Papers for Wednesday, Jul 02 2025

Catalog maintenance of space objects by limited number of ground-based sensors presents a formidable challenging task to the space community. This article presents a methodology for time-invariant tracking and surveillance of space objects in low Earth orbit (LEO) by optimally directing ground sensors. Our methodology aims to maximize the expected number of space objects from a set of ground stations by utilizing concepts from stochastic geometry, particularly the Poisson point process. We have provided a systematic framework to understand visibility patterns and enhance the efficiency of tracking multiple objects simultaneously. Our approach contributes to more informed decision-making in space operations, ultimately supporting efforts to maintain safety and sustainability in LEO.

We demonstrates that the single-field inflation field system exhibits a symmetry that constrains its evolution via the Ward identity even for non-attractor inflation. By analyzing loop diagram structures, we derive a superhorizon conserved quantity directly related to the two-point correlation function of curvature perturbations, generalizing previous one-loop results to arbitrary loop orders. This symmetry-based approach provides a framework for understanding quantum conservation laws beyond the leading perturbative order.

Origins of life research is marred by ambiguous questions and goals, creating uncertainty about when research objectives have been achieved. Because of numerous unknowns and disagreements about definitions and theories, the field lacks clear markers of progress. We argue that the origins community should focus on goals that have agreed-upon meaning and can be consensually categorized as achieved or unachieved. The origins community needs these goals to maintain coherence amongst a federation of problems with the shared, but nebulous aspiration of understanding the origins of life. We propose a list of challenges with clear 'Finish Lines'--explicit descriptions of what will be achieved if each goal is reached--similar to the X-prize model. The intent is not to impose top-down research directions, but to compel the community to coalesce around explicit problems of the highest priority, as physics, astronomy, and planetary science communities do when setting science objectives for missions and megaprojects. Even if the generated phenomena are not unequivocally life-like, demonstrating systems that achieve these goals will sharpen the distinction between life itself and the constellation of phenomena that co-occur with life. This document was originally submitted as a whitepaper to the 2025 NASA-DARES (Decadal Astrobiology Research and Exploration Strategy) call for whitepapers (this https URL).

Brightness statistics for satellites of the Starlink, BlueBird, Qianfan, Guowang and OneWeb constellations are reported. The means and standard deviations are compared to acceptable limits set by the International Astronomical Union's Centre for the Protection of the Dark and Quiet Sky From Satellite Constellations Interference. Nearly all these spacecraft exceed the magnitude 7+ brightness limit pertaining to interference with professional research. Most also exceed the magnitude 6 reference where they distract from aesthetic appreciation of the night sky.

Magnetic fields permeate the Universe, including galaxy clusters, and affect the thermodynamical properties of the intra-cluster medium (ICM). Cosmological simulations predict that seed magnetic fields are amplified up to the $\mu$G-level in the ICM, but the magnetic field strength and structure have been studied in only a few clusters. Abell 2142 is a local massive cluster that shows evidence of a post-merger dynamical state. In this work, we aim to constrain the magnetic field intensity, radial profile and power spectrum within its ICM, providing key insights into the nature of this non-thermal component in galaxy clusters. We present MeerKAT observations of Abell 2142 in the L-band (872-1712 MHz), imaged in polarisation for the first time with this purpose. We derive the Rotation Measure (RM) from the radio galaxies' polarised emission by applying the RM synthesis technique and analyse both the RM and fractional polarisation ($\mathrm{F_p}$). To investigate the magnetic field distribution within the ICM, we compare our results with mock RM maps generated from 3D simulations of the cluster. We find that the RM dispersion, $\sigma_{\mathrm{RM}}$, decreases with projected radius, whereas the $\mathrm{F_p}$ increases. Both trends suggest that the magnetic field intensity decreases at larger distances from the cluster center, in agreement with studies on other clusters. Assuming that the magnetic field energy density scales with the gas thermal energy ($B \propto n_e^{0.5}$), a magnetic field with a power spectrum ranging from scales between 7 and 470 kpc, with peak at $\sim 140$ kpc and mean central strength of $9.5 \pm 1.0 \ \mu$G, provides the best fit to our data. The high central magnetic field lies at the upper end of the range observed in other systems and supports the possibility of an hadronic contribution to the diffuse radio emission previously detected at the cluster center.

We analyze the basic cosmological effects of a population of timelike boundaries -- a form of nontrivial spacetime topology -- containing a boundary layer of quantum stress energy. This accumulation of vacuum fluctuations of quantum fields can be consistently negative and UV sensitive, providing an additional source of cosmic energy density strong enough to compete with matter and dark energy. For boundary conditions enabling a solution with fixed comoving boundary size, this effect contributes a qualitatively new term to the Friedmann equation determining the expansion history, scaling like $-1/a$ for scale factor $a$. It naturally dominates at relatively late times ($a\approx1/2$), while leaving intact well-measured early universe physics such as big bang nucleosynthesis and recombination. For a wide window of parameters, the boundaries can be larger than the Planck length throughout their history, back through the start of inflation at any viable scale. We analyze CMB and BAO data sets (Planck, ACT, and DESI) allowing for this component, finding a slight preference ($\sim 2\sigma$) and a relaxation of current tensions in the data (including the neutrino mass) in a physical manner. This novel parameter fits into a larger space of physical parameters beyond-$\Lambda$CDM that may serve this role, including negative spatial curvature, which may also be motivated by topological considerations and chaotic dynamics. Finally, we comment on additional phenomenological prospects for testing for this form of topology in the universe.

Context: Inferring the likely formation channel of giant exoplanets and brown dwarf companions from orbital and atmospheric observables remains a formidable challenge. Further and more precise directly measured dynamical masses of these companions are required to inform and gauge formation, evolutionary, and atmospheric models. We present an updated study of HIP 99770 b based on observations conducted with VLTI/GRAVITY. Aims: Combining the new data with previous observations from the literature, we characterise HIP 99770 b to better constrain its orbit, dynamical mass, and atmospheric properties, as well as to shed light on its likely formation channel. Methods: We ran a renewed orbit fit to further constrain the dynamical mass of the companion and the orbit solution. We also analysed the GRAVITY K-band spectrum, placing it into context with literature data, and extracting magnitude, age, spectral type, bulk properties and atmospheric characteristics of HIP 99770 b. Results: We detected the companion at a radial separation of $417\,\mathrm{mas}$ from its host. The new orbit fit yields a dynamical mass of $17_{-5}^{+6}\,\mathrm{M}_\mathrm{Jup}$ and an eccentricity of $0.31_{-0.12}^{+0.06}$. We also find that additional relative astrometry epochs in the future will not enable further constraints on the dynamical mass due to the dominating relative uncertainty on the Hipparcos-Gaia proper motion anomaly. The publication of Gaia DR4 will likely ease this predicament. We find that the companion is consistent with spectral type L8 and exhibits a potential metal enrichment in its atmosphere. Conclusions: These results do not yet allow for a definite inference of the companion's formation channel. Nevertheless, the new constraints on its bulk properties and the additional GRAVITY spectrum presented here will aid future efforts to determine the formation history of HIP 99770 b.

The effective-field theory based full-shape analysis with simulation-based priors (EFT-SBP) is the novel analysis of galaxy clustering data that allows one to combine merits of perturbation theory and simulation-based modeling in a unified framework. In this paper we use EFT-SBP with the galaxy clustering power spectrum and bispectrum data from BOSS in order to test the recent preference for dynamical dark energy reported by the DESI collaboration. While dynamical dark energy is preferred by the combination of DESI baryon acoustic oscillation, \textit{Planck} Cosmic Microwave Background, and Pantheon+ supernovae data, we show that this preference disappears once these data sets are combined with the usual BOSS EFT galaxy power spectrum and bispectrum likelihood. The use of the simulation-based priors in this analysis further weakens the case for dynamical dark energy by additionally shrinking the parameter posterior around the cosmological constant region. Specifically, the figure of merit of the dynamical dark energy constraints from the combined data set improves by $\approx 20\%$ over the usual EFT-full-shape analysis with the conservative priors. These results are made possible with a novel modeling approach to the EFT prior distribution with the Gaussian mixture models, which allows us to both accurately capture the EFT priors and retain the ability to analytically marginalize the likelihood over most of the EFT nuisance parameters. Our results challenge the dynamical dark energy interpretation of the DESI data and enable future EFT-SBP analyses of BOSS and DESI in the context of non-minimal cosmological models.

We present high-resolution data of IRAS 23077+6707 (`Dracula's Chivito') with the Submillimeter Array (SMA at 1.33 mm/225.5 GHz) and the Northern Extended Millimeter Array (NOEMA at 2.7 mm/111.7 GHz and 3.1 mm/96.2 GHz). IRAS 23077+6707 is a highly-inclined and newly discovered protoplanetary disk, first reported in 2024. We combine SMA baselines from the Compact, Extended and Very Extended arrays, and NOEMA baselines from its A and C configurations, and present continuum images with resolution ${\lesssim}0.8''$, which constitute the first sub-arcsecond resolution maps of IRAS 23077+6707. The images show extended linear emission that spans $5.6{-}6.1''$ as expected for a radially extended, highly-inclined protoplanetary disk. Accompanied with lower resolution data, we show that the disk has a steep spectral index, ranging from $\alpha=3.2{-}3.9$. We present evidence of multiple radial emission peaks and troughs in emission, which may originate in disk rings and a central cavity. We further present evidence that these radial structures are asymmetric; hosting a a significant brightness asymmetry, with emission enhanced by up to 50% in the north versus the south. We discuss hypotheses about the potential origins of these features, including the possibility that IRAS 23077+6707 hosts a rare example of an eccentric protoplanetary disk, which can induce these radially asymmetric structures. We present a simple eccentric continuum model of IRAS 23077+6707, and show for an eccentricity of $e \approx 0.26$, that this can reproduce the bulk morphology of the emission.

We introduce PyMGal, a Python package for generating optical mock observations of galaxies from hydrodynamical simulations. PyMGal reads the properties of stellar particles from these simulations and generates spectral energy distributions (SEDs) based on a variety of stellar population models that can be customised to fit the user's choice of applications. Given these SEDs, the program can calculate the brightness of particles in different output units for hundreds of unique filters. These quantities can then be projected to a 2D plane mimicking a telescope observation. The software is compatible with different snapshot formats and allows a flexible selection of models, filters, output units, axes of projection, angular resolutions, fields of view, and more. It also supports additional features including dust attenuation, particle smoothing, and the option to output spectral data cubes and maps of mass, age, and metallicity. These synthetic observations can be used to directly compare the simulated objects to reality in order to model galaxy evolution, study different theoretical models, and investigate different observational effects. This package allows the user to perform fast and consistent comparisons between simulation and observation, leading to a better and more precise understanding of what we see in our Universe.

We present JWST/MIRI and complementary ground-based near-infrared observations of the Type II SN 2017eaw taken 6 years post-explosion. SN 2017eaw is still detected out to 25 $\mu$m and there is minimal evolution in the mid-infrared spectral energy distribution (SED) between the newly acquired JWST/MIRI observations and those taken a year earlier. Modeling of the mid-infrared SED reveals a cool $\sim$160 K dust component of $5.5\times10^{-4}\ \mathrm{M}_\odot$ and a hot $\sim$1700 K component of $5.4\times10^{-8}\ \mathrm{M}_\odot$ both composed of silicate dust. Notably there is no evidence of temperature or mass evolution in the cool dust component in the year between JWST observations. We also present new and archival HST and ground-based ultraviolet (UV) and optical observations which reveal reduced but continued circumstellar medium (CSM)-ejecta interaction at $>$2000 days post-explosion. The UV and mid-infrared emission show similar decline rates, suggesting both probe the interface between the ejecta and CSM. Given this, the continued existence of boxy H$\alpha$ emission in the nebular spectra, the low inferred optical depth of the dust, and the lack of temperature and mass evolution, we suggest that the cool dust component in SN 2017eaw may be primarily due to pre-existing dust rather than newly-formed dust in the ejecta or cold dense shell.

We present the high-resolution X-ray spectroscopic observations of the Ophiuchus galaxy cluster core using the XRISM satellite. Despite previous observations revealing multiple cold fronts and dynamical disturbances in the cluster core, our XRISM observations show low gas velocity dispersions of \sigma_v = 115 +/- 7 km s^{-1} in the inner region (~< 25 kpc) and \sigma_v = 186 +/- 9 km s^{-1} in the outer region (~ 25-50 kpc). The gas temperatures are kT = 5.5 +/- 0.2 keV and 8.4 +/- 0.2 keV for the inner and outer regions, respectively, with metal abundances of Z = 0.75 +/- 0.03 Z_sun (inner) and 0.44 +/- 0.02 Z_sun (outer). The measured velocity dispersions correspond to nonthermal pressure fractions of only 1.4 +/- 0.2% (inner) and 2.5 +/- 0.2% (outer), indicating highly subsonic turbulence. Our analysis of the bulk gas motion indicates that the gas in the inner region is nearly at rest relative to the central galaxy (|v_bulk|=8 +/- 7 km s^{-1}), while the outer region exhibits a moderate motion of |v_bulk|=104 +/- 7 km s^{-1}. Assuming the velocity dispersion arises from turbulent motions, the turbulent heating rate is only ~ 40% of the radiative cooling rate, although there is some uncertainty. This suggests that the heating and cooling of the gas are not balanced. The activity of the central active galactic nucleus (AGN) has apparently weakened. The sloshing motion that created the cold fronts may now be approaching a turning point at which the velocity is minimum.

Studying the matter distribution in the universe through the Lyman-$\alpha$ forest allows us to constrain small-scale physics in the high-redshift regime. Spectroscopic quasar surveys are generating increasingly large datasets that require efficient algorithms to compute correlation functions. Moreover, cosmological analyses based on Lyman-$\alpha$ forests can significantly benefit from incorporating higher-order statistics alongside traditional two-point correlations. In this work, we present Lya2pcf, a pipeline designed to compute three-dimensional two-point and three-point correlation functions using Lyman-$\alpha$ forest data. The code implements standard algorithms widely used in current spectroscopic surveys for computing the two-point correlation function with its distortion matrix, covariance matrices; and it naturally extends the two-point estimator to three-point correlations. Thanks to GPU optimization, Lya2pcf achieves a substantial reduction in computational time for both the two-point correlation function and its distortion matrix when compared to the widely used PICCA code. We apply Lya2pcf to data from the Sloan Digital Sky Survey (SDSS) sixteenth data release (DR16) and a Dark Energy Spectroscopic Instrument Year-5 (DESI Y5) mock dataset, demonstrating overall performance gains over PICCA, especially on GPUs. We show the first measurement of the anisotropic three-point correlation function on a large spectroscopic sample for all possible triangles with scales up to 80 Mpc/h. The estimator's fast computation and the resulting signal-to-noise ratio -- above one for many triangle configurations -- demonstrate the viability of incorporating three-point statistics into future cosmological inference analyses, particularly with the larger datasets expected from Stage IV spectroscopic surveys.

In dense environments like globular clusters (GCs), dynamical interactions can disrupt or harden close binaries, nonetheless, detailed comparisons with field binary fractions remain limited. Here, we present an analysis of the close binary fraction in a carefully selected sample of field stars and 10 GCs using Gaia Radial Velocity Spectrometer (RVS) data, which is among the largest samples of GCs analysed using multi-epoch spectroscopy to date. By assessing the peak-to-peak variations of the sources' radial velocity (RV), we estimate the close binary fractions through a method that fits the distribution as the product of two Gaussian distributions. By applying the same RV-variability method to both cluster members and field stars, we ensure a homogeneous and inclusive comparison between the two environments. Despite matching stellar parameters between the field and GC samples, our findings confirm that GCs possess a significantly lower close binary fraction than field stars. Interestingly, we do not detect any clear trend of binary fraction with cluster metallicity; metal-rich and metal-poor GCs are uniformly binary-poor (within uncertainties). We discuss possible interpretations, including dynamical hardening in dense environments and the effects of common envelope evolution, which may lead to companion accretion or merger events.

We performed a spectro-morphological analysis of the diffuse emission in the Galactic center region with H.E.S.S. gamma-ray data. We relied on templates to model the diffuse emissions (the Galactic center ridge and the foreground component) and on a 3D likelihood fitting approach. We first assessed the validity of a continuous injection scenario near the Galactic center by investigating possible deviations from a 1/r profile of the cosmic-ray distribution and potential spectral variations within the Galactic center ridge. We found the data can appropriately be described by a scenario in which a steady source near the Galactic center continuously injects cosmic rays which diffuse through the Central Molecular Zone. We then derived the best-fit spectral parameters of the Galactic center ridge emission and we found a spectral transition near 10-20 TeV.

Modern radio telescopes are revolutionising our understanding of non-thermal phenomena within galaxy clusters, collecting large samples of extended sources with unprecedented sensitivity and angular resolution. In this work, we present novel MeerKAT observations for a sample of 21 galaxy clusters being part of the CHEX-MATE project. These systems were selected based on their high mass and displaying signs of dynamical activity. Thanks to the high-quality data in hand, we detect extended radio emission in every target considered. We report two new halos, three new relics and confirm a previous candidate halo and two candidate radio relics. When investigating the scaling relations with the cluster properties, we confirm the presence of a radio halo power-mass correlation and relate it to a higher radio halo emissivity in more massive clusters. For radio relics, we highlight the MeerKAT capabilities to significantly extend the depth of radio observations to a new, unexplored field of low radio power sources ($\lesssim 10^{23} ~ {\rm W~Hz^{-1}} $ at 1.28 GHz). Thanks to such high-sensitivity data, we show that the radio relic power can display a wide range of values for a given cluster mass and relic size. Ultimately, we discuss how current radio observations, in combination with large radio surveys, are becoming capable of testing numerical simulation predictions and being close to perform direct comparison with them, in order to gain new insights on the evolution of radio relics.

Galactic archaeology--the study of stellar migration histories--provides insights into galaxy formation and evolution. However, establishing causal relationships between observable stellar properties and their birth conditions remains challenging, as key properties like birth radius are not directly observable. We employ Rank-based Latent Causal Discovery (RLCD) to uncover the causal structure governing the chemodynamics of a simulated Milky Way galaxy. Using only five observable properties (metallicity, age, and orbital parameters), we recover in a purely data-driven manner a causal graph containing two latent nodes that correspond to real physical properties: the birth radius and guiding radius of stars. Our study demonstrates the potential of causal discovery models in astrophysics.

We present DeepCHART (Deep learning for Cosmological Heterogeneity and Astrophysical Reconstruction via Tomography), a deep learning framework designed to reconstruct the three-dimensional dark matter density field at redshift $z=2.5$ from Ly$\alpha$ forest spectra. Leveraging a 3D variational autoencoder with a U-Net architecture, DeepCHART performs fast, likelihood-free inference, accurately capturing the non-linear gravitational dynamics and baryonic processes embedded in cosmological hydrodynamical simulations. When applied to joint datasets combining Ly$\alpha$ forest absorption and coeval galaxy positions, the reconstruction quality improves further. For current surveys, such as Subaru/PFS, CLAMATO, and LATIS, with an average transverse sightline spacing of $d_\perp=2.4h^{-1}$cMpc, DeepCHART achieves high-fidelity reconstructions over the density range $0.4<\Delta_{\rm DM}<15$, with a voxel-wise Pearson correlation coefficient of $\rho\simeq 0.77$. These reconstructions are obtained using Ly$\alpha$ forest spectra with signal-to-noise ratios as low as 2 and instrumental resolution $R=2500$, matching Subaru/PFS specifications. For future high-density surveys enabled by instruments such as ELT/MOSAIC and WST/IFS with $d_\perp\simeq 1h^{-1}\mathrm{cMpc}$, the correlation improves to $\rho\simeq 0.90$ across a wider dynamic range ($0.25<\Delta_{\rm DM}<40$). The framework reliably recovers the dark matter density PDF as well as the power spectrum, with only mild suppression at intermediate scales. In terms of cosmic web classification, DeepCHART successfully identifies 81% of voids, 75% of sheets, 63% of filaments, and 43% of nodes. We propose DeepCHART as a powerful and scalable framework for field-level cosmological inference, readily generalisable to other observables, and offering a robust, efficient means of maximising the scientific return of upcoming spectroscopic surveys.

The Small Magellanic Cloud (SMC) hosts 12 known Wolf-Rayet stars (WRs), seven of which apparently single. Their formation is a challenge for current stellar evolution models, because line-driven winds are generally assumed to be quenched at a metallicity Z<0.004. Here, we present a set of MESA models of single stars with zero-age main sequence masses 20-80 M_sun, considering different initial rotation speeds (Omega=0-0.7 Omega_c), metallicities (Z=0.002-0.0045), and wind mass-loss models (optically thin and thick winds). We show that if we account for optically thick winds, as described by Sabhahit+2023, fast rotating (Omega=0.6 Omega_c) single metal-poor O-type stars (with M>20 M_sun) shed their envelope and become WR stars even at the low metallicity of the SMC. The luminosity, effective temperature, evolutionary timescale, surface abundance, and rotational velocity of our simulated WR stars are compatible to the WRs observed in the SMC. We speculate that this scenario can also alleviate the excess of giant stars across the Humphreys-Davidson limit. Our results have key implications for black hole masses, (pair instability) supernova explosions, and other observable signatures.

Supermassive disks are outstanding galaxies whose formation and evolution are still poorly understood. They comprise a large variety of objects, ranging from large, low-surface-brightness galaxies, such as Malin 1, to the most spectacular superluminous spirals. However, we still do not know the physical mechanisms behind its formation, and whether they will be long-lived objects or whether their mass could destroy them in time. We aim to investigate the formation and evolution of these galaxies using the magnetohydrodynamical state-of-the-art simulation IllustrisTNG-100. We defined supermassive disks as galaxies with $\lambda / \sqrt{\varepsilon} \geq 0.31$ or 0.71, and with stellar mass log$_{10}M_\star/M_\odot > 10^{11}$. We studied the color, merging history, AGN history, and environment in which these galaxies reside. Supermassive disk galaxies typically experience a quiescent merging history, with $48\%$ experiencing no significant mergers at $z \leq 1$. Their stellar mass growth is driven mainly by star formation, unlike spheroidal galaxies, which require a significant number of mergers to form. Moreover, the mergers experienced by disk galaxies are generally rich in gas content, irrespective of whether they are minor or major events. Supermassive disks exist across various environments, from isolation to clusters, with $\sim 60\%$ inhabiting in isolation or low-mass groups, $\sim 25\%$ residing in massive groups, and $\sim15\%$ residing within galaxy clusters. When studying the evolution of supermassive disks selected at $z=0.5$, we show that when they gain sufficient mass, the probability of them maintaining their disk-like structure up to $z=0$ is relatively high ($\sim 60\%$). Lastly, while AGN significantly influences the regulation of star formation in galaxies, it does not directly alter their morphological structure.

The work is devoted to the study of the peculiar variable star Khavchenko 1 in Auriga. It was discovered by the 7th grade student Sergey Khavchenko in 2020. The brightness of the star varies with an amplitude of about 0.4 magnitude and the period of 4.213 days. Initially the star could not have been attributed to any known type of variability. Its light curve looks like the upside-down light curve of the eclipsing binary similar to that of luminous red nova V1309 Scorpii a few years before the eruption. The analysis of the new data from the ZTF project gathered from 2020 till 2024 has shown the cyclic variations of the light curve amplitude. We have proposed several possible models of this system which can explain such an unusual behavior of this star. The continued observations of this star are necessary to reveal the period changes and to estimate the possible eruption date.

Hypervelocity stars are unique objects moving through the Milky Way at speeds exceeding the local escape velocity, providing valuable insights into the Galactic gravitational potential and the properties of its central supermassive black hole. The advent of Gaia DR3 offers an unprecedented astrometric precision, enabling the discovery of new hypervelocity stars and facilitating their characterization. This study seeks to identify and characterize hypervelocity star candidates using Gaia DR3 data, focusing on stars lacking radial velocity measurements. Our goal was to estimate the total velocities of these stars and establish their origin within the Galactic framework, if possible. We applied strict selection criteria to Gaia DR3 data, focusing on sources with low parallax uncertainties and high astrometric fidelity. The distributions of the total velocities in the Galactic rest frame were derived and used to identify candidates. Spectroscopic follow-up with VLT/FORS2 provided radial velocity measurements for a subset of these candidates. We evaluated the probabilities of stars exceeding local escape velocities under different Galactic potential models and traced their past orbits to identify possible origins. From Gaia DR3, we identified 149 hypervelocity star candidates with Pesc > 50% of exceeding local escape velocities. Our follow-up spectroscopy for 23 of those sources confirms that the selected targets are traveling at high velocities, with many appearing to escape the Galaxy, depending on the Galactic potential adopted. Our analysis suggests that nearly one-third of the stars may have an extra-Galactic origin. These findings highlight the need for more precise astrometric and spectroscopic data to conclusively determine the origins of hypervelocity stars and improve models of the Galactic potential.

In this work, we investigate the feasibility of measuring the cosmic growth-rate parameter, $f\sigma_8$, using peculiar velocities (PVs) derived from Type Ia supernovae (SNe Ia) in the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). We produce simulations of different SN types using a realistic LSST observing strategy, incorporating noise, photometric detection from the Difference Image Analysis (DIA) pipeline, and a PV field modeled from the Uchuu UniverseMachine simulations. We test three observational scenarios, ranging from ideal conditions with spectroscopic host-galaxy redshifts and spectroscopic SN classification, to more realistic settings involving photometric classification and contamination from non-Ia supernovae. Using a maximum-likelihood technique, we show that LSST can measure $f\sigma_8$ with a precision of $10\%$ in the redshift range $ 0.02 < z < 0.14 $ in the most realistic case. Using three tomographic bins, LSST can constrain the growth-rate parameter with errors below $18\%$ up to $z = 0.14$. We also test the impact of contamination on the maximum likelihood method and find that for contamination fractions below $\sim 2\%$, the measurement remains unbiased. These results highlight the potential of the LSST SN Ia sample to complement redshift-space distortion measurements at high redshift, providing a novel avenue for testing general relativity and dark energy models.

The Habitable Worlds Observatory (HWO) aims to telescopically constrain the frequency and abundance of biospheres in the solar neighborhood. Origin-of-life theories vary in their predictions for the environmental requirements and the expected frequency of abiogenesis, meaning that constraints on the frequency and distribution of life on exoplanets from HWO can in principle directly test theories of abiogenesis. We categorize origin-of-life theories into three broad classes and discuss how HWO could potentially test them. Nondetection of biology on a large sample of habitable planets would provide prior-independent evidence in favor of the class of abiogenesis theory which holds that the origin of life is a contingent, vanishingly unlikely event, whereas detection of event a single biosphere would falsify this class of theories. Correlations of candidate biospheres with planetary parameters such as UV irradiation, the presence of oceans, and the presence of continents can test specific origin-of-life theories. Simulated surveys with Bayesian analysis are required to quantify the ability of HWO to execute this science case. However, a clear theme from the limited such studies that have already been conducted is the need for large sample sizes ($\gtrsim50$ planets characterized) to provide meaningful constraints on abiogenesis theories, favoring a larger design sample for HWO.

The Habitable Worlds Observatory (HWO) aims to characterize habitable exoplanets in search of signs of life. However, detectable life may be rare, either because abiogenesis is intrinsically contingent and unlikely, or because biospheres may efficiently recycle their products. Here, we explore the potential of HWO to test theories of life in the universe even if detectable life is rare by searching for "prebiosignature gases". Prebiosignatures gases are gases whose detection constrains theories of the evolution of prebiotic (habitable but uninhabited) planets, thereby testing theories of abiogenesis and guiding laboratory investigations of the origin of life. We catalog 5 theories of prebiotic environments that are potentially testable by HWO, identify their observational tests, and rank them by perceived detection plausibility. The prebiosignature paradigm is novel and potentially compelling, but considerable work is required to mature it and assess its practical relevance for HWO, especially simulated spectral observation and retrieval studies. However, consideration of the absorption properties of prebiosignature observables alone reveals that coverage at NUV wavelengths (200-400 nm) will be required to effectively realize a prebiosignature science case for HWO, supporting the argument for UV capabilities for HWO.

We report the discovery of an SX Phoenicis-type pulsating variable star via 217 epochs of time-series photometry from the Vera C. Rubin Observatory's Data Preview 1. The star, designated LSST-DP1-O- 614435753623041404 (or LSST-C25_var1 for short), has mean magnitudes of $(\langle g\rangle, \langle r\rangle) = (18.65, 18.63)$, with pulsation amplitudes of (0.60, 0.38)~mag in these bands. Its period is 0.0767 days (1.841 hours), typical of SX Phe pulsators. We derive a distance to the star of 16.6 kpc based on an SX Phe period-luminosity relation. Its position $\sim5$ kpc from the Galactic plane, in the outer Milky Way disk at a Galactocentric distance of $\sim22$ kpc, and its proper motion suggest that LSST-C25_var1 is part of the Monoceros Ring structure. This star is presented as a small taste of the many thousands of variable stars expected in Rubin/LSST data.

The cycle of metals between the gas and the dust phases in the neutral interstellar medium (ISM) is an integral part of the baryon cycle in galaxies. The resulting variations in the abundance and properties of interstellar dust have important implications for how accurately we can trace the chemical enrichment of the universe over cosmic time. Multi-object UV spectroscopy with HWO can provide the large samples of abundance and dust depletion measurements needed to understand how the abundance and properties of interstellar dust vary within and between galaxies, thereby observationally addressing important questions about chemical enrichment and galaxy evolution. Medium-resolution (R~50,000) spectroscopy in the full UV range (950-3150 A) toward massive stars in Local Volume galaxies (D < 10 Mpc) will enable gas- and dust-phase abundance measurements of key elements, such as Fe, Si, Mg, S, Zn. These measurements will provide an estimate of how the dust abundance varies with environment, in particular metallicity and gas density. However, measuring the carbon and oxygen contents of dust requires very high resolution (R > 100,000) and high signal-to-noise (S/N > 100) owing to the non-saturated UV transitions for those elements being extremely weak. Since carbon and oxygen in the neutral ISM contribute the largest metal mass reservoir for dust, it is critical that the HWO design include a grating similar to the HST STIS H gratings providing very high resolution, as well as FUV and NUV detectors capable of reaching very high S/N.

Future space observatories that seek to perform imaging and spectroscopy of faint astronomical sources will require ultra-low-noise detectors that are sensitive over a broad wavelength range. Silicon charge-coupled devices (CCDs), such as EMCCDs, skipper CCDs, multi-amplifier sensing (MAS) CCDs, and single-electron sensitive read out (SiSeRO) CCDs have demonstrated the ability to detect and measure single photons from X-ray energies to near the silicon band gap (~1.1 $\mu$m), making them candidate technologies for this application. In this context, we study a relatively unexplored source of low-energy background coming from Cherenkov radiation produced by energetic cosmic rays traversing a silicon detector. We present a model for Cherenkov photon production and absorption that is calibrated to laboratory data, and we use this model to characterize the residual background rate for ultra-low-noise silicon detectors in space. We study how the Cherenkov background rate depends on detector thickness, variations in solar activity, and the contribution of heavy cosmic ray species (Z > 2). We find that for thick silicon detectors, such as those required to achieve high quantum efficiency at long wavelengths, the rate of cosmic-ray-induced Cherenkov photon production is comparable to other detector and astrophysical backgrounds. We apply our Cherenkov background model to simulated spectroscopic observations of extra-solar planets, and we find that thick detectors continue to outperform their thinner counterparts at longer wavelengths despite a larger Cherenkov background rate. Furthermore, we find that minimal masking of cosmic-ray tracks continues to maximize the signal-to-noise of very faint sources despite the existence of extended halos of Cherenkov photons.

We report magnetic field measurements spanning about 15 years of four massive ($7.5-15 M_\odot$) supergiant stars: $\alpha$ Per (HD\,20902, F5Iab), $\alpha$ Lep (HD\,36673A, F0Ib), $\eta$ Leo (HD\,87737, A0Ib) and 13 Mon (HD\,46300, A1Ib). For each star, spectropolarimetric observations were collected using ESPaDOnS at the Canada-France-Hawaii Telescope. The observed spectra were co-added, normalized, then processed using Least Squares Deconvolution (LSD) to yield mean Stokes $I$ and $V$ profiles. Each spectrum was analyzed to infer the False Alarm Probability of signal detection, and the longitudinal magnetic field was measured. This process yielded persistent detection of magnetic fields in all four stars. The median $1\sigma$ longitudinal field uncertainty of the Zeeman detections was 0.6~G. The maximum unsigned longitudinal magnetic fields measured from the detections are rather weak, ranging from $0.34\pm 0.19$ G for $\alpha$ Lep to $2.61\pm 0.55$ G for 13 Mon. The Zeeman signatures show different levels of complexity; those of the two hotter stars are relatively simple, while those of the two cooler stars are more complex. The stars also exhibited different levels of variability of their Zeeman signatures and longitudinal fields. We report periodic variability of the longitudinal field and (complex) Stokes $V$ profiles of $\alpha$ Per with a period of either 50.75 or 90 days. The (simple) Stokes $V$ profiles of 13~Mon, and probably those of $\eta$ Leo, show global polarity changes once during the period of observation, but the data are insufficient to place strong constraints on the variability timescales.

The distribution of absorption lines in the spectra of distant quasars, called the Lyman-$\alpha$ (Ly-$\alpha$) forest, is a unique probe of cosmology and the intergalactic medium at high redshifts and small scales. The statistical power of ongoing redshift surveys demands precise theoretical tools to model the Ly-$\alpha$ forest. We address this challenge by developing an analytic, perturbative forward model to predict the Ly-$\alpha$ forest at the field level for a given set of cosmological initial conditions. Our model shows a remarkable performance when compared with the Sherwood hydrodynamic simulations: it reproduces the flux distribution, the Ly-$\alpha$ - dark matter halo cross-correlations, and the count-in-cell statistics at the percent level down to scales of a few Mpc. Our work provides crucial tools that bridge analytic modeling on large scales with simulations on small-scales, enabling field-level inference from Ly-$\alpha$ forest data and simulation-based priors for cosmological analyses. This is especially timely for realizing the full scientific potential of the Ly-$\alpha$ forest measurements by the Dark Energy Spectroscopic Instrument.

We examine the impact of repulsive self-interactions of moderate strength on fuzzy dark matter halos focusing on the core and granule size, the spatial dependence of the field's coherence, the turbulent vortex tangle and the oscillation frequency of the central soliton. Our analysis extends across the range from quantum-pressure-dominated to self-interaction-dominated stabilisation of the gravitationally bound solitonic core. Within this examined range of self-coupling strengths, we find that mergers with a given initial spatial configuration and an increasing self-interaction strength $g$, result in cores with increased size that exhibit a reduced central density and oscillate with decreased frequency. All of these features are in accordance with expectations from the study of isolated Self-interacting Fuzzy Dark Matter (SFDM) solitons. The characteristic size of the granules in the surrounding halo also grows but by a much smaller amount relative to the core; accordingly, typical inter-vortex distances are also only mildly affected. We also measure the total length of the vortex network which, although less robust, shows no clear dependence on increasing $g$ and no signs of decay over the timescales of our simulations. Measures of coherence of the field behave as in the non-interacting case, again clearly separating the coherent core form the quasi-coherent halo. Interestingly, we observe a relative increase of incoherent fluctuations coexisting with the coherent mode at the centre of the halo with increasing self-coupling strength, a phenomenon also observed in laboratory condensates at non-zero temperature.

Z-sources are a particular class of neutron star low-mass X-ray binaries characterized by a wide Z-like track in their hard colorsoft color (or hardness-intensity) diagrams, with three branches: the horizontal (HB), the normal (NB), and the flaring branch (FB). Spectropolarimetric observations with the Imaging X-ray Polarimetry Explorer (IXPE) show that the polarization in these sources varies along the Z-track, reaching unexpectedly high values in the HB. In this work, we collected all the polarimetric results obtained so far from observations of Z-sources with IXPE, using a model-independent analysis with ixpeobssim. We first performed a detailed characterization of the spectral state of each source along the Z-track using IXPE, along with the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) data and then estimated the polarization for each branch. Although we confirm that the average polarization in the 2-8 keV band decreases moving from the HB to the NB for all three Z-sources observed in these branches, we also observe a qualitatively increasing trend from the NB to the FB. Whereas this increase is clearly significant for Cyg X-2 and Sco X-1, the polarization remains consistent at the 90% confidence level for GX 5-1 and GX 349+2, while for XTE J1701-462 and GX 340+0 only upper limits are found in the FB. For most sources, the average polarization angle in the 2-8 keV range remains consistent along the CCD; however, we observe a significant rotation for both Sco X1 and GX 349+2 (at the 90% confidence level) as they move from the NB to the FB. In addition, we observe a significant increase in the polarization degree with energy in most of the observed Z-sources, with some also exhibiting a rotation of the polarization angle with energy (approximately by 20-30 deg).

Gamma-Dor stars are ideal targets for studies of stellar innermost dynamical properties due to their rich asteroseismic spectrum of gravity modes. Integrating internal magnetism to the picture appears as the next milestone of detailed asteroseismic studies, for its prime importance on stellar evolution. The inertial dip in prograde dipole modes period-spacing pattern of gamma-Dors stands out as a unique window on the convective core structure and dynamics. Recent studies have highlighted the dependence of the dip structure on core density stratification, contrast of the near-core Brunt-Väisälä frequency and rotation rate, as well as the core-to-near-core differential rotation. In the meantime, the effect of magnetism has been derived on envelope modes. We aim to revisit the inertial dip formation including core and envelope magnetism, and explore the probing power of this feature on dynamo-generated core fields. We consider a toroidal magnetic field with a bi-layer (core and envelope) Alfvén frequency. This configuration allows us to revisit the coupling problem using our knowledge on both core magneto-inertial modes and envelope magneto-gravito-inertial modes. We stay in an analytical framework to exhibit the magnetic effects on the inertial dip shape and location, setting up a laboratory towards the comprehension of magnetic effects on the dip structure. We show a shift of the inertial dip towards lower spin parameter values and a thinner dip with increasing core magnetic field, quite similar to the signature of differential rotation. The magnetic effects become sizeable when the ratio between the magnetic and the Coriolis effects is large enough. We explore the degeneracy of the magnetic effects with differential rotation. We study the detectability of core magnetism, considering observational constraints on the modes periods and potential gravito-inertial mode suppression.

We present the results of astrochemical modeling of complex organic molecules (COMs) in the ice and gas of the prestellar core L1544 with the recently updated MONACO rate equations-based model. The model includes, in particular, non-diffusive processes, new laboratory verified chemical routes for acetaldehyde and methane ice formation and variation of H and $\rm H_2$ desorption energies depending on the surface coverage by $\rm H_2$ molecules. For the first time, we simultaneously reproduce the abundances of several oxygen-bearing COMs in the gas phase, the approximate location of the peak of methanol emission, as well as the abundance of methanol in the icy mantles of L1544. Radical-radical reactions on grains surface between species such as $\rm CH_3$, $\rm CH_3O$ and $\rm HCO$ efficiently proceed non-diffusively. COMs are delivered to the gas phase via chemical desorption amplified by the loops of H-addition/abstraction surface reactions. However, gas-phase chemical reactions as well provide a noticeable input to the formation of COMs in the gas, but not to the COMs solid-state abundances. This particularly applies for CH$_3$CHO and CH$_3$OCH$_3$. The simulated abundances of COMs in the ice are in the range 1\%--2\% (for methyl formate ice) or $\sim$~0.1\% (for CH$_3$CHO and CH$_3$OCH$_3$) with respect to the abundance of H$_2$O ice. We stress a similarity between the simulated abundances of icy COMs in L1544 and the abundances of COMs in the gas phase of hot cores/corinos. We compare our non-diffusive model with the diffusive model and provide constraints for the species' diffusion-to-desorption energy ratios.

We present the radio continuum counterparts to the enigmatic ultra-compact X-ray binaries (UCXBs); a black hole or neutron star accreting from a hydrogen-deficient white dwarf donor star, with short orbital periods ($<$ 80 minutes). For the sample of UCXBs hosted by globular clusters (GCs), we search for whether certain GC properties are more likely to enhance UCXB formation. We determine that GCs which host UCXBs are drawn from a distinct population in terms of cluster concentration, core radius and half-light radius, but are similar to other well-studied GCs in metallicity and cluster mass. In particular, UCXB-hosting GCs tend to be on average more compact, with a higher concentration than other GCs, with significantly higher encounter rates. We investigate whether a correlation exists between radio luminosity and orbital period, using new and archival observations. We determine that there is not a clear connection between the two observable quantities.

We present Dark from Light (DfL) - a novel method to infer the dark sector in wide-field galaxy surveys, leveraging a machine learning approach trained on contemporary cosmological simulations. The aim of this algorithm is to provide a fast, straightforward, and accurate route to estimating dark matter halo masses and group membership in wide-field spectroscopic galaxy surveys. This approach requires a highly limited number of input parameters and yields full probability distribution functions for the output halo masses. To achieve this, we train a series of Random Forest (RF) regression models on the IllustrisTNG and EAGLE simulations at z=0-3, which provide model-dependent mappings from luminous tracers to dark matter halo properties. We incorporate the individual regression models into a virial group-finding algorithm (DfL), which outputs halo properties for observational-like input data. We test the method at z=0-2 for both the EAGLE and IllustrisTNG models, as well as in a cross-validation mode. We demonstrate that known halo masses can be recovered with a mean systematic bias of $\langle b \rangle = \pm 0.10\,$dex (resulting from simulation choice), a mean statistical uncertainty of $\langle \sigma \rangle = 0.12 \,$dex across epochs, and a central - (core) satellite classification accuracy of 96%. We establish that this approach yields superior halo mass recovery to standard abundance matching applied to groups identified through a friends-of-friends algorithm. Additionally, we compare the outputs of DfL to observational constraints on the $M_* - M_{\rm Halo}$ relation from strong gravitational lensing at $z \sim 0$, demonstrating the promise of this novel approach. Finally, we systematically quantify how DfL performs on observational-like input data with varying stellar mass uncertainty and spectroscopic incompleteness, enabling robust error calibration.

We present the searches conducted with the Zwicky Transient Facility (ZTF) in response to S250206dm, a bona fide event with a false alarm rate of one in 25 years, detected by the International Gravitational Wave Network (IGWN). Although the event is significant, the nature of the compact objects involved remains unclear, with at least one likely neutron star. ZTF covered 68% of the localization region, though we did not identify any likely optical counterpart. We describe the ZTF strategy, potential candidates, and the observations that helped rule out candidates, including sources circulated by other collaborations. Similar to Ahumada et al. 2024, we perform a frequentist analysis, using simsurvey, as well as Bayesian analysis, using nimbus, to quantify the efficiency of our searches. We find that, given the nominal distance to this event of 373$\pm$104 Mpc, our efficiencies are above 10% for KNe brighter than $-17.5$ absolute magnitude. Assuming the optical counterpart known as kilonova (KN) lies within the ZTF footprint, our limits constrain the brightest end of the KN parameter space. Through dedicated radiative transfer simulations of KNe from binary neutron star (BNS) and black hole-neutron star (BHNS) mergers, we exclude parts of the BNS KN parameter space. Up to 35% of the models with high wind ejecta mass ($M_{\rm wind} \approx 0.13$ M$_{\odot}$) are ruled out when viewed face-on ($\cos\theta_{\rm obs} = 1.0$). Finally, we present a joint analysis using the combined coverage from ZTF and the Gravitational Wave Multimessenger Dark Energy Camera Survey (GW-MMADS). The joint observations cover 73% of the localization region, and the combined efficiency has a stronger impact on rising and slowly fading models, allowing us to rule out 55% of the high-mass KN models viewed face-on.

Among the most fundamental properties of a dark matter halo is its density profile. Motivated by the recent proposal by García et al. [R. García et. al., MNRAS 521, 2464 (2023)] to define a dynamical halo as the collection of orbiting particles in a gravitationally bound structure, we characterize the mean and scatter of the orbiting profile of dynamical halos as a function of their orbiting mass. We demonstrate that the orbiting profile of individual halos at fixed mass depends on a single dynamical variable -- the halo radius $r_{\rm h}$ -- which characterizes the spatial extent of the profile. The scatter in halo radius at fixed orbiting mass is $\approx 16\%$. Only a small fraction of this scatter arises due to differences in halo formation time, with late-forming halos being more compact (smaller halo radii). Accounting for this additional correlation results in an $\approx 11\%$ scatter in halo radius at fixed mass and halo formation time.

The detection of circumstellar atomic hydrogen (\ion{H}{1}) via the 21\,cm line remains a persistent challenge in planetary nebula (PN) studies, primarily due to contamination from ubiquitous interstellar \ion{H}{1} 21\,cm emission. In this paper, we report the results of a \ion{H}{1} survey of 12 high surface brightness PNe located at Galactic latitudes $|b|\geq10\arcdeg$, performed with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), which is currently the most sensitive telescope in the $L$ band. Although the contamination from interstellar emission is still severe, we detect or tentatively detect circumstellar \ion{H}{1} 21\,cm absorption associated with two PNe: NGC\,6905 and NGC\,7662. \ion{H}{1} exhibits a comparatively high detection frequency in bipolar PNe. We estimate the \ion{H}{1} masses of the two PNe to range from 0.01 to 0.14 $M_{\sun}$, resulting in atomic-to-ionized hydrogen ratios of 0.02--0.3. The \ion{H}{1} shells have dynamical ages of 2100--2400 years. Our measurements confirm previous findings that the optical depth of \ion{H}{1} decreases with increasing linear radius of the nebula. The mass loss rates traced by the \ion{H}{1} absorption are larger than 10$^{-5}$\,M$_\sun$ yr$^{-1}$, indicating that they originate from the superwind phase at the tip of the asymptotic giant branch.

IRC+10216 is the brightest infrared source in the northern sky, known for its rich chemical composition. It is often used as a standard reference for studying the circumstellar envelope (CSE) of carbon-rich stars. While pioneering 3\,mm spectral surveys have laid foundational datasets, their system temperature limitations rendered spectral line detection thresholds inadequate for probing the source's complex organic molecule inventory at this band, which made superseding observations necessary. We aim to gain an unbiased view regarding circumstellar chemistry and investigate whether IRC+10216 is typical or anomalous in terms of its chemical composition. We carried out an in-depth spectral line survey of the circumstellar envelope of IRC+10216 utilizing the Arizona Radio Observatory 12\,m telescope. We achieved complete spectral sampling across the 90--116 GHz atmospheric window ($\lambda=2.6$--3.3\,mm). A total of 214 emission lines belonging to 43 molecular species are identified in the CSE of IRC+10216, among which 28 lines are newly detected in this object and four emission lines remain unidentified. The excitation temperatures and column densities of 16 molecules are determined through rotation diagrams. We estimate the isotopic ratios of carbon, oxygen, and silicon elements. For the majority of the molecular species, the line intensity ratios between IRC+10216 and CIT\,6 are inversely proportional to the square of their distance, which suggests that the chemical processes occurring within them are similar. Nevertheless, there is evidence suggesting that the emission of C$_{4}$H and C$_{3}$N in IRC+10216 is unusually strong. These observations stand as the most sensitive and unbiased line survey of IRC+10216 within the $\lambda=3$ window carried out by a single-dish telescope. They offer a valuable reference for the astronomical community. (Abridged)

This study investigates the potential of a cosmological model termed $\Lambda w$DM, in which a cosmological constant play the role of dark energy and dark matter is barotropic and has a constant equation of state parameter ($w_{\rm dm}$), to address the $S_8$ tension between early- and late- universe observations. By incorporating the latest cosmological datasets -- including Planck Cosmic Microwave Background (CMB), Baryon Acoustic Oscillation (BAO), Ia supernovae (SNe Ia), Redshift Space Distortions (RSD), and weak lensing (WL) -- we constrain the $\Lambda w$DM compared to $\Lambda$CDM. Our analysis reveals a marginal preference for a non-zero $w_{\rm dm}=2.7^{+2.0}_{-1.9}\times10^{-7}$( at 95\% confidence level) when combining CMB, SDSS BAO, SNe Ia, RSD, and WL data, and a marginal preference for a non-zero $w_{\rm dm} = 2.29^{+1.9}_{-2.0} \times 10^{-7}$( at 95\% confidence level) when combining CMB, DESI Y1 BAO, SNe Ia, RSD, and WL data. In addition, we find that, compared to $\Lambda$CDM, $\Lambda w$DM can alleviate the $S_8$ tension from $>3\sigma$ to $<1\sigma$. Furthermore, we find that, for CMB+SDSS+PP+RSD+WL datasets, the $\Lambda w$DM model is close to being positively preferred over the $\Lambda$CDM model.

A quantitative understanding of the nature and composition of low-mass rocky exo(planet) atmospheres during their evolution is needed to interpret observations. The magma ocean stage of terrestrial- and sub-Neptune planets permits mass exchange between their interiors and atmospheres, during which the mass and speciation of the atmosphere is dictated by the planet's volatile budget, chemical equilibria, and gas/fluid solubility in molten rock. As the atmosphere cools, it is modified by gas-phase reactions and condensation. We combine these processes into an open-source Python package built using JAX called Atmodeller, and perform calculations for planet sizes and conditions analogous to TRAPPIST-1e and K2-18b. For TRAPPIST-1e-like planets, our simulations indicate that CO-dominated atmospheres are prevalent during the magma ocean stage, which, upon isochemical cooling, predominantly evolve into CO2-rich atmospheres of a few hundred bar at 280 K. Around 40% of our simulations predict the coexistence of liquid water, graphite, sulfur, and ammonium chloride-key ingredients for surface habitability. For sub-Neptune gas dwarfs, pressures are sufficiently high (few GPa) to deviate the fugacities of gases from ideality, thereby drastically enhancing their solubilities. This buffers the total atmospheric pressure to lower values than for the ideal case. These effects conspire to produce CH4-rich sub-Neptune atmospheres for total pressures exceeding around 3.5 GPa, provided H/C is approximately 100x solar and fO2 moderately reducing (3 log10 units below the iron-wüstite buffer). Otherwise, molecular hydrogen remains the predominant species at lower total pressures and/or higher H/C. For all planets at high temperature, solubility enriches C/H in the atmosphere relative to the initial composition.

The in-flight instrumental background of the Follow-up X-ray Telescope (FXT) onboard Einstein Probe (EP) mission is analysed in this work by utilizing observations collected during Performance Verification phase and subsequent dedicated filter wheel closed observations. The instrumental backgrounds of the two FXT modules are consistent with each other, with an average rate of $\sim 4\times10^{-2}$\,counts/s/keV at 0.5--10\,keV for each module. The background is nearly uniformly distributed across the detector pixels, with a minor increase ($<8\%$) observed along rows. The spatial distribution shows significant modulation by the geomagnetic field. The spectral shapes remain unchanged in 0.5--10\,keV at different rates. The long-term temporal variation indicates a periodic change associated with the orbital precession ($\sim 57$ days). The innovative design of FXT full-frame readout mode enables simultaneous recording of events in both the imaging area (IMG) and the frame store area (FSA) of the pnCCD. FSA event rates show a strong linear correlation with the IMG, based on which the IMG instrumental background modelling is established.

We investigate the 2018-2019 main outburst and the subsequent mini-outbursts of the black hole low-mass X-ray binary MAXI J1820+070 using optical/ultraviolet data from the Las Cumbres Observatory (LCO), the American Association of Variable Star Observers (AAVSO), and $\textit{Swift}$/UVOT, as well as X-ray data from $\textit{Insight}$-HXMT and $\textit{Swift}$/XRT. Given the high-cadence observations, we identify a broad dip-like feature in both the optical and X-ray light curves preceding the transition to the soft state, with the X-ray dip lagging the optical dip by approximately 10 days. We propose that the dip is caused by a brief decrease followed by an increase in the mass accretion rate as it propagates through the disc, ultimately triggering the transition to the soft state. This might be a potential tool to predict impending hard-to-soft state transitions, although such a dip has not yet been observed in many sources. Additionally, we find that optical colour ($g^{\prime}-i^{\prime}$) becomes bluer and less variable before the transition to the intermediate state, preceding a dramatic change in the hardness ratio. This appears to be an unusual case, differing from the typical scenario where the optical colour changes usually along with the transition to the soft state. Finally, we explore the implications of the complex evolution of optical/X-ray correlation during both main outbursts and mini-outbursts. In particular, we find a loop-like evolutionary track before the transition to the soft state, which is linked to the optical/X-ray dips in the light curves.

We conducted a comprehensive study of daily delays using multi-wavelength data from a sample of well-studied black hole X-ray binaries, specifically focusing on the sources GX 339-4, 4U 1543-47, and XTE J1550-564. The Interpolated-Correlation Function method was employed to investigate the temporal relationship between the X-ray (Compton component) and optical-infrared (OIR) emissions. Our results show that during the rising hard state, the Compton emission consistently lags behind OIR emission for several days. In contrast, during the decaying hard state, the OIR emission lags behind the Compton emission by approximately 6 to 35 days. This measurement can potentially be used in models of accretion physics and disk instability. We explore the underlying mechanisms responsible for these time delays, highlighting the critical role of viscous heating in the accretion disk in generating OIR luminosity for these sources. The observed time delays during both the rising and decaying hard states are well explained by the disk instability model.

[Abridged] The physical conditions in stellar atmospheres can be obtained from the interpretation of solar spectro-polarimetric observations. However, traditional inversion codes are computationally demanding, especially for lines whose formation is complex. The necessity of faster alternatives has motivated the emergence of machine learning solutions. This paper introduces an approach to the inversion and synthesis of Stokes profiles inspired by neural machine translation. Our aim is to develop a generative model that treats Stokes profiles and atmospheric models as two distinct ``languages'' encoding the same physical reality. We build a model that learns how to translate between them, also providing estimates of the uncertainty. We employ a tokenization strategy for both Stokes parameters and model atmospheres, which is learned using a VQ-VAE, a neural model used to compress the data into a lower dimensionality form. The core of our inversion code utilizes a transformer encoder-decoder architecture to perform the translation between these tokenized representations. The model is trained on a database of synthetic Stokes profiles derived from perturbations to various semi-empirical solar atmospheric models, ensuring a wide range of expected solar physical conditions. The method effectively reconstructs atmospheric models from observed Stokes profiles, showing better constrained models within the region of sensitivity of the considered spectral lines. The latent representation induced by the VQ-VAE helps accelerate the inversion by compressing the length of the Stokes profiles and model atmospheres. Additionally, it helps regularize the solution by reducing the chances of obtaining unphysical models. As a final advantage, the method provides the generative nature of our model, which naturally yields an estimate of the uncertainty in the solution.

We perform head-on collision simulations of compact dark matter subhalos using distinct numerical methods for fuzzy dark matter (FDM) and cold dark matter (CDM) models. For FDM, we solve the Schrödinger-Poisson equations with a pseudospectral solver, while for CDM, we utilize a smoothed particle hydrodynamics N-body code. Our results show that velocity decrease of subhalos is significantly greater in FDM model than in CDM, particularly at lower initial velocities, attributed to gravitational cooling-a unique mechanism of stabilizing in FDM with dissipating kinetic energy. This stark contrast in energy dissipation between two DM models suggests that FDM may offer valuable insights into understanding the dynamic behaviors of DM during galaxy cluster collisions, such as those observed in the Bullet cluster and Abell 520. These findings strongly suggest that FDM is not only capable of explaining these complex astrophysical phenomena but also serves as a compelling alternative to the traditional CDM model, offering resolutions to longstanding discrepancies in DM behavior.

In this work, we observe the nearby pulsar, PSR B1929$+$10, using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We find, for the first time, two new emission components with an extremely weak observed flux density of about $10^{-4}$ of the magnitude of the peak radio emission of PSR B1929$+$10. Our results show that the intrinsic radio emission of PSR B1929$+$10 covers the $360^{\circ}$ of longitude, demonstrating that this pulsar is a whole $360^{\circ}$ of longitude emission pulsar. We find at least 15 components of pulse emission in the average pulse profile. Additionally, we identify 5 modes of subpulse modulation in different emission regions, which differ from the pulse components. Moreover, the narrowband emission feature and the frequent jumps in the observed linear polarization position angle (PPA) are also detected in the single pulse of this pulsar. To understand the magnetosphere of this pulsar, we analyze the observed PPA variations across the whole $360^{\circ}$ of longitude and fit them using the classical rotating vector model (RVM). For the best-fit model, the inclination angle,$\alpha$, and the impact angle, $\beta$, of this pulsar are $55^{\circ}.56$ and $53^{\circ}.47$, respectively. Using the rotating magnetosphere approximation of the magnetic dipole field, we investigate the three-dimensional pulsar magnetosphere and the sparking pattern on the polar cap surface. Our analysis indicates that the extremely narrow zone of the polar cap, which is associated with a high-altitude magnetospheric region, is responsible for the weak emission window. This pulsar has extremely high-altitude magnetospheric radio emissions.

In this work, we performed an energy-dependent study of low-frequency oscillations observed in GX 13+1 using \textit{AstroSat} (Large Area X-ray Proportional Counter and Soft X-ray Telescope). The hardness-intensity diagram (HID) of the observation resembles a `$\nu$'-shaped track, while the color-color diagram exhibits a `$<$'-shaped track, similar to the horizontal and normal branches of the Z source. We conducted flux-resolved temporal studies focusing on low-frequency variability and divided the HID into five regions: A, B, C, D, and E. Low-frequency quasi-periodic oscillations (QPOs) were detected in Regions A, B, and C. The QPO in Region A has a frequency of $5.06^{+0.54}_{-0.48}$ Hz with a quality factor (Q-factor) of 2.80. In Region B, the QPO was detected at $4.52^{+0.14}_{-0.13}$ Hz with a Q-factor of 5.79, while in Region C, it was observed at $4.70^{+0.62}_{-0.42}$ Hz with a Q-factor of 4.35. The QPO frequencies, Q-factors, and low root-mean-square (rms) values (1.32\%, 1.34\%, and 0.7\%) suggest that these oscillations are Normal Branch Oscillations, similar to those reported in GX 340+0. We modeled the rms and lag of the QPOs using a propagative model, considering variations in blackbody temperature, coronal heating rate, and optical depth. Our findings indicate that the observed QPOs are likely driven by interactions between the corona and variations in the blackbody temperature.

Mean-field dynamo theory, describing the evolution of large-scale magnetic fields, has been the mainstay of theoretical interpretation of magnetism in astrophysical objects such as the Sun for several decades. More recently, three-dimensional magnetohydrodynamic simulations have reached a level of fidelity where they capture dynamo action self-consistently on local and global scales without resorting to parametrization of unresolved scales. Recent global simulations also capture many of the observed characteristics of solar and stellar large-scale magnetic fields and cycles. Successful explanation of the results of such simulations with corresponding mean-field models is a crucial validation step for mean-field dynamo theory. Here the connections between mean-field theory and current dynamo simulations are reviewed. These connections range from the numerical computation of turbulent transport coefficients to mean-field models of simulations, and their relevance to the solar dynamo. Finally, the most notable successes and current challenges in mean-field theoretical interpretations of simulations are summarized.

Our aim is to characterize the effects of the local magnetic fields in quiet regions of stellar atmospheres. We compute magneto-hydrodynamic and purely hydrodynamic simulations of G2V, K0V and M2V star. The magnetic simulations are started from the hydrodynamical ones, adding the Biermann battery term in the induction equation to produce a magnetic seed, that is enhanced by the action of the small-scale dynamo. Once the magnetic field is saturated, we compare the simulations with and without magnetic fields and characterize the differences in statistics of velocities, appearance of granulation, and the mean stratification of a number of relevant parameters. These differences are also compared with the deviations produced by different treatments of the opacity in the simulations. The saturation values of the magnetic fields are $\sim 100$ G for the three stars in their surface, consistent with the recent results for cool stars, and other results for the Sun in the literature. The local magnetic fields have a negligible effect on the velocities of the plasma or the mean stratifications of the simulated stars. In contrast, they produce changes in the bolometric intensity of the intergranular lanes and the power spectrum at small scales of the temperature and vertical velocity of downflows. Significant differences between the hydrodynamic and magneto-hydrodynamic simulations are also found for the kinetic energy. This difference in energy can be explained by the transformation of kinetic into magnetic energy, which is consistent with the action of the small-scale dynamo.

The precise calculation of gravitational wave (GW) and particle emissions from cosmic string networks is of significant theoretical and experimental interest. In this Letter, we perform numerical simulations of near-global and local string networks, comparing the GW spectra predictions from both lattice field simulation and the Nambu-Goto (NG) approximation methods. We find the discrepancy between the GW spectra computed via the NG approximation and the lattice field simulation is negligible for near-global string and grow with increasing gauge coupling. Additionally, we confirm that particle emission significantly dominates energy emission, with the ratio of GW energy to particle energy approximately $10^{-3}$ to $10^{-2}$ for both near-global and local string scenarios.

Ultralight dark matter refers to the lightest potential dark matter candidates. We will focus on the mass range that has been studied using astrophysical and cosmological observations, corresponding to a mass $10^{-24} \, \mathrm{eV} \lesssim m \lesssim 10^{-18} \, \mathrm{eV}$. We will discuss the motivations for this mass range. The most studied model in this range corresponds to a minimally coupled, single, classical, spin-0 field comprising all dark matter. However, the work exploring extensions of this model (for example, higher spin, self-coupled, multiple field, and mixed models) will be one of the focuses of this review. The phenomenology associated with ultralight dark matter is rich and includes linear effects on the primordial power spectrum, core structures forming at the center of halos, nonlinear effects resulting in heating of stellar distributions, and non-relativistic effects relating to pulsar signals and black hole superradiance, to name a few. This set of effects has been studied using an equally extensive set of numerical tools. We will summarize the most common ones and discuss their applications and limitations. Ultralight dark matter also has a wide variety of observational constraints, including halo mass functions, the Lyman-alpha forest, halo density profiles, stellar dynamics, and black hole spins. We will review them focusing on the observations made, the method of study, and the major systematics. We will end with a discussion of the current status of the field and future work needed.

A bombardment of comets is thought to have occurred in the inner solar system as a result of a dynamical instability among the giant planets after gas disk dispersal. Vesta, the second largest asteroid in the main asteroid belt, likely differentiated before gas disk dispersal, implying its crust witnessed the cometary bombardment. The composition of HED meteorites, which represent fragments of Vesta's crust, could therefore have been altered by cometary impacts. Here we combine noble gas mass spectrometry measurements, N-body simulations, collision rate calculations, and impact simulations to estimate the cometary contribution to Vesta. While our dynamical simulations indicate that Vesta likely underwent a significant number of collisions with large comets, we find no xenon cometary signature in HED meteorites. This apparent contradiction arises due to the fact that cometary impacts were at high speeds and Vesta's weak gravitational attraction made it incapable of retaining cometary material. Smaller asteroids are even less likely to retain such material. Therefore, if a cometary xenon signature is ever detected in an asteroid belt object, it must have been acquired during formation, within the same source region as comet 67P/Churyumov-Gerasimenko, and have been implanted later into the asteroid belt.

I identified a point-symmetric morphology in the core-collapse supernova (CCSN) remnant (CCSNR) N132D, composed of two symmetry axes: the short symmetry axis extending from the northwest ear and through the center of the iron-rich emission on the other side, and the second along the long dimension of N132D and coincides with the extension of the central oxygen-rich gas to the northeast. Namely, the point-symmetry of the outer zones of CCSNR N132D correlates with that of the oxygen-rich gas near the center. The surrounding gas cannot shape the inner oxygen-rich material, implying that the point-symmetric morphology is a property of the explosion mechanism, as predicted by the jittering jets explosion mechanism (JJEM). The oxygen-rich material is known to be in a torus. According to the JJEM, an energetic pair of opposite jets, more or less perpendicular to the plane of the torus, has shaped the torus; this pair is along the short symmetry axis. Another energetic pair, perpendicular to the first one, shaped the elongated, large-scale structure of CCSNR N132D. I discuss how the JJEM accounts for two perpendicular pairs of jets and the unequal jets in each pair. CCSNR N132D is the fifteenth CCSNR with an identified point-symmetric morphology attributed to the JJEM. Because the neutrino-driven mechanism cannot explain such morphologies, this study further strengthens the claim that the JJEM is the primary explosion mechanism of CCSNe.

Recent claims of biosignature gases in sub-Neptune atmospheres have renewed interest in water-rich sub-Neptunes with surface oceans, often referred to as Hycean planets. These planets are hypothesized to form beyond the snow line, accreting large amounts of H$_2$O >10 wt%) before migrating inward. However, current interior models often neglect chemical equilibration between primordial atmospheres and molten interiors. Here, we compute global chemical equilibrium states for a synthetic population of sub-Neptunes with magma oceans. Although many initially accrete 5-30 wt% water, interior-atmosphere interactions destroy most of it, reducing final H$_2$O mass fractions to below 1.5 wt%. As a result, none meet the threshold for Hycean planets. Despite that, we find H$_2$O-dominated atmospheres exclusively on planets that accreted the least ice. These planets form inside the snow line, are depleted in carbon and hydrogen, and develop small envelopes with envelope mass fractions below 1%, dominated by endogenic water. In contrast, planets formed beyond the snow line accrete more volatiles, but their water is largely converted to H$_2$ gas or sequestered into the interior, resulting in low atmospheric H$_2$O mass fractions. Most H$_2$O-rich envelopes are also fully miscible with H$_2$, making a separate water layer unlikely. Our results topple the conventional link between ice accretion and water-rich atmospheres, showing instead that H$_2$O-dominated envelopes emerge through chemical equilibration in hydrogen-poor planets formed inside the snow line.

This study presents new, high-quality, optical photometric observations of three W UMa type contact binaries. The analysis of the corresponding light curves is made using Djurasevic's inverse problem method. To explain the light curve asymmetries and variations, we used the Roche model that involved regions containing spots on the components. The fundamental parameters of these systems were derived, including the mass ratios determined using the q-search method. Hypotheses involving active surface regions, such as dark spots on the primary and secondary components, or bright spots in the neck region due to magnetic activity or continuous mass transfer between components, were examined to explain the varying amplitudes of maxima and nearly equal minima depths in the light curves. Using the derived orbital and physical parameters, three-dimensional models were constructed for various orbital phases.

We investigate constraints on the abundance of primordial black holes (PBHs) as dark matter (DM) candidates using five years of microlensing data from the OGLE survey. While the majority of OGLE's $\sim 2000$ microlensing events are well-explained by stellar populations such as brown dwarfs, main-sequence stars, and compact remnants, a subset of six ultrashort-timescale events ($t_E \sim 0.1 - 0.3$ days) may signal the presence of PBHs. Building upon prior work that adopted the Navarro-Frenk-White (NFW) DM profile, we examine how alternative DM halo models -- specifically the Einasto and Burkert profiles -- affect microlensing predictions and the constraints on PBH abundance. We computed differential microlensing event rates for both profiles, using the main-sequence star rate as an observational benchmark. Our results show that neither the Einasto nor Burkert profiles reproduce the distribution of main-sequence star events, yet both allow for viable explanations of the ultrashort-timescale events with PBH masses $M_{\mathrm{PBH}} \sim 10^{-5} M_\odot$. Using a Poisson likelihood analysis under the null hypothesis that no PBH is observed in OGLE dataset, we derive 95\% C.L. upper bounds on $f_{\mathrm{PBH}}$, finding that the constraints are significantly relaxed under the Einasto and Burkert profiles compared to the NFW case. These results underscore the sensitivity of PBH constraints to the assumed DM halo structure and highlight the importance of accurately modeling the inner Galactic density profile to robustly assess PBH dark matter scenarios.

We explore the possibility of phase transitions between different quark matter phases occurring within quark stars, giving rise to the hybrid quark stars (HybQSs). Utilizing a well-established general parameterization of interacting quark matter, we construct quark star models featuring sharp first-order quark-quark phase transitions of various types, in contrast to the hadron-quark transition in conventional hybrid stars. We systematically investigate how recent observations, such as the pulsar mass measurements $M_{\rm TOV}\gtrsim2M_{\odot}$ and the GW170817's tidal deformability bound $\Lambda_{1.4M_{\odot}}<800$, constrain the viable parameter space. We also identified twin stars in some of the HybQS parameter space. This work unveils new possibilities of phase transitions and the resulting new types of compact stars in realistic astrophysical scenarios.

The DESI collaboration just obtained a set of precise BAO measurements, that combined with CMB and SNIa datasets show that the $\omega_0 \omega_a$CDM model is preferred over $\Lambda$CDM, at more than $4\,\sigma$, to describe the dynamics of the expanding Universe. This raises the question whether this model also suitably describes the clumpy Universe. Also lately, detailed analyses of diverse cosmic tracers resulted in a new dataset of measurements of an observable from the clumpy Universe: $\sigma_8(z)$, spanning a high-redshift data $z \in [0.013, 3.8]$. In this work we use this dataset of 15 $\sigma_8(z_i)$ measurements to study the viability of the $\omega_0 \omega_a$CDM cosmological model to explain the clustered Universe. Our analyses compare the $\omega_0 \omega_a$CDM model with the $\sigma_8(z)$ function reconstructed from the data points using Gaussian Process. Moreover, we perform a similar evaluation of the $\Lambda$CDM model considering Planck and~DESI best-fit parameters. In addition, we implemented robustness tests regarding Gaussian Process reconstruction to support our results.

In the past decade, hundreds of exoplanets have been discovered in extremely short orbits below 10 days. Unlike in the Solar System, planets in these systems orbit their host stars close enough to disturb the stellar magnetic field lines. The interaction can enhance the star's magnetic activity, such as its chromospheric and radio emission, or flaring. So far, the search for magnetic star-planet interactions has remained inconclusive. Here, we report the first detection of planet-induced flares on HIP 67522, a 17 million-year-old G dwarf star with two known close-in planets. Combining space-borne photometry from TESS and dedicated CHEOPS observations over a span of 5 years, we find that the 15 flares in HIP 67522 cluster near the innermost planet's transit phase, indicating persistent magnetic star-planet interaction in the system. The stability of interaction implies that the innermost planet is continuously self-inflicting a six time higher flare rate than it would experience without interaction. The subsequent flux of energetic radiation and particles bombarding HIP 67522 b may explain the planet's remarkably extended atmosphere, recently detected with the James Webb Space Telescope. HIP 67522 is therefore an archetype to understand the impact of magnetic star-planet interaction on the atmospheres of nascent exoplanets.

HIP 67522 is a 17 Myr old 1.2$M_\odot$ dwarf, and the only such young star known to host two close-in gas giant planets. The inner planet likely orbits close enough to its host to power magnetic star-planet interactions. In the radio domain, magnetic star-planet interaction is expected to produce a unique signature: electron cyclotron maser emission (ECME), beamed in phase with the orbit of the close-in planet. We conducted the longest radio monitoring campaign of a G dwarf host star to date to search for ECME, totaling $135\,$h on HIP 67522 over a period of five months with the Australia Telescope Compact Array (ATCA) between $1.1-3.1$GHz. We find that HIP 67522 is active in the radio, with emission that varies stochastically, with a duty cycle of $69\%$ above $0.24$mJy, and frequent bursts. Both the bursts and the quiescent emission are consistent with the canonical Güdel-Benz relation, and show a positive spectral index and brightness temperatures $\geq 10^{10}$K, indicating likely a flaring origin. Our observations cover $61\%$ of the innermost planet's orbit, including multiple visits of the quadrature where planet-induced ECME detection is most likely for this system. However, no orbital modulation or persistent polarization of the radio emission was detected. Our upper limit on circularly polarized emission from HIP 67522 suggests a $<0.7\%$ conversion efficiency of the magnetic power generated in the star-planet interaction into radio waves, unless the emission was missed by our phase or frequency coverage, or was absorbed in the circumstellar plasma. HIP 67522 is a system with one of the highest expected powers of star-planet interaction among known systems and shows strong indication of planet-induced flaring, motivating observations at other wavelengths to probe for further dissipation pathways.

The Carina Nebula is an active star-forming region with several open clusters rich in massive OB stars, thus making it an optimal target for studying stellar properties such as rotation for large samples of these early-type stars. We studied a sample of early-type stars probable members of the 8 open clusters in the Carina Complex. The observational data consist of high-resolution spectra from the Gaia-ESO public Spectroscopic Survey. Astrometric and photometric data from Gaia EDR3 and radial velocities measured from the observed spectra are used to confirm the cluster members. The projected rotational velocities of 330 early-type stars of Carina are derived from the widths of \ion{He}{i} lines at 4388 and 4471 Å. The reported \Vsini\ values are the first estimates for 222 early-type stars. The \Vsini\ distribution for the Carina clusters peaks at $\sim$100-150 \kms, consistent with the distributions for B stars in Galactic clusters. \Vsini\ estimates for stars members of the clusters Trumpler 15, Collinder 228, Collinder 232, and Bochum 11 are presented for the first time in the literature. For a subsample of stars with earlier spectral types from B0 to B3, we find a bimodal distribution, with a third, small peak towards the upper values of \Vsini. When the full sample is split according to the parent cluster, we find that the oldest cluster in our sample, NGC 3293, presents a higher concentration of rapidly rotating stars. In contrast, Collinder 228 presents a larger number of stars with lower \Vsini.

High-resolution optical spectra of sixteen red giants, two early asymptotic giant branch (AGB) stars, and two supergiants, having no/minimal to super lithium (Li)-rich abundances, are analyzed to investigate the helium (He)-enhancement. The spectra of eight giants were obtained from the Himalayan Chandra Telescope, and for the rest of the program stars the spectral data were collected from various public archives. Our detailed abundance analyses of the program stars involve the determination of stellar parameters and abundances for about 20 elements among the key abundances of He, Li, C, N, O and the 12C/13C ratios. The difference in the Mg-abundance derived from Mg I lines and the MgH band, and the difference in carbon abundance from C I and the CH-band, are used as a clue to the mild hydrogen-deficiency/helium-enhancement. From this analysis, four red giants, an early-AGB star and a supergiant star were found to be enhanced in helium. All these He-enhanced stars are also found to be super Li-rich except for the supergiant. Since the He-rich red giants are Li-rich as well, this implies, that He-enrichment is accompanied by Li-enrichment but not vice-versa. This is the first spectroscopic measurement of photospheric He-abundance in normal and Li-rich field giants. The Li-enrichment is observed across the giant branch from RGB-bump (KIC 9821622) to AGB phase, unlike that expected from the RGB-tip to RC-phase. A plausible scenario for the enrichment of He and as well as Li in giants is the fresh synthesis of Li in the interiors of giants and dredging up along with He to the surface, from deeper layers. However, there could be multiple scenarios operating in tandem. This analysis of He- and Li-enrichment along with other key elements provides more insights to decipher the mystery of Li-enrichment in giants.

Star cluster formation and assembly occurs inside filamentary and turbulent molecular clouds, which imprints both spatial and kinematic substructure on the young cluster. In this paper, we quantify the amount and evolution of this substructure in simulations of star cluster formation that include radiation magnetohydrodynamical evolution of the gas, coupled with detailed stellar dynamics, binary formation and evolution, and stellar feedback. We find that both spatial and kinematic substructure are present at early times. Both are erased as the cluster assembles through the formation of new stars as well as the merger of sub-clusters. Spatial substructure is erased over a timescale of approximately 2.5 times the initial free-fall time of the cloud. Kinematic substructure persists for longer, and is still present to the end of our simulations. We also explored our simulations for evidence of early dynamical mass segregation, and conclude that the presence of a population of binary stars can accelerate and enhance the mass segregation process.

As an update on the initial findings of DESI, the new results provide the first hint of potential deviations from a cosmological constant ($w=-1$), which, if confirmed with significance $>5\sigma$, will falsify the $\Lambda$CDM model. We consider a novel generalised form of an emergent dark energy model and confront this through various data sets (Baryon Acoustic Oscillation (BAO) data from Dark Energy Spectroscopic Instrument Data Release (DESI DR2), Type Ia Supernovae (SNe Ia) compilation, and Cosmic Microwave Background (CMB) distance priors) and simultaneously constrain the dark energy (DE) equation of state and energy density $f_{DE}(z)$. The results for the joint posteriors of cosmological parameters and the reconstructed dark energy EoS $w(z)$ with the energy density $f_{DE}(z)$ for various combinations of data sets are discussed, which favors quintessence nature. Specifically, $w(0) = -0.820$ with DESI DR2 + CMB, $-0.845$ with DESI DR2 + CMB + PP$^+$, $-0.828$ with DESI DR2 + CMB + Union3, and $-0.804$ with DESI DR2 + CMB + DESY5. We adopted a novel method to probe shifts in the generalized emergent dark energy (GEDE) parameter ($\Delta$) by mapping 2D marginalized posterior distributions in the $\Delta-\Omega_{m0}$ plane. Our analysis consistently reveals a preference for negative $\Delta$ across multiple combinations of observational datasets. Incorporating these values into the matter power spectrum further supports the GEDE framework's viability. We quantify the model's performance using the Bayes factor.

Carbon dioxide is one of the three most abundant species within the ice mantles around dust grains inside molecular clouds. Since a substantial amount of interstellar grains is made of siliceous materials, we have studied the infrared profile of CO2 deposited on top of a bare and ice-coated amorphous silicate (MgFeSiO4) film using reflection absorption infrared spectroscopy (RAIRS). In contrast to a metal surface, the CO2 IR profile shows a relaxation of the metal surface selection rule in the presence of the bare MgFeSiO4 dust grain analog, which brings the IR profile closer to the observational spectra while maintaining the sensitivity of RAIRS. Experiments with the underlying CO and CH4 ices show that their presence facilitates structural changes toward crystalline ice for the deposited CO2 at much lower temperatures than on the polar ice layers. Warming-up experiments of CO2 showed that it tends to stay on the silicate surface for much longer than on the gold surface without the silicate layer. We noticed for the first time a split in the 13CO2 IR feature on the pure or ice-covered silicate grain as a marker for the onset of diffusion. The laboratory 13CO2 profile then closely resembles recent JWST observations of this feature around young and embedded protostars, suggesting that it can be linked to the observed feature.

In star-forming regions, molecular cloud history and dynamics set the trend in the chemical composition. Ice formation, in particular, is affected by the evolution of physical conditions, which can lead to different ice compositions within the same cloud. In cold cores with medium densities >1e4 cm-3, low temperatures <15 K, and low UV radiation <G0, most COMs are formed on dust grain surfaces and are released back into the gas phase through non-thermal mechanisms. Studying both gas- and solid-phases can help observers to add constraints on the chemical and dynamical evolution of cold cores. We present a study of the cold core L694, observed with the IRAM 30m telescope. Observed species include CO (and its isotopologues) and CH3OH. We applied an inverted non-LTE radiative transfer code in order to obtain gas-phase abundances by deriving the column densities of the detected species from the spectroscopic parameters of the targeted molecular transitions, and from physical parameters derived from archival observations. This allowed us to probe the molecular abundances as a function of density and visual extinction. In parallel, we ran chemical models (both static and dynamic) to constrain the evolution time of the core by directly comparing the observations with the model outputs. We then compared the compositions of the cold cores L429-C and L694. The gas-phase abundances in L694 all exhibit a common depletion profile (with high variability in the depletion factor), as the core is identified to be in a more advanced (infalling) state compared to L429-C. The physical parameters of the two cores are, however, very similar, leading to close evolutionary timescales in our static models. The dynamical model fails to reproduce the CO gas-phase abundances at high density, predicting an evolutionary timescale that is too short compared to static models.

Accurate photometric redshift estimation is critical for observational cosmology, especially in large-scale surveys where spectroscopic measurements are impractical. Traditional approaches include template fitting and machine learning, each with distinct strengths and limitations. We present a hybrid method that integrates template fitting with deep learning using physics-guided neural networks. By embedding spectral energy distribution templates into the network architecture, our model encodes physical priors into the training process. The system employs a multimodal design, incorporating cross-attention mechanisms to fuse photometric and image data, along with Bayesian layers for uncertainty estimation. We evaluate our model on the publicly available PREML dataset, which includes approximately 400,000 galaxies from the Hyper Suprime-Cam PDR3 release, with 5-band photometry, multi-band imaging, and spectroscopic redshifts. Our approach achieves an RMS error of 0.0507, a 3-sigma catastrophic outlier rate of 0.13%, and a bias of 0.0028. The model satisfies two of the three LSST photometric redshift requirements for redshifts below 3. These results highlight the potential of combining physically motivated templates with data-driven models for robust redshift estimation in upcoming cosmological surveys.

The existence of billion-solar-mass quasars at redshifts $z \gtrsim 7$ poses a formidable challenge to theories of black hole formation, requiring pathways for the rapid growth of massive seeds. Population III.1 stars, forming in pristine, dense dark matter (DM) minihalos, are compelling progenitors. This study presents a suite of stellar evolution models for accreting Pop III.1 protostars, calculated with the \textsc{GENEC} code. We systematically explore a wide parameter space, spanning ambient WIMP densities of $\rho_\chi \sim 10^{12}\mbox{-}10^{16}\,\mathrm{GeV\,cm^{-3}}$ and gas accretion rates of $10^{-3}\mbox{-}10^{-1}\,M_\odot\,\mathrm{yr^{-1}}$, to quantify the effects of DM annihilation. A central finding is that for a protostar to grow to supermassive scales ($\gtrsim 10^5 \, M_{\odot}$), the ambient DM density in the immediate vicinity of the star must exceed a critical threshold of $\rho_{\chi} \gtrsim 5 \times 10^{14} \, \text{GeV cm}^{-3}$. The energy injected by WIMP annihilation inflates the protostar, lowering its surface temperature, which suppresses the ionizing feedback that would otherwise halt accretion and significantly delays the onset of hydrogen fusion. This heating also governs the star's final fate: in dense halos ($\rho_\chi \gtrsim 10^{15}\,\mathrm{GeV\,cm^{-3}}$), stars remain stable against general relativistic instability beyond $10^6 \, M_{\odot}$, whereas at lower densities ($\rho_\chi \lesssim 10^{13}\,\mathrm{GeV\,cm^{-3}}$), they collapse at masses of $\sim 5 \times 10^5 \, M_{\odot}$. Once the DM fuel is exhausted and core burning commences, the protostar contracts and its ionising photon output can reach very high levels $\sim 10^{53} s^{-1}$. These distinct evolutionary phases offer clear observational signatures for the JWST, providing a robust, physically-grounded pathway for forming heavy black hole seeds in the early universe.

Gamma-ray bursts (GRBs), the brightest electromagnetic bursts in the universe, are believed to originate from ultra-relativistic jets launched by the rapidly rotating central engine, either a disk-surrounded newly formed black hole (BH) or a magnetar. Such a central engine potentially possesses rapidly evolving physical characteristics, as it is just born. The caught of time-increasing frequency in the gravitational wave signals is the evidence of upon opinion. Here we report a possible oscillatory signal identified in GRB 131122B with periods increasing from 1.27 seconds to 4.02 seconds in a time interval of 16.75 seconds. Such a peculiar oscillation signal has not been identified in GRBs before and its periodic evolution could also be the quickest one found in the electromagnetic radiation window of astrophysics. The precession of a misaligned accretion disk caused by the tidal disruption of a star by an intermediate-mass BH may be responsible for this signal. This finding could open a new window to reveal the nature of the hiding central engine of GRBs.

In this work, we perform reconstruction of \( f(Q) \) gravity inspired by the New Agegraphic Dark Energy (NADE) model, aiming to account for the Universe's late time acceleration without invoking a cosmological constant. Utilizing a power law scale factor \( a(t) = a_0 t^h \), we derive an analytic form for \( f(Q) \) based on a correspondence with NADE, where the conformal time serves as the infrared cutoff. The resulting model naturally recovers General Relativity in the limit and exhibits a geometrically motivated dark energy component. We constrain the model parameters using recent Baryon Acoustic Oscillation (BAO) data from DESI DR2 BAO and previous BAO observations through the Markov Chain Monte Carlo (MCMC) analysis. The reconstructed Hubble parameter \( H(z) \) demonstrates excellent agreement with observational data, achieving high \( R^2 \) values and low \(\chi^2_{\min}\), AIC, and BIC scores, outperforming the standard \( \Lambda \)CDM model. Further, we investigate the cosmological evolution using the deceleration parameter \( q(z) \), effective equation of state \( \omega_{\mathrm{eff}}(z) \), and Om diagnostics. The model exhibits a clear transition from deceleration to acceleration with a present value \( q(0) \in \left[-0.5879, -0.3333\right] \) and transition redshift $z_{\mathrm{tr}} \sim 0.5209-0.8126$, while maintaining \( -1 < \omega_{\mathrm{eff}}(z) < -1/3 \), indicating quintessence like behavior. Om diagnostics consistently show a negative slope, further confirming deviation from \( \Lambda \)CDM. Energy condition analysis reveals that WEC, DEC, and NEC are satisfied, while SEC is violated only at low redshifts which is consistent with cosmic acceleration. Overall, the reconstructed \( f(Q) \) model provides a viable, observationally consistent, and theoretically motivated alternative to standard dark energy scenarios.

Acoustic modes are excited by turbulent convection in the outer convective envelope of solar-like stars. Observational results from asteroseismic studies show that 44% of solar-like stars do not present detectable stochastically-excited acoustic modes. This phenomenon appears to be related to their rotation rate and magnetic activity. In a first paper, we showed that uniform rotation tends to diminish the mode amplitudes significantly. However, convective envelopes in solar-type stars are differentially rotating: the rotation rate difference between mid-latitudes and the equator can go up to 60%, as shown by recent asteroseismic works. In this paper, we examine the impact of differential rotation on the stochastic excitation of acoustic modes in solar-like stars. We provide theoretical predictions for the excitation of acoustic modes in a differentially rotating solar-like star. We use the Rotating Mixing-Length Theory approach to model the local influence of differential rotation on convection. We then estimate the resulting impact on power injection by turbulent convection into oscillation modes numerically, using a combination of the MESA stellar structure and evolution code and GYRE stellar pulsation code. We show that the power injected in acoustic modes differs by up to 30 % for stars with the same mean rotation rate $5 \Omega_{\odot}$ but a distinct differential rotation rate. The excitation of axisymmetric acoustic modes is further inhibited in the anti-solar differential rotation regime where the pole of stars rotates faster than their equator when compared to the uniform rotation case. This could hinder mode detection in such configurations. This study permits a first prediction of the excitation of acoustic modes as a function of the differential rotation in solar-like pulsators.

Titan, with its thick and hazy atmosphere, is a key world in our solar system for understanding light scattering processes. NASA's Cassini mission monitored Titan between 2004 and 2017, where the derived dataset includes a large number of whole disk observations. Once spatially integrated, these whole disk observations reveal Titan's phase-dependent brightness which can serve as an analog for how hazy worlds might appear around other stars. To explore Titan's phase curve, we present a pipeline for whole disk Titan observations acquired by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) spanning 0.9--5.1 $\mu$m. Application of the pipeline finds over 4,400 quality spatially- and spectrally-resolved datacubes that were then integrated over Titan's disk to yield phase curves spanning 2--165\degree{} in phase angle. Spectra at near-full phase provide a useful approximation for Titan's geometric albedo, thus extending the spectral coverage of previous work. Crescent phase brightness enhancements in the Cassini VIMS phase curves are often more extreme than analogous results seen at optical wavelengths, which can be explained by atmospheric transparency and haze scattering processes. These results provide validation opportunities for exoplanet-focused spectral models and also shed light on how extreme aerosol forward scattering could influence exoplanet observations and interpretations.

Rocky exoplanet characterization has been a top priority for early James Webb Space Telescope (JWST) science operations. Several milestones have been achieved, including the most precise rocky planet transmission spectra measured to date, and the first detection of thermal emission for rocky worlds below 800 Kelvin. Despite these advances, no atmospheres have been definitively detected. Several transmission spectra show tentative evidence for molecular absorption features, but these hints are marginally significant and the spectra may be affected by stellar contamination. Features from many plausible atmospheres, including those dominated by oxygen, nitrogen, and carbon dioxide, are below the current noise level. Meanwhile, the emerging picture from thermal emission spectra is that the planets have hot daysides, consistent with either a bare rock composition or low surface pressure atmospheres (< 10 bar). Higher surface pressures and high carbon dioxide abundances are generally ruled out, assuming cloud-free atmosphere models. The absence of strong CO$_2$ features hints at a limited initial volatile inventory or rapid atmospheric escape during the planets' early lifetimes. Taken together, these results motivate a push towards higher precision data, as well as observations of cooler planets that may be more likely to retain atmospheres. As a goal for future transmission spectroscopy, we suggest a "five scale height challenge," to achieve the precision necessary to detect CO$_2$ features in nitrogen-rich atmospheres. Detecting rocky planet atmospheres remains challenging, but with JWST's excellent performance and a continuing investment of telescope time, we are optimistic these uncharted atmospheres will be detected in coming years.

We propose a possible binary evolution model for the formation of ultra-long period pulsars (ULPPs). The model involves two key stages: first, a neutron star (NS) in wide binaries undergoes an effective spin-down phase through wind-fed accretion from its massive stellar companion; second, the supernova explosion of the companion leads to the disruption of the binary system, and produces two isolated compact stars. One of the them is the first-born, slowly rotating NSs, and our binary and spin evolution calculations show that the spin periods range from $\lesssim 0.1$ s to $\gtrsim 10^8$ s. This offers a possible formation channel for some of the long-period radio transients. We estimate that the formation rate of such systems in the Milky Way is approximately about $10^{-6}$ $\rm yr^{-1}$.

We investigate the consequences of non-ideal mixing between silicate, iron metal, and hydrogen for the structures of the cores of sub-Neptunes with implications for super-Earths, warm Neptunes, and ice giants. A method of extrapolating what we know about the miscibility in the three bounding binary systems MgSiO$_3$-H$_2$, MgSiO$_3$-Fe, and Fe-H$_2$ to the ternary composition space is used to deduce the phase equilibria of this system at relevant temperature and pressure conditions. We find that while separate silicate and metal phases can exist at shallow depths, the phases become entirely miscible deeper in the cores, thus altering the density structure of the cores. The assumption that the interiors of large rocky planets, either with extant magma oceans beneath H$_2$-rich envelopes, or evolved from such bodies, are composed of a differentiated metal core overlain by a silicate mantle is inconsistent with our understanding of the phase equilibria of these bodies.

The particle acceleration and transport process during solar eruptions is one of the critical and long-standing problems in space plasma physics. Through decades of research, it is well accepted that particles with higher energies released during a solar eruption arrive at observers earlier than the particles with lower energies, forming a well-known structure in the dynamic energy spectrum called particle velocity dispersion (VD), as frequently observed by space missions. However, this picture is challenged by new observations from NASA's Parker Solar Probe and ESA's Solar Orbiter which show an unexpected inverse velocity dispersion (IVD) phenomenon, where particles with higher-energies arrive later at the observer. Facing on the challenge, we here report the recent discovery of such IVD structures with 10 solar energetic proton events observed by Solar Orbiter, and then analyze the mechanisms causing this unusual phenomenon. We suggest that shock diffusive acceleration, with respect to magnetic reconnection, is probably a dominant mechanism to accelerate protons to tens of MeV in such events where particles need longer time to reach higher energies. And we determine, innovatively, the physical conditions and time scales during the actual shock acceleration process that cannot be observed directly.

The T and Y spectral classes represent the coolest and lowest-mass population of brown dwarfs, yet their census remains incomplete due to limited statistics. Existing detection frameworks are often constrained to identifying M, L, and early T dwarfs, owing to the sparse observational sample of ultracool dwarfs (UCDs) at later types. This paper presents a novel machine learning framework capable of detecting and classifying late-T and Y dwarfs, trained entirely on synthetic photometry from atmospheric models. Utilizing grids from the ATMO 2020 and Sonora Bobcat models, I produce a training dataset over two orders of magnitude larger than any empirical set of >T6 UCDs. Polynomial color relations fitted to the model photometry are used to assign spectral types to these synthetic models, which in turn train an ensemble of classifiers to identify and classify the spectral type of late UCDs. The model is highly performant when validating on both synthetic and empirical datasets, verifying catalogs of known UCDs with object classification metrics >99% and an average spectral type precision within 0.35 +/- 0.37 subtypes. Application of the model to a 1.5 degree region around Pisces and the UKIDSS UDS field results in the discovery of one previously uncatalogued T8.2 candidate, demonstrating the ability of this model-trained approach in discovering faint, late-type UCDs from photometric catalogs.

This work is dedicated to the discovery of the eclipsing variable star Grigoriev 1 and determining the parameters of its binary system. The star was found through the systematic checking of ultraviolet sources of GALEX space observatory in Pegasus constellation. Analysis of the ZTF project data has shown the presence of eclipses with two magnitudes depth and a period of 6.5997 days. The duration of eclipse covers only 1% of the orbital period, and the partial phases are at least 30 times shorter. Those parameters imply that the star is a detached binary system with a white dwarf seen edge-on. The new object was added to the International Variable Star Index AAVSO VSX as Grigoriev 1. Over the 10 million objects in VSX database there are only 188 variable stars of EA/WD type. Grigoriev 1 has the longest orbital period out of those. Moreover, its absolute magnitude M at maximum light from Gaia space observatory data is about +6.8. On the color-luminosity diagram it occupies the intermediate position between hot subdwarfs and white dwarfs which makes it even more interesting and worth studying at professional telescopes.

The population of bright galaxies at $z\gtrsim10$ discovered by JWST, including the so-called "blue monsters", has been difficult to reconcile with standard galaxy evolution models. To shed light on this extraordinary population, we study the $z\sim8$ galaxies discovered by the BoRG-$JWST$ survey. These slightly-lower redshift analogs are comparable in UV luminosity to the blue monsters, and their lower redshift makes it much easier to access key rest frame optical diagnostics with NIRspec. We find that BoRG-$JWST$ galaxies are consistent with being dust-poor based on their blue UV slopes and Balmer decrement ratios. We find no strong evidence for dominant active galactic nuclei contribution to the UV brightness, based on line-ratio diagnostics, though some contribution cannot be excluded. We further infer the stellar mass, star formation and UV-brightness history of the BoRG-$JWST$ galaxies by fitting their rest-frame UV-optical spectra. We see evidence for stochastic episodes of star formation for all the BoRG-$JWST$ galaxies, providing a temporal boosting of UV luminosity in short timescales. The UV-bright blue monsters at $z\gtrsim10$ can be explained by the presence of stars with ages below 100 Myr.

Purpose: The subject of research is the spatio-temporal charged particles in the Earth's magnetosphere outside the South Atlantic magnetic Anomaly during the 11-year cycle of solar activity minimum. The work aims at searching for and clarifying the sustained and unstable new spatial zones of enhanced subrelativistic electron fluxes at the altitudes of the low Earth orbit satellites. Design/methodology/approach: Finding and ascertainment of new radiation belts of the Earth were made by using the data analysis from the D1e channel of recording the electrons of energies of $\Delta E_e =180$-510 keV and protons of energies $\Delta E_p=3.5$-3.7 MeV of the position-sensitive silicon matrix detector and onto the solid angle of view of the detector head of the instrument was used. Findings: A sustained structure of three electron radiation belts in the Earth's magnetosphere was found at the low solar and geomagnetic activity in May 2009. The two belts are known since the beginning of the space age as the Van Allen radiation belts, and an additional permanent layer is formed around the drift shell with the McIlwaine parameter of $L\approx1.65$. On some days in May 2009, the two new inner radiation belts were observed simultaneously, one of those latter being recorded between the investigated sustained belt at $L\approx1.65$ and the Van Allen inner belt at $L\approx2.52$. Conclusions: The new found inner radiation belts are recorded in a wide range of geographic longitudes, both at the ascending and descending nodes of the satellite orbit. Key words: radiation belt, STEP-F instrument, electrons, magnetosphere, drift $L$-shell, particle flux density

The study guide (textbook) is part of a set of materials designed to support high-quality practical training in physics. It includes a collection of tasks for organizing both in-class and independent work. The guide serves as a foundation for further study in physics-related disciplines and aligns with current educational programs. This textbook presents a curated set of 120 physics problems with detailed solutions, structured according to the first-year bachelor's curriculum. Each section addresses common student questions and emphasizes conceptual understanding. Problem-solving is essential in physics education. It not only tests knowledge but also transforms theory into practical skills. Applying physical laws to real-world scenarios enhances comprehension and fosters analytical thinking. Through solving problems, students gain deeper insight into physical phenomena and develop effective strategies for analysis, and develop solutions to tasks-making the learning process truly comprehensive.

As an alternative to the ultraviolet light emitting diode(UV LED), the feasibility of utilizing UV micro-LED in the charge management in the detection of gravitational waves in space is experimentally studied. Compared with UV LED, micro-LED is more compact in size, has better current spreading, faster response time and longer operating life. Performance characteristics of micro-LEDs were measured, with peak wavelength of 254 nm, 262 nm, 274 nm, and 282 nm for each respective micro-LED, and the photoelectric effect was demonstrated. The effectiveness of micro-LED based charge management experiments were demonstrated using above micro-LEDs mounted on a cubical test mass, and different discharge rates were achieved by varying the drive current and duty cycle using pulse width modulation(PWM). Laboratory data was also shown to demonstrate the space qualification of the micro-LED device, the key electrical and optical characteristics of the micro-LEDs showed less than 5% variation. The results of the qualification bring the micro-LED device Technology Readiness Level(TRL) to TRL-5. TRL-6 will be reached provided additional radiation and thermal tests are conducted and in a position ready to be flown and further tested in space.

In this paper, we present 52 new numerical-relativity (NR) simulations of black-hole-neutron-star merger (BHNS) mergers and employ the data to inform TEOBResumS-Dalí: a multipolar effective-one-body model also including precession and eccentricity. Our simulations target quasicircular mergers and the parameter space region characterized by significant tidal disruption of the star. Convergent gravitational waveforms are produced with a detailed error budget after extensive numerical tests. We study in detail the multipolar amplitude hierarchy and identify a characteristic tidal signature in the $(\ell,m)=(2,0)$, and $(3,0)$ modes. We also develop new NR-informed models for the remnant black hole and for the recoil velocity. The numerical data is then used to inform next-to-quasicircular corrections and the ringdown of TEOBResumS-Dalí for BHNS. We show an overall order of magnitude improvement in the waveform's amplitude at merger and more consistent multipoles over our older TEOBResumS-GIOTTO for BHNS. TEOBResumS-Dalí is further validated with a new 12 orbit precessing simulation, showing phase and relative amplitude differences below $\sim 0.5$ (rad) throughout the inspiral. The computed mismatches including all the modes lie at the one percent level for low inclinations. Finally, we demonstrate for the first time that TEOBResumS-Dalí can produce robust waveforms with both eccentricity and precession, and use the model to identify the most urgent BHNS to simulate for waveform development. Our new numerical data are publicly released as part of the CoRe database.

Eccentric binaries are key targets for current and future gravitational wave (GW) detectors, offering unique insights into the formation and environments of compact binaries. However, accurately and efficiently modeling eccentric waveforms remains challenging, in part due to their complex harmonic structure. In this work, we develop a post-Newtonian (PN) framework to compute the Fourier amplitudes of GWs from eccentric binaries, deriving simple expressions at 1PN order for all relevant $(l, m)$ multipoles, valid for arbitrary eccentricities. We then characterize the GW emission by analyzing the contribution of each $(l, m)$ mode to the strain, its mean frequency, frequency spread, and asymptotic behavior at high frequencies. Additionally, we introduce a method to determine the minimal set of Fourier modes needed to reconstruct the waveform to a given accuracy. Finally, we also discuss how our framework can be extended to higher PN orders, obtaining closed-form expressions for the leading-order tail and spin contributions and outlining the steps required to include higher-order corrections. Our results provide both a deeper theoretical understanding of eccentric GW emission and practical tools for developing more accurate and efficient waveform models.

The paper presents preliminary results of studying variations in the annual component in the Earth's polar motion. For this purpose, a signal with an annual period was extracted, firstly, from the series of pole coordinates of the International Earth Rotation and Reference Systems Service (IERS), and secondly, from the combined series of Pulkovo latitude variations for 1840--2017. For this purpose, one-dimensional and multidimensional singular spectrum analysis was used. The Hilbert transform was used to calculate the change in the amplitude and phase of the annual oscillation over time. As a result, it turned out that over an interval of about 180 years, an almost monotonic increase in the amplitude of the annual oscillation from $\approx$60~mas to $\approx$90~mas and an almost monotonic phase shift of $\approx$45$^\circ$ are observed. A correlation was also found between the amplitude of the annual component and the difference in average temperatures from November to March in the northern and southern hemispheres.

We investigate the dynamics of the Friedmann-Lemaître-Robertson-Walker spacetime within the framework of $f(R)$ gravity using a compact, model-independent dynamical systems approach. By assuming a power-law scale factor, we explore ekpyrotic and accelerating solutions to address the big bang singularity. Our analysis demonstrates that a cosmological bounce, characterized by a transition from contraction to expansion, possibly avoids the singularity without directly using the Raychaudhuri equation, unlike previous approaches using specific $f(R) \simeq R^n$ forms. We identify a key fixed point in the phase space corresponding to the bounce, supported by perturbation analysis and qualitative description of trajectories in the phase space. The results suggest that $f(R)$ gravity provides a robust framework for non-singular cosmologies.

We analyze the quasinormal modes (QNMs) of scalar, electromagnetic, and Dirac test fields in the background of a black hole immersed in a galactic dark matter halo. The analytic black hole solution considered here is sourced by a physically motivated halo density profile that leads to a flat galactic rotation curve. Using the sixth-order WKB method with Padé approximants, we compute the QNM spectra for various field spins and parameter values, and provide numerical data in tabulated form. In addition to the numerical analysis, we derive analytic expressions for the quasinormal frequencies in the eikonal limit and beyond, by means of an expansion in inverse powers of the multipole number. We also calculate the Unruh temperature perceived by a static observer in the halo-modified spacetime. Our results demonstrate that the presence of the dark matter halo leads to observable modifications in the QNM spectra only if the density or compactness of the galactic halo is extraordinary high, so that quasinormal ringing a reliable observable for testing the black hole geometry, even in the presence of galactic environments.

The stability of thin shell wormholes and black holes to linearized spherically symmetric perturbations about a static equilibrium is analyzed. Thin shell formalism is explored and junctions formed from combinations of Schwarzschild, Schwarzschild - de Sitter, and Schwarzschild - anti-de Sitter, as well as Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetimes are considered. The regions of stability for these different combinations are thoroughly described and plotted as a function of mass ratios of the Schwarzschild masses and radii of the wormhole throats. A taxonomy of the qualitative features of the various configurations and parameter spaces is developed, illustrating the stability regions when present. The considered wormholes are all found to be unstable in the causal region.

Dark matter particles with sufficiently large interactions with ordinary matter can scatter in the Earth before reaching and scattering in a detector. This induces a modulation in the signal rate with a period of one sidereal day. We calculate this modulation for sub-GeV dark matter particles that interact either with a heavy or an ultralight dark-photon mediator and investigate the resulting signal in low-threshold detectors consisting of silicon, xenon, or argon targets. The scattering in the Earth is dominated by dark matter scatters off nuclei, while the signal in the detector is easiest to observe from dark matter scattering off electrons. We investigate the properties of the modulation signal and provide projections of the sensitivity of future experiments. We find that a search for a modulation signal can probe new regions of parameter space near the energy thresholds of current experiments, where the data are typically dominated by backgrounds.

We present uniform rate inflation in a modified $f(T, \mathcal{T}) $ gravity. It is found that early inflation can be realized even with a scalar field field with a quadratic potential and a negative cosmological constant. We construct inflationary model for the inflaton field without slow-roll approximation. The inflaton field rolling at a constant speed permits a universe with sufficient inflation which encompasses the present universe fairly well. The initial value of the scalar satisfies a lower limit which is sufficiently large compared to the field required for chaotic inflation. The Planck prediction for cosmological perturbations are estimated. It is found that the cosmological model is stable.

TRIDENT experiment is a planned neutrino observatory at West Pacific Ocean to search for astrophysical neutrinos. The final full-scale detector array is expected to have about 1000 strings, each of which consists of 20 hybrid digital optical modules. Each module will contain a number of photomultiplier tubes (PMTs) and silicon photomultipliers to detect Cherenkov lights. In this paper, we present a custom designed digitization mainboard for the TRIDENT experiment. It includes PMT waveform digitization at a sampling rate of 125 MS/s using commercial analog-to-digital converters, and time digitization using time-to-digital converters implemented in a Field Programmable Gate Array (FPGA). We present its design and the first performances.

With no binary neutron star (BNS) merger detected yet during the fourth observing run (O4) of the LIGO-Virgo-KAGRA (LVK) gravitational wave (GW) detector network, despite the time-volume (VT) surveyed with respect to the end of O3 increased by more than a factor of three, a pressing question is how likely the detection of at least one BNS merger is in the remainder of the run. I present here a simple and general method to address such a question, which constitutes the basis for the predictions that have been presented in the LVK Public Alerts User Guide during the hiatus between the O4a and O4b parts of the run. The method, which can be applied to neutron star - black hole (NSBH) mergers as well, is based on simple Poisson statistics and on an estimate of the ratio of the VT span by the future run to that span by previous runs. An attractive advantage of this method is that its predictions are independent from the mass distribution of the merging compact binaries, which is very uncertain at the present moment. The results, not surprisingly, show that the most likely outcome of the final part of O4 is the absence of any BNS merger detection. Still, the probability of a non-zero number of detections is 34-46\%. For NSBH mergers, the probability of at least one additional detection is 64-71\%. The prospects for the next observing run O5 are more promising, with predicted numbers $N_\mathrm{BNS,O5}=28_{-21}^{+44}$, and the NSBH detections to be $N_\mathrm{NSBH,O5}=65_{-38}^{+61}$ (median and 90\% symmetric credible range), based on the current LVK detector target sensitivities for the run. The calculations presented here also lead to an update of the LVK local BNS merger rate density estimate that accounts for the absence of BNS merger detections in O4 so far, that reads $2.8\,\mathrm{Gpc^{-3}\,yr^{-1}}\leq R_0\leq 480\,\mathrm{Gpc^{-3}\,yr^{-1}}$.

The population of unresolved stellar-mass black hole binaries (sBBHs) is expected to produce a stochastic gravitational-wave background (SGWB) potentially detectable by the Laser Interferometer Space Antenna (LISA). In this work, we compute the imprint of astrophysical environmental effect--such as gas dynamical friction and accretion--on this background. Using the sBBHs population constraints obtained by the LIGO--Virgo--Kagra collaboration, we compute the expected SGWB and develop a phenomenological parametric model that can accurately capture the effect of dynamical friction and accretion. Using our model, we perform Bayesian inference on simulated signals to assess the detectability of these environmental effects. We find that even for large injected values of the Eddington ratio, the effect of accretion in the SGWB is undetectable by LISA. However, LISA will be able to constrain the effect of dynamical friction with an upper bound on the gas density of $\rho \lesssim 7.6 \times 10^{-10} \mathrm{g \, cm^{-3}}$, thus probing the sBBH environment forming in typical thin accretion disks around Active Galactic Nuclei (AGNs). For injected densities of $\rho \sim 10^{-10}-10^{-9} \mathrm{g} \, \mathrm{cm}^{-3}$, dynamical friction effects can be well measured and clearly distinguished from vacuum, with Bayes factors reaching up to $\sim$ 60, even when the Galactic foreground is included.

Based on considerations of quantum gravity, global symmetries which lead to axions as pseudo Nambu-Goldstone bosons after low scale symmetry breaking cannot be exact at the Planck scale. Here, we show that Planck-suppressed terms which yield this symmetry breaking may provide a non-inflationary misalignment mechanism which can generate coherent oscillations of the axion and axion-like particle (ALP) fields at low temperatures.

We study perturbative unitarity bounds on the field-space curvature in de Sitter spacetime, using the momentum-space entanglement approach recently proposed by Pueyo, Goodhew, McCulloch, and Pajer. As an illustration, we perform a perturbative computation of the purity in two-scalar models and compare the resulting unitarity bounds with those obtained via a flat space approximation. In particular, we find that perturbative unitarity imposes an upper bound on the field-space curvature of the Hubble scale order, in addition to a bound analogous to the flat space result. This reflects the thermal nature of de Sitter spacetime. We also discuss generalizations to higher-dimensional field spaces.

Higher-derivative modifications of general relativity are generically expected from effective field theory approaches to quantum gravity, and they arise naturally in Lorentz-violating theories such as Einstein-Ether gravity. In this work, we investigate black hole spacetimes within Einstein-Ether theory supplemented by quadratic curvature corrections, including terms proportional to $R^2$, $R_{\mu\nu} R^{\mu\nu}$, and $R_{\mu\nu\lambda\rho} R^{\mu\nu\lambda\rho}$. We derive the corrected static, spherically symmetric metric perturbatively and examine its effects on the geodesic structure and gravitational wave emission. In particular, we analyze periodic timelike orbits in this background and compute the associated tensor-mode gravitational waveforms using the quadrupole approximation. Our results demonstrate that even small higher-derivative corrections can induce distinguishable shifts in the orbital dynamics and imprint characteristic phase modulations and harmonic deformations in the gravitational wave signal. These effects modify the frequency spectrum and amplitude envelope of $h_{+}$ and $h_{\times}$ in a manner sensitive to the coupling constants $\alpha$, $\beta$, and $\gamma$, and the Ether parameter $c_{13}$. The resulting signatures provide a potential observational window into ultraviolet deviations from general relativity and Lorentz symmetry in the strong-field regime.

We propose an alternative scalar-tensor theory based on the Khronon scalar field labeling a family of space-like three-dimensional hypersurfaces. This theory leads to modified Newtonian dynamics (MOND) at galactic scales for stationary systems, recovers GR plus a cosmological constant in the strong field regime, and is in agreement with the standard cosmological model and the observed cosmic microwave background anisotropies.

We present a comprehensive analysis of the interactions of neutrinos with the dark sector within the simplified model framework. We first derive the exact analytic formulas for the differential scattering cross sections of neutrinos with scalar, fermion, and vector dark matter (DM) for light dark sector models with mediators of different types. We then implement the full catalog of constraints on the parameter space of the neutrino-DM and neutrino-mediator couplings and masses, including cosmological and astrophysical bounds coming from Big Bang Nucleosynthesis, Cosmic Microwave Background, DM and neutrino self-interactions, DM collisional damping, and astrophysical neutrino sources, as well as laboratory constraints from 3-body meson decays and invisible $Z$ decays. We find that most of the benchmarks in the DM mass-coupling plane adopted in previous studies to get an observable neutrino-DM interaction effect are actually ruled out by a combination of the above-mentioned constraints, especially the laboratory ones which are robust against astrophysical uncertainties and independent of the cosmological history. To illustrate the consequences of our new results, we take the galactic supernova neutrinos in the MeV energy range as a concrete example and highlight the difficulties in finding any observable effect of neutrino-DM interactions. Finally, we identify new benchmark points potentially promising for future observational prospects of the attenuation of the galactic supernova neutrino flux and comment on their implications for the detection prospects in future large-volume neutrino experiments such as JUNO, Hyper-K, and DUNE. We also comment on the ultraviolet-embedding of the effective neutrino-DM couplings.