra of the stars that lie in the range 12 000 < Teff < 33 000 K, and 7 <= log g < 9.2. To assess the impact of input physics, we employed two mass-radius relations in the fitting and compared the results with previous studies. The comparisons suggest the COS Teff are systematically lower by 3 per cent on average than Balmer line fits while they differ by only 1.5 per cent from optical photometric studies. The mass distributions indicate that the COS masses are smaller by approximately 0.05 Msol and 0.02 Msol than Balmer lines and photometric masses, respectively. Performing several tests, we find that the discrepancies are either arising due to issues with the COS calibration, broadening theories for hydrogen lines, or interstellar reddening which needs further examination. Based on comparative analysis, we identify 30 binary candidates drawing attention for follow-up studies to confirm their nature.

As first proposed by Gruzinov, a charged particle moving in strong electromagnetic fields can enter an equilibrium state where the power input from the electric field is balanced by radiative losses. When this occurs, the particle moves at nearly light speed along special directions called the principal null directions (PNDs) of the electromagnetic field. This equilibrium is "Aristotelian" in that the particle velocity, rather than acceleration, is determined by the local electromagnetic field. In paper I of this series, we analytically derived the complete formula for the particle velocity at leading order in its deviation from the PND, starting from the fundamental Landau-Lifshitz (LL) equation governing charged particle motion, and demonstrated agreement with numerical solutions of the LL equation. We also identified five necessary conditions on the field configuration for the equilibrium to occur. In this paper we study the entry into equilibrium using a similar combination of analytical and numerical techniques. We simplify the necessary conditions and provide strong numerical evidence that they are also sufficient for equilibrium to occur. Based on exact and approximate solutions to the LL equation, we identify key timescales and properties of entry into equilibrium and show quantitative agreement with numerical simulations. Part of this analysis shows analytically that the equilibrium is linearly stable and identifies the presence of oscillations during entry, which may have distinctive radiative signatures. Our results provide a solid foundation for using the Aristotelian approximation when modeling relativistic plasmas with strong electromagnetic fields.

Compact disc galaxies (CDGs) with high surface brightness were identified in the Sloan Digital Sky Survey (SDSS) data. We determined the surface profiles of the CDGs and compared them to those of normal-sized disk galaxies (NDGs). The CDGs have higher central brightness and older stellar age than the NDGs. Furthermore, the brightness profiles of the CDGs fit a S{\'e}rsic model with $n \approx 2.11$ and have a zero $g^{\prime}-r^{\prime}$ color gradient on average. By contrast, the NDGs fit an exponential profile and have a negative color gradient on average. These results indicate that the structure and stellar population of the CDGs and NDGs differ. We suggest that the CDGs are ancient galaxies in the quenching phase following the initial central starburst.

"Hot atoms", which are atoms in their excited states, transfer their energy to the surrounding atmosphere through collisions. This process of energy transfer is known as thermalization, and it plays a crucial role in various astrophysical and atmospheric processes. Thermalization of hot atoms is mainly governed by the amount of species present in the surrounding atmosphere and the collision cross-section between the hot atoms and surrounding species. In this work, we investigated the elastic and inelastic collisions between hot oxygen atoms and neutral N$_2$ molecules, relevant to oxygen gas escape from the martian atmosphere and for characterizing the chemical reactions in hypersonic flows. We conducted a series of quantum scattering calculations between various isotopes of O($^3P$) atoms and N$_2$ molecules across a range of collision energies (0.3 to 4 eV), and computed both their differential and collision cross-sections using quantum time$-$independent coupled-channel approach. Our differential cross-section results indicate a strong preference for forward scattering over sideways or backward scattering, and this anisotropy in scattering is further pronounced at higher collision energies. By comparing the cross-sections of three oxygen isotopes, we find that the heavier isotopes consistently have larger collision cross-sections than the lighter isotopes over the entire collision energy range examined. However, for all the isotopes, the variation of collision cross-section with respect to collision energy is the same. As a whole, the present study contributes to a better understanding of the energy distribution and thermalization processes of hot atoms within atmospheric environments. Specifically, the cross$-$sectional data presented in this work is directly useful in improving the accuracy of energy relaxation modeling of O and N$_2$ collisions over Mars and Venus atmospheres.

We take a sample of 94 ultraluminous, optical quasars from the search of over 14,486 deg^2 by Onken et al. 2022 in the range 4.4<redshift<5.2 and match them against the Rapid ASKAP Continuum Survey (RACS) observed on the Australian Square Kilometre Array Pathfinder (ASKAP). From this most complete sample of the bright end of the redshift ~5 quasar luminosity function, there are 10 radio continuum detections of which 8 are considered radio-loud quasars. The radio-loud fraction for this sample is 8.5 \pm 2.9 per cent. Jiang et al. 2007 found that there is a decrease in the radio-loud fraction of quasars with increasing redshift and an increase with increasing absolute magnitude at rest frame 2500 Angstroms. We show that the radio-loud fraction of our quasar sample is consistent with that predicted by Jiang et al. 2007, extending their result to higher redshifts.

When examining the abundance of elements in the placid interstellar medium, a deep hollow between helium and carbon becomes apparent. Notably, the fragile light nuclei Lithium, Beryllium, and Boron (collectively known as LiBeB) are not formed, with the exception of Li7, during the process of Big Bang nucleosynthesis, nor do they arise as byproducts of stellar lifecycles. In contrast to the majority of elements, these species owe their existence to the most energetic particles in the Universe. Cosmic rays, originating in the most powerful Milky Way's particle accelerators, reach the Earth after traversing tangled and lengthy paths spanning millions of years. During their journey, these primary particles undergo transformations through collisions with interstellar matter. This process, known as spallation, alters their composition and introduces secondary light elements in the cosmic-ray beam. In light of this, the relatively large abundance of LiBeB in the cosmic radiation provides remarkable insights into the mechanisms of particle acceleration, as well as the micro-physics of confinement within galactic magnetic fields. These lecture notes are intended to equip readers with basic knowledge necessary for examining the chemical and isotopic composition, as well as the energy spectra, of cosmic rays, finally fostering a more profound comprehension of the complex high-energy astrophysical processes occurring within our Galaxy.

The observed correlation between the radio and X-ray fluxes in the hard state of black-hole X-ray binaries (BHXRBs) has been around for more than two decades. It is currently accepted that the hard X-rays in BHXRBs come from Comptonization in the corona and the radio emission from the relativistic jet (Lorentz $\gamma >> 1$), which is a narrow structure of a few $R_g=GM/c^2$ at its base. The relativistic jet and the corona, however, are separate entities with hardly any communication between them, apart from the fact that both are fed from the accreting matter. It is also widely accepted that the accretion flow around black holes in BHXRBs consists of an outer thin disk and an inner hot flow. From this hot inner flow, an outflow emanates in the hard and hard-intermediate states of the source. By considering Compton up-scattering of soft disk photons in the outflow (i.e., in the outflowing corona, which is a wider structure, tens to hundreds of $R_g$ at its base, with low Lorentz gamma) as the mechanism that produces the hard X-ray spectrum, we have been able to explain quantitatively a number of observed correlations. Here, we demonstrate that this outflowing corona can also explain quantitatively the observed radio - X-ray correlation. In addition, we make the following theoretical predictions for GX 339-4: 1) the radio flux in the hard and hard-intermediate states should be a bell-shaped curve as a function of the photon-number spectral index Gamma, 2) the radio - X-ray correlation should break down when the source moves from the hard to the hard-intermediate state and instead the radio flux should first increase sharply in the hard-intermediate state and then decrease also sharply, in a very narrow range of the X-ray flux, and 3) the X-ray polarization will be parallel to the outflow in the hard state and perpendicular to it in the hard-intermediate one.

H2S is thought to be the main sulphur reservoir in the ice, being therefore a key molecule to understand sulphur chemistry in the star formation process and to solve the missing sulphur problem. The H2S deuterium fraction can be used to constrain its formation pathways. We investigate for the first time the H2S deuteration in a large sample of starless cores (SC). We use observations of the GEMS IRAM 30m Large Program and complementary IRAM 30m observations. We consider a sample of 19 SC in Taurus, Perseus, and Orion, detecting HDS in 10 and D2S in five. The H2S single and double deuterium fractions are analysed with regard to their relation with the cloud physical parameters, their comparison with other interstellar sources, and their comparison with deuterium fractions in early stage star-forming sources of c-C3H2, H2CS, H2O, H2CO, and CH3OH. We obtain a range of X(HDS)/X(H2S)~0.025-0.2 and X(D2S)/X(HDS)~0.05-0.3. H2S single deuteration shows an inverse relation with the cloud kinetic temperature. H2S deuteration values in SC are similar to those observed in Class 0. Comparison with other molecules in other sources reveals a general trend of decreasing deuteration with increasing temperature. In SC and Class 0 objects H2CS and H2CO present higher deuteration fractions than c-C3H2, H2S, H2O, and CH3OH. H2O shows single and double deuteration values one order of magnitude lower than those of H2S and CH3OH. Differences between c-C3H2, H2CS and H2CO deuterium fractions and those of H2S, H2O, and CH3OH are related to deuteration processes produced in gas or solid phases, respectively. We interpret the differences between H2S and CH3OH deuterations and that of H2O as a consequence of differences on the formation routes in the solid phase, particularly in terms of the different occurrence of the D-H and H-D substitution reactions in the ice, together with the chemical desorption processes.

The M dwarf star GJ 436 hosts a warm-Neptune that is losing substantial amount of atmosphere, which is then shaped by the interactions with the wind of the host star. The stellar wind is formed by particles and magnetic fields that shape the exo-space weather around the exoplanet GJ 436 b. Here, we use the recently published magnetic map of GJ 436 to model its 3D Alfv\'en-wave driven wind. By comparing our results with previous transmission spectroscopic models and measurements of non-thermal velocities at the transition region of GJ 436, our models indicate that the wind of GJ 436 is powered by a smaller flux of Alfv\'en waves than that powering the wind of the Sun. This suggests that the canonical flux of Alfv\'en waves assumed in solar wind models might not be applicable to the winds of old M dwarf stars. Compared to the solar wind, GJ 436's wind has a weaker acceleration and an extended sub-Alfv\'enic region. This is important because it places the orbit of GJ 436 b inside the region dominated by the stellar magnetic field (i.e., inside the Alfv\'en surface). Due to the sub-Alfv\'enic motion of the planet through the stellar wind, magnetohydrodynamic waves and particles released in reconnection events can travel along the magnetic field lines towards the star, which could power the anomalous ultraviolet flare distribution recently observed in the system. For an assumed planetary magnetic field of $B_p \simeq 2$ G, we derive the power released by stellar wind-planet interactions as $\mathcal{P} \sim 10^{22}$ -- $10^{23}$ erg s$^{-1}$, which is consistent with the upper limit of $10^{26}$ erg s$^{-1}$ derived from ultraviolet lines. We further highlight that, because star-planet interactions depend on stellar wind properties, observations that probe these interactions and the magnetic map used in 3D stellar wind simulations should be contemporaneous for deriving realistic results.

A key test of the isotropy of the Universe on large scales consists in comparing the dipole in the Cosmic Microwave Background (CMB) temperature with the dipole in the distribution of sources at low redshift. Current analyses find a dipole in the number counts of quasars and radio sources that is 2-5 times larger than expected from the CMB, leading to a tension reaching 5$\sigma$. In this paper, we derive a consistent framework to measure the dipole independently from gravitational wave (GW) detections. We exploit the fact that the observer velocity does not only change the distribution of events in the sky, but also the luminosity distance and redshifted chirp mass, that can be extracted from the GW waveform. We show that the estimator with higher signal-to-noise ratio is the dipole in the chirp mass measured from a population of binary neutron stars. Combining all estimators (accounting for their covariance) improves the detectability of the dipole by 30-50 percent compared to number counting of binary black holes alone. We find that a few $10^6$ events are necessary to detect a dipole consistent with the CMB one, whereas if the dipole is as large as predicted by radio sources, it will already be detectable with $10^5$ events, which would correspond to a single year of observation with next generation GW detectors. GW sources provide therefore a robust and independent way of testing the isotropy of the Universe.

In this work, we explore the possibility that Early Dark Energy (EDE) is dynamical in nature and study its effect on cosmological observables. We introduce a parameterization of the equation of state allowing for an equation of state $w$ differing considerably from cosmological constant (cc, $w={-1}$) and vary both the initial $w_i$ as well final $w_f$ equation of state of the EDE fluid. This idea is motivated by the fact that in many models of EDE, the scalar field may have some kinetic energy when it starts to behave like EDE before the CMB decoupling. We find that the present data have a mild preference for non-cc early dark energy $( w_i= -0.78)$ using Planck+BAO+Pantheon+S$H_0$ES data sets, leading to $\Delta \chi^2_{\rm min}$ improvement of -2.5 at the expense of one more parameter. However, $w_i$ is only weakly constrained, with $w_i < -0.56$ at $1\sigma$. We argue that allowing for $w_i\neq -1$ can play a role in decreasing the $\sigma_8$ parameter. Yet, in practice the decrease is only $\sim0.4\sigma$ and $\sigma_8$ is still larger than weak lensing measurements. We conclude that while promising, a dynamical EDE cannot resolve both $H_0$ and $\sigma_8$ tensions simultaneously.

WR21 and WR31 are two WR+O binaries with short periods, quite similar to the case of V444 Cyg. The XMM-Newton observatory has monitored these two objects and clearly revealed phase-locked variations as expected from colliding winds. The changes are maximum in the soft band (0.5--2.keV, variations by a factor 3--4) where they are intrinsically linked to absorption effects. The increase in absorption due to the dense WR wind is confirmed by the spectral analysis. The flux maximum is however not detected exactly at conjunction with the O star in front but slightly afterwards, suggesting Coriolis deflection of the collision zone as in V444 Cyg. In the hard band (2.--10. keV), the variations (by a factor of 1.5--2.0) are much more limited. Because of the lower orbital inclinations, eclipses as observed for V444 Cyg are not detected in these systems.

Blazars exhibit relentless variability across diverse spatial and temporal frequencies. The study of long- and short-term variability properties observed in the X-ray band provides insights into the inner workings of the central engine. In this work, we present timing and spectral analyses of the blazar 3C 273 using the X-ray observations from the $\textit{XMM-Newton}$ telescope covering the period from 2000 to 2020. The methods of timing analyses include estimation of fractional variability, long- and short-term flux distribution, rms-flux relation, and power spectral density analysis. The spectral analysis include estimating a model independent flux hardness ratio and fitting the observations with multiplicative and additive spectral models such as \textit{power-law}, \textit{log-parabola}, \textit{broken power-law}, and \textit{black body}. The \textit{black body} represents the thermal emission from the accretion disk, while the other models represent the possible energy distributions of the particles emitting synchrotron radiation in the jet. During the past two decades, the source flux changed by of a factor of three, with a considerable fractional variability of 27\%. However, the intraday variation was found to be moderate. Flux distributions of the individual observations were consistent with a normal or log-normal distribution, while the overall flux distribution including entire observations appear to be rather multi-modal and of a complex shape. The spectral analyses indicate that \textit{log-parabola} added with a \textit{black body} gives the best fit for most of the observations. The results indicate a complex scenario in which the variability can be attributed to the intricate interaction between the disk/corona system and the jet.

We present a detailed kinematical and dynamical study of the galaxy cluster RXCJ1111.6+4050 (RXCJ1111), at z = 0.0756 using 104 new spectroscopic redshifts of galaxies observed at the TNG 3.5m telescope and SDSS DR16 public archive. Our analysis is performed in a multiwavelength context in order to study and compare mainly optical and X-ray properties using XMM-Newton data. We find that RXCJ1111 is a galaxy cluster showing a velocity distribution with clear deviations from Gaussianity, that we are able to explain by the presence of a substructure within the cluster. The two cluster components show velocity dispersions of $644 \pm 56$ km/s and $410 \pm 123$ km/s, which yield dynamical masses of M$_{200}$=$1.9 \pm 0.4 \times10^{14}$ M$_{\odot}$ and $0.6 \pm 0.4 \times 10^{14}$ M$_{\odot}$ for the main system and substructure, respectively. RXCJ1111 presents an elongation in the North-South direction and a gradient of 250-350 km/s/Mpc in the velocity field, suggest that the merger axis between the main system and substructure is slightly tilted with respect to the line-of-sight. The substructure is characterized by a magnitude gap $\Delta m_{12} \ge 1.8$, so it fits the "fossil-like" definition of a galaxy group. Mass estimates derived from X-ray and optical are in good agreement when two galaxy components are considered separately. We propose a 3D merging model and find that the fossil group is in an early phase of collision with the RXCJ1111 main cluster and almost aligned with the line-of-sight. This merging model would explain the slight increase found in the T$_X$ with respect to what we would expect for relaxed clusters. Due to the presence of several brightest galaxies, after this collision, the substructure would presumably lose its fossil condition. Therefore, RXCJ1111 represents the observational evidence that the fossil stage of a system can be temporary and transitional.

(99942) Apophis is a potentially hazardous asteroid that will closely approach the Earth on April 13, 2029. Although the likelihood of an impact has been ruled out, this close encounter represents a unique opportunity for planetary science and defense. By investigating the physical and dynamical changes induced by this interaction, valuable insights into asteroid cohesion, strength, and internal structure can be obtained. In light of these circumstances, a fast mission to Apophis holds great scientific importance and potential for understanding potentially hazardous asteroids. To this aim, ESA proposed the mission RAMSES (Rapid Apophis Mission for SEcurity and Safety) to reach Apophis before its close encounter. In this context, the paper focuses on the reachability analysis of (99942) Apophis, examining thousands of trajectories departing from Earth and reaching the asteroid before the fly-by, using a low-thrust spacecraft. A two-layer approach combining direct sequential convex programming and an indirect method is employed for fast and reliable trajectory optimization. The results reveal multiple feasible launch windows and provide essential information for mission planning and system design.

We present high-resolution, high-sensitivity observations of the Class 0 protostar RCrA IRS5N as part of the Atacama Large Milimeter/submilimeter Array (ALMA) large program Early Planet Formation in Embedded Disks (eDisk). The 1.3 mm continuum emission reveals a flattened continuum structure around IRS5N, consistent with a protostellar disk in the early phases of evolution. The continuum emission appears smooth and shows no substructures. However, a brightness asymmetry is observed along the minor axis of the disk, suggesting the disk is optically and geometrically thick. We estimate the disk mass to be between 0.007 and 0.02 M$_{\odot}$. Furthermore, molecular emission has been detected from various species, including C$^{18}$O (2$-$1), $^{12}$CO (2$-$1), $^{13}$CO (2$-$1), and H$_2$CO (3$_{0,3}-2_{0,2}$, 3$_{2,1}-2_{2,0}$, and 3$_{2,2}-2_{2,1}$). By conducting a position-velocity analysis of the C$^{18}$O (2$-$1) emission, we find that the disk of IRS5N exhibits characteristics consistent with Keplerian rotation around a central protostar with a mass of approximately 0.3 M$_{\odot}$. Additionally, we observe dust continuum emission from the nearby binary source, IRS5a/b. The emission in $^{12}$CO toward IRS5a/b seems to emanate from IRS5b and flow into IRS5a, suggesting material transport between their mutual orbits. The lack of a detected outflow and large-scale negatives in \tlvco~observed toward IRS5N suggests that much of the flux from IRS5N is being resolved out. Due to this substantial surrounding envelope, the central IRS5N protostar is expected to be significantly more massive in the future.

Cluster galaxies are affected by the surrounding environment, which influences, in particular, their gas, stellar content and morphology. In particular, the ram-pressure exerted by the intracluster medium promotes the formation of multi-phase tails of stripped gas detectable both at optical wavelengths and in the sub-mm and radio regimes, tracing the cold molecular and atomic gas components, respectively. In this work we analyze a sample of sixteen galaxies belonging to clusters at redshift $\sim 0.05$ showing evidence of an asymmetric HI morphology (based on MeerKAT observations) with and without a star forming tail. To this sample we add three galaxies with evidence of a star forming tail and no HI detection. Here we present the galaxies $\rm H_{2}$ gas content from APEX observations of the CO(2-1) emission. We find that in most galaxies with a star forming tail the $\rm H_{2}$ global content is enhanced with respect to undisturbed field galaxies with similar stellar masses, suggesting an evolutionary path driven by the ram-pressure stripping. As galaxies enter into the clusters their HI is displaced but also partially converted into $\rm H_{2}$, so that they are $\rm H_{2}$ enriched when they pass close to the pericenter, i. e. when they develop the star forming tails that are visible in UV/B broad bands and in H$\alpha$ emission. An inspection of the phase-space diagram for our sample suggests an anticorrelation between the HI and $\rm H_{2}$ gas phases as galaxies fall into the cluster potential. This peculiar behaviour is a key signature of the ram-pressure stripping in action.

We present Atacama Large Millimeter/sub-millimeter Array (ALMA) neutral carbon, [C I](1-0), line observations that probe molecular hydrogen gas (H$_2$) within seven radio galaxies at $z = 2.9 - 4.5$ surrounded by extended ($\gtrsim100$ kpc) Ly-$\alpha$ nebulae. We extract [C I](1-0) emission from the radio-active galactic nuclei (AGN) host galaxies whose positions are set by near-infrared detections and radio detections of the cores. Additionally, we place constraints on the galaxies' systemic redshifts via He II $\lambda$1640 lines seen with the Multi-Unit Spectroscopic Explorer (MUSE). We detect faint [C I] emission in four out of seven sources. In two of these galaxies, we discover narrow line emission of full width at half maximum $\lesssim100$ km s$^{-1}$ which may trace emission from bright kpc-scale gas clouds within the ISM. In the other two [C I]-detected galaxies, line dispersions range from $\sim100 - 600$ km s$^{-1}$ and may be tracing the rotational component of the cold gas. Overall, the [C I] line luminosities correspond to H$_2$ masses of M$_{\rm H_2,[C I]} \simeq (0.5 - 3) \times 10^{10} M_\odot$ for the detections and M$_{H_2,[C I]} < 0.65 \times 10^{10} M_\odot$ for the [C I] non-detections in three out of seven galaxies within the sample. The molecular gas masses in our sample are relatively low in comparison to previously reported measures for similar galaxies which are M$_{H_2,[C I]} \simeq (3 - 4) \times 10^{10}.$ Our results imply that the observed faintness in carbon emission is representative of a decline in molecular gas supply from previous star-formation epochs and/or a displacement of molecular gas from the ISM due to jet-powered outflows.

We present a list of quasar candidates including photometric redshift estimates from the miniJPAS Data Release constructed using SQUEzE. This work is based on machine-learning classification of photometric data of quasar candidates using SQUEzE. It has the advantage that its classification procedure can be explained to some extent, making it less of a `black box' when compared with other classifiers. Another key advantage is that using user-defined metrics means the user has more control over the classification. While SQUEzE was designed for spectroscopic data, here we adapt it for multi-band photometric data, i.e. we treat multiple narrow-band filters as very low-resolution spectra. We train our models using specialized mocks from Queiroz et al. (2022). We estimate our redshift precision using the normalized median absolute deviation, $\sigma_{\rm NMAD}$ applied to our test sample. Our test sample returns an $f_1$ score (effectively the purity and completeness) of 0.49 for quasars down to magnitude $r=24.3$ with $z\geq2.1$ and 0.24 for quasars with $z<2.1$. For high-z quasars, this goes up to 0.9 for $r<21.0$. We present two catalogues of quasar candidates including redshift estimates: 301 from point-like sources and 1049 when also including extended sources. We discuss the impact of including extended sources in our predictions (they are not included in the mocks), as well as the impact of changing the noise model of the mocks. We also give an explanation of SQUEzE reasoning. Our estimates for the redshift precision using the test sample indicate a $\sigma_{NMAD}=0.92\%$ for the entire sample, reduced to 0.81\% for $r<22.5$ and 0.74\% for $r<21.3$. Spectroscopic follow-up of the candidates is required in order to confirm the validity of our findings.

The main goal of this work is to evaluate the correlation between Li abundance, age, and mass. Using high-quality ESO/HARPS data (R $\simeq$ 115 000; 270 $\leq$ SNR $\leq$ 1000), we measured Li abundances via spectral synthesis of the 6707.8 \r{A} $^7$Li line in 74 solar twins and analogs. Our joint analysis of 151 Sun-like stars (72 from our sample plus 79 solar twins from a previous study) confirms the strong Li abundance-age correlation reported by other works. Mass and convective envelope size also seem to be connected with Li abundance but with lower significance. We have found a link between the presence of planets and low Li abundances in a sample of 192 stars with a high significance. Our results agree qualitatively with non-standard models, and indicate that several extra transport mechanisms must be taken into account to explain the behaviour of Li abundance for stars with different masses and ages.

Estimates of the size of the feeding zone of the planet Proxima Centauri c have been made at initial orbital eccentricities of planetesimals equal to 0.02 or 0.15. The research is based on the results of modeling of the evolution of planetesimals' orbits under the influence of the star and planets Proxima Centauri c and b. The considered time interval reached a billion years. It was found that after the accumulation of the planet Proxima Centauri c some planetesimals may have continues to move in stable elliptical orbits within its feeding zone, largely cleared of planetesimals. Usually such planetesimals can move in some resonances with the planet (Proxima Centauri c), for example, in the resonance 1:1 (as Jupiter Trojans), 5:4 and 3:4 and usually have small eccentricities. Some planetesimals that moved for a long time (1-2 million years) along chaotic orbits fell into the resonances 5:2 and 3:10 with the planet Proxima Centauri c and moved in them at least tens of millions of years.

Context. Deuterium in H-bearing species is enhanced during the early stages of star formation, however, only a small number of high spatial resolution deuteration studies exist towards protostellar objects, leaving the small-scale structures unrevealed and understudied. Aims. We aim to constrain the deuterium fractionation ratios in a Class 0/I protostellar object in formaldehyde (H2CO), which has abundant deuterated isotopologues in this environment. Methods. We observed the Class 0/I protobinary system [BHB2007] 11, whose emission components are embedded in circumstellar disks that have radii of 2-3 au, using ALMA within the context of the Large Program FAUST. The system is surrounded by a complex filamentary structure connecting to the larger circumbinary disk. In this work we present the first study of formaldehyde D-fractionation towards this source with detections of H2CO 3(0,3)-2(0,2), combined with HDCO 4(2,2)-3(2,1), HDCO 4(1,4)-3(1,3) and D2CO 4(0,4)-3(0,3). These observations enable multiple velocity components associated with the methanol hotspots also uncovered by FAUST data, as well as the external envelope, to be resolved. In addition, based on the kinematics seen in the observations of the H2CO emission, we propose the presence of a second large scale outflow. Results. HDCO and D2CO are only found in the central regions of the core while H2CO is found more ubiquitously. From radiative transfer modelling, the column densities ranges found for H2CO, HDCO and D2CO are (3-8)x10$^{14}$ cm$^{-2}$, (0.8-2.9)x10$^{13}$ cm$^{-2}$ and (2.6-4.3)x10$^{12}$ cm$^{-2}$, respectively, yielding an average D/H ratio of 0.01-0.04. Following the results of kinematic modelling, the second large scale feature is inconsistent with a streamer-like nature and we thus tentatively conclude that the feature is an asymmetric molecular outflow launched by a wide-angle disk wind.

Gamma-Ray Bursts are among the most powerful events in the Universe. Despite half a century of observations of these transient sources, many open questions remain about their nature. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. With the aim of characterizing the polarization of these prompt emissions, a compact Compton polarimeter, called POLAR, has been launched to space in September 2016. Time integrated polarization analysis of the POLAR GRB catalog have shown that the prompt emission is lowly polarized or fully unpolarized. However, time resolved analysis depicted strong hints of an evolving polarization angle within single pulses, washing out the polarization degree in time integrated analyses. Here we will for the first time present energy resolved polarization measurements with the POLAR data. The novel analysis, performed on several GRBs, will provide new insights and alter our understanding of GRB polarization. The analysis was performed using the 3ML framework to fit polarization parameters versus energy in parallel to the spectral parameters. Although limited by statistics, the results could provide a very relevant input to disentangle between existing theoretical models. In order to gather more statistics per GRB and perform joint time and energy resolved analysis, a successor instrument, called POLAR-2, is under development with a launch window early 2025 to the CSS. After presenting the first energy resolved polarization results of the POLAR mission, we will present the prospects for such measurements with the upcoming POLAR-2 mission.

Giant exoplanets seem to have on average a much larger heavy element content than the solar system giants. Past attempts to explain these heavy element contents include collisions between planets, accretion of volatile rich gas and accretion of gas enriched in micro-metre sized solids. However, these different theories individually could not explain the heavy element content of giants and the volatile to refractory ratios in atmospheres of giant planets at the same time. Here we combine the approaches of gas accretion enhanced with vapor and small micro-meter sized dust grains. As pebbles drift inwards, the volatile component evaporates and enriches the disc, while the smaller silicate core of the pebble continues to move inwards. The smaller silicate pebbles drift slower, leading to a pile-up of material interior to the water ice line, increasing the dust-to-gas ratio interior to the ice line. Under the assumption that these small dust grains follow the motion of the gas, gas accreting giants accrete large fractions of small solids in addition to the volatile vapor. The effectiveness of the solid enrichment requires a large disc radius to maintain the pebble flux for a long time and a large viscosity that reduces the size and inward drift of the small dust grains. However, this process depends crucially on the debated size difference of the pebbles interior and exterior of the water ice line. On the other hand, the volatile component released by the inward drifting pebbles can lead to a large enrichment with heavy element vapor, independently of a size difference of pebbles interior and exterior to the water ice line. Our model stresses the importance of the disc's radius and viscosity on the enrichment of dust and vapor. Consequently we show how our model could explain the heavy element content of the majority of giant planets by using combined estimates of dust and vapor enrichment.

The POLAR-2 Gamma-Ray Burst (GRB) Polarimetry mission is a follow-up to the successful POLAR mission. POLAR collected six months of data in 2016-2017 on board the Tiangong-2 Chinese Space laboratory. From a polarization study on 14 GRBs, POLAR measured an overall low polarization and a hint for an unexpected complexity in the time evolution of polarization during GRBs. Energy-dependent measurements of the GRB polarization will be presented by N. de Angelis in GA21-09 (August 2nd). These results demonstrate the need for measurements with significantly improved accuracy. Moreover, the recent discovery of gravitational waves and their connection to GRBs justifies a high-precision GRB polarimeter that can provide both high-precision polarimetry and detection of very faint GRBs. The POLAR-2 polarimeter is based on the same Compton scattering measurement principle as POLAR, but with an extended energy range and an order of magnitude increase in total effective area for polarized events. Proposed and developed by a joint effort of Switzerland, China, Poland and Germany, the device was selected for installation on the China Space Station and is scheduled to start operation for at least 2 years in 2025.

The point-spread function (PSF) is a fundamental property of any astronomical instrument. In interferometers, differing array configurations combined with their $uv$ coverage, and various weighting schemes can produce an irregular but deterministic PSF. As a result, the PSF is often deconvolved using CLEAN-style algorithms to improve image fidelity. In this paper, we revisit a significant effect that causes the flux densities measured with any interferometer to be systematically offset from the true values. Using a suite of carefully controlled simulations, we show that the systematic offset originates from a mismatch in the units of the image produced by these CLEAN-style algorithms. We illustrate that this systematic error can be significant, ranging from a few to tens of per cent. Accounting for this effect is important for current and future interferometric arrays, such as MeerKAT, LOFAR and the SKA, whose core-dominated configuration naturally causes an irregular PSF. We show that this offset is independent of other systematics, and can worsen due to some factors such as the goodness of the fit to the PSF, the deconvolution depth, and the signal-to-noise of the source. Finally, we present several methods that can reduce this effect to just a few per cent.

The nature of Type Ia Supernova (SN Ia) explosions remains an open issue, with several contending progenitor scenarios actively being considered. One such scenario involves a SN Ia explosion inside a planetary nebula (PN) in the aftermath of a stellar merger triggered by a common envelope (CE) episode. We examine this scenario using hydrodynamic and non-equilibrium ionization simulations of the interaction between the SN ejecta and the PN cocoon into the supernova remnant (SNR) phase, focusing on the impact of the delay between the CE episode and the SN explosion. We compare the bulk dynamics and X-ray spectra of our simulated SNRs to the observed properties of known Type Ia SNRs in the Milky Way and the Magellanic Clouds. We conclude that models where the SN explosion happens in the immediate aftermath of the CE episode (with a delay $\lesssim$1,000 yr) are hard to reconcile with the observations, because the interaction with the dense PN cocoon results in ionization timescales much higher than those found in any known Type Ia SNR. Models with a longer delay between the CE episode and the SN explosion ($\sim$10,000 yr) are closer to the observations, and may be able to explain the bulk properties of some Type Ia SNRs.

Recent observations have resulted in the detection of chemical gradients on ultra-hot gas giants. Notwithstanding their high temperature, chemical reactions in ultra-hot atmospheres may occur in disequilibrium, due to vigorous day-night circulation and intense UV radiation from their stellar hosts. The goal of this work is to explore whether photochemistry is affecting the composition of ultra-hot giant planets, and if it can introduce horizontal chemical gradients. In particular, we focus on hydrogen cyanide (HCN) on WASP-76 b, as it is a photochemically active molecule with a reported detection on only one side of this planet. We use a pseudo-2D chemical kinetics code to model the chemical composition of WASP-76 b along its equator. Our approach improves on chemical equilibrium models by computing vertical mixing, horizontal advection, and photochemistry. We find that production of HCN is initiated through thermal and photochemical dissociation of CO and N2 on the day side of WASP-76 b, which are subsequently transported to the night side via the equatorial jet stream. This process results in an HCN gradient with a maximal abundance on the planet's morning limb. We verified that photochemical dissociation is a necessary condition for this mechanism, as thermal dissociation alone proves insufficient. Other species produced via night-side disequilibrium chemistry are SO2 and S2. Our model acts as a proof of concept for chemical gradients on ultra-hot exoplanets. We demonstrate that even ultra-hot planets can exhibit disequilibrium chemistry and recommend that future studies do not neglect photochemistry in their analyses of ultra-hot planets.

The new generation of galaxy surveys will provide unprecedented data allowing us to test gravity at cosmological scales. A robust cosmological analysis of the large-scale structure demands exploiting the nonlinear information encoded in the cosmic web. Machine Learning techniques provide such tools, however, do not provide a priori assessment of uncertainties. This study aims at extracting cosmological parameters from modified gravity (MG) simulations through deep neural networks endowed with uncertainty estimations. We implement Bayesian neural networks (BNNs) with an enriched approximate posterior distribution considering two cases: one with a single Bayesian last layer (BLL), and another one with Bayesian layers at all levels (FullB). We train both BNNs with real-space density fields and power-spectra from a suite of 2000 dark matter only particle mesh $N$-body simulations including modified gravity models relying on MG-PICOLA covering 256 $h^{-1}$ Mpc side cubical volumes with 128$^3$ particles. BNNs excel in accurately predicting parameters for $\Omega_m$ and $\sigma_8$ and their respective correlation with the MG parameter. We find out that BNNs yield well-calibrated uncertainty estimates overcoming the over- and under-estimation issues in traditional neural networks. We observe that the presence of MG parameter leads to a significant degeneracy with $\sigma_8$ being one of the possible explanations of the poor MG predictions. Ignoring MG, we obtain a deviation of the relative errors in $\Omega_m$ and $\sigma_8$ by at least $30\%$. Moreover, we report consistent results from the density field and power spectra analysis, and comparable results between BLL and FullB experiments which permits us to save computing time by a factor of two. This work contributes in setting the path to extract cosmological parameters from complete small cosmic volumes towards the highly nonlinear regime.

Over the last few decades, a plethora of modifications to general relativity have been proposed to solve a host of cosmological and astrophysical problems. Many modified gravity models are now ruled out with further astrophysical observations; some theories are still viable, with, at best, bounds on their parameters set by observations to date. More recently, observations of Fast Radio Bursts have proven to be remarkably powerful tools to constrain cosmology and fundamental physics. In this work, we consider a generic modified gravity theory and consider the implications for gravitational lensing with Fast Radio Bursts. We use a set of Fast Radio Burst observations to constrain the fraction of dark matter made up of primordial black holes in such a theory. We further show that modified gravity adds a screening effect on gravitational lensing similar to the case when there is plasma in the path of the light ray acting as a scattering screen.

Increasingly precise astrophysical observations of the last decade in combination with intense theoretical studies allow for drawing a conclusion about Quark Matter presence in Neutron Stars interiors. Quark Matter may form the Neutron Star inner core or be immersed in the form of bubbles, or droplets. We demonstrate that the last scenario leads to a highly anomalous character of the sound propagation and the sound speed.

We put forward a new procedure for measuring the spin of a black hole with unprecedented accuracy based on gravitational lensing of millisecond pulsars. The deflection angle of light increases by increasing the rotation parameter. For primary and secondary images the angular positions are larger for rotating black holes by an amount of the order of microarcseconds. Also, the differential time delay for the case of a rotating black hole is larger than that for the non-rotating case and the difference could be as large as a few seconds. We show that this quantity could help us achieve an extremely precise measurement of the black hole spin, much more accurate than the current and near future achievable estimation of black hole spin through other methods.

Numerical relativity waveforms are a critical resource in the quest to deepen our understanding of the dynamics of, and gravitational waves emitted from, merging binary systems. We present 181 new numerical relativity simulations as the second MAYA catalog of binary black hole waveforms (a sequel to the Georgia Tech waveform catalog). Most importantly, these include 55 high mass ratio (q >= 4), 48 precessing, and 92 eccentric (e > 0.01) simulations, including 7 simulations which are both eccentric and precessing. With these significant additions, this new catalog fills in considerable gaps in existing public numerical relativity waveform catalogs. The waveforms presented in this catalog are shown to be convergent and are consistent with current gravitational wave models. They are available to the public at https://cgp.ph.utexas.edu/waveform.

We simulate, using a particle-in-cell code, the chain of acceleration processes at work during the Compton-based interaction of a dilute electron-ion plasma with an extreme-intensity, incoherent gamma-ray flux with a photon density several orders of magnitude above the particle density. The plasma electrons are initially accelerated in the radiative flux direction through Compton scattering. In turn, the charge-separation field from the induced current drives forward the plasma ions to near-relativistic speed and accelerates backwards the non-scattered electrons to energies easily exceeding those of the driving photons. The dynamics of those energized electrons is determined by the interplay of electrostatic acceleration, bulk plasma motion, inverse Compton scattering and deflections off the mobile magnetic fluctuations generated by a Weibel-type instability. The latter Fermi-like effect notably gives rise to a forward-directed suprathermal electron tail. We provide simple analytical descriptions for most of those phenomena and examine numerically their sensitivity to the parameters of the problem.

We define a minimal model of dark matter with a fermion singlet $\chi$ coupled to the visible sector through the Higgs portal and with a heavy Dirac neutrino $N$ that opens the annihilation channel $\chi \chi \to N \nu$. The model provides the observed relic abundance consistently with bounds from direct searches and implies a monochromatic neutrino signal at 10 GeV-1 TeV in indirect searches. In particular, we obtain the capture rate of $\chi$ by the Sun and show that the signal could be above the "neutrino floor" produced by cosmic rays showering in the solar surface. In most benchmark models this solar astrophysical background is above the expected dark matter signal, so the model that we propose is a canonical example of WIMP not excluded by direct searches that could be studied at neutrino telescopes and also at colliders.

Dark matter direct detection experiments impose the strong bounds on thermal dark matter scenarios. The bound can naturally be evaded if the cross section is momentum transfer dependent or velocity dependent. One can test such thermal dark matter scenarios if dark matter particles are boosted by some mechanism. In this work, we consider a specific semi-annihilation $\chi\chi\to \nu\overline{\chi}$ where $\chi$ ($\overline{\chi}$) is dark matter (anti-dark matter), and search for simultaneous detection of the neutrino and the boosted dark matter in the final state at DUNE. We find that the energies of the neutrino and boosted dark matter are reconstructed well due to the precise angular resolution of the DUNE detector. In addition, we find that both signals can be testable at DUNE if the dark matter mass is below 30 GeV, and the scattering cross section is momentum transfer dependent.

Doppler anisotropies, induced by our relative motion with respect to the source rest frame, are a guaranteed property of stochastic gravitational wave backgrounds of cosmological origin. If detected by future pulsar timing array measurements, they will provide interesting information on the physics sourcing gravitational waves, which is hard or even impossible to extract from measurements of the isotropic part of the background only. We analytically determine the pulsar response function to kinematic anisotropies, including possible effects due to parity violation, to features in the frequency dependence of the isotropic part of the spectrum, as well as to the presence of extra scalar and vector polarizations. For the first time, we show how the sensitivity to different effects crucially depends on the pulsar configuration with respect to the relative motion among frames. Correspondingly, we propose examples of strategies of detection, each aimed at exploiting future measurements of kinematic anisotropies for characterizing distinct features of the cosmological gravitational wave background.

We investigate non-radial oscillations of anisotropic neutron stars within the framework of general relativity. Our study involves nonrotating, spherically symmetric anisotropic neutron stars as the unperturbed equilibrium configuration. We employ the BSk21 equation of state to describe neutron star matter and introduce a phenomenological ansatz to account for local anisotropy. Through considering small and adiabatic polar perturbations (even parity), we derive oscillation equations from the linearized Einstein equations. Notably, these oscillation equations explicitly incorporate the influence of pressure anisotropy. We calculate the frequencies and damping times of the fundamental (f) mode for various choices of anisotropic pressure strength. Interestingly, we observe that the f-mode frequencies continue to scale linearly with the average density of neutron stars, even in the presence of anisotropy. We conduct a comprehensive analysis of how anisotropy affects both the f-mode frequency and its associated damping time.

Axion-like particles (ALPs) can be naturally lighter than the electroweak scale. We consider an ALP that couples to the Standard Model Higgs to achieve the strong first-order electroweak phase transition. We discuss the two-field dynamics of the phase transition and the associated computation in detail and identify the viable parameter space. The ALP mass can be from the MeV to GeV scale. Baryon asymmetry can be explained by local baryogenesis without violating the electron electric dipole moment bound. The viable parameter space can be probed through Higgs exotic decay, rare kaon decay, the electron electric dipole moment, and the effective number of neutrinos in the cosmic microwave background. The gravitational-wave signal is too weak to be detected.

Ancient mesoamerican cultures built a short ritual 260 day calendar and used it for daily routinary life. Using simple arithmetic calculations, it is shown in this work that by forcing the introduction of the fundamental number 13 to calculate days in a calendar, a 364 day count can be built and from this, the short mesoamerican calendar of 260 days is constructed. This short calendar inherits some properties of the full 365 day calendar and others from the 360 cycle used by mesoamerican cultures. These cultures also used particular fractions or monads of the numbers of days of the approximate solar 364 day and the full solar 365 day counts in order to align with particular sunsets and sunrises some of their architectural monuments. It is also shown that the basic mesoamerican relation between the full solar 365 day calendar and the short one of 260 days given by: 365 x 52 = 260 x 73 is Kepler's third law of orbital motion between Earth's period of time about the Sun and an imaginary synodic orbit with a 260 day period.