Papers for Friday, Mar 07 2025

The metallicity of galaxies, and its variation with galactocentric radius, provides key insights into the formation histories of galaxies and the physical processes driving their evolution. In this work, we analyze the radial metallicity gradients of star forming galaxies in the EAGLE, Illustris, IllustrisTNG, and SIMBA cosmological simulations across a broad mass ($10^{8.0}M_\odot\leq M_\star \lesssim10^{12.0}M_\odot$) and redshift ($0\leq z\leq8$) range. We find that all simulations predict strong negative (i.e., radially decreasing) metallicity gradients at early cosmic times, likely due to their similar treatments of relatively smooth stellar feedback allowing for sustained inside-out growth. The strongest redshift evolution occurs in galaxies with stellar masses of $10^{10.0}-10^{11.0}M_\odot$, while galaxies with stellar masses $< 10^{10}M_\odot$ and $>10^{11}M_\odot$ exhibit weaker redshift evolution. Our results of negative gradients at high-redshift contrast with the many positive and flat gradients in the $1<z<4$ observational literature. At $z>6$, the negative gradients observed with JWST and ALMA are flatter than those in simulations, albeit with closer agreement than at lower redshift. Overall, we suggest that these smooth stellar feedback galaxy simulations may not sufficiently mix their metal content, and that either stronger stellar feedback or additional subgrid turbulent metal diffusion models may be required to better reproduce observed metallicity gradients.

Population III (Pop III) stars are the first stars in the Universe, forming from pristine, metal-free gas and marking the end of the cosmic dark ages. Their formation rate is expected to sharply decline after redshift $z \approx 15$ due to metal enrichment from previous generations of stars. In this paper, we analyze 14 zoom-in simulations from the THESAN-ZOOM project, which evolves different haloes from the THESAN-1 cosmological box down to redshift $z=3$. The high mass resolution of up to $142 M_\odot$ per cell in the gas phase combined with a multiphase model of the interstellar medium (ISM), radiative transfer including Lyman-Werner radiation, dust physics, and a non-equilibrium chemistry network that tracks molecular hydrogen, allows for a realistic but still approximate description of Pop III star formation in pristine gas. Our results show that Pop III stars continue to form in low-mass haloes ranging from $10^6 M_\odot$ to $10^9 M_\odot$ until the end of reionization at around $z=5$. At this stage, photoevaporation suppresses further star formation in these minihaloes, which subsequently merge into larger central haloes. Hence, the remnants of Pop III stars primarily reside in the satellite galaxies of larger haloes at lower redshifts. While direct detection of Pop III stars remains elusive, these results hint that lingering primordial star formation could leave observable imprints or indirectly affect the properties of high-redshift galaxies. Explicit Pop III feedback and specialized initial mass function modelling within the THESAN-ZOOM framework would further help interpreting emerging constraints from the James Webb Space Telescope.

A Uranus orbiter would be well positioned to detect the planet's free oscillation modes, whose frequencies can resolve questions about Uranus's weakly constrained interior. We calculate the spectra that may manifest in resonances with ring orbits or in Doppler imaging of Uranus's visible surface, using a wide range of interior models that satisfy the present constraints. Recent work has shown that Uranus's fundamental (f) and internal gravity (g) modes have appropriate frequencies to resonate with Uranus's narrow rings. We show that even a single $\ell=2$ f or g mode detected in ring imaging or occultations can constrain Uranus's core extent and density. Fully fluid models typically have $\ell=2-7$ f mode frequencies slightly too high to resonate among the narrow rings. If Uranus has a solid core that f modes cannot penetrate, their frequencies are reduced, rendering them more likely to be observed. A single $\ell\gtrsim7$ f mode detection would constrain Uranus's unknown rotation period. Meanwhile, the different technique of Doppler imaging seismology requires specialized instrumentation but could deliver many detections, with best sensitivity to acoustic (p) modes at mHz frequencies. Deviations from uniform frequency spacing can be used to locate density interfaces in Uranus's interior, such as a sharp core boundary. Shallower nonadiabaticity and condensation layers complicate this approach, but higher-order frequency differences can be analyzed to disentangle deep and near-surface effects. The detection of normal modes by a Uranus orbiter would help to discern among the degenerate solutions permitted by conventional measurements of the planet's static gravity field.

The detection of over a hundred gravitational wave signals from double compacts objects have confirmed the existence of such binaries with tight orbits. Two main formation channels are generally considered to explain the formation of these merging binary black holes (BBHs): the isolated evolution of stellar binaries, and the dynamical assembly in dense environments, namely star clusters. Although their relative contributions remain unclear, several analyses indicate that the detected BBH mergers probably originate from a mixture of these two distinct scenarios. We study the formation of massive star clusters across time and at a cosmological scale to estimate the contribution of these dense stellar structures to the overall population of BBH mergers. To this end, we propose three different models of massive star cluster formation based on results obtained with zoom-in simulations of individual galaxies. We apply these models to a large sample of realistic galaxies identified in the $(22.1\ \mathrm{Mpc})^3$ cosmological volume simulation \firebox. Each galaxy in this simulation has a unique star formation rate, with its own history of halo mergers and metallicity evolution. Combined with predictions obtained with the Cluster Monte Carlo code for stellar dynamics, we are able to estimate populations of dynamically formed BBHs in a collection of realistic galaxies. Across our three models, we infer a local merger rate of BBHs formed in massive star clusters consistently in the range $1-10\ \mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$. Compared with the local BBH merger rate inferred by the LIGO-Virgo-KAGRA Collaboration (in the range $17.9-44\ \mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ at $z=0.2$), this could potentially represent up to half of all BBH mergers in the nearby Universe. This shows the importance of this formation channel in the astrophysical production of merging BBHs.

In classic time-dependent 1D accretion disk models, the inner radiation pressure dominated regime is viscously unstable. However, late-time observations of accretion disks formed in tidal disruption events (TDEs) do not exhibit evidence of such instabilities. The common theoretical response is to modify the viscosity parametrization, but typically used viscosity parametrization are generally ad hoc. In this study, we take a different approach, and investigate a time-dependent 1D $\alpha$-disk model in which the pressure is dominated by magnetic fields rather than photons. We compare the time evolution of thermally stable, strongly magnetized TDE disks to the simpler linear viscosity model. We find that the light curves of magnetized disks evolve as $L_{\rm UV}\propto t^{-5/6}$ for decades to centuries, and that this same evolution can be reproduced by the linear viscosity model for specific parameter choices. Additionally, we show that TDEs remain UV-bright for many years, suggesting we could possibly find fossil TDEs decades after their bursts. We estimate that ULTRASAT could detect hundreds of such events, providing an opportunity to study late-stage TDE physics and supermassive black hole (SMBH) properties. Finally, we explore the connection between TDE disks and quasi-periodic eruptions (QPEs) suggested by recent observations. One theoretical explanation involves TDE disks expanding to interact with extreme mass ratio inspirals (EMRIs), which produce X-ray flares as the EMRI passes through the disk. Our estimates indicate that magnetized TDE disks should exhibit QPEs earlier than those observed in AT2019qiz, suggesting that the QPEs may have begun before their first detection.

The Dark Matter (DM) distribution in dwarf galaxies provides crucial insights into both structure formation and the particle nature of DM. GraphNPE (Graph Neural Posterior Estimator), first introduced in Nguyen et al. (2023), is a novel simulation-based inference framework that combines graph neural networks and normalizing flows to infer the DM density profile from line-of-sight stellar velocities. Here, we apply GraphNPE to satellite dwarf galaxies in the FIRE-2 Latte simulation suite of Milky Way-mass halos, testing it against both Cold and Self-Interacting DM scenarios. Our method demonstrates superior precision compared to conventional Jeans-based approaches, recovering DM density profiles to within the 95% confidence level even in systems with as few as 30 tracers. Moreover, we present the first evaluation of mass modeling methods in constraining two key parameters from realistic simulations: the peak circular velocity, $V_\mathrm{max}$, and the peak virial mass, $M_\mathrm{200m}^\mathrm{peak}$. Using only line-of-sight velocities, GraphNPE can reliably recover both $V_\mathrm{max}$ and $M_\mathrm{200m}^\mathrm{peak}$ within our quoted uncertainties, including those experiencing tidal effects ($\gtrsim$ 63% of systems are recovered with our 68% confidence intervals and $\gtrsim$ 92% within our 95% confidence intervals). The method achieves 10-20% accuracy in $V_\mathrm{max}$ recovery, while $M_\mathrm{200m}^\mathrm{peak}$ is recovered to 0.1-0.4 dex accuracy. This work establishes GraphNPE as a robust tool for inferring DM density profiles in dwarf galaxies, offering promising avenues for constraining DM models. The framework's potential extends beyond this study, as it can be adapted to non-spherical and disequilibrium models, showcasing the broader utility of simulation-based inference and graph-based learning in astrophysics.

We present a new suite of EDGE (`Engineering Dwarfs at Galaxy formation's Edge') cosmological zoom simulations. The suite includes 15 radiation-hydrodynamical dwarf galaxies covering the ultra-faint to the dwarf irregular regime ($10^4 \leq M_{\star}(z=0) \leq 10^8 \, M_{\odot}$) to enable comparisons with observed scaling relations. Each object in the suite is evolved at high resolution ($\approx 3 \, \text{pc}$) and includes stellar radiation, winds and supernova feedback channels. We compare with previous EDGE simulations without radiation, finding that radiative feedback results in significantly weaker galactic outflows. This generalises our previous findings to a wide mass range, and reveals that the effect is most significant at low $M_{\star}$. Despite this difference, stellar masses stay within a factor of two of each other, and key scaling relations of dwarf galaxies (size-mass, neutral gas-stellar mass, gas-phase mass-metallicity) emerge correctly in both simulation suites. Only the stellar mass -- stellar metallicity relation is strongly sensitive to the change in feedback. This highlights how obtaining statistical samples of dwarf galaxy stellar abundances with next-generation spectrographs will be key to probing and constraining the baryon cycle of dwarf galaxies.

We present the first transmission spectroscopy study of an exoplanet atmosphere with the high-resolution mode of the new Gemini High-resolution Optical SpecTrograph (GHOST) instrument at the Gemini South Observatory. We observed one transit of HAT-P-70 b - an ultra-hot Jupiter with an inflated radius - and made a new detection of the infrared Ca II triplet in its transmission spectrum. The depth of the strongest line implies that a substantial amount of Ca II extends to at least 47% above the bulk planetary radius. The triplet lines are blueshifted between ~ 3 to 5 km/s, indicative of strong dayside-to-nightside winds common on highly irradiated gas giants. Comparing the transmission spectrum with atmospheric models that incorporate non-local thermodynamic equilibrium effects suggests that the planetary mass is likely between 1 to 2 $M_{\rm J}$, much lighter than the upper limit previously derived from radial velocity measurements. Importantly, thanks to the the high signal-to-noise ratio achieved by GHOST/Gemini South, we are able to measure the temporal variation of these signals. Absorption depths and velocity offsets of the individual Ca II lines remain mostly consistent across the transit, except for the egress phases, where weaker absorption and stronger blueshifts are observed, highlighting the atmospheric processes within the trailing limb alone. Our study demonstrates the ability of GHOST to make time-resolved detections of individual spectral lines, providing valuable insights into the 3D nature of exoplanet atmospheres by probing different planetary longitudes as the tidally locked planet rotates during the transit.

Atomic hydrogen (HI) is an ideal tracer of gas flows in and around galaxies, and it is uniquely observable in the nearby Universe. Here we make use of wide-field (~1 square degree), spatially resolved (down to 22"), high-sensitivity (~$10^{18}$ cm$^{-2}$) HI observations of 5 nearby galaxies with stellar mass of $5\times10^{10}$ M$_\odot$, taken with the MeerKAT radio telescope. Four of these were observed as part of the MHONGOOSE survey. We characterise their main HI properties and compare these with synthetic HI data from a sample of 25 similarly massive star-forming galaxies from the TNG50 (20) and FIRE-2 (5) suites of cosmological hydrodynamical simulations. Globally, the simulated systems have HI and molecular hydrogen (H$_2$) masses in good agreement with the observations, but only when the H$_2$ recipe of Blitz & Rosolowsky (2006) is employed. The other recipes that we tested overestimate the H$_2$-to-HI mass fraction by up to an order of magnitude. On a local scale, we find two main discrepancies between observed and simulated data. First, the simulated galaxies show a more irregular HI morphology than the observed ones due to the presence of HI with column density $<10^{20}$ cm$^{-2}$ up to ~100 kpc from the galaxy centre, in spite of the fact that they inhabit more isolated environments than the observed targets. Second, the simulated galaxies and in particular those from the FIRE-2 suite, feature more complex and overall broader HI line profiles than the observed ones. We interpret this as being due to the combined effect of stellar feedback and gas accretion, which lead to a large-scale gas circulation that is more vigorous than in the observed galaxies. Our results indicate that, with respect to the simulations, gentler processes of gas inflows and outflows are at work in the nearby Universe, leading to more regular and less turbulent HI discs.

Binary population synthesis simulations allow detailed modelling of gravitational-wave sources from a variety of formation channels. These population models can be compared to the observed catalogue of merging binaries to infer the uncertain astrophysical input parameters describing binary formation and evolution, as well as relative rates between various formation pathways. However, it is computationally infeasible to run population synthesis simulations for all variations of uncertain input physics. We demonstrate the use of normalising flows to emulate population synthesis results and interpolate between astrophysical input parameters. Using current gravitational-wave observations of binary black holes, we use our trained normalising flows to infer branching ratios between multiple formation channels, and simultaneously infer common-envelope efficiency and natal spins across a continuous parameter range. Given our set of formation channel models, we infer the natal spin to be $0.04^{+0.04}_{-0.01}$, and the common-envelope efficiency to be $>3.7$ at 90% credibility, with the majority of underlying mergers coming from the common-envelope channel. Our framework allows us to measure population synthesis inputs where we do not have simulations, and better constrain the astrophysics underlying current gravitational-wave populations.

We study particle acceleration in strongly turbulent pair plasmas using novel 3D Particle-in-Cell simulations, featuring particle injection from an external heat bath and diffusive escape. We demonstrate the formation of steady-state, nonthermal particle distributions with maximum energies reaching the Hillas limit. The steady state is characterized by the equilibration of plasma kinetic and magnetic pressures, which imposes upper limits on the acceleration rate. With growing cold plasma magnetization $\sigma_0$, nonthermal power-law spectra become harder, and the fraction of energy channeled into escaping cosmic rays increases. At $\sigma_0 \gtrsim 1$, the escaping cosmic rays amount to more than 50\% of the dissipated energy. Our method allows for kinetic studies of particle acceleration under steady-state conditions, with applications to a variety of astrophysical systems.

Lyman-Alpha (Lya) photons emitted in star-forming regions inside galaxies experience a complex radiative transfer process until they reach the observer. The Lya line profile that we measured on Earth is, thus, the convolution of the gas properties in the interstellar (ISM), circumgalactic (CGM), and intergalactic medium (IGM). We make use of the open source package zELDA (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters) to disentangle the galactic and IGM components of the Lya profiles to study both the evolution of the intrinsic galactic emission and the IGM transmission across cosmic time. zELDA includes different artificial neural networks that reconstruct IGM attenuated Lya line profiles. These models are trained using mock Lya line profiles. A Monte Carlo radiative transfer code computes the galactic component for the so-called thin shell model. Moreover, the IGM component is included through the IGM transmission curves generated from the IllustrisTNG100 cosmological galaxy formation simulation. We recover their intrinsic galactic spectra by applying the zELDA to 313 Lya line profiles observed with HST/COS and MUSE. Sources at z < 0.5 show weak IGM attenuation, while at z > 3, ZELDA reveals significant IGM suppression of the blue peak in several sources. After separating the IGM effects, the stacked intrinsic galactic Lya profiles show a minimal evolution from z = 0 to 6. The mean IGM transmission for z < 0.5 in HST/COS data exceeds 90%, while the MUSE data show an evolution from 0.85 at z = 3.0 to 0.55 at z = 5.0.

We measure H$\alpha$ luminosity functions (LFs) at redshifts $z \sim 4.5$ and 6.3 using the JWST MAGNIF (Medium-band Astrophysics with the Grism of NIRCam In Frontier fields) survey. MAGNIF obtained NIRCam grism spectra with the F360M and F480M filters in four Frontier Fields. We identify 248 H$\alpha$ emitters based on the grism spectra and photometric redshifts from combined HST and JWST imaging data. The numbers of the H$\alpha$ emitters show a large field-to-field variation, highlighting the necessity of multiple fields to mitigate cosmic variance. We calculate both observed and dust-corrected H$\alpha$ LFs in the two redshift bins. Thanks to the gravitational lensing, the measured H$\alpha$ LFs span three orders of magnitude in luminosity, and the faint-end luminosity reaches $L_{\mathrm{H}\alpha} \sim 10^{40.3} \mathrm{erg} \mathrm{s}^{-1}$ at $z \sim 4.5$ and $10^{41.5} \mathrm{erg} \mathrm{s}^{-1}$ at $z \sim 6.3$, corresponding to star-formation rates (SFRs) of $\sim$ 0.1 and 1.7 $\mathrm{M}_\odot \mathrm{yr}^{-1}$. We conclude no or weak redshift evolution of the faint-end slope of H$\alpha$ LF across $z\simeq0.4-6.3$, and the comparison with the faint-end slopes of UV LF indicates stochastic star formation history among low-mass H$\alpha$ emitters. The derived cosmic SFR densities are $0.058^{+0.008}_{-0.006}\ \ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$ at $z \sim 4.5$ and $0.025^{+0.009}_{-0.007}\ \ M_\odot\ \mathrm{yr}^{-1}\ \mathrm{Mpc}^{-3}$ at $z \sim 6.3$. These are approximately 2.2 times higher than previous estimates based on dust-corrected UV LFs, but consistent with recent measurements from infrared surveys. We discuss uncertainties in the H$\alpha$ LF measurements, including those propagate from the lens models, cosmic variance, and AGN contribution.

The impact of neutrino flavor conversion on the supernova mechanism is yet to be fully understood. We present multi-energy and multi-angle solutions of the neutrino quantum kinetic equations in three flavors, taking into account neutrino advection and non-forward collisions with the background medium. Flavor evolution is explored within a spherically symmetric shell surrounding the region of neutrino decoupling in the interior of a core-collapse supernova, relying on the outputs of a spherically symmetric core-collapse supernova model with a mass of $18.6 M_\odot$. We select two representative post-bounce times: $t_{\rm pb} = 0.25$ s (no angular crossings are present and flavor conversion is triggered by slow collective effects) and $t_{\rm pb} = 1$ s (angular crossings trigger fast flavor instabilities). We find that flavor equipartition is achieved in the antineutrino sector between $\bar\nu_e$ and $\bar\nu_x = (\bar\nu_\mu + \bar\nu_\tau)/2$ for both post-bounce times. In the neutrino sector, flavor equipartition between $\nu_e$ and $\nu_x$ seems more likely at later post-bounce times, where the neutrino emission properties among different flavors tend to approach each other, but it is not a generic feature. The exponential growth of the $\nu_\mu$--$\nu_\tau$ asymmetry due to three-flavor effects is responsible for differences between the quasi-steady configurations obtained in the three-flavor solution and in the two-flavor approximation. This has consequences on the neutrino heating rate, which is generally larger when all three flavors are taken into account and can increase up to $30\%$ with respect to the case where flavor conversion is neglected.

We have performed a detailed abundance analysis of 10 red giant members of the heavily obscured bulge globular cluster HP~1 using high-resolution, high S/N near-infrared spectra collected with the Apache Point Observatory Galactic Evolution Experiment II survey (APOGEE-2), obtained as part of the bulge Cluster APOgee Survey (CAPOS). We investigate chemical abundances for a variety of species including the light (C,N), odd-Z (Al), $\alpha$ (O,Mg,Si,S,Ca and Ti), Fe-peak (Ni,Fe), and neutron-capture (Ce) elements. The derived mean cluster metallicity is [Fe/H]$=-1.15\pm0.03$, with no evidence for an intrinsic metallicity spread. HP~1 exhibits a typical $\alpha$-enrichment that follows the trend for similar metallicity Galactic GCs, such as NGC~288 and NGC~5904, although our [Si/Fe] abundances are relatively high. We find a significant nitrogen spread ($\sim 1$ dex), and a large fraction of nitrogen-enhanced ([N/Fe]$>+0.7$) stars that populate the cluster. We also detect intrinsic star-to-star spreads in [C/Fe], [O/Fe], [Al/Fe], and [Ca/Fe], which are (anti)correlated with several chemical species, indicating the prevalence of the multiple-population phenomenon in HP 1. We have uncovered for the first time a possible correlation between Ca and Al, although the sample is small. The mean $\langle$[Mg/Fe]$\rangle = +0.29$ and $\langle$[Al/Fe]$\rangle = +0.46$ place HP~1 into the region dominated by \textit{in-situ} GCs, supporting the \textit{in-situ} nature of this cluster.

Many stars exist in binary or multiple systems where tidal interactions modify rotational evolution. In single stars, magnetic braking slows rotation, but in close binaries, tidal forces synchronize rotation, leading to high spin rates. Thus, fast rotators are often synchronized binaries or planetary systems. We analyze stellar rotation in the Kepler field to identify non-single systems photometrically. By studying young clusters, we derive an initial rotation temperature relation for single stars, validated through magnitude excess and previous binarity studies, identifying 1219 candidate non-single systems with Prot smaller than 3 days. For ultra-fast rotators (Prot smaller than 3 days), we compile a catalog of 1296 candidate ultra short period binaries, often part of hierarchical triples, reinforcing the link between rapid spins and multiplicity. Applying our method to planet-host stars, we uncover two potential circumbinary systems (Kepler 1184, Kepler 1521) and two systems possibly synchronized by close-in planets (Kepler 493, Kepler 957), with five additional cases as potential false positives. Our analysis of known non-single stars reveals clear tidal features: period synchronization, orbit circularization, and a constraint on the minimal pericenter, where rp scales as (Porb/Prot)^0.77. These findings provide new insights into tidal evolution and offer a robust method for identifying stellar multiplicity, with implications for stellar evolution, binary formation, and exoplanet dynamics.

We present photometric and spectroscopic data of the type IIb supernova (SN) 2024abfo in NGC 1493 (at 11 Mpc). The ATLAS survey discovered the object just a few hours after the explosion, and observed a fast rise on the first day. Signs of the sharp shock break-out peak and the subsequent cooling phase are observed in the ultraviolet and the bluest optical bands in the first couple of days, while no peak is visible in the reddest filters. Subsequently, in analogy with normal SNe IIb, the light curve of SN 2024abfo rises again in all bands to the broad peak, with the maximum light reached around one month after the explosion. Its absolute magnitude at peak is $M_r=-16.5\pm0.1$ mag, making it a faint SN IIb. The early spectra are dominated by Balmer lines with broad P-Cygni profiles indicating ejecta velocity of 22,500 \kms. One month after the explosion, the spectra display a transition towards being He-dominated, though the H lines do not completely disappear, supporting the classification of SN 2024abfo as a relatively H-rich SN IIb. We identify the progenitor of SN 2024abfo in archival images of the Hubble Space Telescope, the Dark Energy Survey, and the XMM-Newton space telescope, in multiple optical filters. From its spectral energy distribution, the progenitor is consistent with being a white supergiant, Deneb-like star, with a photospheric temperature of 8110 K, a radius of 176 \Rsun, a luminosity of $\log(L/L_{\odot})=5.08$, having an initial mass of 15-16 \Msun. This detection supports an emerging trend of SN IIb progenitors being more luminous and hotter than SN II ones, and being primaries of massive binaries. Within the SN IIb class, fainter events such as SN 2024abfo tend to have cooler and more expanded progenitors than luminous SNe IIb.

We present a 3-D morphological and field reconstruction of a coronal mass ejection (CME) from 2023 November 28, which hits three spacecraft near 1 au: Wind at Earth's L1 Lagrange point; STEREO-A with a longitudinal separation of $6.5^{\circ}$ west of Earth; and Solar Orbiter (SolO) at $10.7^{\circ}$ east of Earth. The reconstruction assumes a magnetic flux rope (MFR) structure for the CME. With this event, we test whether field tracings observed by a spacecraft passing near the central axis of a CME MFR (STEREO-A) can be used to successfullly predict the field behavior seen by a spacecraft $17^{\circ}$ away (SolO), which has a more grazing encounter with the CME. We find that the MFR model does have significant success in simultaneously reproducing the field signs and rotations seen at STEREO-A, Wind, and SolO. This provides support for the MFR paradigm for CME structure. However, the SolO measurements, which are farthest from the central axis of the MFR, show less defined MFR signatures, presumably due to a greater degree of erosion and degradation of the MFR structure far from its central axis.

The James Webb Space Telescope (JWST) has revealed low-luminosity active galactic nuclei (AGNs) at redshifts of $z\gtrsim 4-7$, many of which host accreting massive black holes (BHs) with BH-to-galaxy mass ($M_{\rm BH}/M_{\star}$) ratios exceeding the local values by more than an order of magnitude. The origin of these overmassive BHs remains unclear but requires potential contributions from heavy seeds and/or episodes of super-Eddington accretion. We present a growth model coupled with dark matter halo assembly to explore the evolution of the $M_{\rm BH}/M_{\star}$ ratio under different seeding and feedback scenarios. Given the gas inflow rates in protogalaxies, BHs grow episodically at moderate super-Eddington rates and the mass ratio increases early on, despite significant mass loss through feedback. Regardless of seeding mechanisms, the mass ratio converges to a universal value $\sim 0.1-0.3$, set by the balance between gas feeding and star formation efficiency in the nucleus. This behavior defines an attractor in the $M_{\rm BH}-M_{\star}$ diagram, where overmassive BHs grow more slowly than their hosts, while undermassive seeds experience rapid growth before aligning with the attractor. We derive an analytical expression for the universal mass ratio, linking it to feedback strength and halo growth. The convergence of evolutionary tracks erases seeding information from the mass ratio by $z\sim 4-6$. Detecting BHs with $\sim 10^{5-6}~M_\odot$ at higher redshifts that deviate from convergence trend would provide key diagnostics of their birth conditions.

Cislunar space is the volume between Earth's geosynchronous orbit and beyond the Moon, including the lunar Lagrange points. Understanding the stability of orbits within this space is crucial for the successful planning and execution of space missions. Orbits in cislunar space are influenced by the gravitational forces of the Sun, Earth, Moon, and other Solar System planets leading to typically unpredictable and chaotic behavior. It is therefore difficult to predict the stability of an orbit from a set of initial orbital elements. We simulate one million cislunar orbits and use a self-organizing map (SOM) to cluster the orbits into families based on how long they remain stable within the cislunar regime. Utilizing Lawrence Livermore National Laboratory's (LLNL) High Performance Computers (HPC) we develop a highly adaptable SOM capable of efficiently characterizing observations from individual events. We are able to predict the lifetime from the initial three line element (TLE) to within 10 percent for 8 percent of the test dataset, within 50 percent for 43 percent of the dataset, and within 100 percent for 75 percent of the dataset. The fractional absolute deviation peaks at 1 for all lifetimes. Multi-modal clustering in the SOM suggests that a variety of orbital morphologies have similar lifetimes. The trained SOMs use an average of 2.73 milliseconds of computational time to produce an orbital stability prediction. The outcomes of this research enhance our understanding of cislunar orbital dynamics and also provide insights for mission planning, enabling the rapid identification of stable orbital regions and pathways for future space exploration. As demonstrated in this study, an SOM can generate orbital lifetime estimates from minimal observational data, such as a single TLE, making it essential for early warning systems and large-scale sensor network operations.

Although Neptunian-sized (2 - 5 R$_{Earth}$) planets appear to be extremely common in the Galaxy, many mysteries remain about their overall nature. To date, only eleven Neptunian-sized planets have had their atmospheres spectroscopically characterized, and these observations hint at interesting diversity within this class of planets. Much of our understanding of these worlds and others derive from transmission spectroscopy with the Hubble Space Telescope's Wide Field Camera 3 (HST/WFC3). One key outcome of HST/WFC3 observations has been the consistent detection of water but no methane in Neptunian atmospheres, though recent JWST observations are potentially starting to overturn this "missing methane" paradigm. In this work, we present the transmission spectrum of the hot Neptune HD 219666 b from 1.1 - 1.6 $\mu$m from two transit observations using HST/WFC3 G141. Our fiducial atmospheric retrieval detects water at ~3-$\sigma$ in HD 219666 b's atmosphere and prefers no contribution from methane, similar to these previous observations of other planets. Motivated by recent detections of methane in Neptunian atmospheres by JWST, we explore additional models and find that a methane-only scenario could adequately fit the data, though it is not preferred and likely unphysical. We discuss the impact of this methane detection challenge on our understanding of planetary atmospheres based on HST/WFC3 observations alone, and where JWST observations offer a solution.

The current populations trapped in Neptune's main mean motion resonances in the Kuiper belt, Plutinos in the 3:2 and Twotinos in the 2:1, contain some of the best-characterized minor objects in the Solar System, given their dynamical importance. In particular, Twotinos may hide evidence of Neptune's early migration. However, these populations vary in time, declining at a rate that has not been previously clearly established. In this work, we use numerical simulations to study the long-term evolution of the Plutino and Twotino populations. We use two data sources: the most up-to-date observations and the theoretical debiased model of the Kuiper belt known as L7. In addition to studying the giant planets' effect on these populations over 4 Gyr, we analyze the additional impact produced by the most massive trans-Neptunian objects (TNOs) closest to these resonances. We find that the decay rate in each resonance can be modeled as a stochastic process well described by an exponential decay with an offset determined by an underlying long-term stable population. The most massive TNOs, particularly Pluto, influence this decay rate significantly, as expected for the 3:2 resonance. Still, despite its distance, Pluto also strongly influences the 2:1 resonance's evolution.

Mapping out the first billion years using the 21-cm line with the Square Kilometer Array (SKA) will revolutionize our understanding of the cosmic dawn, reionization and the galaxies that drove these milestones. However, synergies with other telescopes in the form of cross correlations will be fundamental in making and confirming initial, low signal-to-noise claims of a detection. Participants of the 2023 European Southern Observatory (ESO) - SKA Observatory workshop discussed such synergies for Epoch of Reionization (EoR) and Cosmic Dawn (CD) science. Here we highlight some of the most promising candidates for cross-correlating SKA EoR/CD observations with ESO instruments such as the Multi-Object Optical and Near-infrared Spectrograph (MOONS), the MOSAIC multi-object spectrograph, and the ArmazoNes high Dispersion Echelle Spectrograph (ANDES).

We discuss the possible synergies for cosmology between SKAO and ESO facilities, focusing on the combinations SKA-Mid with the Multi-Object Spectrograph Telescope (4MOST) instrument built for ESO's Visible and Infrared Survey Telescope for Astronomy (VISTA), and SKA-Low with ESO's Extremely Large Telescope (ELT) multi-object spectrograph MOSAIC. Combining multiple tracers allows for tackling systematics and lifting parameter degeneracies. It will play a crucial role in the pursuit of precision cosmology.

One of the most prolific methods of studying exoplanet atmospheres is transmission spectroscopy, which measures the difference between the depth of an exoplanet's transit signal at various wavelengths and attempts to correlate the depth changes to potential features in the exoplanet's atmosphere. Here we present reconnaissance observations of 21 exoplanet atmospheres measured with the Exoplanet Transmission Spectroscopy Imager (ETSI), a recently deployed spectro-photometer on the McDonald Observatory Otto Struve 2.1 m telescope. ETSI measurements are mostly free of systematics through the use of a novel observing technique called common-path multi-band imaging (CMI), which has been shown to achieve photometric color precision on-par with space-based observations (300ppm or 0.03%). This work also describes the various statistical tests performed on the data to evaluate the efficacy of the CMI method and the ETSI instrument in combination. We find that none of the 8 comparisons of exoplanet atmospheres measured with ETSI and other observatories (including the Hubble Space Telescope) provide evidence that the spectra are statistically dissimilar. These results suggest that ETSI can provide initial transmission spectroscopy observations for a fraction of the observational and monetary overhead previously required to detect an exoplanet's atmosphere. Ultimately these reconnaissance observations increase the number of planets with transmission spectroscopy measurements by ~10% and provide an immediate prioritization of 21 exoplanets for future follow-up with more precious observatories, such as the James Webb Space Telescope. The reconnaissance spectra are available through the Filtergraph visualization portal at the URL: this https URL.

The Exoplanet Transmission Spectroscopy Imager (ETSI) amalgamates a low resolution slitless prism spectrometer with custom multi-band filters to simultaneously image 15 spectral bandpasses between 430 nm and 975 nm with an average spectral resolution of $R = \lambda/\delta\lambda \sim 20$. ETSI requires only moderate telescope apertures ($\sim2$ m) and is capable of characterizing an exoplanet atmosphere in as little as a single transit, enabling selection of the most interesting targets for further characterization with other ground and space-based observatories and is also well suited to multi-band observations of other variable and transient objects. This enables a new technique, common-path multi-band imaging (CMI), used to observe transmission spectra of exoplanets transiting bright (V$<$14 magnitude) stars. ETSI is capable of near photon-limited observations, with a systematic noise floor on par with the Hubble Space Telescope and below the Earth's atmospheric amplitude scintillation noise limit. We report the as-built instrument optical and optomechanical design, detectors, control system, telescope hardware and software interfaces, and data reduction pipeline. A summary of ETSI's science capabilities and initial results are also included.

We present a new pipeline designed for the robust inference of cosmological parameters using both second- and third-order shear statistics. We build a theoretical model for rapid evaluation of three-point correlations using our fastnc code and integrate it into the CosmoSIS framework. We measure the two-point functions $\xi_{\pm}$ and the full configuration-dependent three-point shear correlation functions across all auto- and cross-redshift bins. We compress the three-point functions into the mass aperture statistic $\langle M_{\rm ap}^3\rangle$ for a set of 796 simulated shear maps designed to model the Dark Energy Survey (DES) Year 3 data. We estimate from it the full covariance matrix and model the effects of intrinsic alignments, shear calibration biases and photometric redshift uncertainties. We apply scale cuts to minimize the contamination from the baryonic signal as modeled through hydrodynamical simulations. We find a significant improvement of $83\%$ on the Figure of Merit in the $\Omega_{\rm m}$-$S_8$ plane when we add the $\langle M_{\rm ap}^3\rangle$ data to the $\xi_{\pm}$ information. We present our findings for all relevant cosmological and systematic uncertainty parameters and discuss the complementarity of third-order and second-order statistics.

In view of the great uncertainty of the equation of state (EOS) of high-density nuclear matter, establishing EOS-independent universal relations between global properties of neutron stars provides a practical way to constrain the unobservable or difficult-to-observe properties through astronomical observations. It is common to construct universal relations between EOS-dependent properties (e.g., moment of inertia, tidal deformation, etc.) or combined properties (e.g., compactness). Improving the precision of the universal relations may provide stricter constraint on the properties of neutron star. We find that in 3-dimensional space with mass and radius as the base coordinates, the points corresponding to a certain property of neutron star described by different EOSs are almost located in the same surface. Thus the universal relation between the property and the stellar mass-radius can be expressed through describing the surface. It is shown that the resulting universal relations have higher precisions. As an example, we construct high-precision universal relations for the moment of inertia, the $f$-mode frequency, and the dimensionless tidal deformation respect to the mass-radius. As the observational data of neutron star mass and radius from NICER grows in data and accuracy, these universal relations allow for more precise constraints on the unobservable or difficult-to-observe properties.

Modern Imaging Atmospheric Cherenkov Telescopes (IACTs) generate a huge amount of data that must be classified automatically, ideally in real time. Currently, machine learning-based solutions are increasingly being used to solve classification problems. However, these classifiers require proper training data sets to work correctly. The problem with training neural networks on real IACT data is that these data need to be pre-labeled, whereas such labeling is difficult and its results are estimates. In addition, the distribution of incoming events is highly imbalanced. Firstly, there is an imbalance in the types of events, since the number of detected gamma quanta is significantly less than the number of protons. Secondly, the energy distribution of particles of the same type is also imbalanced, since high-energy particles are extremely rare. This imbalance results in poorly trained classifiers that, once trained, do not handle rare events correctly. Using only conventional Monte Carlo event simulation methods to solve this problem is possible, but extremely resource-intensive and time-consuming. To address this issue, we propose to perform data augmentation with artificially generated events of the desired type and energy using conditional generative adversarial networks (cGANs), distinguishing classes by energy values. In the paper, we describe a simple algorithm for generating balanced data sets using cGANs. Thus, the proposed neural network model produces both imbalanced data sets for physical analysis as well as balanced data sets suitable for training other neural networks.

Photoevaporation caused by X-rays and ultraviolet radiation from the central star has attracted attention as a key process driving the dispersal of protoplanetary discs. Although numerous models have been used to investigate the photoevaporation process, their conclusions vary, partly due to differences in the adopted radiation spectra of the host star in particular in the extreme ultraviolet (EUV) and soft X-ray bands. This study aims to construct the EUV and (soft) X-ray emission spectrum from pre-main-sequence stars using a physics-based model. While the high-energy radiation sources of pre-main-sequence stars include accretion shocks and magnetically heated coronae, this study focuses on the latter. An MHD model capable of reproducing the coronal emission of main-sequence stars is applied to a pre-main-sequence star TW Hya, and its feasibility is assessed by comparing the predicted and observed emission-line intensities. We find that the emission lines formed at coronal temperatures ($T = 4-13 \times 10^6$ K) are reproduced in intensity within a factor of three. Emission lines from lower-temperature ($T < 4 \times 10^6$ K) plasmas are systematically underestimated, with typical intensities at 10-30% of observed values, consistent with previous findings that these emissions predominantly originate from accretion shocks. Emission lines emitted at extremely high temperatures ($T > 13 \times 10^6$ K) account for only about 1-10% of the observed values, likely due to the neglect of transient heating associated with flares. These results indicate that the quiescent coronal emission of pre-main-sequence stars can be adequately modeled using a physics-based approach.

Supergiant Fast X-ray Transients (SFXT) are a sub-class of High Mass X-ray Binaries (HMXB) in which a compact object accretes part of the clumpy wind of the blue supergiant companion, triggering a series of brief, X-ray flares lasting a few kiloseconds. Currently, only about fifteen SFXTs are known. The EXTraS catalog provides the timing signatures of every source observed by the EPIC instrument on-board XMM-Newton. Among the most peculiar sources, in terms of variability, we selected 4XMM J181330.1-17511 (J1813). We analyzed all publicly available X-ray data pointed at the J1813 position to determine the source's duty cycle and to provide a comprehensive description of its timing and spectral behavior during its active phase. Additionally, we searched for the optical and infrared counterpart of the X-ray source in public databases and fitted its Spectral Energy Distribution (SED). The optical-to-MIR SED of J1813 is consistent with a highly-absorbed (A$_V\sim38$) B0 star at $\sim$10 kpc. During its X-ray active phase, the source is characterized by continuous $\sim$thousands seconds-long flares with peak luminosities (2-12 keV) ranging from $10^{34}$ to $4 \times 10^{35}$ erg s$^{-1}$. Its X-ray spectrum is consistent with a high-absorbed power-law model with N$_H \sim 1.8 \times 10^{23}$ cm$^{-2}$ and $\Gamma \sim 1.66$. No spectral variability was observed as a function of time or flux. J1813 is in a quiescent state $\sim$60\% of the time, with an upper-limit luminosity of $8 \times 10^{32}$ erg s$^{-1}$ (at 10 kpc), implying an observed long-term X-ray flux variability $>$500. The optical counterpart alone indicates J1813 is a HMXB. Its transient nature, duty cycle, the amplitude of observed X-ray variability, the shape and luminosity of the X-ray flares -- and the lack of known X-ray outbursts ($>10^{36}$ erg s$^{-1}$) -- strongly support the identification of J1813 as an SFXT.

This study investigates polarimetric characteristics of the blazar 3C~454.3 at 22-129~GHz using decadal~(2011-2022) data sets. In addition, we also delve into the origin of the polarization flare observed in 2019. The data sets were obtained from the single-dish mode observations of the Korean VLBI Network~(KVN) and the 43-GHz Very Long Baseline Array~(VLBA). We compared the consistency of the measurements between milli-arcsecond and arcsecond scales. The Faraday rotation measure values were obtained via two approaches, model fitting to a linear function in all frequency ranges, and calculation from adjacent frequency pairs. We found that the linear polarization angle is preferred to be $\sim100^{\circ}$ when the source is highly polarized. At 43~GHz, we found that the polarized emission at scales of mas and arcsecond is consistent when we compare its flux density and polarization angle. The ratio of quasi-simultaneously measured polarized flux density is $1.02\pm0.07$, and the polarization angles display similar rotation. These suggest that the extended jet beyond the scale of VLBA 43~GHz has a negligible convolution effect on the polarization angle from the KVN. We found an interesting, notable flaring event in the KVN single-dish data from the polarized emission in 2019 in the frequency range of 22-129~GHz. During the flare, the observed polarization angles~($\chi_{\rm obs}$) rotate from $\sim150^{\circ}$ to $\sim100^{\circ}$ at all frequencies with a chromatic polarization degree~($m_{\rm p}$). Based on the observed $m_{\rm p}$ and $\chi_{\rm obs}$, and also the Faraday rotation measure, we suggest that the polarization flare in 2019 is attributed to the shock-shock interaction in the stationary jet region. The change in the viewing angle of the jet alone is insufficient to describe the increase in brightness temperature, indicating the presence of source intrinsic processes.

Recent JWST observations have uncovered high-redshift galaxies characterized by multiple star-forming clumps, many of which appear to be undergoing mergers. Such mergers are powerful drivers of galaxy evolution, triggering intense star formation that accelerates the formation of massive quiescent galaxies. Mergers can also expel and redistribute the metal-enriched gas from galaxies into their circum-galactic medium (CGM), regulating the chemical component of their environments and creating channels of ionized gas through which ionizing radiation escapes. Here, we report a merger of at least five galaxies, dubbed JWST's Quintet (JQ), at redshift 6.7, discovered in the JWST GOODS-South field. This system resides in a small area $\sim4.5''\times4.5''$ ($24.6\times24.6$ pkpc$^2$), containing over 17 galaxy-size clumps with a total stellar mass of $10^{10}\ M_\odot$. The JQ system has a total star formation rate of 240-270 $M_\odot$ yr$^{-1}$, placing it $\sim1$ dex above the median star formation rate-mass main sequence at this epoch. The high mass and star formation rate of the JQ galaxies are sufficient to produce massive, inactive galaxies identified at later times, by redshift 4, suggesting this may be a progenitor event for such systems. We detect a large \foiii+H$\beta$ emitting gaseous halo surrounding and connecting four galaxies in the JQ, consistent with the interaction between them. This indicates that the CGM of JQ is already enriched by the heavy elements generated from the galaxies through merger-induced tidal stripping or galactic outflows. Our findings offer a plausible evolutionary pathway for the formation of massive quiescent galaxies observed at lower redshifts and provide direct evidence for the metal enrichment of their environments through galaxy mergers, just 800 Myr after the Big Bang.

In this work, we numerically explore the dynamics of a point mass (e.g., a stellar-mass black hole) moving within a thin accretion disk of a massive object (i.e., a supermassive black hole) with three dimensional hydrodynamical simulations using \texttt{Athena++}. We are particularly interested in the regime that the Hill radius of the point mass is greater than the disk thickness, but the point mass is not sufficiently massive to open a ``gap" in a high viscosity disk. This parameter regime may be seen for stellar-mass objects moving within thin accretion disks of massive black holes, but less studied for the planet migration scenario in protoplanetary disks. We find that the disk migration may be significantly slower than the type I migration, depending on the surface density gradient of the disk. Furthermore, the circumsingle disk around the point mass plays an important role in damping the orbital eccentricity. If the gravitational interaction between the point mass and circumsingle disk material is turned off, the orbital eccentricity may be pumped to $\mathcal{O}(10^{-2})$ level. Because space-borne gravitational wave detectors such as LISA (Laser Interferometer Space Antenna) is able to measure the eccentricity of extreme mass-ratio inspirals to the level of $\mathcal{O}(10^{-5})$, this finding highlights the importance of understanding stellar-mass black hole feedback mechanisms which will modify the structures of the circumsingle disk, as they will impact LISA observables such as the eccentricity.

Swift J1727.8--1613 is a black hole X-ray binary that differs from other black hole X-ray binaries in that it has an extra hard component in addition to a reflection component. We perform spectral analysis with simultaneous Insight-HXMT, NICER and NuSTAR observations when the source was in the hard and hard intermediate states. For the presentation of the extra components, we investigate the correlation between the relxill parameters. We find that the correlation between the spectral index and the reflection fraction is consistent with MAXI J1820+070 when the jet dominates the reflection. This provides the second sample to have such a correlation during an outburst. Interestingly, when the reflection component is attributed to the corona, the spectral fit results in a small reflection fraction and the correlation between the spectral index and reflection fraction is in agreement with the overall trend built-in You et al. 2023 with a large sample of outbursts from other X-ray binaries. Hence Swift J1727.8--1613 turns out to be the first sample to bridge the MAXI J1820+070 to the majority of X-ray binaries according to the dual correlations observed between the spectral index and the reflection fraction. We speculate that a configuration of a jet plus a hot inner flow may account for this peculiar outburst behavior of Swift J1727.8--1613.

One of the more surprising astrophysical discoveries of the last decade has been the presence of enormous quantities of dust at megaparsec distances from galaxies, which has important implications for galaxy evolution, the circumgalactic and intergalactic medium, and observational cosmology. In this work, we present a novel method for studying these vast halos of circumgalactic dust: a maximum-likelihood estimator for dust-induced extinction of background galaxies. This estimator can accommodate a broad range of archival photometric data and can incorporate different dust reddening prescriptions, making it applicable to diverse galaxy types and redshifts. We apply the estimator to the redMaGiC catalog of luminous red galaxies, selected for their tight dispersion in color and well-constrained photometric redshifts, and measure the resulting extinction as a function of projected distance from WISExSuperCOSMOS and redMaGiC foreground galaxies. We detect significant dust-induced extinction profiles extending to at least 1 megaparsec from galactic disks, with noticeable differences between star-forming and quiescent galaxies: star-forming galaxies exhibit a pronounced rise in extinction within the inner 50 kiloparsecs and a steep decline beyond 1 megaparsec, while the quiescent galaxies host little dust in the inner halo but have detectable extinction out to 30 megaparsecs. We test the robustness of our results using star catalogs and inverted foreground and background samples and find no evidence for significant systematic error. Our approach provides a powerful tool for studying the interplay between circumgalactic dust, galaxy evolution, and large-scale structure, with potential applications in a number of astrophysical subfields.

Understanding the physical mechanisms that drive star formation is crucial for advancing our knowledge of galaxy evolution. We explore the interrelationships between key galaxy properties associated with star formation, with a particular focus on the impact of dark matter halos. Given the sensitivity of atomic hydrogen (HI) to external processes, we concentrate exclusively on central spiral galaxies. We find that the molecular-to-atomic gas mass ratio ($M_{\rm H_2}/M_{\rm HI}$) strongly depends on stellar mass and specific star formation rate (sSFR). In the star formation efficiency (SFE)-sSFR plane, most galaxies fall below the H$_2$ fundamental formation relation (FFR), with SFE$_{\rm HI}$ being consistently lower than SFE$_{\rm H_2}$. Using the improved halo masses derived by Zhao et al. (2025), for star-forming galaxies, both SFE$_{\rm HI}$ and $M_{\rm H_2}/M_{\rm HI}$ increase rapidly and monotonically with halo mass, indicating a higher efficiency in converting HI to H$_2$ in more massive halos. This trend ultimately leads to the unsustainable state where SFE$_{\rm HI}$ exceeds SFE$_{\rm H_2}$ at halo mass around $10^{12} \hbox{$M_{\odot}$}$. For halos with masses exceeding $10^{12} \hbox{$M_{\odot}$}$, galaxies predominantly experience quenching. We propose a plausible evolutionary scenario in which the growth of halo mass regulates the conversion of HI to H$_2$, star formation, and the eventual quenching of galaxies. The disk size, primarily regulated by the mass, spin and concentration of the dark matter halo, also significantly influences HI to H$_2$ conversion and star formation. These findings underscore the critical role of dark matter halos as a global regulator of galaxy-wide star formation, a key factor that has been largely underappreciated in previous studies.

In this work, we discuss model-independent reconstruction of the expansion history of the late Universe. We use Gaussian Process Regression to reconstruct the evolution of various cosmological parameters such as H(z) and slow-roll parameter using observational data to train the GP model. We look at the GP reconstruction of these parameters using stationary and non-stationary kernel functions. We examine the effect of the choice of kernel functions on the reconstructions. We find that non-stationary kernels such as polynomial kernels might be a better choice for the reconstruction if the training data set is noisy (such as H(z) data) as it helps to avoid fitting the error in the data. We also look at the kernel dependence of other cosmological parameters such as the redshift of transition to the accelerated expansion. This has been achieved by reconstructing the derivatives of the expansion history (H(z)) such as the deceleration parameter/slow-roll parameter.

Axions are well-motivated dark matter particles. Many experiments are looking for their experimental evidence. For haloscopes, the problem reduces to the identification of a peak above a noisy baseline. Its modeling, however, may problematic. State-of-the-art analysis rely on the Savitzky-Golay (SG) filtering, which is intrinsically affected by any possible over fluctuation, leading to biased results. In this paper we study the efficiency that different extensions of SG can provide in the peak reconstruction in a standard haloscope-like experiment. We show that, once the correlations among bins are taken into account, there is no appreciable difference. The standard SG remains the advisable choice because of its numerical efficiency.

We present multiband observations and analysis of EP240801a, a low-energy, extremely soft gamma-ray burst (GRB) discovered on August 1, 2024 by the Einstein Probe (EP) satellite, with a weak contemporaneous signal also detected by Fermi/GBM. Optical spectroscopy of the afterglow, obtained by GTC and Keck, identified the redshift of $z = 1.6734$. EP240801a exhibits a burst duration of 148 s in X-rays and 22.3 s in gamma-rays, with X-rays leading by 80.61 s. Spectral lag analysis indicates the gamma-ray signal arrived 8.3 s earlier than the X-rays. Joint spectral fitting of EP/WXT and Fermi/GBM data yields an isotropic energy $E_{\gamma,\rm{iso}} = (5.57^{+0.54}_{-0.50})\times 10^{51}\,\rm{erg}$, a peak energy $E_{\rm{peak}} = 14.90^{+7.08}_{-4.71}\,\rm{keV}$, a fluence ratio $\rm S(25-50\,\rm{keV})/S(50-100\,\rm{keV}) = 1.67^{+0.74}_{-0.46}$, classifying EP240801a as an X-ray flash (XRF). The host-galaxy continuum spectrum, inferred using Prospector, was used to correct its contribution for the observed outburst optical data. Unusual early $R$-band behavior and EP/FXT observations suggest multiple components in the afterglow. Three models are considered: two-component jet model, forward-reverse shock model and forward-shock model with energy injection. Both three provide reasonable explanations. The two-component jet model and the energy injection model imply a relatively small initial energy and velocity of the jet in the line of sight, while the forward-reverse shock model remains typical. Under the two-component jet model, EP240801a may resemble GRB 221009A (BOAT) if the bright narrow beam is viewed on-axis. Therefore, EP240801a can be interpreted as an off-beam (narrow) jet or an intrinsically weak GRB jet. Our findings provide crucial clues for uncovering the origin of XRFs.

We investigate the axially symmetric accretion of low angular momentum hydrodynamic matter onto a rotating black hole. The gravitational field under consideration is assumed to be described by a pseudo-Newtonian Kerr potential. The accreting matter consists of different species defined by a relativistic equation of state with a variable adiabatic this http URL construct and solve the hydrodynamical conservation equations governing such a flow, and find out the corresponding stationary integral solutions. We find that depending on the values of initial boundary conditions, accretion flow may exhibit multi-transonic behaviour, and a standing shock may form. We investigate, in minute detail, how the spin angular momentum of the black hole, as well as the composition of the accreting matter influence the dynamics of accretion flow and the astrophysics of shock formation in the aforementioned accreting black hole systems.

Context. M dwarfs are an ideal laboratory for hunting Earth-like planets, and the study of chromospheric activity is an important part of this task. On the one hand, its short-term activity show high levels of magnetic activity that can affect habitability and make it difficult to detect exoplanets orbiting around them. But on the other hand, long-term activity studies can show whether these stars exhibit cyclical behavior or not in their activity, facilitating the detection of planets in those periods of low magnetic activity. Aims. The long-term cyclical behavior of magnetic activity can be detected studying several spectral lines and explained by different stellar dynamo models. In this work, we studied the Mount Wilson $S$-index to search for evidence of activity cycles possibly driven by a solar-type dynamo. Methods. We studied a sample of 35 dM with spectral classes ranging from dM0 to dM6. To perform this, we used 2965 spectra in the optical range to build time series with extensions of up to 21 years. We have analysed thesm with different time-domain techniques to detect cyclical patterns. In addition, we have also studied the potential impact of chromospheric activity on the surface brightness. Results. Using the color index (V-Ks), we have computed the chromospheric emission levels and we found that the majority of the stars in the sample have low emission levels. In this work, we have detected 13 potential activity cycles with a duration between 3 and 19 years and with false alarm probabilities (FAPs) less than 0.1%. For stars with non-cyclic behaviour, we have found that the mean value of the $S$-Index varies between 0.350 and 1.765 and its mean variability and chromospheric emission level are around 12% and -5.110 dex, respectively. We do not find any impact of chromospheric activity on the surface brightness in the domain of -5.6 < log $R'_{HK}$ < -4.5.

The Hilda population of asteroids is located in a large orbital zone of long-term stability associated with the Jupiter J3/2 mean motion resonance. They are a sister population of the Jupiter Trojans, since both of them are likely made up of objects captured from the primordial Kuiper belt early in the solar system history. Comparisons between the orbital and physical properties of the Hilda and Trojan populations thus represent a test of outer planet formation models. Here we use a decade of observations from the Catalina Sky Survey (G96 site) to determine the bias-corrected orbital and magnitude distributions of Hildas. We also identify collisional families and the background population by computing a new catalog of synthetic proper elements for Hildas. We model the cumulative magnitude distribution of the background population using a local power-law representation with slope $\gamma(H)$, where $H$ is the absolute magnitude. For the largest Hildas, we find $\gamma\simeq 0.5$ with large uncertainty due to the limited population. Beyond $H\simeq 11$, we find that $\gamma$ transitions to a mean value ${\bar \gamma}=0.32\pm 0.04$ with a slight dependence on $H$ (significantly smaller than Jupiter Trojans with ${\bar \gamma}=0.43\pm 0.02$). We find that members of identified collisional families represent more than $60$\% of the total population (both bias counts). The bias-corrected populations contain about the same number of Hildas within the families and the background for $H\leq 16$, but this number may increase to $60$\% families when their location in the orbital space is further improved in the future.

Numerical simulations of multidimensional astrophysical fluids present considerable challenges. However, the development of exascale computing has significantly enhanced computational capabilities, motivating the development of new codes that can take full advantage of these resources. In this article, we introduce HERACLES++, a new hydrodynamics code with high portability, optimized for exascale machines with different architectures and running efficiently both on CPUs and GPUs. The code is Eulerian and employs a Godunov finite-volume method to solve the hydrodynamics equations, which ensures accuracy in capturing shocks and discontinuities. It includes different Riemann solvers, equations of state, and gravity solvers. It works in Cartesian and spherical coordinates, either in 1-D, 2-D, or 3-D, and uses passive scalars to handle gases with several species. The code accepts a user-supplied heating or cooling term to treat a variety of astrophysical contexts. In addition to the usual series of benchmarking tests, we use HERACLES++ to simulate the propagation of a supernova shock in a red-supergiant star envelope, from minutes after core collapse until shock emergence. In 1-D, the results from HERACLES++ are in agreement with those of V1D for the same configuration. In 3-D, the Rayleigh-Taylor instability develops and modifies the 1-D picture by introducing density and composition fluctuations as well as turbulence. The focus on a wedge, rather than the full solid angle, and the ability of running HERACLES++ with a large number of GPUs allow for long-term simulations of 3-D supernova ejecta with a sub-degree resolution. Future development is to extend HERACLES++ to a radiation-hydrodynamics code.

This paper introduces Firmamento, a new online platform designed for astronomical research, particularly for studying blazars and other multi-messenger emitters. Firmamento provides access to a wealth of astronomical data, including imaging, spectral, and timing information, along with tools for data analysis and machine learning. A key feature is the Error Region Counterpart Identifier (ERCI), which helps locate potential counterparts to gamma-ray and other high-energy sources pinpointing objects exhibiting blazar-like characteristics. Firmamento grants access to spectral data across the entire electromagnetic spectrum, offering well-populated SED generation and VHE detectability estimation. The platform also supports user-provided data, allowing researchers to incorporate their own source lists.

Magnetars are the most magnetic objects in the Universe, serving as unique laboratories to test physics under extreme magnetic conditions that cannot be replicated on Earth. They were discovered in the late 1970s through their powerful X-ray flares, and were subsequently identified as neutron stars characterized by steady and transient emission across the radio, infrared, optical, X-ray, and gamma-ray bands. In this chapter, we summarize the current state of our experimental and theoretical knowledge on magnetars, as well as briefly discussing their relationship with supernovae, gamma-ray bursts, fast radio bursts, and the transient multi-band sky at large.

The detection of gravitational waves from binary black holes (BBHs) started the hunt for their pre-merger electromagnetic emission. In that respect, numerical simulations have been looking for the "smoking gun" signal that could help identify pre-merger systems. Here we study if any of the expected features of circumbinary discs, such as the periodic modulation from the orbiting "lump", could be used to identify pre-merger BBHs or if they could be easily confused with other systems. Indeed, while the timing feature associated with the "lump" seems to be present for a large part of the parameter space defined by the binary separation and mass ratio in circular binaries, it was recently proposed to form thanks to an instability occurring naturally at the edge of accretion discs around single black holes (SBH). In order to check if features of a circumbinary disc could be reproduced by a SBH system, we search for at least one SBH fit able to replicate the given synthetic observations of a circumbinary disc. We found that many of the features from a circumbinary disc can be reproduced by a SBH system with different masses, distances or inner disc positions. Interestingly, while we can always find a SBH model providing a good enough fit to the data, the presence of two variabilities, associated with the lump and the binary, or binary-lump beat, period, is a necessary condition for a wide range of BBH system parameters and should be used as a test to disqualify some BBH candidates.

Magnetic field investigations of Sun-like stars, using Zeeman splitting of non-polarised spectra, in the optical and H-band have found significantly different magnetic field strengths for the same stars, the cause of which is currently unknown. We aim to further investigate this issue by systematically analysing the magnetic field of $\xi$ Boo A, a magnetically active G7 dwarf, using spectral lines at different wavelengths. We used polarised radiative transfer accounting for the departures from local thermodynamic equilibrium to generate synthetic spectra. To find the magnetic field strengths in the optical, H-band, and K-band, we employed MCMC sampling analysis of high-resolution spectra observed with the spectrographs CRIRES$^+$, ESPaDOnS, NARVAL, and UVES. We also determine the formation depth of different lines by calculating the contribution functions for each line employed in the analysis. We find that the magnetic field strength discrepancy between lines in the optical and H-band persists even when treating the different wavelength regions consistently. In addition, the magnetic measurements derived from the K-band appear to more closely align with the optical. The H-band appears to yield magnetic field strengths $\sim$ 0.4 kG with a statistically significant variation while the optical and K-band is stable at $\sim$ 0.6 kG for observations spanning about two decades. The contribution functions reveal that the optical lines form at a significantly higher altitude in the photosphere compared to those in the H- and K-band. While we find that the discrepancy remains, the variation of formation depths could indicate that the disagreement between magnetic field measurements obtained at different wavelengths is linked to the variation of the magnetic field along the line of sight and between different structures, such as star spots and faculae, in the stellar photosphere.

The Pallas collisional family of asteroids, named after (2) Pallas, is notable for its high orbital inclination and the distinct blue color of Pallas and a few larger B-type family members. While Pallas itself, as one of the largest asteroids, has been studied in detail, most of its smaller family members still remain unexplored. This study aims to characterize the physical properties of medium- to small-sized Pallas family asteroids to investigate the origin of their unusual blueness. Additionally, we explore the relationship between the Pallas family and the near-Earth object (NEO) (3200) Phaethon. We conducted near-infrared (NIR) spectroscopy with the NASA Infrared Telescope Facility (IRTF) to collect reflectance spectra for 22 asteroids, including one from the IRTF Legacy Archive. Spectroscopic and dynamical analyses were carried out to identify outliers, while additional data from NEOWISE and Gaia were incorporated to examine potential correlations among their physical properties. Meteorite analogs were identified through chi-square matching using samples from the RELAB database. The observed Pallas family asteroids exhibit nearly identical spectral profiles, suggesting a homogeneous composition of ejected material. Small variations in spectral slopes are observed, which may result from different levels of alteration experienced by individual asteroids, with some influence from variations in grain size. Most of the observed spectra of the Pallas asteroids, from 0.8 to 2.2 micron, closely resemble those of the CY and CI meteorites. The blueness of asteroid surfaces is likely due to the presence of magnetite, troilite, or phyllosilicates, which are products of aqueous alteration. The striking spectral similarity between (3200) Phaethon and Pallas family members of comparable sizes suggests a potential common origin.

The study of the atmosphere of exoplanets orbiting white dwarfs is a largely unexplored field. With WD\,0806-661\,b, we present the first deep dive into the atmospheric physics and chemistry of a cold exoplanet around a white dwarf. We observed WD 0806-661 b using JWST's Mid-InfraRed Instrument Low-Resolution Spectrometer (MIRI-LRS), covering the wavelength range from 5 -- 12~$\mu \rm{m}$, and the Imager, providing us with 12.8, 15, 18 and 21\,$\mu$m photometric measurements. We carried the data reduction of those datasets, tackling second-order effects to ensure a reliable retrieval analysis. Using the \textsc{TauREx} retrieval code, we inferred the pressure-temperature structure, atmospheric chemistry, mass, and radius of the planet. The spectrum of WD 0806-661 b is shaped by molecular absorption of water, ammonia, and methane, consistent with a cold Jupiter atmosphere, allowing us to retrieve their abundances. From the mixing ratio of water, ammonia and methane we derive $\rm{C/O} = 0.34 \pm 0.06$, $\rm{C/N} = 14.4 ^{+2.5}_{-1.8}$ and $\rm{N/O} = 0.023 \pm 0.004$ and the ratio of detected metals as proxy for metallicity. We also derive upper limits for the abundance of CO and $\rm{CO_2}$ ($1.2\cdot10^{-6} \rm{\,and\,} 1.6\cdot10^{-7}$ respectively), which were not detected by our retrieval models. While our interpretation of WD\,0806-661\,b's atmosphere is mostly consistent with our theoretical understanding, some results -- such as the lack of evidence for water clouds, an apparent increase in the mixing ratio of ammonia at low pressure, or the retrieved mass at odds with the supposed age -- remain surprising and require follow-up observational and theoretical studies to be confirmed.

Low-luminosity Active Galactic Nuclei (AGN) are believed to be surrounded by a collisionless, highly magnetized accretion flow. As a result, Particle-in-Cell simulations are the best tools to study the immediate vicinity of the event horizons of these supermassive black holes. We present a GPU-based general relativistic particle-in-cell (GRPIC) code framework called Aperture. Aperture is developed in C++, with compute kernels written in CUDA and HIP to take advantage of the massive acceleration modern GPUs enable. The code is organized in a fully modular way, allowing easy extensions to new physics problems. In this paper, we describe in detail the particle pusher, field solver, and charge-conserving current deposition algorithms employed in Aperture, and present test cases to validate their correctness. Then, we apply the code to study spark gaps and plasma injection in black hole magnetospheres. We find that the apparent location and time-evolution of the gap depend on the observer. Our results reconcile the previous conflicting findings from 1D and 2D simulations in the literature.

Oph-S1 is the most luminous and massive stellar member of the nearby Ophiuchus star-forming region. Previous Very Long Baseline Array (VLBA) observations have shown it to be an intermediate-mass binary system ($\sim 5\,{\rm M}_\odot$) with an orbital period of about 21 months, but a paucity of radio detections of the secondary near periastron could potentially have affected the determination of its orbital parameters. Here, we present nine new VLBA observations of Oph-S1 focused on its periastron passage in early 2024. We detect the primary in all observations and the secondary at five epochs, including three within about a month of periastron passage. The updated orbit, determined by combining our new data with 35 previous observations, agrees well with previous calculations and yields masses of $4.115 \pm0.039 \,{\rm M}_\odot$ and $0.814\pm0.006 \,{\rm M}_\odot$ for the two stars in the system.

The Wide Field Camera 3 (WFC3) instrument on the Hubble Space Telescope has provided an abundance of exoplanet spectra over the years. These spectra have enabled analysis studies using atmospheric retrievals to constrain the properties of these objects. However, follow-up observations from the James Webb Space Telescope have called into question some of the results from these older datasets, and highlighted the need to properly understand the degeneracies associated with retrievals of WFC3 spectra. In this study, we perform atmospheric retrievals of 38 transmission spectra from WFC3 and use model comparison to determine the complexity required to fit the data. We explore the effect of retrieving system parameters such as the stellar radius and planet's surface gravity, and thoroughly investigate the degeneracies between individual model parameters -- specifically the temperature, abundance of water, and cloud-top level. We focus on three case studies (HD 209458b, WASP-12b, and WASP-39b) in an attempt to diagnose some of the issues with these retrievals, in particular the low retrieved temperatures when compared to the equilibrium values. Our study advocates for the careful consideration of parameter degeneracies when interpreting retrieval results, as well as the importance of wider wavelength coverage to break these degeneracies, in agreement with previous studies. The combination of data from multiple instruments, as well as analysis from multiple data reductions and retrieval codes, will allow us to robustly characterise the atmosphere of these exoplanets.

We analyse pre-DESI clustering data using a dark energy equation of state $w(z)$ parametrised by $(w_0, w_a)$, finding a $2.8-3.9\sigma$ preference for evolving dark energy over the cosmological constant $\Lambda$ when combined with cosmic microwave background data from Planck and supernova data from Pantheon+, Union3, or DESY5. Our constraints, consistent with DESI Y1 results, are derived from the power spectrum and bispectrum of SDSS/BOSS galaxies using the Effective Field Theory of Large Scale Structure (EFTofLSS) at one loop. The evidence remains robust across analysis variations but disappears without the one-loop bispectrum. When combining DESI baryon acoustic oscillations with BOSS full-shape data, while marginalising over the sound horizon in the latter to prevent unaccounted correlations, the significance increases to $3.7-4.4\sigma$, depending on the supernova dataset. Using a data-driven reconstruction of $w(z)$, we show that the evidence arises from deviations from $\Lambda$ at multiple redshifts. In addition, our findings are interpreted within the Effective Field Theory of Dark Energy (EFTofDE), from which we explicitly track the non-standard time evolution in EFTofLSS predictions. For perturbatively stable theories in the $w < -1$ regime, the evidence persists in the clustering limit $(c_s^2 \rightarrow 0)$ when higher-derivative corrections are present, as well as in the quasi-static limit $(c_s^2 \rightarrow 1)$ when additional EFTofDE parameters are considered.

Ultralight Dark Matter (ULDM) offers an alternative to cold dark matter, characterized by wavelike behavior on galactic scales. This contribution summarizes our work~\cite{Blas:2024duy} on how solitonic cores induced by ULDM affect gravitational waves (GWs), enabling their detection through next-generation observatories like LISA, Einstein Telescope and Cosmic Explorer. We show that continuous GWs from spinning neutron stars near the Galactic Center (GC) can probe solitons for \(m \lesssim 10^{-22}\, \mathrm{eV}\) and surpass current constraints on the ULDM couplings to the Standard Model for masses \(m \lesssim 10^{-20}\, \mathrm{eV}\). Additionally, GW modulation could reveal solitons in extragalactic systems, particularly in more massive halos, highlighting the broad potential of GW-based methods for uncovering ULDM properties.

Blazars are interesting source candidates for astrophysical neutrino emission. Multi-messenger lepto-hadronic models based on proton-photon (p-gamma) interactions result in predictions for the neutrino spectra which are typically strongly peaked at high energies. In contrast, statistical analyses looking to associate blazars and neutrinos often assume a power-law spectral shape, putting the emphasis at lower energies. We aim to examine the impact of such spectral modelling assumptions on the associations of neutrinos with blazars. We use hierarchical_nu, a Bayesian framework for point source searches, and incorporate the theoretical predictions for neutrino spectra through a dedicated spectral model and priors on the relevant parameters. Our spectral model is based on the predictions presented in Rodrigues et al. (2024) for a selection of intermediate and high synchrotron peaked blazars that have been connected with IceCube neutrino alert events. We apply our model to the 10 years of publicly available IceCube data, focusing on the Northern hemisphere. Out of 29 source candidates, we find five sources, including TXS 0506+056, that have an association probability greater than 0.5 to at least one event. The p-gamma spectra typically lead to a lower overall number of associated events compared to the power-law case, but retain or even enhance strong associations to high-energy events. Our results demonstrate that including more information from theoretical predictions can allow for more interpretable source-neutrino connections.

The birth of giant planets in protoplanetary disks is known to alter the structure and evolution of the disk environment, but most of our knowledge focuses on its effects on the observable gas and dust. The impact on the evolution of the invisible planetesimal population is still limitedly studied, yet mounting evidence from the Solar System shows how the appearance of its giant planets played a key role in shaping the habitability of the terrestrial planets. We investigate the dynamical and collisional transport processes of volatile elements by planetesimals in protoplanetary disks that host young giant planets using the HD163296 system as our case study. HD163296 is one of the best characterised protoplanetary disks that has been proposed to host at least four giant planets on wide orbits as well as a massive planetesimal disk. The formation of giant planets in the HD163296 system creates a large population of dynamically excited planetesimals, the majority of which originate from beyond the CO snowline. The excited planetesimals are both transported to the inner disk regions and scattered outward beyond the protoplanetary disk and into interstellar space. Existing solid planets can be enriched in volatile elements to levels comparable or larger than those of the Earth, while giant planets can be enriched to the levels of Jupiter and Saturn. The formation of giant planets on wide orbits impacts the compositional evolution of protoplanetary disks and young planetary bodies on a global scale. The collisional enrichment of the atmospheres of giant planets can alter or mask the signatures of their formation environments, but can provide independent constraints on the disk mass. Protoplanetary disks with giant planets on wide orbits prove efficient factories of interstellar objects.

We study the cosmological signatures of new light relics that are collisionless like standard neutrinos or are strongly interacting. We provide a simple and succinct rephrasing of their physical effects in the cosmic microwave background, as well as the resulting parameter degeneracies with other cosmological parameters, in terms of the total radiation abundance and the fraction thereof that freely streams. In these more general terms, interacting and noninteracting light relics are differentiated by their respective decrease and increase of the free-streaming fraction, and, moreover, the scale-dependent interplay thereof with a common, correlated reduction of the fraction of matter in baryons. We then derive updated constraints on various dark-radiation scenarios with the latest cosmological observations, employing this language to identify the physical origin of the impact of each dataset. The "PR4" reanalyses of Planck CMB data prefer a larger primordial helium yield and therefore also slightly more radiation than the 2018 analysis, whose origin we identify in a number of poorly fit polarization measurements. Smaller free-streaming fractions are disfavored by the excess lensing of the CMB measured in lensing reconstruction data from Planck and the Atacama Cosmology Telescope. On the other hand, baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument drive marginal detections of new, strongly interacting light relics due to that data's preference for lower matter fractions. Finally, we forecast measurements from the CMB-S4 experiment.

White dwarfs (WD) with main-sequence (MS) companions are crucial probes of stellar evolution. However, due to the significant difference in their luminosities, the WD is often outshined by the MS star. The aim of this work is to find hidden companions in Gaia's sample of single WD candidates. Our methodology involves applying an unsupervised machine learning algorithm for dimensionality reduction and clustering, known as Self-Organizing Map (SOM), to Gaia BP/RP (XP) spectra. This strategy allows us to naturally separate WDMS binaries from single WDs from the detection of subtle red flux excesses in the XP spectra that are indicative of low-mass MS companions. We validate our approach using confirmed WDMS binary pairs from the SDSS and LAMOST surveys, achieving a precision of $\sim 90\%$. Applying our SOM to 90,667 sources, we identify 993 WDMS candidates, 801 of which have not been previously reported in the literature. If confirmed, our sample will increase the known WDMS binaries by $20\%$, making it a valuable source for stellar evolution studies. Additionally, we use the Virtual Observatory Spectral Energy Distribution Analyzer (VOSA) tool to further refine and parameterize a "golden sample" of 136 WDMS candidates through multi-wavelength photometry and a two-body Spectral Energy Distribution fitting. These high-confidence WDMS binaries are composed by low-mass WDs ($\sim 0.41 M_{\odot}$), with cool MS companions ($\sim 2800$ K). Finally, 13 systems exhibit periodic variability consistent with eclipsing binaries, making them prime targets for further follow-up observations.

The level and uncertainty of the particle induced background in CCD detectors plays a crucial role for future X-ray instruments, such as the Wide Field Imager (WFI) onboard Athena. To mitigate the background systematic uncertainties, which will limit the Athena science goals, we aim to understand the relationship between the energetic charged particles interacting in the detector and satellite, and the instrumental science background to an unprecedented level. These particles produce easily identified "cosmic-ray tracks" along with less easily identified signals produced by secondary particles, e.g., X-rays generated by particle interactions with the instrument and indistinguishable from genuine sky X-rays. We utilize the Small Window Mode of the PN camera onboard XMM-Newton to understand the time, spatial and energy dependence of the various background components, particularly the particle induced background. While the distribution of particle events follows expected detector readout patterns, we find a particle track length distribution inconsistent with the simple, isotropic model. We also find that the detector mode-specific readout results in a shifted Cu fluorescent line. We illustrate that on long timescales the variability of the particle background correlates well with the solar cycle. This 20-year lightcurve, can be reproduced by a particle detector onboard Chandra, the HRC anti-coincidence shield. We conclude that the self-anti-coincidence method of removing X-ray-like events near detected particle tracks in the same frame can be optimized with the inclusion of additional information, such as the energy of the X-ray. The results presented here are relevant for any future pixelated X-ray imaging detector, and could allow the WFI to probe to truly faint X-ray surface brightness.

We present simple analytic corrections to the standard blackbody fitting used for early kilonova emission. We consider a spherical, relativistically expanding shell that radiates thermally at a single temperature in its own rest frame. Due to relativistic effects, including Doppler boosting, time delay, and temperature evolution -- the observed temperature is smeared across different polar angles by approximately $\sim10\%$. While the observed spectrum remains roughly consistent with a single-temperature blackbody, neglecting relativistic effects leads to significant systematic inaccuracies: the inferred photospheric velocity and temperature are overestimated by up to $\sim50\%$ for mildly relativistic velocities. By applying our analytic corrections, these deviations are reduced to within $10\%$, even in cases where the photosphere is receding and cooling is considered. Applying our corrections to observed kilonovae (AT2017gfo and the thermal component of GRB211211A) reveals that standard blackbody fitting overestimated the inferred velocities and temperatures by $10\%-40\%$.

The increasing precision of Cosmic Microwave Background (CMB) observations has unveiled significant tensions between different datasets, notably between Planck and the Atacama Cosmology Telescope (ACT), as well as with the late-Universe measurements of the Hubble constant. In this work, we explore a variety of $\Lambda$CDM extensions to assess their ability to reconcile these discrepancies. The statistical preference for these extensions remains moderate, and imposing $n_s=1$ often worsens model performance. Our findings highlight the limitations of incremental modifications to $\Lambda$CDM and suggest that either more complex new physics or, more likely, improved systematic understanding in the CMB sector may be required to fully address the observed tensions. While CMB experiments are often considered the gold standard of precision cosmology, our results reinforce that these measurements are not immune to systematic uncertainties, which may be underestimated in current analyses.

We present a study on using delensing to enhance cosmic birefringence measurements based on full-sky, map-based simulations. In our analysis, we neglect foreground contamination and instrumental systematics to isolate the intrinsic impact of delensing on both isotropic and anisotropic birefringence. For the isotropic case, assuming a constant rotation angle of $\beta = 0.35^\circ$, delensing reduces the lensing-induced variance in the EB power spectrum, yielding an improvement in sensitivity of approximately 10% at 6 $\mu$K-arcmin noise and 25-40% at lower noise levels. For the anisotropic case, using simulations at 1 $\mu$K-arcmin noise, we reconstruct the birefringence angle for a scale-invariant spectrum and mitigate lensing bias by delensing, achieving a 50% reduction in the leading $N_{(0)}$ bias and a 30% improvement in the constraints on the amplitude $A_{CB}$. Our results demonstrate that delensing is an effective tool for enhancing the detectability of subtle parity-violating signals in the cosmic microwave background with forthcoming experiments such as the Simons Observatory, CMB-S4, and LiteBIRD.

Based on the iron and hydrogen similar elliptical morphologies of the type Ia supernova (SN Ia) remnant (SNR) 0509-67.5, I suggest that the ambient gas shaped the SN ejecta, that it is a remnant of an old planetary nebula, and that the explosion was more or less spherical. Adding that there is no observed stellar survivor in this SNR, I conclude that the SN Ia scenarios that best account for the explosion of this SN inside a planetary nebula (SNIP), are the lonely white dwarf scenarios, i.e., the core-degenerate (CD) and the double degenerate (DD) with merger to explosion delay (MED) time, i.e., the DD-MED scenario. Other scenarios encounter challenges, but I cannot completely rule them out. If true, the suggestion of SNR~0509-67.5 being a SNIP implies that the fraction of SNIPs might be higher than the previously estimated 50 percent of all normal SNe Ia. In the frame of the CD and the DD-MED scenarios, I attribute the observed double-shell structure in calcium to Rayleigh-Taylor instability during the explosion process: the caps of the Rayleigh-Taylor instability mushrooms form the outer shell. Instabilities during the explosion process might form clumps of some elements moving much faster than their mean velocity, possibly explaining fast-moving intermediate-mass elements.

It has been known for many years that there is an apparent trend for the spectral index ({\alpha}) of radio sources to steepen with redshift z, which has led to attempts to select high-redshift objects by searching for radio sources with steep spectra. In this study we use data from the MeerKAT, LOFAR, GMRT, and uGMRT telescopes, particularly using the MIGHTEE and superMIGHTEE surveys, to select compact sources over a wide range of redshifts and luminosities. We investigate the relationship between spectral index, luminosity and redshift and compare our results to those of previous studies. Although there is a correlation between {\alpha} and z in our sample for some combinations of frequency where good data are available, there is a clear offset between the {\alpha}-z relations in our sample and those derived previously from samples of more luminous objects; in other words, the {\alpha}-z relation is different for low and high luminosity sources. The relationships between {\alpha} and luminosity are also weak in our sample but in general the most luminous sources are steeper-spectrum and this trend is extended by samples from previous studies. In detail, we argue that both a {\alpha}-luminosity relation and an {\alpha}-z relation can be found in the data, but it is the former that drives the apparent {\alpha}-z relation observed in earlier work, which only appears because of the strong redshift-luminosity relation in bright, flux density-limited samples. Steep-spectrum selection should be applied with caution in searching for high-z sources in future deep surveys.

Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or geometric configuration variation in a binary system. Here we report an abrupt magneto-ionic environment variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift 0.1839. Initially, its Faraday rotation measure (RM) was $21 \pm 96~{\rm rad~m^{-2}}$ over 17 months. In December 2023, it jumped to $1976.9~{\rm rad~m^{-2}}$, exceeding twenty times of the standard deviation of the previous RM variation, and returned to the typical values within two weeks. Such a drastic RM variation suggests a dense magnetized clump moving across the line of sight, possibly due to coronal mass ejection associated with a stellar flare. It indicates that the FRB likely has a companion star that produced the stellar flare.

This work introduces a novel deep learning-based approach for gravitational wave anomaly detection, aiming to overcome the limitations of traditional matched filtering techniques in identifying unknown waveform gravitational wave signals. We introduce a modified convolutional neural network architecture inspired by ResNet that leverages residual blocks to extract high-dimensional features, effectively capturing subtle differences between background noise and gravitational wave signals. This network architecture learns a high-dimensional projection while preserving discrepancies with the original input, facilitating precise identification of gravitational wave signals. In our experiments, we implement an innovative data augmentation strategy that generates new data by computing the arithmetic mean of multiple signal samples while retaining the key features of the original signals. In the NSF HDR A3D3: Detecting Anomalous Gravitational Wave Signals competition, it is honorable for us (group name: easonyan123) to get to the first place at the end with our model achieving a true negative rate (TNR) of 0.9708 during development/validation phase and 0.9832 on an unseen challenge dataset during final/testing phase, the highest among all competitors. These results demonstrate that our method not only achieves excellent generalization performance but also maintains robust adaptability in addressing the complex uncertainties inherent in gravitational wave anomaly detection.

We study the $1+1$ flat spacetime dynamics of a classical field configuration corresponding to an ensemble of sine-Gordon kinks and antikinks, semi-classically coupled to a quantum field. This coupling breaks the integrability of the sine-Gordon model resulting in the background's decay into quantum radiation as kink-antikink pairs annihilate. We find evidence that, on average, the energy of the ensemble scales as $t^{-\alpha}$ with $\alpha<1$ and independent of the coupling strength or the mass of the quantum field. The generalization of this result to domain wall networks in higher spacetime dimensions could be relevant to particle production in the early universe.

We constrain the neutrino-dark matter cross-section using the $13 \pm 5$ neutrino event excess observed by IceCube in 2014-2015 from the direction of the blazar TXS 0506+056. Our analysis takes advantage of the dark matter overdensity spike surrounding the supermassive black hole at the center of the blazar. In our results, we take into account uncertainties related to the different types of neutrino emission models and the features of the dark matter spike, considering cross-sections that scale with energy as $\sigma \propto (E_{\nu} /E_0)^n$, for values of $n = 1, 0, -1, -2$. In our best-case scenario, we obtain limits competitive with those derived from other active galaxies, tidal disruption events (TDEs), and the IC-170922A event.

In order to explain the large amplitude of the nano-Hertz stochastic gravitational wave background observed in pulsar timing arrays (PTA), primordial sources must be particularly energetic. This is correlated to the generation of large density fluctuations, later collapsing into ultra-compact mini-halo (UCMHs). We demonstrate that if dark matter is made of WIMPs, then photon and neutrino fluxes from UCMHs produced by curvature peaks, first-order phase transition and domain wall interpretations of the PTA signal, exceed current bounds.

The next generation of gravitational-wave observatories will achieve unprecedented strain sensitivities with an expanded observing band. They will detect ${\cal O}(10^5)$ binary neutron star (BNS) mergers every year, the loudest of which will be in the band for $\approx 90$ minutes with signal-to-noise ratios $\approx 1500$. Current techniques will not be able to determine the astrophysical parameters of the loudest of next-gen BNS signals. We show that subtleties arising from the rotation of the Earth and the free-spectral range of gravitational-wave interferometers dramatically increases the complexity of next-gen BNS signals compared to the one-minute signals seen by LIGO--Virgo. Various compression methods currently relied upon to speed up the most expensive BNS calculations -- reduced-order quadrature, multi-banding, and relative binning -- will no longer be effective. We carry out reduced-order inference on a simulated next-gen BNS signal taking into account the Earth's rotation and the observatories' free-spectral range. We show that standard data compression techniques become impractical, and the full problem becomes computationally infeasible, when we include data below $\approx 16$Hz -- a part of the observing band that is critical for precise sky localisation. We discuss potential paths towards solving this complex problem.

The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling evidence for their role as a dark matter candidate, particularly through the observation of their Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-the-SM particle emissions. A particularly promising avenue involves production of dark photons by PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the trident decay of dark photons focusing on their primary emission from PBHs. We assume that the dark photons produced via Hawking radiation decay into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The energy spectrum of the photons decaying from the dark photons is distinct from that of direct Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in the gamma-ray signal. Using the asteroid-mass PBHs as a case study, we demonstrate that future gamma-ray missions could detect dark-photon signatures and distinguish them from conventional Hawking radiation. This approach enables the exploration of previously inaccessible parameter spaces in dark photon mass $m_{A^{\prime}}$ and their coupling to photons, offering a novel pathway to uncover the properties of dark sectors and the nature of PBHs.

We present the first extensive analysis of K/Ka-band ranging post-fit residuals of an official Level-2 product, characterised as Line-of-Sight Gravity Differences (LGD), which exhibit and showcase interesting sub-monthly geophysical signals. These residuals, provided by CSR, were derived from the difference between spherical harmonic coefficient least-squares fits and reduced Level-1B range-rate observations. We classified the geophysical signals into four distinct categories: oceanic, meteorological, hydrological, and solid Earth, focusing primarily on the first three categories in this study. In our examination of oceanic processes, we identified notable mass anomalies in the Argentine basin, specifically within the Zapiola Rise, where persistent remnants of the rotating dipole-like modes are evident in the LGD post-fit residuals. Our analysis extended to the Gulf of Carpentaria and Australia during the 2013 Oswald cyclone, revealing significant LGD residual anomalies that correlate with cyclone tracking and precipitation data. Additionally, we investigated the monsoon seasons in Bangladesh, particularly from June to September 2007, where we observed peaks in sub-monthly variability. These findings were further validated by demonstrating high spatial and temporal correlations between gridded LGD residuals and ITSG-Grace2018 daily solutions. Given that these anomalies are associated with significant mass change phenomena, it is essential to integrate the post-fit residuals into a high-frequency mass change framework, with the purpose of providing enhanced spatial resolution compared to conventional Kalman-filtered methods.

The velocity-dependent Newtonian analogous potentials (NAPs) corresponding to general relativistic (GR) spacetimes accurately capture most of the relativistic features, including all classical tests of GR, effectively representing spacetime geometries in Newtonian terms. The NAP formulated by Tejeda \& Rosswog (TR13) for Schwarzschild spacetime has been applied to the standard thin accretion disk around a black hole (BH) as well as in the context of streamlines of noninteracting particles accreting onto a Schwarzschild BH, showing good agreement with the exact relativistic solutions. As a further application, here we explore the extent to which TR13 NAP could describe a transonic hydrodynamical spherical accretion flow in Schwarzschild spacetime within the framework of standard Newtonian hydrodynamics. Instead of obtaining a typical single "saddle-type" sonic transition, a "saddle-spiral pair" is produced, with the inner sonic point being an (unphysical) "spiral type" and the outer being a usual "saddle type." The Bondi accretion rate at outer sonic radii, however, remains consistent with that of the GR case. The primary reason for the deviation of our findings from the classical Bondi solution is likely due to the inconsistency between the Euler-type equation in the presence of velocity-dependent TR13 NAP within the standard Newtonian hydrodynamics framework, and the corresponding GR Euler equation, regardless of the fluid's energy. Our study suggests that a (modified) hydrodynamical formalism is needed to effectively implement such potentials in transonic accretion studies that align with the spirit of TR13-like NAP, while remaining consistent with the GR hydrodynamics. This could then essentially circumvent GR hydrodynamics or GR magnetohydrodynamics equations.

In this work, we investigate the tidal deformability of regular black holes (RBHs). Employing different phenomenological models, we analyze their response to both test fields and gravitational perturbations, interpreting the latter within the framework of Einstein's field equations in the presence of an appropriate exotic matter distribution. Numerical and analytical methods reveal that RBHs exhibit non-trivial tidal responses, influenced by their regularization parameters and exotic matter distributions. The results obtained for test fields and gravitational perturbations are in qualitative agreement. This hints at the possibility that similar conclusions could hold if these spacetimes were interpreted as solutions of a modified gravitational action. Our findings suggest that RBHs possess distinct, though subtle, tidal signatures, which may serve as observational probes of their internal structure in gravitational wave detections.

The recent observation of the ultra-high-energy neutrino event KM3-230213A by the KM3NeT experiment offers a compelling avenue to explore physics beyond the Standard Model. In this work, we explore a simplest possibility that this event originates from the decay of a super-heavy dark matter (SHDM). We consider a minimal extension of the type-I seesaw by including a singlet scalar and a singlet fermion DM, both being odd under a $Z_2$ symmetry. At high scale, the $Z_2$ symmetry is spontaneously broken by the vev of the $Z_2$ odd scalar, leading to i) mixing between DM and heavy right-handed neutrinos and ii) formation of domain walls (DW). In the former case, the decay of the DM to $\nu,h$ can give rise to the PeV neutrino event KM3-230213A. While, in the latter case, the disappearance of the DW can give rise to stochastic gravitational waves. We derive constraints on the DM lifetime as a function of DM mass ensuring consistency with IceCube, Auger upper limits and the observed KM3-230213A event. We found that KM3-230213A gives stringent constraint on DM mass ranging from $1.7\times10^8$ GeV to $5.5\times10^9$ GeV with lifetime $6.3\times10^{29}$ s to $3.6\times10^{29}$ s.

In recent years, numerous experiments have been proposed and conducted to search for ultralight bosonic dark matter (ULBDM). Signals from ULBDM in such experiments are characterized by extremely narrow spectral widths. A near-optimal detection strategy is to divide the data based on the signal coherence time and sum the power across these segments. However, the signal coherence time can extend beyond a day, making it challenging to construct contiguous segments of such a duration due to detector instabilities. In this work, we present a novel detection statistic that can coherently extract ULBDM signals from segments of arbitrary durations. Our detection statistic, which we refer to as coherent SNR, is a weighed sum of data correlations, whose weights are determined by the expected signal correlations. We demonstrate that coherent SNR achieves sensitivity independent of segment duration and surpasses the performance of the conventional incoherent-sum approach, through analytical arguments and numerical experiments.

Identifying weak gravitational wave signals in noise and estimating the source properties require high-precision waveform templates. Numerical relativity (NR) simulations can provide the most accurate waveforms. However, it is challenging to compute waveform templates in high-dimensional parameter space using NR simulations due to high computational costs. In this work, we implement a novel waveform mapping method, which is an alternative approach to the existing analytical approximations, based on closed-form continuous-time neural networks. This machine-learning-based method greatly improves the efficiency of calculating waveform templates for arbitrary source parameters, such as the binary mass ratio and the spins of component black holes. Based on this method, we present \textit{BHP2NRMLSur}, a class of models (including nonspinning and spin-aligned ones) that maps point-particle black hole perturbation theory waveforms into NR and surrogate waveforms. The nonspinning model provides highly accurate waveforms that match the NR waveforms to the level of $\gtrsim 0.995$. The spin-aligned model reduces the required input parameters and hence improves the efficiency of the waveform generation -- it takes a factor of $\sim 50$ less time than existing NR surrogate models to generate $100,000$ waveforms, with a mismatch of $<0.01$ compared to the NR waveforms from the Simulating eXtreme Spacetimes collaboration.

In this article, we consider Dark Matter (DM) interactions, and study the same in the light of the Cosmic Microwave Background Radiation (CMBR) data. In particular, we focus on the DM-electron interactions. Assuming that such interactions are mediated by rather heavy mediators, we consider effective operators describing the relevant interaction terms in the lagrangian. The presence of such interaction terms lead to both DM annihilation and DM-electron scattering (drag). We focus on operators which lead to velocity-independent DM annihilation and DM-electron scattering cross-sections. Using the CMBR data, we study the the implications of both of these effects imposing constraints on the respective effective operators. This analysis underscores the importance of taking both scattering and annihilation processes into consideration in the study of DM interactions. We observe that the constraints on the DM annihilation and scattering cross-sections can change, up to about 14% and 13% respectively, for the benchmark scenarios we considered, depending on the mass of DM, as compared to the scenario where only DM annihilation is accounted for.

We obtain stringent bounds on neutrino quantum decoherence from the analysis of SN1987A data. We show that for the decoherence model considered here, which allows for neutrino-loss along the trajectory, the bounds are many orders of magnitude stronger than the ones that can be obtained from the analysis of data from reactor neutrino oscillation experiments or neutrino telescopes.

We investigate the indirect detection search of the two-body decay of dark matter particles into final states containing a photon, a process predicted in various promising dark matter models such as axion-like particles and sterile neutrinos. Recent and near-future photon detectors with a resolution $ R \equiv \lambda/\Delta\lambda = O(1000) $ are primarily optimized for the velocity dispersion of dark matter in the Milky Way. When performing indirect detection of dark matter in objects other than the Milky Way, one should take into account the contribution from Milky Way dark matter. As a result, the dark matter signal observed by a detector is predicted to exhibit a two-peak structure in many targets, owing to the Doppler shift, differences in radial velocities and the good energy resolution. An analysis incorporating this two-peak effect was performed using the latest XRISM observation data of the Centaurus galaxy cluster~\cite{XRISM:2025axf}. Although, due to the relatively short observation time, our derived limit is weaker than some existing limits, among dark matter searches in galaxy clusters our limit is one of the most stringent (at least in certain mass ranges). We also perform the usual single-peak analysis, for considering the various scenarios, that prefer narrow-line photon from the faraway galaxy cluster. Future data releases from XRISM as well as other observatories will further strengthen our conclusions.