Papers for Tuesday, Jan 14 2025

We present a catalog of individual stellar and dust extinction properties along close to 500,000 sight lines in the southwest bar of the Small Magellanic Cloud (SMC). The catalog is based on multiband Hubble Space Telescope photometric data spanning near-ultraviolet to near-infrared wavelengths from the Small Magellanic Cloud Investigation of Dust and Gas Evolution survey (SMIDGE) covering a 100 x 200 pc area. We use the probabilistic technique of the Bayesian Extinction And Stellar Tool (BEAST) to model the spectral energy distributions of individual stars in SMIDGE and include the effects of observational uncertainties in the data. We compare BEAST-derived dust extinction properties with tracers of the interstellar medium, such as the emission from the 12CO (2-1) transition (I(CO)), the dust mass surface density ({\Sigma}dust) from far-IR emission, the H I column density (N(HI)) from the 21cm transition, and the mass fraction of polycyclic aromatic hydrocarbons (PAHs; qPAH, derived from IR emission). We find that the dust extinction (A(V )) in the SMIDGE field is strongly correlated with {\Sigma}dust and I(CO), and less so with N(HI) and qPAH, and suggest potential explanations. Our extinction measurements are also sensitive to the presence of the 2175 Å bump in the extinction curve toward UV bright stars. While most do not show evidence for the bump, we identify ~200 lines of sight that are 2175 Å bump candidates. Furthermore, we find distinct structures in the dust extinction-distance distributions that provide insights into the 3D geometry of the SMC.

Traditional microlensing event vetting methods require highly trained human experts, and the process is both complex and time-consuming. This reliance on manual inspection often leads to inefficiencies and constrains the ability to scale for widespread exoplanet detection, ultimately hindering discovery rates. To address the limits of traditional microlensing event vetting, we have developed LensNet, a machine learning pipeline specifically designed to distinguish legitimate microlensing events from false positives caused by instrumental artifacts, such as pixel bleed trails and diffraction spikes. Our system operates in conjunction with a preliminary algorithm that detects increasing trends in flux. These flagged instances are then passed to LensNet for further classification, allowing for timely alerts and follow-up observations. Tailored for the multi-observatory setup of the Korea Microlensing Telescope Network (KMTNet) and trained on a rich dataset of manually classified events, LensNet is optimized for early detection and warning of microlensing occurrences, enabling astronomers to organize follow-up observations promptly. The internal model of the pipeline employs a multi-branch Recurrent Neural Network (RNN) architecture that evaluates time-series flux data with contextual information, including sky background, the full width at half maximum of the target star, flux errors, PSF quality flags, and air mass for each observation. We demonstrate a classification accuracy above 87.5%, and anticipate further improvements as we expand our training set and continue to refine the algorithm.

We present VIRAC2, a catalogue of positions, proper motions, parallaxes and $Z$, $Y$, $J$, $H$, and $K_s$ near-infrared photometric time series of 545 346 537 unique stars. The catalogue is based on a point spread function fitting reduction of nearly a decade of VISTA VVV and VVVX images, which cover $560~{\rm deg}^2$ of the Southern Galactic plane and bulge. The catalogue is complete at the $>90$ per cent level for $11<K_s~{\rm mag}<16$ sources, but extends to $K_s\approx{}17.5$ mag in most fields. Astrometric performance for $11<K_s~{\rm mag}<14$ sources is typically $\approx{}0.37~{\rm mas~yr}^{-1}$ per dimension for proper motion, and $1~{\rm mas}$ for parallax. At $K_s=16$ the equivalent values are around $1.5~{\rm mas~yr}^{-1}$ and $5~{\rm mas}$. These uncertainties are validated against Gaia DR3 and Hubble Space Telescope astrometry. The complete catalogues are available via the ESO archive. We perform an initial search of the catalogue for nearby ultracool dwarf candidates. In total we find 26 new sources whose parallaxes place them within 50 parsecs of the Sun. Among them we find two high-confidence T dwarfs and a number of other sources that appear to lie close to the L/T transition.

We present Goku, a suite of cosmological $N$-body simulations, and the corresponding 10-dimensional emulator, GokuEmu, for the nonlinear matter power spectrum. The simulations span the base parameters of $\Lambda$CDM cosmology and its extensions, including dynamical dark energy ($w_0$, $w_a$), the sum of the neutrino masses ($\sum m_\nu$), the effective number of neutrinos ($N_\text{eff}$), and the running of the scalar spectral index ($\alpha_\text{s}$). Designed within the MF-Box framework, which integrates multi-scale and multi-fidelity simulations, the suite includes high-fidelity simulations evolving $3000^3$ particles in $1\,(\text{Gpc}/h)^3$ volumes and low-fidelity simulations with $750^3$ particles across varying box sizes. This approach achieves percent-level accuracy in high-likelihood regions and 5% accuracy across broader parameter ranges, while reducing computational costs by over 90% compared to single-fidelity methods. The simulations adopt an accurate treatment of massive neutrinos, enhancing predictions of the matter power spectrum on nonlinear scales. Key innovations include an adaptive sampling strategy and the use of beam search to optimize generalization accuracy. The emulator is valid for redshifts $z \leq 3$ and scales $0.01 \lesssim k / (h \, \text{Mpc}^{-1}) \lesssim 10$. Beyond the matter power spectrum, the simulations also support analyses of other statistical measures, such as the halo mass function. The emulator and its training data are publicly available at this https URL, providing a valuable resource for cosmological parameter inference and model testing.

Many studies conclude that galaxies quench from the inside-out by examining profiles of specific star-formation rate (sSFR). These are usually measured by fitting spectral energy distributions (SEDs) assuming a fixed dust law and uniform priors on all parameters. Here, we examine the effects of more physically motivated priors: a flexible dust law, an exponential prior on the dust attenuation $A_V$, and Gaussian priors that favor extended star-formation histories. This results in model colors that better trace observations. We then perform radial SED fits to multi-band flux profiles measured from Hubble images for 1,440 galaxies at $0.4<z<1.5$ of stellar masses $10^{10}-10^{11.5}\ M_{\odot}$ using both the traditional and the more physically motivated assumptions. This results in SFR and $A_V$ profiles that agree with measurements from spectroscopy and $A_V$ profiles that behave correctly as a function of inclination. Since green valley galaxies at $z\sim1.3$ are expected to evolve into quiescent galaxies at $z\sim0.9$, we compare their sSFR profiles using the more physically motivated assumptions. Their slopes are similar at all masses ($0.06 - 0.08~\textrm{dex}~\textrm{kpc}^{-1}$), and the normalizations for the quiescent galaxies are lower. Therefore, the sSFR profiles decline with time as quenching occurs at all radii simultaneously. We compare profiles of green valley galaxies at $z\sim0.9$ and quiescent galaxies at $z\sim0.5$. The former are shallower at all masses by $\sim0.1~\textrm{dex}~\textrm{kpc}^{-1}$. The sSFR profiles steepen with time as galaxies quench from the inside-out. In summary, galaxies at $z\sim1$ quench at all radii simultaneously while galaxies at $z\sim0.7$ quench from the inside-out.

We present the first constraints on primordial magnetic fields from the Lyman-$\alpha$ forest using full cosmological hydrodynamic simulations. At the scales and redshifts probed by the data, the flux power spectrum is extremely sensitive to the extra power induced by primordial magnetic fields in the linear matter power spectrum, at a scale that we parametrize with $k_{\rm peak}$. We rely on a set of more than a quarter million flux models obtained by varying thermal, reionization histories and cosmological parameters. We find a hint of extra power that is well fitted by the PMF model with $B\sim 0.2$ nG, corresponding to $k_{\rm peak}\sim 20$ Mpc$^{-1}$. However, when applying very conservative assumptions on the modelling of the noise, we obtain a 3$\sigma$ C.L. lower limit $k_{\rm peak}> 30$ Mpc$^{-1}$ which translates into the tightest bounds on the strength of primordial intergalactic magnetic fields: $B < 0.30$ nG (for fixed, nearly scale-invariant $n_{\rm B}=-2.9$).

Detection of electron cyclotron maser (ECM) emission from exoplanets in the 10-40 MHz radio band is likely the only way to measure an exoplanet's magnetic field directly. However, no definitive detection of exoplanetary ECM emission has been made to date. A detection of the hot Jupiter Tau Boötis b was reported but with an observing mode that is not immune to confusion from off-axis interference, making the detection tentative. We searched for radio emissions from Tau Boötis b using the Low Frequency Array (LOFAR) in interferometric mode, which employs direction-of-arrival information to discriminate genuine signals from interference. Our aim was to confirm the previous tentative detection or establish an upper limit in the case of a non-detection. We conducted observations using LOFAR's Low Band Antenna in interferometric mode, which totalled 64, hours spread over 8, nights. We created a custom data-processing pipeline to mitigate common challenges in decametric radio astronomy, including radio frequency interference, ionospheric distortions, and sidelobe noise from nearby bright radio sources. We used this pipeline to image the field around Tau Boötis b, searching for both quiescent and bursting emission from the direction of Tau Boötis b. Despite the high sensitivity of the interferometric observations and extensive data processing, no significant emission was detected from Tau Boötis b in Stokes V. We establish an upper limit of 2 sigma at 24 mJy for any continuous emission from the exoplanet. The previous tentative detection of 400 mJy is thus not confirmed by the interferometric observations. The previous tentative detection is unlikely to be a bona fide astrophysical signal. Our upper limit is lower than the flux density predicted by scaling laws, meaning either the scaling laws need to be revised or the emission from this particular system is beamed away from Earth.

We present a measurement of the supermassive black hole (SMBH) mass of the nearby lenticular galaxy NGC 383, based on Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the $^{12}$CO(2-1) emission line with an angular resolution of $0.''050\times0.''024$ ($\approx16\times8$ pc$^2$). These observations spatially resolve the nuclear molecular gas disc down to $\approx41,300$ Schwarzschild radii and the SMBH sphere of influence by a factor of $\approx24$ radially, better than any other SMBH mass measurement using molecular gas to date. The high resolution enables us to probe material with a maximum circular velocity of $\approx1040$ km/s, even higher than those of the highest-resolution SMBH mass measurements using megamasers. We detect a clear Keplerian increase (from the outside in) of the line-of-sight rotation velocities, a slight offset between the gas disc kinematic (i.e. the position of the SMBH) and morphological (i.e. the centre of the molecular gas emission) centres, an asymmetry of the innermost rotation velocity peaks and evidence for a mild position angle warp and/or non-circular motions within the central $\approx0.''3$. By forward modelling the mass distribution and ALMA data cube, we infer a SMBH mass of $(3.58\pm0.19)\times10^9$ M$_\odot$ ($1\sigma$ confidence interval), more precise ($5\%$) but consistent within $\approx1.4\sigma$ with the previous measurement using lower-resolution molecular gas data. Our measurement emphasises the importance of high spatial resolution observations for precise SMBH mass determinations.

The next-generation Very Large Array (ngVLA) is intended to be the premier centimeter-wavelength facility for astronomy and astrophysics, building on the substantial scientific legacies of the Karl G. Jansky Very Large Array (VLA) and the Very Long Baseline Array (VLBA). The ngVLA would open a new window on the Universe through ultra-sensitive imaging of thermal line and continuum emission to milliarcsecond resolution, while delivering unprecedented broad-band continuum imaging and polarimetry of non-thermal emission. The ngVLA would provide a critical electromagnetic complement to a suite of particle detectors and gravitational-wave observatories, as well as space- and ground-based telescopes operating from infrared to gamma-ray wavelengths, hence enabling multi-messenger and multi-band astronomy and astrophysics. Current construction plans call for the ngVLA to leverage some of the physical infrastructure of both the VLA and the VLBA, potentially drawing on overlapping personnel and information infrastructure. Multiple options can be envisioned for a VLA+VLBA to ngVLA transition. In order to assess risks and benefits of possible transition plans, the ngVLA project established the VLA+VLBA to ngVLA Transition Advisory Group (TAG). The primary deliverable from the TAG is a ``VLA+VLBA to ngVLA Transition Option Concepts'' report (this report) that includes a prioritized list of transition options.

We employ the XGBoost machine learning (ML) method for the morphological classification of galaxies into two (early-type, late-type) and five (E, S0--S0a, Sa--Sb, Sbc--Scd, Sd--Irr) classes, using a combination of non-parametric ($C,\,A,\,S,\,A_S,\,\mathrm{Gini},\,M_{20},\,c_{5090}$), parametric (Sérsic index, $n$), geometric (axial ratio, $BA$), global colour ($g-i,\,u-r,\,u-i$), colour gradient ($\Delta (g - i)$), and asymmetry gradient ($\Delta A_{9050}$) information, all estimated for a local galaxy sample ($z<0.15$) compiled from the Sloan Digital Sky Survey (SDSS) imaging data. We train the XGBoost model and evaluate its performance through multiple standard metrics. Our findings reveal better performance when utilizing all fourteen parameters, achieving accuracies of 88\% and 65\% for the two-class and five-class classification tasks, respectively. In addition, we investigate a hierarchical classification approach for the five-class scenario, combining three XGBoost classifiers. We observe comparable performance to the ``direct'' five-class classification, with discrepancies of only up to 3\%. Using SHAP (an advanced interpretation tool), we analyse how galaxy parameters impact the model's classifications, providing valuable insights into the influence of these features on classification outcomes. Finally, we compare our results with previous studies and find them consistently aligned.

We present the spectroscopic characterization of cyclopropenethione (c-C3H2S) in the laboratory and detect it in space using the Green Bank Telescope (GBT) Observations of TMC-1: Hunting Aromatic Molecules (GOTHAM) survey. The detection of this molecule - the missing link in understanding the C3H2S isomeric family in TMC-1 - completes the detection of all 3 low-energy isomers of C3H2S as both CH2CCS and HCCCHS have been previously detected in this source. The total column density of this molecule (N_T of 5.72+2.65/-1.61x10^10 cm^-2 at an excitation temperature of 4.7+1.3/-1.1 K) is smaller than both CH2CCS and HCCCHS and follows nicely the relative dipole principle (RDP), a kinetic rule-of-thumb for predicting isomer abundances which suggests that, all other chemistry among a family of isomers being the same, the member with the smallest dipole should be the most abundant. The RDP now holds for the astronomical abundance ratios of both the S-bearing and O-bearing counterparts observed in TMC-1; however, CH2CCO continues to elude detection in any astronomical source.

Understanding the stability of exoplanet systems is crucial for constraining planetary formation and evolution theories. We use the machine-learning stability indicator, SPOCK, to characterize the stability of 126 high-multiplicity systems from the California Kepler Survey (CKS). We constrain the range of stable eccentricities for each system, adopting the value associated with a 50% chance of stability as the characteristic eccentricity. We confirm characteristic eccentricities via a small suite of N-body integrations. In studying correlations between characteristic eccentricity and various planet-pair and system-level metrics we find that minimum period ratio correlates most strongly with characteristic eccentricity. These characteristic eccentricities are approximately 20% of the eccentricities necessary for two-body mean-motion resonance overlap, suggesting three-body dynamics are needed to drive future instabilities. Systems in which the eccentricities would need to be high (> 0.15) to drive instability are likely dynamically relaxed and might be the fossils of a previous epoch of giant impacts that increased the typical planet-planet spacing.

Global solar photospheric magnetic maps play a critical role in solar and heliospheric physics research. Routine magnetograph measurements of the field occur only along the Sun-Earth line, leaving the far-side of the Sun unobserved. Surface Flux Transport (SFT) models attempt to mitigate this by modeling the surface evolution of the field. While such models have long been established in the community (with several releasing public full-Sun maps), none are open source. The Open Source Flux Transport (OFT) model seeks to fill this gap by providing an open and user-extensible SFT model that also builds on the knowledge of previous models with updated numerical and data acquisition/assimilation methods along with additional user-defined features. In this first of a series of papers on OFT, we introduce its computational core: the High-performance Flux Transport (HipFT) code (this http URL). HipFT implements advection, diffusion, and data assimilation in a modular design that supports a variety of flow models and options. It can compute multiple realizations in a single run across model parameters to create ensembles of maps for uncertainty quantification and is high-performance through the use of multi-CPU and multi-GPU parallelism. HipFT is designed to enable users to easily write extensions, enhancing its flexibility and adaptability. We describe HipFT's model features, validations of its numerical methods, performance of its parallel and GPU-accelerated code implementation, analysis/post-processing options, and example use cases.

The optical star in the T Tauri triple system is the prototype of young sun-like stars in our galaxy. This complex and dynamic system has evidence for misaligned disks and outflows, and molecular material in a circumbinary ring that obscures the southern infrared binary, T Tau South. Observations by members of the American Association of Variable Star Observers (AAVSO) show that T Tau North, the optical star, has dimmed by up to ~2 magnitudes in the visual over the course of the past decade. The dimming across the B, V, R and I bands has a color character typical of changes in ISM extinction, suggesting an increase in obscuration along the line of sight to T Tau North. Material associated with the circumbinary ring around T Tau South has been predicted to occult the optical star via wide-scale orbital motion of the system. Through analysis of the geometrical configuration and motion of dust structures in the system, it seems that a great dimming of T Tau North by line-of-sight material associated with the T Tau South binary has, in fact, begun. Based on the extent and motion of the circumbinary ring material associated with the southern binary, T Tau North will likely experience dimming events for decades to come and may disappear entirely from the optical sky as the densest mid-plane region of the ring traverses our line of sight.

In this letter, I discuss the macroscopic properties of the ultracompact object XTE J1814-338, whose inferred mass and radius read $M$ = 1.21 $\pm$ 0.05 $M_\odot$ and R = 7.0 $\pm$ 0.4 km. By using the neutralino as WIMP dark matter with a fixed Fermi momentum, I calculated the maximum possible mass of this object, the moment of inertia, the gravitational redshift, the dimensionless tidal parameter, and the total amount of dark matter for a 1.2$M_\odot$ star.

The inflated radii of hot Jupiters have been explored by various theoretical mechanisms. By connecting planetary thermal evolution models with the observed properties of hot Jupiters using hierarchical Bayesian models, a theoretical parameter called the heating efficiency has been introduced to describe the heating of the interiors of these planets. Previous studies have shown that the marginal distribution of this heating efficiency parameter has a single-peak distribution along the planetary equilibrium temperature (Teq). Since the foundation of these Bayesian inference models are the observed properties of hot Jupiters, there must be a corresponding feature in the observed data that leads to the inferred single-peak distribution of the heating efficiency. This study aims to find the underlying cause of the single-peak heating efficiency distribution without relying on specific theoretical models. By analyzing the relationship between different observed physical properties, we obtained a similar single-peak distribution of the radius expansion efficiency of hot Jupiters along Teq, which can be explained by the correlation with the stellar effective temperature. However, a detailed investigation suggests that this single-peak distribution is actually the result of straightforward physical processes. Specifically, the increase in heating efficiency can be attributed to the increase in incident stellar flux, while the decrease in heating efficiency can be attributed to the rise in gravitational binding energy associated with the increase in planetary mass.

Remote brightening (RB) is compact brightening at footpoints of magnetic loops, which are remotely-connecting to and confining an eruption in the solar atmosphere. Here, we report on observations of an RB resulting from an EUV jet with a speed of about 90\,km\,s$^{-1}$. The loops connecting the RB and the jet have an apparent length of about 59\,Mm. Intriguingly, the RB exhibits at least two episodes of brightenings, as characterised by two peaks in its lightcurve. The energies, which sustain the first and second peaks of the RB, are $6.3\times10^{26}$\,erg and $8.4\times10^{26}$\,erg, respectively, and take a significant proportion of the total energy. The first peak of the RB brightenings coincides with the jet's peak with a time delay of 12 seconds, while the second peak lags behind by 108 seconds. Besides the flows of the ejecta, we have identified two additional flows originating from the eruption site. One is relatively cool with a temperature of $log_{10}T/K=5.8-6.1$ and has a speed of about $275\pm15$\,km\,s$^{-1}$. The other is hot with a temperature of $log_{10}T/K=7.0-7.3$ and travels much faster with a speed of about 750$\pm$\,70\,km\,s$^{-1}$. We attribute the second peak of RB directly to this hot flow, which our numerical experiments suggest is the result of a slow shock wave. Considering the minimal time delay between the first peak of RB and the eruption, we infer this first episode is due to heating by nonthermal electrons. Our research demonstrates that the dynamics in an RB can offer vital insights into the nature of the corresponding eruption and help understand how the energy is distributed throughout the solar atmosphere.

We analyze rotation curves of five \textsc{Hi}-rich galaxies recently discovered with MeerKAT. These galaxies exhibit sharply rising rotation curves, while their baryonic components are not dynamically dominant, suggesting that their dark matter halos have high inner densities. When fitting the standard Navarro-Frenk-White (NFW) halo model, four galaxies require extremely high halo concentrations, exceeding the cosmological median by $5\sigma$. In contrast, self-interacting dark matter (SIDM) halos in the core-collapse phase naturally account for the high densities in these galaxies. For halos with masses around $10^{11}~{\rm M_\odot}$, those in cosmic filaments exhibit concentrations consistent with the cosmological average, while halos in cosmic nodes show relatively higher concentrations that align with the SIDM fits but remain insufficient for the NFW fits. Our analysis indicates that these \textsc{Hi}-rich galaxies may have formed in cosmic nodes of dark matter with significant self-interactions.

The XRISM (X-Ray Imaging and Spectroscopy Mission) satellite was successfully launched and put into a low-Earth orbit on September 6, 2023 (UT). The Resolve instrument onboard XRISM hosts an x-ray microcalorimeter detector, which was designed to achieve a high-resolution ($\leq$7 eV FWHM at 6 keV), high-throughput, and non-dispersive spectroscopy over a wide energy range. It also excels in a low background with a requirement of $< 2 \times 10^{-3}$ s$^{-1}$ keV$^{-1}$ (0.3--12.0 keV), which is equivalent to only one background event per spectral bin per 100 ks exposure. Event screening to discriminate x-ray events from background is a key to meeting the requirement. We present the result of the Resolve event screening using data sets recorded on the ground and in orbit based on the heritage of the preceding x-ray microcalorimeter missions, in particular, the Soft X-ray Spectrometer (SXS) onboard ASTRO-H. We optimize and evaluate 19 screening items of three types based on (1) the event pulse shape, (2) relative arrival times among multiple events, and (3) good time intervals. We show that the initial screening, which is applied for science data products in the performance verification phase, reduces the background rate to $1.8 \times 10^{-3}$ s$^{-1}$ keV$^{-1}$ meeting the requirement. We further evaluate the additional screening utilizing the correlation among some pulse shape properties of x-ray events and show that it further reduces the background rate particularly in the $<$2 keV band. Over 0.3--12 keV, the background rate becomes $1.0 \times 10^{-3}$ s$^{-1}$ keV$^{-1}$.

Modern cosmology is built on the assumption that the Universe is homogeneous and isotropic on large scales - but this is challenged by results of the Ellis-Baldwin test that show an unexplained anomaly in the distribution of distant galaxies and quasars.

The equation of state is fundamental in describing matter under the extreme conditions characteristic of neutron stars and is central to advancing our understanding of dense matter physics. A critical challenge, however, lies in accurately modelling first-order phase transitions while ensuring thermodynamic consistency and aligning with astrophysical observations. This study explores two frameworks for constructing EoSs with first-order phase transitions: the polytropic interpolation method and the randomized speed-of-sound interpolation approach. It is found that the mass-radius relation and pressure vs. energy density relation are blind towards the thermodynamic consistency check. The polytropic interpolation method can exhibit discontinuities in the chemical potential for first-order phase transition, raising concerns regarding potential causality violations and thermodynamic inconsistencies. In contrast, the speed of sound interpolation approach ensures continuity in the chemical potential, offering a more thermodynamically consistent and reliable framework. Moreover, the sound speed method effectively captures the softer segment of the mass-radius spectrum, a capability not achieved by the consistent piecewise-polytropic approach due to its monotonic stiffness constraints. The speed of sound definition involving number density and chemical potential reveals the thermodynamic inconsistency, making it a more consistent and robust definition. These findings underscore the importance of thermodynamic consistency in EoS construction and highlight the advantages of the randomized speed-of-sound method for modelling phase transitions in dense matter.

Polycyclic Aromatic Hydrocarbons are prevalent in the universe and interstellar medium but are primarily attributed to anthropogenic sources on Earth, such as fossil fuel combustion and firewood burning. Drawing upon the idea of PAHs as suitable candidates for technosignatures, we investigate the detectability of those PAHs that have available absorption cross-sections in the atmospheres of Earth-like exoplanets (orbiting G-type stars at a distance of 10 parsecs) with an 8m mirror of Habitable Worlds Observatory (HWO). Specifically, we focus on Naphthalene, Anthracene, Phenanthrene, and Pyrene. Our simulations indicate that under current Earth-like conditions, detecting PAH signatures between 0.2-0.515 $\mathrm{\mu m}$ is infeasible. To account for the historical decline in PAH production post-industrial revolution, we explore varying PAH concentrations to assess instrumental capabilities to detect civilizations resembling modern Earth. We also evaluate telescope architectures (6m, 8m, and 10m mirror diameters) to put our results into the context of the future HWO mission. With these four molecules, PAH detection remains infeasible, even at concentrations ten times higher than current levels. While larger mirrors provide some advantages, they fail to resolve the spectral signatures of these molecules with significant signal-to-noise ratios. The UV absorption features of PAHs, caused by $\mathrm{\pi}$-orbital $\rightarrow$ $\mathrm{\pi^*}$-orbital electronic transitions, serve as valuable markers due to their distinct and detectable nature, preserved by the aromatic stability of PAHs. Additional lab measurements are necessary to gather absorption cross-section data beyond UV for more abundant PAHs. This may help further in improving the detectability of these molecules.

Stellar lightcurves from edge-on double white dwarf systems(DWDs) have periodic lensing/eclipsing signals at times of alignment between two components as seen by the observer. Here, we study the characterization and detection of these signals. In common DWDs, the Einstein radii have similar orders of magnitude with WDs' radii, and the projected source and lens radii normalized to the Einstein radius ($\rho_{\star}$, and $\rho_{\rm l}$) are $\sim 1$. Both of them are reduced with the orbital period and the lens mass. If $\rho_{\rm l}\simeq 1$ the lensing-induced minor image is always blocked by the lens which results lower magnification factors. If $\rho_{\rm l}\lesssim 1$ and in transit events the finite-lens effects decrease the lightcurves' width. When $\rho_{\rm l}\gtrsim1$ (happens for close DWDs including one low-mass and one massive WD) deep or complete eclipses dominate to lensing effects. The self-lensing signals maximize for massive DWDs in wide orbits. We study the detect-ability of lensing/eclipsing signals in edge-on DWDs in observations by The NASA's Transiting Exoplanet Survey Satellite(TESS), The Vera Rubin Observatory(LSST) and The Nancy Grace Roman Space Telescope. We simulate stellar lightcurves due to edge-on DWDs and generate synthetic data points based on their observing strategies. Detection efficiency maximizes for extremely low-mass WDs in close orbits, and the numbers of DWDs within 100 pc and an observing cone with detectable lensing/eclipsing signals in one $27.4$-day TESS and $62$-day Roman observing window are $\sim1$ and $<1$, respectively. Detecting these signals by LSST is barely possible because of its long cadence.

When comparing modern fundamental reference frames in the radio (International Celestial Reference Frame) and optical (Gaia), a couple of bright radio reference sources appear to have very large radio-optical offsets, from tens up to hundreds of milliarcseconds (mas). The amount of these positional misalignments exceeds the uncertainty of each individual technique by at least an order of magnitude. In most cases, complex and extended radio structure and its time variability, and thus the difficulty in pinpointing the true location of the central engine, is responsible for the large apparent offsets. Sometimes distant parts of the radio structure are not properly detected due to a lack of shorter interferometer baselines. For our 5-GHz very long baseline interferometry (VLBI) experiment using antennas of the European VLBI Network and the enhanced Multi Element Radio Linked Interferometer Network, we selected 10 bright radio-loud active galactic nuclei with extremely large radio-optical offsets. Sensitive imaging involving a wide range of projected baseline lengths, as well as phase-referencing to nearby sources shed light on the possible causes of positional inconsistencies. Here we show results for 3 selected sources from this project.

Accurate and reliable photometric redshifts determination is one of the key aspects for wide-field photometric surveys. Determination of photometric redshift for galaxies, has been traditionally solved by use of machine-learning and artificial intelligence techniques trained on a calibration sample of galaxies, where both photometry and spectrometry are determined. On this paper, we present a new algorithmic approach for determining photometric redshifts of galaxies using Conditional Generative Adversarial Networks (CGANs). Proposed CGAN implementation, approaches photometric redshift determination as a probabilistic regression, where instead of determining a single value for the estimated redshift of the galaxy, a full probability density is computed. The methodology proposed, is tested with data from Dark Energy Survey (DES) Y1 data and compared with other existing algorithm such as a Random Forest regressor.

One of the main unknowns in galaxy evolution is how gas flows into and out of galaxies in the circumgalactic medium (CGM). Studies observing the CGM in absorption using multiple or extended background objects suggest a high degree of variation on relatively small ($\lesssim 1$ kpc) spatial scales. Similarly, high-resolution simulations generally exhibit small-scale substructure in the gas around galaxies. We examine the small-scale structure of the $z = 1$ CGM using simulations from the FOGGIE (Figuring Out Gas & Galaxies in Enzo) project. We select gaseous substructures ("clumps") by their local overdensity and investigate their physical properties, including temperature, metallicity, and kinematics with respect to the galaxy and the nearby surroundings. FOGGIE resolves clumps down to sphericalized radii $R \sim 0.25$ kpc at $z = 1$. The distribution of clumps peaks at $\sim 10^5$ $\rm M_{\odot}$ and $10^{4}$ K, consistent with relatively condensed, cool gas with a slight preference for inflow-like velocities. Many clumps show internal temperature and density variations, and thus internally varying ionization levels for key diagnostic ions such as HI, MgII, and OVI. The average metallicity in clumps is about a factor 1.5--2$\times$ lower in metallicity than nearby gas, suggesting that the metals are not well-mixed between structured and diffuse CGM, which may have implications for observational metallicity estimations of dense CGM clouds. We estimate the survivability of CGM clumps and find that structures larger than 0.5 kpc are generally long-lived. Finally, we qualitatively compare the simulated cloud properties to Milky Way high-velocity clouds.

During thermal inflation, the temperature determines the number of e-folds of expansion of the universe and so thermal fluctuations are magnified into curvature perturbations. We use classical thermodynamics to calculate the subhorizon thermal fluctuations and trace their evolution into superhorizon temperature perturbations. We convert the temperature perturbations into curvature perturbations using the $\delta N$-formalism, or equivalently the junction condition of curvature perturbations at the end of thermal inflation, denoted by subscript c, and show that the late-time power spectrum is $P_\mathcal{R} = \frac{15}{4\pi^4} \frac{H^3_\mathrm{c}}{g_* T^3_\mathrm{c}} \frac{k^3}{k^3_\mathrm{c}}$.

In mid-2024, asteroid 2019 UO$_{14}$ was identified as the first-ever Saturn Trojan through ground-based archival observations and numerical simulations. Trojans, including those associated with Jupiter and other planets, raise important questions about the formation processes of our solar system. Exploring this Trojan object with spacecraft may provide direct answers and definitive evidence regarding these questions. This paper thoroughly investigates potential mission scenarios to the first Saturn Trojan, 2019 UO$_{14}$, to determine the necessary launch window and spacecraft specifications. First, by assuming a ballistic flight using chemical engines, optimal sequences of events, including (powered) gravity-assist maneuvers and deep-space maneuvers, are identified through a meta-heuristic global trajectory optimization algorithm. The analysis indicates that flyby exploration is feasible with a launch window around 2034 and a $\Delta V$ ranging from 92 m/s to 1041 m/s within an 11-year mission duration, while a rendezvous can be achieved with a departure around 2035 and a $\Delta V$ of 2-3 km/s. Specifically, the itinerary via Saturn requires a $\Delta V$ of 2 km/s and a flight time of 24.6 years, while the route via Jupiter results in a $\Delta V$ of 3 km/s and a flight time of 13.4 years. Given that the orbital motion of outer solar system objects is relatively slow, low-thrust propulsion, which gradually accelerates the spacecraft, proves to be effective. Consequently, low-thrust trajectories to 2019 UO$_{14}$ were examined. The results demonstrate that a rendezvous can be accomplished with nearly the same departure epoch, time of flight, and $\Delta V$ as in the ballistic flight, suggesting that low-thrust propulsion is highly compatible with the rendezvous scenario, as it significantly reduces the propellant mass fraction.

In this study, we perform a comprehensive analysis of the Hubble constant (\(H_0\)) and matter clustering (\(S_8\)) tensions within the framework of non-interacting and interacting Barrow Holographic Dark Energy (BHDE) models. Utilizing a combination of observational datasets, including the Cosmic Microwave Background (CMB), Baryon Acoustic Oscillations (BAO), cosmic chronometers (CC), Pantheon, and lensing data, we assess the degree of tension relative to the Planck 2018 results and recent measurements such as the Riess et al. 2022 (R22) value for \(H_0 = 73.04 \pm 1.04 \ \text{km s}^{-1} \text{Mpc}^{-1}\) in 68\% C.L and KiDS-1000 and DES-Y3 for \(S_8\). Our findings show that both BHDE models mitigate the \(H_0\) and \(S_8\) tensions compared to the standard \(\Lambda\) Cold Dark Matter (\(\Lambda\)CDM) model. The non-interacting BHDE model achieves a moderate reduction in the \(H_0\) tension, while the interacting BHDE model offers a better fit for both parameters, suggesting it is more effective in addressing the tensions. Additionally, the quantum-gravitational deformation parameter \(\Delta\), constrained using the CMB+All dataset, indicates significant quantum effects in both models. The interacting scenario provides tighter constraints on \(\Delta\) and total neutrino mass \(\sum m_{\nu}\), offering a more precise representation of these effects. This study highlights the potential of BHDE models as viable alternatives to the \(\Lambda\)CDM framework for resolving cosmological tensions.

White dwarf stars have attracted considerable attention in the past 15 years as hosts for potentially habitable planets, but their low luminosity and continuous cooling are major challenges for habitability. Recently, astronomers have found that about 6% of massive white dwarfs seem to have "paused" their cooling for up to ~10 Gyr. The leading explanation for this cooling delay is the distillation of neutron-rich isotopes such as $^{22}$Ne in the white dwarf's interior, which releases a considerable amount of gravitational energy as the star's internal structure rearranges. Here, we consider the impact of $^{22}$Ne distillation on the evolution of white dwarf habitable zones. We find that $^{22}$Ne distillation in the white dwarf host dramatically increases the time that a planet can continuously reside within the habitable zone (giving more time for life to arise) and that long-lasting habitable zones are located farther from the star (decreasing the impact of tidal forces). These properties may make white dwarfs undergoing $^{22}$Ne distillation more promising locations for habitability than white dwarfs undergoing standard cooling.

We present a comprehensive analysis of the optical and infrared (IR) properties of high-mass X-ray binary (HMXB) IC 10 X-2, classified as a super-giant HMXB and super-fast X-ray transient (SFXT) by previous work. Our analysis of regular (daily and weekly) observations by both the Zwicky Transient Factory and Las Cumbres Observatory over a ~5 year period indicates both periodic flares and variations in the apparent magnitude and color with a $\sim26.5$~d period -- likely the orbital period of this binary system. The periodic flaring suggests the stellar companion is a Be star, with flares resulting from increased accretion onto the neutron star when it enters the stellar decretion disk. The periodic variations in the optical/IR brightness and color likely result from orbital variations in the Hydrogen column density along the line of sight or a transient accretion disk around the neutron star. Lastly, the numerous, short duration, episodes where IC 10 X-2 is significantly ``redder'' or ``bluer'' than normal likely result from from clumps within this system -- which can accrete onto the neutron star (causing IC 10 X-2 to appear bluer), or pass through the line of sight (causing IC 10 X-2 to appear redder). These results substantially increase our understanding of the evolution of this source, a significant source of ionizing photons in its host galaxy IC 10, a low mass, metal-poor starburst galaxy similar in many respect to those thought to be common in the early Universe.

Unlike neutrinos and photons arriving from extra-galactic sources, ultra-high energy cosmic rays (UHECRs) do not trace back to their origins due to propagation effects such as magnetic deflections and energy losses. For ankle energies, UHECRs can propagate for hundreds of megaparsecs with negligible energy losses but the directional information is lost after a few megaparsecs. On the other hand, at the highest energies the directions are kept for larger distances due to the increased rigidity but the interaction rates with the cosmic microwave background strongly suppress the cosmic rays within a few to tens of megaparsecs. Therefore, UHECRs with energies $E > 10^{20}$ eV (extreme-energy cosmic rays (ExECRs)) such as the Amaterasu event recently reported by Telescope Array, are of particular interest to identify the sources within our galactic neighborhood. However, photonuclear interactions are stochastic in nature and produce changes in the nuclear species emitted, which makes it difficult the task of estimating the likelihood distribution of its origin. This work discusses a novel procedure to estimate the likelihood of the origin for extreme-energy cosmic rays based on probability distributions for UHECR stochastic interactions. The method is applied to the Amaterasu event and compared to recently published works which employ Monte Carlo codes (e.g. CRPropa) in their analysis. The advantages of the method presented here are demonstrated by the increased resolution and the ease of computation unlike other approaches employed so far. The results presented indicate that the localization of the origin of extreme energy cosmic rays could be possible in some cases without knowledge of the original composition.

The detection of gravitational waves has brought to light a population of binary black holes that merge within a Hubble time. Multiple formation channels can contribute to this population, making it difficult to definitively associate particular population features with underlying stellar physics. Black hole spins are considered an important discriminator between various channels, but they are less well-measured than masses, making conclusive astrophysical statements using spins difficult thus far. In this paper, we consider the distribution of the effective inspiral spin $\chi_{\rm eff}$ -- a quantity much better measured than individual component spins. We show that non-Gaussian features like skewness, asymmetry about zero, and multimodality can naturally arise in the $\chi_{\rm eff}$ distribution when multiple channels contribute to the population. Searching for such features, we find signs of skewness and asymmetry already in the current catalogs, but no statistically significant signs of bimodality. These features provide robust evidence for the presence of a subpopulation with spins preferentially aligned to the binary's orbital angular momentum; and we conservatively estimate the fraction of this subpopulation to be at least $12 \% - 17\%$ (at $90\%$ credibility). Our models do not find an excess of non-spinning systems and instead find that at least $\sim 20 \%$ of the binaries have some degree of negative $\chi_{\rm eff}$. The data also suggest that, if preferentially aligned mergers form a significant fraction of the population, they must have small spins.

Quasar outflows often consist of two clouds with velocity separations matching the doublet spacings of common UV resonance transitions, a phenomenon known as line-locking, which is commonly observed in quasar spectra. Multiple clouds can be locked together through multi-ion doublets, forming 'line-locking web'. In the second paper of the TOLL project, we present discovery of one of the largest 'line-locking web' known to date from the VLT/UVES spectra of QSO J151352+085555. We identify 12 associated narrow absorption line systems through the C IV, N V, Si IV, O VI, and multiple Lyman lines (Ly${\alpha}$ to Ly${\epsilon}$), and find 10 out of the 12 absorbers are line-locked together by comparing velocity separations between different absorption systems. By conducting photoionization modeling with CLOUDY, we measure the total hydrogen column densities, metallicities, and ionization parameters of these absorbers, which suggests the absorbers likely have sub-solar metallicities. A preliminary statistical analysis demonstrates the shadowed clouds tend to have similar ionization states comparing to the shadowing ones. Identification of one of the largest line-locking webs implies that radiative acceleration plays an important role in sorting out cloud velocities in quasar outflows, and highlights the need for more sophisticated theoretical models to explain its formation and evolution.

We reexamine the weak interaction nuclei having largest contribution to the lepton to baryon fraction Ye by coupling the stellar weak rates and mass abundances for post silicon burning conditions during the presupernova evolution of massive stars. The stellar weak rates were recently calculated by Nabi et al. 2021 employing the fully microscopic pnQRPA model without invoking the Brink Axel hypothesis. We compute the mass abundances for a total of 728 nuclei, with A equal 1to 100, using Sahas equation and assuming nuclear statistical equilibrium with the incorporation of Coulomb correction factor to the chemical potential. We compile a list of top 50 electron capture ec and \b{eta} decay bd nuclei on the basis of largest contribution to Ye forpost silicon burning conditions where 11 percent ec and 6percent bd nuclei debuted dueto Coulomb corrections. The calculated mass abundances and corresponding Ye values are enhanced up to 3 orders of magnitude for heavier nuclei once Coulomb corrections were incorporated. This enhancement led to anincrement in total Y bde and Yece values, at Ye equal to 0.425 (\r{ho} equal 2.20 multiply 109 g/cm3 of 80percent and 91percent respectively. After incorporating the Coulomb corrections we propose a revised interval of Ye equal 0.423 0.455 where bd rates surpass thecompeting ec rates and is 3.2 percent bigger than the one suggested by Nabi et al. (2021).

In this study, we analyze the observational images of a Konoplya-Zhidenko rotating non-Kerr black hole, wherein a thin accretion disk, serving as the sole background light source, is situated on the equatorial plane of the black hole. The inner boundary of the thin accretion disk extends to the event horizon, and the accretion material in the disk exhibits two different motion behaviors, that is, it moves along the critical plunging orbit inside the innermost stable circular orbit (ISCO) and follows the Keplerian orbit outside the ISCO. The shadow image is captured on the imaging plane of a zero angular momentum observer utilizing advanced fisheye camera ray-tracing techniques. The results demonstrate that an image consistently reveals a dark region encircled by a narrow photon ring, which is called the inner shadow. At low observation inclination angles, the observation intensity is highly concentrated, with the lensed image of accretion disk being superimposed on the direct image. As observation inclination angle increases, the direct and lensed images gradually separate, becoming distinctly distinguishable and forming a hat-like structure. Furthermore, variations in the parameter space and observation angle will influence pertinent image characteristics, including image symmetry, the range or deformation degree of the inner shadow. We further examined the distinctive characteristics of images observed in both prograde and retrograde accretion disk scenarios. Subsequently, we also examined the redshift distribution on the disk. The findings indicate that while variations in relevant parameters do influence the redshift distribution, the primary factor is the change in observational inclination. The observer can detect both redshift and blueshift phenomena on the screen when viewed at a higher observation angle.

Massive stars can end their lives with a successful supernova explosion (leaving behind a neutron star or, more rarely, a black hole), or a failed explosion that leaves behind a black hole. The density structure of the pre-collapse progenitor star already encodes much of the information regarding the outcome and properties of the explosion. However, the complexity of the collapse and subsequent shock expansion phases prevents drawing a straightforward connection between the pre-collapse and post-explosion properties. In order to derive such a connection several explodability studies have been performed in recent years. However, different studies can predict different explosion outcomes. In this article, we show how compactness, which is related to the average density of the star's core, has an important role in determining the efficiency of neutrino heating, and therefore the outcome of the explosion. Commonly, high-compactness progenitors are assumed to yield failed explosions, due to their large mass accretion rates, preventing the shock from expanding. We show by analyzing $\sim$ 150 2D FLASH and Fornax simulations and 20 3D Fornax simulations that this is not the case. Instead, due to the rapid increase of neutrino heating with compactness, high-compactness progenitors lead to successful shock revival. We also show that 1D+ simulations that include $\nu$-driven convection using a mixing-length theory approach correctly reproduce this trend. Finally, we compare 1D+ models, which we show can reproduce some aspects of multi-D simulations with reasonable accuracy, with other widely used 1D models in the literature.

Estimating physical quantities such as the star formation rate, stellar mass and active galactic nucleus (AGN) fraction of galaxies is a key step in understanding galaxy formation and evolution. In order to estimate the uncertainties in the predicted values for these quantities, in this paper we explore the impact of adopting four different AGN torus models in fitting the multi-wavelength spectral energy distributions (SED) of galaxies. We also explore the impact of adopting two different geometries for the host, a spheroidal geometry, more appropriate for late-stage mergers, and a disc geometry, more appropriate for galaxies forming stars with secular processes. We use optical to submillimeter photometry from the Herschel Extragalactic Legacy Project (HELP) and utilize a Markov chain Monte Carlo SED-fitting code. We use exclusively radiative transfer models for the AGN torus as well as for the starburst and host galaxy. We concentrate on a sample of 200 galaxies at z~2, selected in the ELAIS-N1 field. All galaxies have a detection at 250um which ensures the presence of a starburst. We find that the stellar mass and star formation rate of the galaxies can be robustly estimated by the SED fitting but the AGN fraction depends very much on the adopted torus model. We also find that the vast majority of the galaxies in our sample are better fitted by a spheroidal geometry and lie above the main sequence. Our method predicts systematically higher SFR and lower stellar mass than the popular energy balance method CIGALE.

Using the full four-year SPTpol 500 deg$^2$ dataset in both the 95 GHz and 150 GHz frequency bands, we present measurements of the temperature and $E$-mode polarization of the cosmic microwave background (CMB), as well as the $E$-mode polarization auto-power spectrum ($EE$) and temperature-$E$-mode cross-power spectrum ($TE$) in the angular multipole range $50<\ell<8000$. We find the SPTpol dataset to be self-consistent, passing several internal consistency tests based on maps, frequency bands, bandpowers, and cosmological parameters. The full SPTpol dataset is well-fit by the $\Lambda CDM$ model, for which we find $H_0=70.48\pm2.16$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_m=0.271\pm0.026$, when using only the SPTpol data and a Planck-based prior on the optical depth to reionization. The $\Lambda CDM$ parameter constraints are consistent across the 95 GHz-only, 150 GHz-only, $TE$-only, and $EE$-only data splits. Between the $\ell<1000$ and $\ell>1000$ data splits, the $\Lambda CDM$ parameter constraints are borderline consistent at the $\sim2\sigma$ level. This consistency improves when including a parameter $A_L$, the degree of lensing of the CMB inferred from the smearing of acoustic peaks. When marginalized over $A_L$, the $\Lambda CDM$ parameter constraints from SPTpol are consistent with those from Planck. The power spectra presented here are the most sensitive measurements of the lensed CMB damping tail to date for roughly $\ell > 1700$ in $TE$ and $\ell > 2000$ in $EE$.

A remarkable feature of dark matter consisting of ultralight bosonic particles is the emergence of superfluid Bose-Einstein condensate structures on galactic scales. We investigate the oscillations of the solitonic dark matter structure in the central galactic region by numerically solving the Bogoliubov-de Gennes problem, accounting for perturbations in the gravitational potential and local self-interactions. Our findings reveal that the central solitonic core, formed by the balance of gravitational attraction, quantum pressure, and repulsive interactions, exhibits significant oscillatory behaviour. These oscillations, characterized by distinct eigenmodes, provide insights into the dynamical properties of solitonic dark matter structures and their observational implications and contributions to galactic structure formation and evolution.

High-energy particles may be accelerated widely in stellar coronae; probably by the same processes we find in the Sun. Here, we have learned of two physical mechanisms that dominate the acceleration of solar energetic particles (SEPs). The highest energies and intensities are produced in "gradual" events at shock waves driven from the Sun by fast, wide coronal mass ejections (CMEs). Smaller, but more numerous, "impulsive" events with unusual particle composition are produced during magnetic reconnection in solar jets and flares. Jets provide open magnetic field lines where SEPs escape; closed magnetic loops contain this energy to produce bright, hot flares, perhaps even contributing to heating the low corona in profuse nanoflares. Streaming protons amplify Alfven waves upstream of the shocks. These waves scatter and trap SEPs and, in large events, modify the element abundances and flatten the low-energy spectra upstream. Shocks also reaccelerate residual ions from earlier impulsive events, when available, that characteristically dominate the energetic heavy-ion abundances. The large CME-driven shock waves develop an extremely wide longitude span, filling much of the inner heliosphere with energetic particles.

Weak lensing mass mapping algorithms, which reconstruct the convergence field from galaxy shear measurements, are crucial for extracting higher-order statistics to constrain cosmological parameters. However, only limited research has explored whether the choice of mass mapping algorithm affects the inference of cosmological parameters from weak lensing higher-order statistics. This study aims to evaluate the impact of different mass mapping algorithms on the inference of cosmological parameters measured with weak lensing peak counts. We employ Kaiser-Squires, inpainting Kaiser-Squires, and MCALens mass mapping algorithms to reconstruct the convergence field from simulated weak lensing data. Using these maps, we compute the peak counts and wavelet peak counts as data vectors and perform Bayesian analysis with MCMC sampling to estimate posterior distributions of cosmological parameters. Our results indicate that the choice of mass mapping algorithm significantly affects the constraints on cosmological parameters, with the MCALens method improving constraints by up to 157$\%$ compared to the standard Kaiser-Squires method. This improvement arises from MCALens' ability to better capture small-scale structures. In contrast, inpainting Kaiser-Squires yields constraints similar to Kaiser-Squires, indicating limited benefit from inpainting for cosmological parameter estimation with peaks. The accuracy of mass mapping algorithms is thus critical for cosmological inference from weak lensing data. Advanced algorithms like MCALens, which offer superior reconstruction of the convergence field, can substantially enhance the precision of cosmological parameter estimates. These findings underscore the importance of selecting appropriate mass mapping techniques in weak lensing studies to fully exploit the potential of higher-order statistics for cosmological research.

The upcoming Vera C. Rubin Legacy Survey of Space and Time (LSST) will discover tens of thousands of astrophysical transients per night, far outpacing available spectroscopic follow-up capabilities. Carefully prioritising candidates for follow-up observations will maximise the scientific return from small telescopes with a single-object spectrograph. We introduce AAS2RTO, an astrophysical transient candidate prioritisation tool written in Python. AAS2RTO is flexible in that any number of criteria that consider observed properties of transients can be implemented. The visibility of candidates from a given observing site is also considered. The prioritised list of candidates provided by AAS2RTO is continually updated when new transient data are made available. Therefore, it can be applied to observing campaigns with a wide variety of scientific motivations. AAS2RTO uses a greedy algorithm to prioritise candidates. Candidates are represented by a single numerical value, or `score'. Scores are computed by constructing simple numerical factors which individually consider the competing facets of a candidate which make it suitable for follow-up observation. AAS2RTO is currently configured to work primarily with photometric data from the Zwicky Transient Facility (ZTF), distributed by certified LSST community brokers. We provide an example of how AAS2RTO can be used by defining a set of criteria to prioritise observations of type Ia supernovae (SNe Ia) close to peak brightness, in preparation for observations with the spectrograph at the Danish-1.54m telescope. Using a sample of archival alerts from ZTF, we evaluate the criteria we have designed to estimate the number of SNe Ia that we will be able to observe with a 1.5m telescope. Finally, we evaluate the performance of our criteria when applied to mock LSST observations of SNe Ia.

As gravitational wave detections increase the number of observed compact binaries (consisting of neutron stars or blacks), we begin to probe the different conditions producing these binaries. Most studies of compact remnant formation focus either on stellar collapse from the evolution of field binary stars in gas-free environments or the formation of stars in clusters where dynamical interactions capture the compact objects, forming binaries. But a third scenario exists. In this paper, we study the fate of massive stars formed, accrete gas, and evolve in the dense disks surrounding supermassive black holes. We calculate the explosions produced and compact objects formed by the collapse of these massive stars. Nucleosynthetic yields may provide an ideal, directly observable, diagnostic of the formation and fate of these stars in active galactic nuclei. We present a first study of the explosive yields from these stars, comparing these yields with the observed nucleosynthetic signatures in the disks around supermassive stars with quasars. We show that, even though these stars tend to form black holes, their rapid rotation leads to disks that can eject a considerable amount of iron during the collapse of the star. The nucleosynthetic yields from these stars can produce constraints on the number of systems formed in this manner, but further work is needed to exploit variations from the initial models presented in this paper.

W Serpentis is an eclipsing binary system and the prototype of the Serpentid class of variable stars. These are interacting binaries experiencing intense mass transfer and mass loss. However, the identities and properties of both stars in W Ser remain a mystery. Here we present an observational analysis of high quality, visible-band spectroscopy made with the Apache Point Observatory 3.5 m telescope and ARCES spectrograph plus the first near-IR, long-baseline interferometric observations obtained with the CHARA Array. We present examples of the appearance and radial velocities of the main spectral components: prominent emission lines, strong shell absorption lines, and weak absorption lines. We show that some of the weak absorption features are associated with the cool mass donor, and we present the first radial velocity curve for the donor star. The donor's absorption lines are rotationally broadened, and we derive a ratio of donor to gainer mass of 0.36 +/- 0.09 based on the assumptions that the donor fills its Roche lobe and rotates synchronously with the orbit. We use a fit of the ASAS light curve to determine the orbital inclination and mass estimates of 2.0 and 5.7 solar masses for the donor and gainer, respectively. The partially resolved interferometric measurements of orbital motion are consistent with our derived orbital properties and the distance from Gaia EDR3. Spectroscopic evidence indicates that the gainer is enshrouded in an opaque disk that channels the mass transfer stream into an outflow through the L3 region and into a circumbinary disk.

The stochastic gravitational wave background (SGWB) can be observed in the nanohertz band using a pulsar timing array (PTA). Here a computationally efficient state-space framework is developed for analysing SGWB data, in which the stochastic gravitational wave strain at Earth is tracked with a non-linear Kalman filter and separated simultaneously from intrinsic, achromatic pulsar spin wandering. The filter is combined with a nested sampler to estimate the parameters of the model, and to calculate a Bayes factor for selecting between models with and without a SGWB. The procedure extends previous state-space formulations of PTA data analysis applied to individually resolvable binary black hole sources. The performance of the new algorithm is tested on synthetic data from the first International PTA Mock Data Challenge. It is shown that the algorithm distinguishes a SGWB from pure noise for $A_{\rm gw} \geq 3 \times 10^{-14}$, where $A_{\rm gw}$ denotes the standard normalization factor for a power spectral density with power-law exponent $-13/3$. Additional, systematic validation tests are also performed with synthetic data generated independently by adjusting the injected parameters to cover astrophysically plausible ranges. Full posterior distributions are recovered and tested for accuracy. The state-space procedure is memory-light and evaluates the likelihood for a standard-sized PTA dataset in $\lesssim 10^{-1}$ s without optimization on a standard central processing unit.

Understanding dark matter halo dynamics can be pivotal in unravelling the nature of dark matter particles. Analytical treatment of the multistream flows inside the turnaround region of a collapsed cold dark matter (CDM) halo using various self-similar approaches already exist. In this work, we aim to determine the extent of self-similarity in 2D halo dynamics and the factors leading to deviations from it by studying numerical simulations of monolithically growing CDM halos. We have adapted the Fillmore and Goldreich (FG) self-similar solutions assuming cylindrical symmetry to data from 2D Vlasov-Poisson (ColDICE package) simulations of CDM halos seeded by sine wave initial conditions. We measured trajectories in position and phase-space, mass and density profiles and compared these to predictions from the FG model. We find that after turn-around and subsequent shell crossing, particles undergo a period of relaxation, typically about 1-2 oscillations about the center before they start to trace the self-similar fits and continue to do so as long as their orbits are predominantly radial. Overplotting the trajectories from different snapshots in scale-free position-time and phase spaces shows strikingly good superposition, a defining feature of self-similarity. The radial density profiles measured from simulations: $\rho \propto r^{-\alpha}, \alpha = 0.9 - 1.0$ are consistent with FG's prediction $\alpha=1$ for 2D halos. Deviations from the model, on the other hand, are evidently linked to relaxation, inhibited motion due to periodic boundaries, transverse motion in the halo interior, and deficit of infalling mass in limited simulation volume. It could not be conclusively established if the halos tend to grow circular over time. Extension of this work to actual 3D CDM cosmologies necessitates further detailed study of self-similar solutions with ellipsoidal collapse and transverse motion.

Detection of the weak cosmological signal from high-redshift hydrogen demands careful data analysis and an understanding of the full instrument signal chain. Here we use the WODEN simulation pipeline to produce realistic data from the Murchison Widefield Array Epoch of Reionisation experiment, and test the effects of different instrumental systematics through the AusEoRPipe analysis pipeline. The simulations include a realistic full sky model, direction-independent calibration, and both random and systematic instrumental effects. Results are compared to matched real observations. We find that, (i) with a sky-based calibration and power spectrum approach we have need to subtract more than 90% of all unresolved point source flux (10mJy apparent) to recover 21-cm signal in the absence of instrumental effects; (ii) when including diffuse emission in simulations, some k-modes cannot be accessed, leading to a need for some diffuse emission removal; (iii) the single greatest cause of leakage is an incomplete sky model; (iv) other sources of errors, such as cable reflections, flagged channels and gain errors, impart comparable systematic power to one another, and less power than the incomplete skymodel.

The magnetar SGR J1935+2154 entered a new active episode on October 10, 2022, with X-ray bursts and enhanced persistent emission. At the tail of high burst rate interval, lasting several hours, radio bursts were detected, revealing the connection between the X-ray activities and radio emissions. We analyzed observations of SGR J1935+2154 for nearly three months, using data from Neutron Star Interior Composition Explorer (NICER). We report the timing and spectral results following the onset of this outburst. In general, the X-ray flux of the persistent emission decays exponentially. While a flare is evident on the light curve, a fast radio burst (FRB) was detected immediately following the peak of this flare. We found a phase jump of pulse profile, with a deviation of $0.16\pm0.03$ phase, which is related to the glitch. The spectra are well fit with the combination of a blackbody and a power law model. The decay of the outburst is dominated by the drop of the non-thermal component, which also leads to the increase of thermal proportion. The photon index of the power law is inversely correlated with both the unabsorbed flux and the burst rate. We find that unlike the large variety of the persistent emission around FRB 221014, the X-ray properties are very stable when FRBs 221021 and 221201 happened. These results manifest the connection between glitch, phase jump, X-ray burst, and radio burst, crucial for studying the mutation in twisted magnetic fields and constraining the trigger mechanism of radio bursts.

We investigate the structural and observable impacts of dark matter (DM) on neutron stars using a combined equation of state that integrates the relativistic mean field (RMF) model for baryonic matter with a variable density profile for DM, incorporating DM-baryon interactions mediated by the Higgs field. Employing three RMF parameter sets (NL3, BigApple, and IOPB-I) for baryonic matter, we analyze mass-radius relations, maximum mass, and tidal deformability, focusing on DM density scaling ($\alpha$) and steepness ($\beta$) parameters. Our findings reveal that increased DM concentration significantly enhances NS compactness, shifting mass-radius profiles and reducing tidal deformability. The DM influence strongly depends on the steepness of the DM density profile, where high $\beta$ values lead to strongly confined DM within the NS core, resulting in more compact and less deformable configurations. Observational constraints from PSR J0740+6620 and GW170817 impose consistent structural limits on DM fractions across different equations of state models, narrowing the allowable parameter space for DM and linking specific combinations of $\alpha M_{\chi}$ ($M_{\chi}$ being the mass of dark matter particle) and $\beta$ values to viable NS structures. This study highlights the interplay among DM concentration, nuclear stiffness, and observational data in shaping NS structure, offering insights into future constraints on DM in high-density astrophysical environments.

We define two regimes of the parameter space of symbiotic systems based on the dominant mass transfer mechanism. A wide range of white dwarf (WD) mass, donor mass, and donor radius combinations are explored to determine the separation, for each parameter combination, below which wind Roche-lobe overflow (WRLOF) will be the dominant mass transfer mechanism. The underlying concept is the premise that the wind accelerates. If it reaches the Roche-lobe before attaining sufficient velocity to escape, it will be trapped, and gravitationally focused through the inner Lagrangian point towards the accreting WD. However, if the wind succeeds in attaining the required velocity to escape from the donor's Roche-lobe, it will disperse isotropically, and the dominant mass transfer mechanism will be the Bondi-Hoyle-Lyttleton (BHL) prescription in which only a fraction of the wind will be accreted onto the WD. We present, these two regimes of the four dimensional parameter space, covering 375 different parameter combinations.

We investigate the relativistic, viscous, advective, neutrino-dominated accretion flows (NDAFs) around rotating stellar mass black holes, incorporating neutrino cooling. By adopting an effective potential to describe the spacetime geometry around the rotating black holes, we self-consistently solve the governing NDAF equations to obtain global transonic accretion solutions. Our findings indicate that, depending on the model parameters, namely energy ($\varepsilon$), angular momentum ($\lambda$), accretion rate ($\dot{m}$), viscosity ($\alpha$) and black hole spin ($a_{\rm k}$), NDAFs may harbor standing shocks where the Rankine-Hugoniot shock conditions (RHCs) are satisfied. Utilizing these shock-induced NDAF solutions, we compute the neutrino luminosity ($L_{\nu}$) and neutrino annihilation luminosity ($L_{\nu \bar{\nu}}$) across a wide range of model parameters. We further calculate maximum neutrino luminosity ($L_{\nu}^{\rm max}$) and neutrino annihilation luminosity ($L_{\nu \bar{\nu}}^{\rm max}$) resulting in $L_{\nu}^{\rm max} \sim 10^{51-53}$ erg s$^{-1}$ ($10^{48-51}$ erg s$^{-1}$) and $L_{\nu \bar{\nu}}^{\rm max} \sim 10^{48-52}$ erg s$^{-1}$ ($10^{42-49}$ erg s$^{-1}$) for $a_{\rm k}=0.99$ (0.0). These findings suggest that shocked NDAF solutions are potentially promising to explain the energy output of gamma-ray bursts (GRBs). We employ our NDAF model formalism to elucidate $L^{\rm obs}_{\nu \bar{\nu}}$ for five GRBs with known redshifts and estimate their accretion rate (${\dot m}$) based on the spin ($a_{\rm k}$) of the central source of GRBs under consideration.

We investigate the absorption signals of a strong diffuse interstellar band, DIB$\lambda4430$, in the circumgalactic medium (CGM) traced by MgII absorption lines. To this end, we make use of approximately 60,000 MgII absorption line spectra within $0.4<z<1.0$ compiled from the Sloan Digital Sky Surveys and obtain composite spectra with uncertainties for absorption line measurements being a few m$Å$. By using MgII absorption strength and dust reddening relation from the literature, we measure the DIB$\lambda4430$ absorption strength as a function of $\rm E(B-V)$ in the CGM, and compare the Milky Way DIB$\lambda4430$ - $\rm E(B-V)$ relation extrapolated down to the CGM $\rm E(B-V)$ region. Our results show no detectable signals of DIB$\lambda4430$ across the entire $\rm E(B-V)$ range in the CGM traced by MgII absorption lines. This lack of detection of DIB$\lambda4430$ in the CGM is inconsistent with the Milky Way signals by $\sim 5 \, \sigma$, indicating that the factors associated with different environments affect the abundance of the DIB$\lambda4430$ carrier.

The giant, star forming clumps in gas-rich, high redshift disks are commonly assumed to form due to gravitational instabilities, in which protoclumps have a Toomre-$Q$ parameter less than unity. However, some cosmological simulations show that clumps can form in regions where $Q\gg1$. In these simulations, there is an excess of compressive modes of turbulence that lead to gravitational collapse of regions that were not supposed to gravitationally collapse, according to linear theory. In contrast, sites of clump formation in isolated simulations do not show this excess, hinting that the origin may be external. We explore two external mechanisms that can induce compressive modes of disk turbulence in protoclumps, namely, compressive tides exerted by the cosmological environment and the direct driving by inflowing streams. We correlate the local strength of compressive tides and the amount of fresh stream material with protoclump regions in zoom-in cosmological simulations. The local strength of compressive tides is derived from the tidal tensor. The local strength of incoming streams is derived from the fractional presence of the stream compared to the average. We find that the tidal field in protoclumps tends to be over-compressive while random patches in the disk show diverging tides. In particular, in $25\%$ of the protoclumps, the tidal field is fully compressive, while no random patch resides in regions of fully compressive tides. In addition, protoclumps tend to reside in regions where the fraction of incoming stream mass is 2-10 times larger than the average at the same galactocentric radius. Both compressive tides and inflowing streams are correlated with the protoclumps and can thus serve as the drivers of excessive compressive turbulence that can initiate clump formation. This constitutes a new, non-linear mode of violent disk instabilities in high-$z$ galaxies.

In this manuscript, we investigate the constraints on dynamical vacuum models within the framework of $\Lambda(t)$CDM cosmology by assuming a parameterization of the vacuum energy density as $\rho_{\Lambda}(t)=\rho_{\Lambda 0} \left[1 + \alpha (1 - a)\right]$, where $\rho_{\Lambda 0}$ is the present vacuum density and $\alpha$ is a free parameter. We use 31 cosmic chronometer data points and 1048 Pantheon type Ia supernova samples to constrain the model parameters. Our statistical analysis employs Markov Chain Monte Carlo (MCMC) simulations. We have found that the universe is currently undergoing accelerated expansion, transitioning from a decelerating phase. The transition redshift $z_t=0.65^{+0.03}_{-0.19}$ obtained from the combined CC+SNe dataset is consistent with recent constraints. The total EoS indicates an accelerating phase, with density parameters for matter and vacuum energy exhibiting expected behaviors. The $Om(z)$ diagnostic shows distinct behaviors for different datasets, and the present value of the jerk parameter deviates slightly from the $\Lambda$CDM model but remains consistent within uncertainties. These findings support the dynamic nature of dark energy and provide valuable constraints on the evolution of the universe.

The James Webb Space Telescope (JWST) has recently conducted observations of massive galaxies at high redshifts, revealing a notable anomaly in their star formation efficiency (SFE). Motivated by the recent identification of three $\sim 10^{6}M_\odot$ dark star candidates, we investigate whether dark stars can be the origin of the SFE excess. It turns out that the excess can be reproduced by a group of dark stars with $M \gtrsim 10^{3}\, \rm M_{\odot}$, because of their domination in generating primary UV radiation in high-redshift galaxies. The genesis of these dark stars is attributed to the capture of Weakly Interacting Massive Particles (WIMPs) within a mass range of tens of GeV to a few TeV. However, if the top-heavy initial mass function of dark stars holds up to $\sim 10^{5}M_\odot$, the relic black holes stemming from their collapse would be too abundant to be consistent with the current observations of Massive Compact Halo Objects (MACHOs). We thus suggest that just a small fraction of SFE excess may be contributed by the very massive dark stars and the majority likely originated from other reasons such as the Population III stars in view of their rather similar UV radiation efficiencies.

Supernova 2018ibb of the PISN category related to the dynamical instability of oxygen core in a supermassive star induced by pair-creation shows at the nebular stage strong [\oiii] emission lines of an uncertain origin. I propose a simple model that demonstrates a possibility of [O III] lines emission from the supernova oxygen matter ionized and heated by the $^{56}$Co radioactive decay. The reason is pinpointed by which the [O III] line luminosity among supernovae of PISN category can vary in a broad range.

Numerical modeling of the interaction of giant planets and the planetesimal disk was carried out for the Nice model, in which the initial orbits of the planets are in resonant configurations. In addition to the standard Nice model, planetesimals in the planetary region were considered and the self-gravity of the planetesimal disk was taken into account. The dynamical evolution of planetary systems has been studied for time intervals on the order of the lifetime of the Solar System. We have found cases in which the planetary systems survive for billions of years, the final orbits of the planets are close to the present orbits, and distant trans-Neptunian objects exist.

We compare the internal stellar structures of central galaxies in the TNG50 and TNG100 simulations and field galaxies in the CALIFA survey. The luminosity fractions of the dynamically cold, warm, and hot components in both TNG50 and TNG100 galaxies exhibit general consistency with those observed in CALIFA galaxies. For example, they all exhibit a minimum luminosity fraction of the dynamically hot component in galaxies with intermediate stellar masses, and the morphology of each orbital component in the TNG50 and TNG100 galaxies closely resembles that found in the CALIFA galaxies. We therefore use the simulations to quantify the physical origins of the different components, focusing on the dynamically hot component in TNG50. We identify three primary regimes and thus physical processes: (1) in low mass galaxies that have not experienced major mergers, stars are born with a wide range of circularity distributions and have remained relatively unchanged until the present day. Consequently, hot stars in such galaxies at redshift 0 are predominantly born hot. (2) In higher mass galaxies lacking major mergers, most stars are initially born cold but are subsequently heated through secular evolution. (3) In galaxies across the entire mass range, mergers, if they occurred, significantly increased the hot orbital fraction. As a result, the dynamically hot bulge within $R_e$ of present-day galaxies does not indicate their past merger histories; instead, the hot stars in the outer regions are mostly heated or accreted by mergers, thus indicating galaxy merger history. The massive galaxies are initially born with cold, rotationally supported structures, consistent with recent observations from the James Webb Space Telescope (JWST) regarding high-redshift galaxies.

Complex CME/ICME structures in the solar wind often arising in the heliosphere as a result of interaction between two or more CMEs are very important due to their enhanced geoefficiency, but their modeling is difficult due to lack of observational data outside the solar corona. The outstanding evidence of such complex structure occurred on May 10-11,2024, when the strongest geomagnetic storm was caused by a series of successive CMEs emerged from the same solar AR13664. The complex formed from the first 4 CMEs of the series triggered a drop of the Dst-index to -412nT. The aim of this study is to consider propagation of these ICMEs in the heliosphere using observations at three stages: at the starting point observed with the LASCO, in the middle heliosphere by the IPS method and in situ at the L1 point with the ACE. The IPS observations were carried out on May 9 and 10 with the BSA LPI, which enables to build in the scanning mode 2D map of scintillation index m2 associated with enhancements of the integrated over the LOS plasma density over a range of the heliocentric distances 0.4-0.8AU. Evolution of the ICMEs in the heliosphere was described using a cone model in the selfsimilar approximation and kinematics according to the DBM. The initial spatial distributions of density at the cone base were determined from the LASCO images of the CMEs at the heights of 20Rsun, and then were rescaled according to radial distances to the position corresponding to the time of the BSA observations. It was shown that the modeled distribution of the ICME complex LOS density N2 over heliocentric distance is consistent with distribution of m2. Some discrepancies may characterize variation of the density structure inside the complex due to CME interaction. The modeled mean volume density of the ICME plasma at the L1 position agreed with in situ ACE measurements, which validates the developed expansion model.

In this work we investigate the influence of neutron stars' crusts on the non-radial $g$-mode oscillations and examine their correlations with nuclear matter properties fixed by adopting 10 different relativistic density functionals. At subsaturation densities, neutron star matter takes non-uniform structures and form the crusts. We find that the Brunt-Väisälä (BV) frequency increases significantly at densities slightly above the neutron drip density (i.e., neutron stars' inner crusts), which leads to crust $g$-mode oscillations with their frequencies insensitive to the adopted density functional. At larger densities, BV frequency increases as well due to the core-crust transitions and emergence of muons, which lead to core $g$-mode oscillations. It is found that the obtained core $g$-mode frequencies generally increase with the slope of nuclear symmetry energy $L$, which eventually intersect with that of the crust $g$ modes adopting large enough $L$. This leads to the avoid-crossing phenomenon for the global $g$ modes that encompass contributions from both the crust and core. The correlation between the global $g_1$ mode and $L$ is identified for neutron stars with masses $M\gtrsim 1.4\ M_{\odot}$, which enables the measurements of $L$ based on gravitational wave observations. In our future study, the effects of the discontinuities in density or shear modulus should be considered, while the temperature, rotation, magnetic field, and superfluid neutron gas in neutron stars could also play important roles.

Understanding the dynamical evolution of asteroids through the secular Yarkovsky effect requires the determination of many physical properties, including the rotation period. We propose a method aimed at obtaining a robust determination of the rotation period of asteroids, while avoiding the pitfalls of aliases. We applied this approach to thousands of asteroid light curves measured by the NASA TESS mission. We developed a robust period-analysis algorithm based on a Fourier series. Our approach includes a comparison of the results from multiple orders and tests on the number of extremes to identify and reject potential aliases. We also provide the uncertainty interval for the result as well as additional periods that may be plausible. We report the rotation period for 4521 asteroids within a precision of 10%. A comparison with the literature (whenever available) reveals a very good agreement and validates the approach presented here. Our approach also highlights cases for which the determination of the period should be considered invalid. The dataset presented here confirms the apparent small number of asteroids with a rotation between 50 and 100 h and correlated with diameter. The amplitude of the light curves is found to increase toward smaller diameters, as asteroids become less and less spherical. Finally, there is a systematic difference between the broad C and S complex in the amplitude-period, revealing the statistically lower density of C-types compared to S-type asteroids. Conclusions. Our approach to the determination of asteroid rotation period is based on simple concepts, yet it is nonetheless robust. It can be applied to large corpora of time series photometry, such as those extracted from exoplanet transit surveys.

A faster than real time forecast system for solar wind and interplanetary magnetic field transients that is driven by hourly updated solar magnetograms is proposed to provide a continuous nowcast of the solar corona ($<0.1$AU) and 24-hours forecast of the solar wind at 1 AU by solving a full 3-D MHD model. This new model has been inspired by the concept of \textit{relativity of simultaneity} used in the theory of special relativity. It is based on time transformation between two coordinate systems: the solar rest frame and a boosted system in which the current observations of the solar magnetic field and tomorrow's measurement of the solar wind at 1 AU are simultaneous. In this paper we derive the modified governing equations for both hydrodynamics (HD) and magnetohydrodynamics (MHD) and present a new numerical algorithm that only modifies the conserved quantities but preserves the original HD/MHD numerical flux. The proposed method enables an efficient numerical implementation, and thus a significantly longer forecast time than the traditional method.

Changing-Look AGN (CLAGN) Mkn 590 recently underwent a sudden \lq re-ignition\rq, marked by substantial increases in optical/UV and X-ray continuum flux since last year. \textit{Swift}-XRT observations revealed the re-emergence of a soft X-ray excess (SXE) as the source transitioned from a low-flux state in July 2023 to a significantly higher flux state in October 2024. This evolution was in response to an order-of-magnitude increase in extreme-UV (EUV) continuum emission, detected by \textit{Swift}-UVOT. Follow-up optical spectra from the Las Cumbres Observatory confirmed the presence of dynamically broadened Balmer lines, He II emission, and the emergence of the Fe II complex. As the Eddington fraction increased by 10\% over the last 15 months, we found clear evidence of formation of a warm corona, strongly linked to the cold accretion disc underneath. A global amplification of ionizing radiation after approximately 11 years is consistent with propagating heating fronts in inflated accretion discs. Based on our multi-wavelength study on recent data, we propose that Mkn 590 is currently becoming a Seyfert-1, similar to 1990s.

We present an extensive optical photometric and spectroscopic investigation into the calcium-rich supernova (SN) - SN2023xwi. Observations from a variety of ground-based telescopes follow the SN from 8 days pre-peak brightness to 87 days post-peak, covering both early-time (photospheric) and late-time (nebular) phases of the supernova. Objects of this class are characterised by nebular spectra that are dominated by [Ca II] $\lambda \lambda$ 7291, 7324 emission. SN 2023xwi displays a unique peculiarity in that its forbidden [Ca II] feature is visible in its peak photospheric spectrum - far earlier than expected in current models. This is one of the strongest and earliest detections of this feature in Ca-rich SNe in photospheric-phase spectra. We investigate the velocity evolution of this spectral feature and show that it cannot be easily explained by conventional progenitor systems. From our observations, we propose a SN progenitor embedded in an environment polluted by a recurrent He-nova AM CVn system.

The adaptation of Large Language Models like ChatGPT for information retrieval from scientific data, software and publications is offering new opportunities to simplify access to and understanding of science for persons from all levels of expertise. They can become tools to both enhance the usability of the open science environment we are building as well as help to provide systematic insight to a long-built corpus of scientific publications. The uptake of Retrieval Augmented Generation-enhanced chat applications in the construction of the open science environment of the KM3NeT neutrino detectors serves as a focus point to explore and exemplify prospects for the wider application of Large Language Models for our science.

We present microlux, which is a Jax-based code that can compute the binary microlensing light curve and its derivatives both efficiently and accurately. The key feature of microlux is the implementation of a modified version of the adaptive sampling algorithm that was originally proposed by V. Bozza to account for the finite-source effect most efficiently. The efficiency and accuracy of microlux have been verified across the relevant parameter space for binary microlensing. As a differentiable code, microlux makes it possible to apply gradient-based algorithms to the search and posterior estimation of the microlensing modeling. As an example, we use microlux to model a real microlensing event and infer the model posterior via both Fisher information matrix and Hamiltonian Monte Carlo, neither of which would have been possible without the access to accurate model gradients.

Gamma-ray bursts detected at high energies provide valuable insights into the emission mechanisms behind these still puzzling enigmatic events. In this study, we focus on GRB 090510, which is an unusual short GRB exhibiting plateau emission observed by the Fermi-LAT. Using the general relativistic magnetohydrodynamic code (HARM), we aim to infer the key properties of this GRB, such as the jet opening angle, the energetics, the Lorentz Gamma factor, the jet structure and its variability, and the progenitor parameters of the compact binary system. We explored both the 2D and 3D models and estimated the variability timescales. Our findings show that the predicted jet opening angle is within $88\%$ of the observed upper limit from observations, and the energetics are in general agreement with observed values when accounting for the evolution of jet opening angle with redshift. This work establishes the foundation for ongoing exploration, which will further align the theoretical model simulations with observational data.

We present case studies comparing the global HI and H$\alpha$ emission line profiles of six galaxy pairs. The six pairs are selected to have different nuclear activities, with two hosting an active galactic nucleus, and in different merging stages (two of each from pre-merging, merging, and post-merger stages). We observe their global HI spectra with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), achieving a noise level of about 0.5 mJy. Five out of the six pair systems have secure detections of HI emissions (signal-to-noise ratio > 10). The HI fraction and star formation efficiency of the six pairs do not deviate from isolated galaxies. For the HI line profiles, common unique asymmetry is observed, indicating disturbances on the atomic gas from the galaxy interaction. The global H$\alpha$ spectra of the merger systems are constructed from the optical integral field spectroscopic observations, by integrating the flux in corresponding line-of-sight velocity bins. The H$\alpha$ spectra tend to show multiple components in the pre-merger phase, and single component line profiles in the post-merger systems, while all HI spectra show single component line profiles regardless of merger stages. The HI and H$\alpha$ spectra show offsets in the central velocities, which appear to decrease from >100 km/s in the pre-merger pair to <10 km/s in post-merger pairs. This trend is consistent with the scenario that, despite the significantly different distribution and kinematics of the atomic and ionized gases, the merging process may contribute to the mixing and eventually align various gas contents.

We present the spectral analysis of J-138717, a post-starburst galaxy observed at $z=1.8845$ with JWST, for which we estimate a stellar mass M$_* = 3.5\pm0.2\times10^{10}$M$_\odot$ and velocity dispersion $\sigma_* = 198\pm10$ km/s. From the fits of the NIRspec low-resolution prism and medium resolution grating spectra, we estimate an age of $\sim0.9$ Gyr, a metallicity of $\sim -0.3$ dex, and a dust attenuation A$_{\rm V} \sim 0.7$ mag. From the H$\alpha$ and [OII] emission lines we derive a star-formation rate (SFR)$\sim 0.1$ M$_\odot$ yr$^{-1}$, corresponding to a specific SFR$\sim 4 \times 10^{-12}$ yr$^{-1}$. By reconstructing its SFH, we find that this galaxy formed most of its stellar mass quickly ($0.4-0.8$ Gyr) and then rapidly quenched about 0.4 Gyr lookback time. The analysis of the emission lines ([OII], [NeIII], [OIII], H$\alpha$, and [NII]) indicates a low-level residual star formation or a weak AGN as the ionization source. Further, the lack of evidence for ongoing outflows in both the absorption and emission lines tracing the neutral and ionized gas argues against the presence of strong AGN feedback. Thanks to the high quality of the data, we carried out a comprehensive analysis of the NIR spectral indices. This is the first time NIR spectral indices have been investigated at such a high redshift. We find that the observed CO and CN indices are generally weak and in better agreement with models with a lower contribution from thermally pulsating (TP-)AGB stars, indicating that either TP-AGB stars do not contribute significantly to the spectrum of J-138717 or the prescriptions in the models for these evolved phases should be substantially improved. In general, we find that all models struggle to reproduce the NIR indices consistently, pointing to the importance of improving state-of-the-art stellar population models in the NIR, especially at young ages.

Context. The intense X-ray and UV emission of some active M stars has raised questions about the habitability of planets around M-type stars. Aims. We aim to determine the unbiased distribution of X-ray luminosities in complete, volume-limited samples of nearby M dwarfs, and compare them to those of K and G dwarfs. Methods. We constructed volume-complete samples of 205 M stars with a spectral type $\leq$ M6 within 10 pc of the Sun, 129 K stars within 16 pc, and 107 G stars within 20 pc. We used X-ray data from Chandra, XMM-Newton, eROSITA, and ROSAT to obtain the X-ray luminosities of the stars. Results. Our samples reach an X-ray detection completeness of 85%, 86%, and 80% for M, K, and G stars, respectively. The fractional X-ray luminosities relative to the bolometric luminosities, $\log(L_\mathrm{X}/L_\mathrm{bol})$, of the M stars show a bimodal distribution, with one peak at around -5, mostly contributed by early M stars (M0--M4), and another peak around -3.5, contributed mainly by M4--M6 stars. The comparison of the different spectral classes shows that 63% of all M stars in our sample (80% of the M stars with a spectral type $<$ M4) have $L_\mathrm{X}/L_\mathrm{bol}$ values that are within the central 80% quantile of the distribution function for G stars. In addition, 55% of all M stars in our sample (and 72% of the M stars with a spectral type $<$ M4) have $L_\mathrm{X}/L_\mathrm{bol}$ less than 10 times the solar value. Conclusions. The X-ray activity levels of the majority ($\ge 60\%$) of nearby M dwarfs no later than M6 are actually not higher than the typical (80% quantile) levels for G-type stars. The X-ray irradiation of habitable-zone planets around these stars should therefore not present a specific problem for their habitability.

We report a spectroscopic observation of comet C/2023 A3 using an 80 mm apochromatic (apo) refractor equipped with a custom-built spectrometer with a resolution of R~2,500 on the night of 4 October 2024. Sodium D lines were detected prominently, while no other emission lines, particularly carbon-bearing species, were observed, which suggests that comet C/2023 A3 may be carbon-depleted. The mobility and flexibility of our observational setup highlight the value of amateur telescopes in observing low-altitude targets like C/2023 A3 as a complement to professional facilities.

The mass-size relation is a fundamental galaxy scaling law closely tied to galaxy formation and evolution. Using added-value products of the Calar Alto Void Integral-field Treasury surveY (CAVITY) and SDSS DR16 images, we examine the effect of large-scale environments on the stellar mass-size relation. We analyse the Petrosian R50 and R90 radii of approximately 140000 galaxies in voids, filaments, and clusters, with a mass range of $10^{8.5} - 10^{11} M_{\odot}$. We explore the relation in terms of galaxy morphology and star formation history, parametrised by T50, T70, and T90. We find that early-type void galaxies are, on average, 10-20% smaller than their counterparts in denser environments, regardless of their mass assembly history. Moreover, the mass-size relation for massive early-type void galaxies has a shallower slope compared to those in denser regions. In contrast, early-type galaxies in filaments, and clusters show a more uniform mass-size relation. Late-type cluster galaxies with stellar masses $log(M_{\star} / M_{\odot}) = 9 - 10.5$ are smaller and more concentrated than their counterparts in lower-density environments, such as filaments, and voids. We conclude that large-scale environments influence the mass-size relation. Early-type galaxies appear to grow most of their mass during the initial formation phase. Subsequent size growth in voids is less significant, likely due to slower evolution, reduced minor merger activity, fewer accretion events, or a combination. The flatter slope for massive void galaxies indicates a lower rate of minor accretion, a trend also observed in late-type void galaxies with $\approx 10^{10.5} M_{\odot}$, where minor mergers contribute to size growth. Conversely, late-type quenched cluster galaxies are smaller due to environmental interactions, with early infallers being most affected.

The X-ray source eRASSU J065715.3+260428 was identified as a likely thermally emitting isolated neutron star in a search in the SRG/eROSITA All-Sky Survey. We investigated the nature and evolutionary state of the source through a dedicated multi-wavelength follow-up campaign with XMM-Newton, NICER, FAST, and ESO-VLT, complemented by the analysis of archival Fermi-LAT observations. The X-ray observations unveiled the rotation period, $P=261.085400(4)$ ms, and spin-down rate, $\dot{P}=6^{+11}_{-4}\times10^{-15}$ s s$^{-1}$, of the source. No optical counterparts are detected down to 27.3 mag ($5\sigma$, R band), implying a large X-ray-to-optical flux ratio above 5200. The X-ray spectrum of the source is best described by a composite phenomenological model consisting of two thermal components, either a double blackbody continuum with temperatures 90 eV and 220 eV or a hydrogen neutron star atmosphere of temperature $\log(T/\mathrm{K})\sim 5.8$ combined with a hot blackbody of 250 eV, in both cases modified by an absorption feature at low energies ($\sim0.3$ keV). The presence of faint non-thermal hard X-ray tails is ruled out above $(2.1\pm1.8)$% of the source unabsorbed flux. Radio searches at $1-1.5$ GHz with FAST yielded negative results, with a deep upper limit on the pulsed flux of 1.4 $\mu$Jy ($10\sigma$). Similarly, no significant spatial or pulsed signals were detected in sixteen years of Fermi-LAT observations. The source is most likely a middle-aged spin-powered pulsar and can also be identified as PSR J0657+2604. The absence of non-thermal X-ray, radio, or gamma-ray emission within current limits suggests either an unfavourable viewing geometry or unusual magnetospheric properties. Additional observations are needed to check for faint hard X-ray tails, investigate the presence of diffuse emission from a pulsar-wind nebula, and obtain a more accurately sampled timing solution.

Producing ultra-deep high-angular-resolution images with current and next-generation radio interferometers introduces significant computational challenges. In particular, the imaging is so demanding that processing large datasets, accumulated over hundreds of hours on the same pointing, is likely infeasible in the current data reduction schemes. In this paper, we revisit a solution to this problem that was considered in the past but is not being used in modern software: sidereal visibility averaging (SVA). This technique combines individual observations taken at different sidereal days into one much smaller dataset by averaging visibilities at similar baseline coordinates. We present our method and validated it using four separate 8-hour observations of the ELAIS-N1 deep field, taken with the International LOw Frequency ARray (LOFAR) Telescope (ILT) at 140~MHz. Additionally, we assessed the accuracy constraints imposed by Earth's orbital motion relative to the observed pointing when combining multiple datasets. We find, with four observations, data volume reductions of a factor of 1.8 and computational time improvements of a factor of 1.6 compared to standard imaging. These factors will increase when more observations are combined with SVA. For instance, with 3000~hours of LOFAR data aimed at achieving sensitivities of the order of {\mu}Jy/beam at sub-arcsecond resolutions, we estimate data volume reductions of up to a factor of 169 and a 14-fold decrease in computing time using our current algorithm. This advancement for imaging large deep interferometric datasets will benefit current generation instruments, such as LOFAR, and upcoming instruments such as the Square Kilometre Array (SKA), provided the calibrated visibility data of the individual observations are retained.

Context. The concomitant observation of gravitational wave and electromagnetic signals from a binary neutron star (BNS) merger in 2017 confirmed that these events can produce relativistic jets responsible for short Gamma-Ray Bursts (sGRBs). The complex interaction between the jet and the surrounding post-merger environment shapes the angular structure of the outflow, which is then imprinted in the prompt and afterglow sGRB emission. Aims. The outcome of relativistic (magneto)hydrodynamic simulations of jets piercing through post-merger environments is often used as input to compute afterglow signals to be compared with observations. However, for reliable comparisons, the jet propagation should be followed until nearly ballistic regimes, in which the jet acceleration is essentially over and the angular structure is no longer evolving. This condition is typically reached in 2D simulations, but not in 3D. Our goal is to extend a (specific) jet simulation in 3D up to a nearly ballistic phase, analysing the overall dynamical evolution from the jet breakout. Methods. Our work is based on a previous 3D magnetohydrodynamic jet simulation employing a realistic environment imported from a BNS merger simulation, extended here far beyond the evolution time originally covered. After approximately 3 seconds of the jet evolution on the original spherical grid, we remap the system into a uniform Cartesian grid and reach about 10 seconds without loss of resolution. Results. The specific jet considered here struggles to pierce the dense surroundings, resulting in a rather asymmetrical emerging outflow with relatively low Lorentz factor. The analysis of the energy conversion processes and corresponding acceleration shows that at the end of our simulation 98% of the energy is in kinetic form. Moreover, at that time the angular structure is frozen. We thus obtain suitable inputs for computing the afterglow emission. Our procedure is general and applicable to any jet simulation of the same kind.

The discovery of an increasing variety of exoplanets in very close orbits around their host stars raised many questions about how stars and planets interact, and to which extent host stars' properties may be influenced by the presence of close-by companions. Understanding how the evolution of stars is impacted by the interactions with their planets is fundamental to disentangle their intrinsic evolution from Star-Planet Interactions (SPI)-induced phenomena. GJ 504 is a promising candidate for a star that underwent strong SPI. Its unusually short rotational period (3.4 days), while being in contrast with what is expected by single-star models, could result from the inward migration of a close-by, massive companion, pushed starward by tides. Moreover, its brighter X-ray luminosity may hint at a rejuvenation of the dynamo process sustaining the stellar magnetic field, consequent to the SPI-induced spin-up. We aim to study the evolution of GJ 504 and establish whether by invoking the engulfment of a planetary companion we can better reproduce its rotational period and X-ray luminosity. We simulate the past evolution assuming two different scenarios: 'Star without close-by planet', 'Star with close-by planet'. In the second scenario, we investigate how inward migration and planetary engulfment driven by tides spin up the stellar surface and rejuvenate its dynamo. We compare our tracks with rotational period and X-ray data collected from the all-sky surveys of the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG). Despite the very uncertain stellar age, we found that the second evolutionary scenario is in better agreement with the short rotational period and the bright X-ray luminosity of GJ 504, thus strongly favouring the inward migration scenario over the one in which close-by planets have no tidal impact on the star.

Previous studies have shown that there is considerable variation in the dust-to-gas density ratio in the vicinity of low-mass planets undergoing growth. This can lead to a significant change in the planetary momentum exerted by the gas and solid material. However, due to the low dust-to-gas mass ratio of protoplanetary disks, the back-reaction of the solid material, is often neglected. We study the effect of the back-reaction of solid material on the torques felt by low-mass planets. We perform locally isothermal, 2D hydrodynamic simulations of planet-disk interactions. Low-mass planets in the range of 0.1-10MEarth accrete only solid material. Simulations are compared with and without taking into account the back-reaction of the solid material on the gas. The solid component is assumed to have a fixed Stokes number in the range 0.01-10. In general, the inclusion of back-reaction results in a greater number of models with positive torque values compared to models that neglect back-reaction. It is clear, therefore, that the simulation of planetary growth and migration via hydrodynamic modeling requires the inclusion of solid-gas back-reaction. As a result of the back-reaction and accretion, a Mars-sized planetary embryo will experience positive total torques from the disk containing coupled solid components St<=0.01. Earth-mass planets also experience positive total torques from the disk containing boulder-sized solid components 2<=St<=5. The accretion of weakly coupled solid material tends to increase the positive torques and decrease the negative torques. Our results suggest that the combined effect of back-reaction and accretion is beneficial to the formation of planetary systems by reducing the likelihood of a young planet being engulfed by the central star.

Accretion disks, swirling structures of matter spiraling into black holes, play a pivotal role in our understanding of binary star systems and their intricate evolutionary processes. While current models often simplify these complex phenomena by neglecting the influence of powerful magnetic fields, particularly within warped or distorted black hole geometries, this study delves into the crucial impact of such fields. Focusing on a thin accretion disk encircling a Schwarzschild black hole, we meticulously investigate how the presence of a quadrupole moment, an inherent distortion in the black hole's shape, affects its spectral characteristics. By analyzing key parameters like total pressure, magnetic pressure, temperature, height scale, surface density, and radiative flux (the energy emitted by the disk) we reveal significant alterations induced by incorporating both magnetic fields and a quadrupole moment. Notably, our findings demonstrate that negative quadrupoles exert a more pronounced influence on these disk properties, highlighting the intricate interplay between these factors. This comprehensive study provides invaluable insights into the dynamics of accretion disks surrounding distorted black holes with magnetic fields, paving the way for a more accurate and nuanced understanding of these fascinating astrophysical systems.

The time-variable emission from the accretion flow of Sgr A*, the supermassive black hole at the Galactic Center, has long been examined in the radio-to-mm, near-infrared (NIR), and X-ray regimes of the electromagnetic spectrum. However, until now, sensitivity and angular resolution have been insufficient in the crucial mid-infrared (MIR) regime. The MIRI instrument on JWST has changed that, and we report the first MIR detection of Sgr A*. The detection was during a flare that lasted about 40 minutes, a duration similar to NIR and X-ray flares, and the source's spectral index steepened as the flare ended. The steepening suggests synchrotron cooling is an important process for Sgr A*'s variability and implies magnetic field strengths $\sim$40--70 Gauss in the emission zone. Observations at $1.3~\mathrm{mm}$ with the Submillimeter Array revealed a counterpart flare lagging the MIR flare by $\approx$10 minutes. The observations can be self-consistently explained as synchrotron radiation from a single population of gradually cooling high-energy electrons accelerated through (a combination of) magnetic reconnection and/or magnetized turbulence.

The advent of new generation radio telescopes is opening new possibilities on the classification and study of extragalactic high-energy sources, specially the underrepresented ones like radio galaxies. Among these, Giant Radio Galaxies (GRG, larger than 0.7 Mpc) are among the most extreme manifestations of the accretion/ejection processes on supermassive black holes. Our recent studies have shown that GRG can be up to four times more abundant in hard X-ray selected (i.e. from INTEGRAL/IBIS and Swift/BAT at $>$20 keV) samples and, most interestingly, the majority of them present signs of restarted radio activity. This makes them the ideal test-bed to study the so far unknown duty cycle of jets in active galactic nuclei. Open questions in the field include: How and when jets are restarted? How jets evolve and what's their dynamic? What is the jet's duty cycle and what triggers them? Our group has recently collected a wealth of radio data on these high-energy selected GRGs, allowing us to study their jet formation and evolution from the pc to kpc scales, across different activity epochs. In particular, thanks to our EVN large programme, we were able to probe the new radio phase in the core of these giants. Furthermore, we are devoting an effort to the exploitation of new radio surveys data for the discovery of new classes of counterparts of Fermi/LAT catalogues. In particular, we are unveiling the hidden population of radio galaxies associated with gamma-ray sources.

We present MeerKAT HI observations of ESO 137-001, a quintessential jellyfish galaxy with long multi-phase tails formed due to the interaction with the intra-cluster medium of its host galaxy cluster, ACO 3627. Our observations reveal the presence of HI in both the disc and outer regions of the galaxy for the first time, with a total HI mass of ($3.5 \pm\ 0.4) \times 10^{8}$ M$_{\odot}$. ESO 137-001 is at an advanced stage of gas stripping; it is extremely HI deficient and seems to have lost 90% of its initial HI mass; about 2/3 of the surviving HI is found at a larger radius than expected for a normal HI disc and forms a $\sim40$ kpc tail coincident with the tail detected at other wavelengths. Only $\sim10$% of the surviving HI is still found within the stellar disc, consistent with the expectation of an outside-in truncation due to ram pressure. Similarly to other jellyfish galaxies, ESO137-001 has a high star formation rate for the low amount of HI detected. We measure an HI depletion time of 0.29 Gyr. However, when taking into account the total gas (HI + H$_2$) content, the depletion time is consistent with typical values measured in nearby spiral galaxies. This suggests that ESO 137-001 is at its current stage of ram pressure interaction characterised by an efficient HI stripping, rather than an enhanced conversion of HI to H$_2$, which was recently observed in some other jellyfish galaxies.

We report the modeling of the millimeter and far-infrared spectral energy distributions of 71 dusty star-forming galaxies (DSFGs) selected by the Atacama Cosmology Telescope (ACT) with a lower flux-density limit of 8 mJy at 220 GHz (1.4 mm). All sources were cross-identified with Herschel surveys at 500, 350, and 250 {\mu}m, and nineteen of our sources were observed at with the Submillimeter Array. A probabilistic cataloging algorithm, PCAT, favors multiple unresolved flux components in the Herschel data for the majority of ACT-selected DSFGs. We compare the derived physical properties of the DSFGs obtained from modeling the flux densities with those from similar studies of both lensed and unlensed DSFG populations. We find the median, 16th and 84th percentiles for the following model parameters: redshift zphot=3.3(+0.7)(-0.6), apparent size {\mu}d=5.2(+0.9)(-2.4) kpc, apparent dust mass log10({\mu}Md/Msun)=9.14(+0.12)(-0.04) and cutoff temperature Tc=35.6(+4.8)(-1.6) K, and the corresponding apparent far-infrared luminosity log10({\mu}LIR/Lsun)=13.6(+0.2)(-0.3), where {\mu} is lensing magnification. While many of the properties broadly agree with those of samples of primarily lensed DSFGs, we exercise caution in interpreting them. ACT's lower flux limit, the PCAT decomposition, and the higher-resolution SMA observations all suggest that some fraction of these DSFGs are likely to be unlensed and possibly multiples. The SMA data indicate that at least fourteen out of nineteen sources are such, either via "missing" flux in comparison to the ensemble model or detection of additional sources in the fields. Additional high-resolution follow-up and targeted redshift observations are needed to better understand this flux-limited sample of DSFGs.

Recent studies have examined the role of tides in the star formation process. They suggest, notably, that the tides determine the characteristic mass of the stellar initial mass function (IMF) by preventing the collapse of density fluctuations that would become gravitationally unstable in the absence of the tidal field generated by a neighboring central mass. However, most of these studies consider the tidal collapse condition as a 1D process or use a scalar virial condition and thus neglect the anisotropy of the tidal field and its compressive effects. In the present paper, we consider a turbulence-induced density perturbation formed in the envelope of a central core. This perturbation is subject to a tidal field generated by the central core. We study its evolution taking dynamical effects and the anisotropy of the tides into account. Based on the general tensorial virial equations, we determine a new collapse condition that takes these mechanisms into account. We identify two regimes: (i) a weak tidal regime in which the dynamics of the perturbation is only slightly modified by the action of the tides and (ii) a strong tidal regime in which the density threshold for collapse can potentially be increased due to the combined effects of the tides and the rotational support generated by the tidal synchronization of the perturbation with the orbital motion. In the case of a turbulence-induced density perturbation formed in the vicinity of a first Larson core, we show that the density threshold above which the perturbation collapses is increased only for low-mass perturbations (less than 2.7 solar mass) and only by at most a factor of 1.5. We conclude that tides likely do not play a major role in the process of star formation or in the determination of the characteristic mass of the IMF. We propose an alternative explanation for the observed value of the characteristic mass of the IMF.

The 3D spectrophotometry measurements of the galaxy NGC~3521, a structural Milky Way analogue (sMWA), were carried out within the Metal-THINGS project. We found that the oxygen abundance in the inner part of NGC~3521 is at a nearly constant level and the O/H gradient is negative at larger radii. The change in the N/H with radius is similar to that for O/H. The radial distributions of the O/H, the gas mass fraction, and the effective oxygen yield in NGC~3521 are compared to that of the Milky Way (MW), with the aim of examining the similarity in their chemical evolutions. The O/H of two HII regions closest to the centre of the MW (at a radii of 4-5 kpc) are close to the binned O/H in NGC~3521 at the same galactocentric distances. The O/H in the outer part of the MW are lower than those in the outer part of NGC~3521. The gas mass fraction in the outer part of the MW is higher than in NGC~3521. The obtained values of the effective oxygen yield, Yeff, in NGC~3521 are close to the empirical estimation of the oxygen yield, Yo. This suggests that mass exchange with the surroundings plays little to no role in the chemical evolution of NGC3521. The values of the Yeff in the MW were determined using two variants of the distribution of the gas mass surface density. The values of the Yeff in the MW obtained with the first distribution are also close to Yo. The Yeff in the MW obtained with the second distribution are below Yo at radii between 6 and 10.4 kpc. This suggests that the mass exchange with the surroundings can play a significant role in the chemical evolution of this part of the MW. To draw a solid conclusion about the role of mass exchange with the surroundings in the chemical evolution of the MW it is essential to determine which of these distributions provides a more adequate description of the gas distribution in the MW.

We investigate the transonic accretion flow in the spacetime of a supermassive black hole (BH) coupled to an anisotropic dark matter fluid, as proposed by Cardoso {\it et al}. We essentially compare the accretion properties of the Cardoso BH with those of an isolated Schwarzschild BH. The Cardoso BH is described by the halo mass ($M_{\rm H}$) and its characteristic length scale ($a_0$). Various classes of accretion solution topologies (e.g., O, A, and I-types), including the shock solutions, are obtained by solving the dynamical equations of the flow in a fully general relativistic framework. We find that the accretion solutions are substantially influenced by the halo parameters ($M_{\rm H}, a_0$) when the dark matter distribution is concentrated near the BH horizon. In this context, we also observe that various shock properties, such as the shock radius, flow density compression, and temperature compression across the shock fronts, are potentially affected by the dark halo. Interestingly, the existing shock parameter space, defined by the flow angular momentum and energy, is largely reduced for higher halo compactness compared to that of the Schwarzschild BH. Furthermore, different observational signatures of the accretion disc, like the spectral energy distribution (SED), slope of the SED, and bolometric luminosity, are found to exhibit strong deviations from the known results in the usual Schwarzschild BH model. These unique features offer a possible valuable tool for characterizing the presence or absence of a dark matter halo around a galactic BH.

One of the most important steps of Cosmic Microwave Background (CMB) data analysis is component separation to recover CMB map by combining the observations contaminated by foregrounds. Needlet Internal Linear Combination (NILC) is one of the successful methods that applies the minimum variance estimation technique to a set of needlet-filtered frequency maps to recover CMB. This work develops a deep convolutional neural network (CNN) model to recover CMB map from needlet-filtered frequency maps over the full sky. The model allows to perform component separation with a multi-resolution representation of spherical data localized on both pixel space and harmonic space with rotational invariant features of CMB. The network model is trained on realistic simulations at Planck frequencies. We demonstrate the network performance for simulations that exhibit different foreground complexities. The model achieves precise recovery of the CMB temperature map and the TT power spectrum exhibits excellent agreement with true value up to $\ell\sim$1100. The residual leakage to the recovered CMB is reduced significantly compared to the CMB map recovered using NILC pipeline. Once validated on the simulations, the network is applied to Planck PR3 data to recover CMB. The recovered CMB map shows excellent agreement with CMB maps of Planck legacy products using NILC and SMICA pipelines. This work demonstrates a powerful component separation method to clean spherical signal data from multi-resolution wavelet-filtered maps.

The effective anisotropic stress $\eta$ is a key variable in the characterization of many classes of modified gravity theories, as it allows the testing for a long-range force additional to gravity. In this paper we forecast the precision with which future large surveys can determine $\eta$ in a way that only relies on directly observable quantities obtained from the spectroscopic measurements of the clustering of galaxies and the photometric based observation of the projected lensing and galaxy clustering correlations and their cross signal. Our method does not require further assumptions about the initial power spectrum, the modified gravity model, the expansion rate, or the bias. We consider various cases: $\eta$ free to vary in space and time, or with only redshift dependence, or constant. We take as a reference specifications that approximate a Euclid-like photometric or a combined one with a DESI-like spectroscopic survey. Among our results, we find that a future large-scale lensing and clustering survey can constrain $\eta$ to at least 30\% if $z$, $k$ independent, and to less than 10\% on average for the $z$ dependence only, to finally reach 5\% values in the constant case.

This study investigates the conditions under which gravitational waves (GWs) are emitted during the merger of hot white dwarfs (WDs) in a binary system. Traditionally, these systems consist of two low-mass stars or a more massive WD paired with a less massive companion. In addition, recent work has investigated the possibility that double white dwarf (DWD) mergers are possibly the leading formation channel of massive, rapidly rotating, high-field magnetic WDs , particularly SDSS J221141.80 + 113604.4 (hereafter J2211+1136) and ZTF J190132.9 + 145808.7 (hereafter J1901 + 14588). Motivated by these findings and the Laser Interferometer Space Antenna (LISA) prospects, this study aims to calculate the tidal Love number, the dimensionless tidal deformability, as well as the frequency and amplitude of GWs of hot WDs. The results indicate that the tidal deformability is more pronounced in stars with higher central temperatures and lower masses, which would lead to reduced emission of GWs. In contrast, more massive stars exhibit less deformability, making them prime candidates for generating stronger GWs. Additionally, the analysis of frequency and amplitude reveals that the frequencies of high-mass binaries are smaller and evolve more rapidly, reaching a limit that aligns with the operational detection capabilities of LISA during its initial phase.

Understanding the evolution of metallic-line (Am) stars requires well determined atmospheric parameters and abundance patterns of the selected candidates. In this study, we presented a detailed abundance analysis of 15 Vul (HD 189849), identified as a marginal Am star, using a combination of equivalent width and spectrum synthesis techniques, under the LTE assumption. We compared our findings to previous analyses of the star, providing critique on both their results and our own. Our results suggest that although 15 Vul exhibits some underabundances of calcium and scandium, which are typically associated with Am stars, it might be more accurately identified as a normal A star in terms of its abundance pattern of all other elements and microturbulence velocity. The star's position on the HR diagram, along with our findings, may indicate that it is potentially a classical Am star that has evolved into the subgiant phase as a "quasi-normal" star. This may be the first identification of an evolved Am star.

The main objective of this work is to derive the distribution of the the metal content of HII galaxies using sulphur as an abundance tracer. This increases the metallicity range that can safely be reached. We selected a sample of emission-line galaxies that we extracted from the SDSS-DR16. These objects have a redshift of z less than 0.04 so that the [SIII] 9069 A emission line and H beta equivalent widths that are higher than 10 A in emission were included, and they are compact in appearance. We used the so-called direct method for objects with the electron-temperature-sensitive [SIII] 6312 A emission line, and an empirical method based on the S23 parameter. The last provided an abundance calibration that monotonically increased up to at least the solar value, and can be applied based on the spectral range from 6000 to 9500 A alone. We show that the bias that is introduced when the [OIII] 4363 A line is required restricts the sample to objects with an [OIII] electron temperature higher than 10,000K, and their temperature distribution is then rather narrow. For objects with determinations of te [SIII], the distribution is flatter and wider, which fits a more realistic scenario better. For the objects in the sample that required the detection of the [OIII] 4363 A line and [SIII] 6312 A, the distribution abundances as traced directly by oxygen and sulphur appear to be very similar to each other. However, when the restriction for weak temperature-sensitive lines is relaxed, the abundance distribution is wider . In summary, the abundance distributions traced by sulphur can reach reliable abundances up to the solar value at least and provide a more complete picture of the metallicity distribution of HII galaxies.

We present the results of combined hydrodynamic and particle tracking post-processing modeling to study the transport of small dust in a protoplanetary disk containing an embedded embryo in 3D. We use a suite of FARGO3D hydrodynamic simulations of disks containing a planetary embryo varying in mass up to 300 $M_\oplus$ on a fixed orbit in both high and low viscosity disks. We then simulate solid particles through the disk as a post-processing step using a Monte Carlo integration, allowing us to track the trajectories of individual particles as they travel throughout the disk. We find that gas advection onto the planet can carry small, well-coupled solids across the gap opened in the disk by the embedded planet for planetary masses above the pebble isolation mass. This mixing between the inner and outer disk can occur in both directions, with solids in the inner disk mixing to the outer disk as well. Additionally, in low viscosity disks, multiple pile-ups in the outer disk may preserve isotopic heterogeneities, possibly providing an outermost tertiary isotopic reservoir. Throughout Jupiter's growth, the extent of mixing between isotopic reservoirs varied depending on dust size, gas turbulence, and the Jovian embryo mass.

Context. Magnetically arrested disks are among the most suitable candidates for describing the gas accretion and observed emission in the vicinity of supermassive black holes. Aims. This work aims to provide a direct correlation between the quasi-periodic flux eruption events, characteristic of MAD accretion disk simulations, and the observed flaring behavior in the Galactic center. Methods. We employ a MAD accretion disk with a distinct counter-clockwise rotation and investigate the evolution of magnetized flux tubes generated during a prominent flux eruption event. Although these flux tubes demonstrate a clockwise pattern, they experience significant dragging by the accretion disk's rotation. This study models the motion of hot spots, formed on the disk's equatorial plane due to magnetic reconnection, as they travel along the magnetized flux tubes at a fraction of the speed of light. Results. Hot spots with a relativistic ejection velocity are able to balance out the counter-clockwise dragging of the flux tube's foot-point on the disk and demonstrate a clockwise motion in the sky, that is in good agreement with the NIR flares in the Galactic center. In addition, our flare models favor face-on inclinations in the range $[0^\circ, 34^\circ]$ and $[163^\circ, 180^\circ]$ for SgrA*. Conclusions. The flux eruption events that arise naturally in the MAD accretion state provide a promising framework for reproducing the observed flaring behavior in the vicinity of SgrA*.

The Hubble crisis is the discrepancy in the values of the Hubble constant inferred from diverse observations in the late and early Universe, being of the order 5$\sigma$. Instead of resolution, the conflict is getting larger with further late-time observations. A fundamental constant should be and remain constant throughout the cosmological history and thus at all redshifts. The fact that it turns out to be a function of redshift in the $\Lambda$CDM model points out that either there is a problem with the current cosmological model, indicating unknown new physics, or there are unknown systematics in some of the observations. In this work, we investigate the redshift dependence of the Hubble constant in the $\gamma\delta$CDM cosmological model, which is a new cosmological model based on $f(R)$ gravity in an anisotropic background. Through data analysis with the Pantheon+ type Ia supernovae, the cosmic chronometers Hubble, and both the old and the Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation data, we establish that the Hubble constant in our model does not evolve with redshift. We also confirm that our model fits the aforementioned data better than the $\Lambda$CDM model by checking various information criteria. The value of the Hubble constant obtained in the $\gamma\delta$CDM model is in the 1$\sigma$ bound of the late Universe observations.

Neutrino transport in compact objects is an inherently challenging multi-dimensional problem. This difficulty is compounded if one includes flavor transformation -- an intrinsically quantum phenomenon requiring one to follow the coherence between flavors and thus necessitating the introduction of complex numbers. To reduce the computational burden, simulations of compact objects that include neutrino transport often make use of momentum-angle-integrated moments (the lowest order ones being commonly referred to as the energy density and flux) and these quantities can be generalized to include neutrino flavor, i.e., they become quantum moments. Numerous finite-volume approaches to solving the moment evolution equations for classical neutrino transport have been developed based on solving a Riemann problem at cell interfaces. In this paper we describe our generalization of a Riemann solver for quantum moments, specifically decomposing complex numbers in terms of a (signed) magnitude and phase instead of real and imaginary parts. We then test our new algorithm in numerous cases showing a neutrino fast flavor instability, varying from toy models with analytic solutions to snapshots from neutron star merger simulations. Compared to previous algorithms for neutrino transport with flavor mixing, we find uniformly smaller growth rates of the flavor transformation along with concomitantly larger length-scales, and that the results are a better match with the growth rates seen from multi-angle codes.

The mechanisms of Ly$\alpha$ photon escape are key to understanding galaxy evolution and cosmic reionization, yet remain poorly understood. We investigate the UV-continuum sizes of 23 Ly$\alpha$ emitters (LAEs) at Cosmic Noon ($1.7 < z < 3.3$), extending previous size analyses to include fainter galaxies ($M_{\rm UV} \simeq -14$) using gravitational lensing. Our results show that these LAEs are unusually small for their luminosity, with a mean effective radius ($r_{\rm eff}$) of $170 \pm 140$ pc. They follow a distinct size-luminosity relation, with an intercept at $M_{\rm UV} = -21$ approximately three times smaller than typical star-forming galaxies (SFGs) at similar redshifts. This relation, however, is consistent with that of low-redshift Green Pea galaxies, suggesting that LAEs maintain compact sizes across redshifts. We also find that Ly$\alpha$ equivalent width (EW(Ly$\alpha$)) increases with decreasing $r_{\rm eff}$, confirming previous findings. The small sizes of LAEs lead to high star formation surface densities ($\Sigma$SFR $= 1-600 M_{\sun} \ \rm{yr}^{-1} \ \rm{kpc^{-2}}$), clearly separating them from typical SFGs in the $\Sigma$SFR vs. $r_{\rm eff}$ space. Given that high $\Sigma$SFR is linked to strong galactic outflows, our findings imply that compact morphology plays a key role in Ly$\alpha$ escape, likely facilitated by outflows that clear under-dense channels in the ISM. Thus, these results demonstrate that compact size and high $\Sigma$SFR can help identify Ly$\alpha$-emitters.

We provide the first reference framework for extremely metal-poor (XMP) OB-type stars. We parsed a grid of 0.10 $Z_{\odot}$ FASTWIND models, covering the parameter space of O stars and early-B supergiants, through contemporary spectral classification criteria to deliver a calibration of key stellar properties as a function of spectral type, and tabulated colours for the most common photometric systems. By using an extensive grid of models, we account for the different combinations of stellar parameters that result in the same spectral morphology and provide a range of parameters and colours compatible with each spectral subtype and luminosity class. We supply updated photometric criteria to optimize candidate selection of OB stars in XMP environments. We find 0.10 $Z_{\odot}$ OB stars are 1-6 kK hotter and produce higher ionizing fluxes than their Galactic analogues. In addition, we find a bimodal distribution of the HeII-ionizing flux with spectral type; because of its known dependence on effective temperature and the wind, $\log~q_{HeII}$ for individual XMP late-O type stars could be underestimated by up to 4 orders of magnitude by other calibrations, some of them used by population synthesis codes. Finally, we used our calibrated colours to map the extinction of the 0.10 $Z_{\odot}$ galaxy Sextans A finding that reddening is non-negligible and uneven.

The Guitar nebula surrounding PSR B2224+65 boasts a pulsar X-ray filament likely aligned with the local magnetic field. We present new RoboPol stellar polarization data distributed along the line-of-sight to the pulsar. The polarizing effect of intervening magnetized dust allows us to extract a model for the dust-weighted magnetic field. We detect a magnetic field angle consistent with the filament if the pulsar is located in the more distant zone of its parallax-estimated distance range.

Large-scale astronomical image data processing and prediction is essential for astronomers, providing crucial insights into celestial objects, the universe's history, and its evolution. While modern deep learning models offer high predictive accuracy, they often demand substantial computational resources, making them resource-intensive and limiting accessibility. We introduce the Cloud-based Astronomy Inference (CAI) framework to address these challenges. This scalable solution integrates pre-trained foundation models with serverless cloud infrastructure through a Function-as-a-Service (FaaS) Message Interface (FMI). CAI enables efficient and scalable inference on astronomical images without extensive hardware. Using a foundation model for redshift prediction as a case study, our extensive experiments cover user devices, HPC (High-Performance Computing) servers, and Cloud. CAI's significant scalability improvement on large data sizes provides an accessible and effective tool for the astronomy community. The code is accessible at this https URL.

The IceCube Neutrino Observatory includes low energy extensions such as the existing DeepCore subarray and the upcoming IceCube Upgrade, which will consist of seven new strings of photosensors with denser instrumentation than the existing array. The setup will allow for the study of neutrino oscillations with greater sensitivity compared to the existing instrumentation, improve neutrino mass ordering studies, and test for the unitarity of the PMNS mixing matrix with high precision. A critical component in these low-energy physics analyses is the accurate reconstruction of event information, particularly the zenith angle of incoming neutrinos. In this study, we discuss the processes that limit the zenith resolution, which include the transverse spread of the hadronic shower, in-ice photon scattering, module resolutions, and module noise. By considering approximations to these processes, we aim to approach the intrinsic zenith resolution limits for purely hadronic events.

A new physics-based model for analytical calculation of Soft Error Rate (SER) in digital memory circuits under the influence of heavy ions in space orbits is proposed. This method is based on parameters that are uniquely determined from the results of ground tests under nor-mal ion incidence. It is shown that preliminary averaging over the total solid angle within the standard inverse cosine model allows one to take into account the effect of isotropic flow, which increases the effective SER. The model includes the ability to estimate the contribution to SER of the low LET spectrum region, which is very important for modern ICs with low Single Event Upset tolerance.

We explore the impact of the back-reaction of evaporation on the quantum state of Primordial Black Holes (PBHs), known as ``memory burden", on the baryon asymmetry production in the Universe through high-scale leptogenesis. Focusing on PBH masses ranging from 1 to 1000 grams, we investigate the interplay between the non-thermal production of heavy sterile neutrinos and the entropy injection within this non-standard cosmological framework. By assuming appropriate values for the memory-burden parameters, $q=1/2$ and $k=1$, we derive mutual exclusion limits between PBHs and thermal leptogenesis in the mixed parameter space. Our analysis reveals that the primary contribution of PBHs to baryon asymmetry stems from entropy injection. Indeed, we find that, differently from earlier studies based on the semi-classical Hawking evaporation, the memory-burden effect suppresses the non-thermal source term in the PBH mass range explored. This has significant implications for understanding baryogenesis in such alternative cosmological scenarios.

The orbiting LISA instrument is designed to detect gravitational waves in the millihertz band, produced by sources including galactic binaries and extreme mass ratio inspirals, among others. The detector consists of three spacecraft, each carrying a pair of free-falling test masses. A technology-demonstration mission, LISA Pathfinder, was launched in 2015, and observed several sudden changes in test mass acceleration, referred to as "glitches." Similar glitches in the full LISA mission have the potential to contaminate the Time-Delay Interferometry outputs that are the detector's primary data product. In this paper, we describe an optimization technique using maximum likelihood estimation for detecting and removing glitches with a known waveform.

A no-go theorem for parity-violation in even $D$-dimensional spacetimes invariant under $ISO(d)$ and dilatations (as well as the implications for odd $D$) is derived. For the case of real massless scalar and gravitons (as well as any massless even integer spin-$s$ field) at $\mathcal{I}^+$, the reality of wavefunction coefficients in Fourier space to all orders in perturbation theory (any order in loops) coming from a local, unitary, IR- and UV-finite theory, which start from the initial \CRT-invariant Bunch-Davies state in the infinite past, is proven. From this it is inferred that a parity-odd correlator with any massless scalar fields and even integer spin-$s$ fields vanishes in the presence of any number of interactions of massless fields. The same is true for correlators with an even number of conformally-coupled and massless odd integer spin-$s$ external fields, which is used to derive the cosmological analogue of Furry's theorem. The fundamental implications of \CRT symmetry for theories with chemical potentials, such as Chern-Simons and Axion inflation, is also discussed. Given the recent interest in parity-violation coming from observational claims of parity-violation detection, these results provide clear constraints on parity-violating models of inflation and establish the measurement of any parity-odd correlator as an exceptionally sensitive probe of new physics beyond vanilla inflation.

We present a realizability-preserving numerical method for solving a spectral two-moment model to simulate the transport of massless, neutral particles interacting with a steady background material moving with relativistic velocities. The model is obtained as the special relativistic limit of a four-momentum-conservative general relativistic two-moment model. Using a maximum-entropy closure, we solve for the Eulerian-frame energy and momentum. The proposed numerical method is designed to preserve moment realizability, which corresponds to moments defined by a nonnegative phase-space density. The realizability-preserving method is achieved with the following key components: (i) a discontinuous Galerkin (DG) phase-space discretization with specially constructed numerical fluxes in the spatial and energy dimensions; (ii) a strong stability-preserving implicit-explicit (IMEX) time-integration method; (iii) a realizability-preserving conserved to primitive moment solver; (iv) a realizability-preserving implicit collision solver; and (v) a realizability-enforcing limiter. Component (iii) is necessitated by the closure procedure, which closes higher order moments nonlinearly in terms of primitive moments. The nonlinear conserved to primitive and the implicit collision solves are formulated as fixed-point problems, which are solved with custom iterative solvers designed to preserve the realizability of each iterate. With a series of numerical tests, we demonstrate the accuracy and robustness of this DG-IMEX method.

Alexei Alexandrovich Starobinsky was outstanding theoretical physicist who made fundamental contributions to gravitational theory and cosmology, based on geometrical ideas in physics, in the spirit of Einstein. One of his greatest achievements is the famous Starobinsky model of cosmological inflation in the early universe, proposed in 1979-1980. In this paper, the Starobinsky inflation model is systematically reviewed from the modern perspective. Its deformation to include production of primordial black holes is proposed, and possible quantum corrections in the context of superstring theory and the Swampland Program are discussed. Starobinsky inflation also leads to the universal reheating mechanism for particle production after inflation.

Plasma, which constitutes 99\% of the visible matter in the universe, is characterized by a wide range of waves and instabilities that play a pivotal role in space physics, astrophysics, laser-plasma interactions, fusion research, and laboratory experiments. The linear physics of these phenomena is described by kinetic dispersion relations (KDR). However, solving KDRs for arbitrary velocity distributions remains a significant challenge, particularly for non-Maxwellian distributions frequently observed in various plasma environments. This work introduces a novel, efficient, and unified numerical framework to address this challenge. The proposed method rapidly and accurately yields all significant solutions of KDRs for nearly arbitrary velocity distributions, supporting both unstable and damped modes across all frequencies and wavevectors. The approach expands plasma species' velocity distribution functions using a series of carefully chosen orthogonal basis functions and employs a highly accurate rational approximation to transform the problem into an equivalent matrix eigenvalue problem, eliminating the need for initial guesses. The efficiency and versatility of this framework are demonstrated, enabling simplified studies of plasma waves with arbitrary distributions. This advancement paves the way for uncovering new physics in natural plasma environments, such as spacecraft observations in space plasmas, and applications like wave heating in fusion research.

Astronomy, of all the sciences, is possibly the one with the most public appeal across all age groups. This is also evidenced by the existence of a large number of planetaria and amateur astronomy societies, which is unique to the field. Astronomy is known as a `gateway science', with an ability to attract students who then proceed to explore their interest in other STEM fields too. Astronomy's link to society is therefore substantive and diverse. In this white paper, six key areas are analysed, namely outreach and communication, astronomy education, history and heritage, astronomy for development, diversity, and hiring practices for outreach personnel. The current status of each of these areas is described, followed by an analysis of what is needed for the future. A set of recommendations for institutions, funding agencies, and individuals are evolved for each specific area. This work charts out the vision for how the astronomy-society connection should take shape in the future, and attempts to provide a road-map for the various stakeholders involved.

We constrain the parameters that govern curvature-induced quantum gravity time-of-flight (TOF) effects. These TOF delays, which occur due to modified dispersion relations of particles in a vacuum, could be a phenomenological signature of quantum gravity. Gamma-ray bursts (GRBs), short, high-energy events from distant galaxies, offer a unique opportunity to impose observational limits on TOF delays and, by extension, on the energy scales of quantum gravity. Using the standard Jacob-Piran relation, which assumes a locally-flat spacetime, the analysis of quantum gravity-induced TOF effects establishes a lower limit of approximately 10 Planck energies on the energy scale of these effects. However, curvature-induced quantum gravity effects may introduce additional contributions. From current GRB observations, we find that, at a 95% credibility level, in the symmetry-deformed scenario, curvature-induced TOF effects may only arise at energies above 0.04 Planck energy. If we consider only curvature-induced effects, this limit is an order of magnitude stronger. Observing more GRBs at different redshifts could improve the constraints on the curvature-induced QG phenomena. However, given the capabilities of current telescopes and the current understanding of GRBs, it is unlikely that these constraints will be significantly extended beyond the present level.

Hierarchical three-body systems offer a compelling framework to explore the subtle interplay between Newtonian and relativistic gravitational effects in astrophysical environments. In this work, we investigate post-Newtonian corrections to the periastron shift within such systems, focusing on the impact of orbital eccentricity and relativistic modifications to the center of mass. Modeling the secondary body's influence as a quadrupolar perturbation, we rigorously compare Newtonian, Schwarzschild, and post-Newtonian quadrupolar contributions to orbital precession. Our analysis demonstrates that Newtonian quadrupolar effects could be observable in the orbit of the S87 star around Sagittarius A* if an intermediate-mass black hole is present. Additionally, post-Newtonian quadrupolar corrections, though subtle, may notably influence the dynamics of small Solar System bodies in the presence of massive companions. These findings provide critical insights into detecting relativistic corrections in astrophysical systems with current high-precision instruments, such as GRAVITY. By bridging classical and relativistic dynamics, this study enhances our understanding of gravitational interactions in multi-body systems and paves the way for testing general relativity in the complex gravitational fields of galactic nuclei and planetary systems.

Axions are hypothetical pseudoscalar particles that have been regarded as promising dark matter (DM) candidates. On the other hand, extended compact objects such as axion stars, which are supported by gravity and axion self interactions, may have also been formed in the early Universe and comprise part of DM. In this work, we consider the lensing of electromagnetic signals from distant sources by axion stars, as a way to constrain the properties of axion stars and fundamental axion parameters. Accounting for the effect of the finite size of the axion star, we study the lensing effect induced by gravity and the axion-photon coupling. The latter effect is frequency dependent, and is relevant in the low frequency band, which motivates the use of fast radio burst (FRB) signals as a probe. We calculate the predicted number of lensed FRB events by specifying the fundamental axion parameters, axion star radial profile, fraction of DM residing in axion stars, and imposing lensing criteria based on the flux ratio and time delay between the brightest images from lensing. Assuming an optimistic case of $10^4$ observed FRB events, and a timing resolution of $1~\mu{\rm s}$, the lack of observed FRB lensing events in CHIME allows us to probe axion stars with mass $ \gtrsim 2 \times 10^{-2} M_\odot$, corresponding to axion masses $\lesssim 10^{-10}{\rm eV}$. We obtain constraints for even lighter axion stars up to $\sim 10^{-3} M_\odot$, when the axion-photon interactions are taken into account. Our results indicate that FRB lensing lead to constraints that are competitive with conventional microlensing searches operating in the optical band.

The moment of inertia and tidal deformability of idealized stars with polytropic equations of state (EOSs) are numerically calculated under both Newtonian gravity and general relativity (GR). The results explicitly confirm that the relation between the moment of inertia and tidal deformability, parameterized by the star's mass, exhibits variations of 1% to 10% for different polytropic indices in Newtonian gravity and GR, respectively. This indicates a more robust I-Love universal relation in the Newtonian framework. The theoretically derived I-Love universal relation for polytropic stars is subsequently tested against observational data for the moment of inertia and tidal deformability of the 8 planets and some moons in our solar system. The analysis reveals that the theoretical I-Love universal relation aligns well with the observational data, suggesting that it can serve as an empirical relation. Consequently, it enables the estimation of either the moment of inertia or the tidal deformability of an exoplanet if one of these quantities, along with the mass of the exoplanet, is known.

Gravitational-wave memory effects are lasting changes in the strain and its time integrals. They can be computed in asymptotically flat spacetimes using the conservation and evolution equations in the Bondi-Sachs framework. Modified theories of gravity have additional degrees of freedom with their own asymptotic evolution equations; these additional fields can produce differences in the memory effects in these theories from those in general relativity. In this work, we study a scalar-tensor theory of gravity known as the Damour-Esposito-Farèse extension of Brans-Dicke theory. We use the Bondi-Sachs framework to compute the field equations in Bondi-Sachs form, the asymptotically flat solutions, and the leading gravitational-wave memory effects. Although Damour-Esposito-Farèse theory has additional nonlinearities not present in Brans-Dicke theory, these nonlinearities are subleading effects; thus, the two theories share many similarities in the leading (and some subleading) solutions to hypersurface equations, asymptotic symmetries, and types of memory effects. The conservation equations for the mass and angular momentum aspects differ between the two theories, primarily because of the differences in the evolution equation for the scalar field. This leads to differences in the time dependence of the gravitational-wave memory signals that are produced during the quasicircular inspiral of compact binaries. These differences, however, are of second-order in a small coupling parameter of these theories, which suggests that it would be challenging to use memory effects to distinguish between these two theories.