Papers for Thursday, Aug 14 2025

We investigate the distribution of an interacting axion-like massive field within a magnetized Neutron Star. For this we consider the effect of an intense density-dependent axially symmetric stellar magnetic field ${\bf B}(r,\theta)$ adding another much weaker, but non-vanishing, electric field. We particularize the latter for the case when a finite chiral charge density is present. The axion field is thus coupled to a generic function $Q(F_0,G_0)$ depending on Lorentz invariants $F_0, G_0$ which can be constructed from these electromagnetic fields. From this, the static axion field equations are solved as function of stellar radial coordinate and angular direction, $a(r,\theta)$, using a prescribed linear form for $Q$. In addition, we use a semi-analytical approach to calculate the stellar structure in this hybrid system where pressure components are treated under a perturbative scheme, provided induced deformations with respect to spherical symmetry are tiny. Our results show that the axion couplings to magnetic and electric fields along with its mass, critically determine the axion spatial distribution. Furthermore, we focus on the possibility that the axion field might accumulate in specific outer regions of the star, particularly within the crust, where it could form a condensate. We explore the possible presence of magnetic flux tubes from superconductor phases in this outer layers and qualitatively show they may enhance local conversion into photons. We explore prospects of detectability through indirect methods.

Exoplanets with and without a magnetic field are predicted to form, behave, and evolve very differently. Therefore, there is great need to directly constrain these fields to holistically understand the properties of exoplanets including their potential habitability. This goal aligns with the Astro2020 Decadal Survey recommendations. Observing planetary auroral radio emissions is among the most promising detection methods, but decades of searching have yet to yield a conclusive detection, though promising hints are now emerging from ground-based radio telescopes. However, these ground-based efforts are fundamentally limited by Earth's ionosphere, which blocks the low-frequency signals (<10 MHz) expected from terrestrial and Neptune-like exoplanets. In this white paper, we outline a strategy to overcome this barrier by utilizing the unique environment of the Moon. We discuss how the upcoming LuSEE-Night and ROLSES pathfinder missions will study our Solar System's planets as exoplanet analogs and place the first meaningful upper limits on exoplanetary radio flux below 10 MHz. Furthermore, we explore the revolutionary potential of the proposed future lunar arrays FarView and FARSIDE. For example, FarView will be sensitive enough to study the magnetic fields of a diverse set of exoplanets (super-Earths to gas giants) and an order of magnitude more Jupiter-like planets than ground-based telescopes, providing crucial tests for dynamo theory. Most significantly, FARSIDE will be able to detect the magnetospheres of nearby terrestrial exoplanets, offering a powerful synergy with atmospheric characterization efforts by JWST and HWO to fully assess their potential habitability. By opening this unexplored low-frequency window, radio astronomy from the Moon is poised to transform the field of exoplanet magnetospheric science. [Abridged]

We present a new independent determination for the age of one of the oldest open clusters, NGC 188: $6.41 \pm 0.33$ Gyr. We utilize a novel approach where we jointly fit the radial velocities (RVs) and spectral energy distributions (SED) of six binary star systems in the cluster. The joint fit has 21 free parameters: 12 stellar masses, 6 orbital inclination angles, as well as a common cluster age, distance, and extinction, $A_V$. The fit to the SEDs utilizes MIST stellar isochrones, and the fitted stellar parameters are presented in HR diagrams (R - $T_{\rm eff}$, R - M, and M - $T_{\rm eff}$) showing the stars' different states of evolution. These isochrones are compared with PARSEC and Y2 isochrones to obtain an estimate of the uncertainties introduced by different stellar models. Of the 3017 stars taken from the NGC 188 field, 333 possible member stars were selected using Gaia data and analyzed separately for their mean distances and proper motions. We find a distance to NGC 188 of $1850 \pm 12$ pc compared with the independent photometric distance found from the SED fitting of $1897 \pm 58$ pc.

The family of multi-plane phase retrieval sensors, such as the curvature and nonlinear curvature wavefront sensors (WFS), contain tip/tilt information embedded in their signals. We have built a nonlinear curvature WFS to study different wavefront reconstruction methods and test the ability to extract tip/tilt information. Using reliable and fast centroiding algorithms, combined with knowledge of the measured z-distance to each measurement plane, we demonstrate that image jitter may be sensed and compensated for using a fast steering mirror and the WFS alone, i.e. without the need for peripheral components such as quad-cells or access to a separate scientific imaging channel. This approach, which is both precise and accurate, corroborates previous numerical simulations and is expected to improve the overall reconstruction accuracy of multi-plane phase retrieval sensors including higher order spatial modes.

Luminous Red Novae (LRNe) are transients associated with mass ejection during stellar mergers and common envelope evolution (CEE). LRNe have the potential to illuminate the poorly understood phases of binary evolution leading up to the CEE, during the mass ejection phase, and in the immediate aftermath. However, the mechanism responsible for powering LRN light curves and the origin of their observed diversity remain open questions. Here, we perform two-dimensional moving-mesh radiation-hydrodynamic simulations of LRNe that take into account hydrogen recombination and relevant opacities. We study a typical high-mass stellar merger, which dynamically ejects 2 $M_\odot$ with a characteristic velocity of 410 km/s. This ejecta collides with 2.7 $M_\odot$ of equatorially concentrated circumbinary material (CBM) left behind from a prior phase of non-conservative runaway mass transfer. We find that the resulting light curve is composed of a short, blue peak followed by a redder, predominantly shock-powered plateau with luminosities reaching up to $10^{41}$ erg/s and durations up to 200 days. These luminosities are significantly higher, and the durations much longer, than those produced by a simple spherical ejection of the same mass. They also depend in a complex way on the radial distribution of the CBM. The shock is embedded in the ejecta and its observational signatures during the optically-thick phase are largely hidden. Our results are broadly compatible with observations of the brightest extragalactic LRNe and pave the way for the transformation of LRNe into powerful probes of binary evolution.

There are several puzzling phenomena from recent JWST observations, which seem to push the standard {\Lambda}CDM cosmology over the edge. All those puzzles can be understood in a coherent way if we assume that first massive black holes (MBHs, the "heavy eggs") formed by directly collapsing from wave CDM haloes, which can be even earlier than the formation of first galaxies (the "chickens"). We elucidate two false obstacles that have been believed to prevent wave CDM haloes from collapsing into black holes (namely "maximum stable mass" and "bosenova") and point out that general-relativistic instabilities (e.g., the non-axisymmetric instability numerically found in spinning scalar-field boson stars) could serve as the concrete mechanisms for direct-collapse black holes (DCBHs) born from wave dark matter. Once the MBHs formed, star formation bursts in and around the accretion flows, characteristic of a special mode in compact regions of high gravitational accelerations.

We study the evolution of white dwarf (WD) magnetic fields that originate from core-convective dynamos during the main-sequence. Using stellar evolution and WD cooling models combined with magnetic field diffusion calculations, we demonstrate that a surviving field from the main-sequence can account for various features observed in magnetic WDs. In particular, the earlier emergence of stronger magnetic fields in more massive WDs, compared to older, less massive, and less magnetic ones, can be explained by this framework. This is because the magnetic boundary at the onset of WD cooling lies deeper in less massive WDs, resulting in a slower and weaker evolution of the surface magnetic field due to increasing electrical conductivity over time. We further show that many of the magnetic field strengths observed across different WD samples can be reproduced if the deep-seated field generated during the main sequence is comparable to predictions from magnetohydrodynamic simulations of core-convective dynamos, or if equipartition provides a valid scaling for the main-sequence dynamo. Additionally, our predictions for surface magnetic fields vary by a factor of 2 to 4 when higher-order modes of poloidal magnetic field expansion and turbulent diffusion driven by crystallization-induced convection are included. These effects should therefore be considered when investigating the origin of magnetic fields in individual WDs.

Accretion of material from a protoplanetary disc on to a forming giant planet can spin the planet up to close to its breakup rate, $\Omega_{\rm b}=(G M_{\rm p}/R_{\rm p}^3)$, where $M_{\rm p}$ is the mass and $R_{\rm p}$ is the radius of the planet. After the protoplanetary disc dissipates, the rapidly rotating planet may eject a decretion (outflowing) disc in a similar way to a Be star. Boundary layer effects in a hydrodynamic disc allow for decretion disc formation at spin rates below the breakup spin rate of the planet. The decretion disc exerts a torque on the planet that slows its spin to an equilibrium value that is sensitive to the planet temperature. By considering steady state circumplanetary decretion disc solutions, we show that the equilibrium spin rate for planets is around $0.4\,\Omega_{\rm b}$ for $H/R=0.2$ and around $0.2\,\Omega_{\rm b}$ for $H/R=0.3$, where $H$ is the disc scale height at radius $R$. These values are in line with the spins of the giant planets in the solar system and observed exoplanet spins.

We present the results of a polarization study based upon relativistic magnetohydrodynamic modelling of jets running into hydrostatic, spherically symmetric cluster atmospheres. For the first time in a numerical simulation, we derive Faraday rotation measure maps (RM maps) from model cluster atmospheres based upon the universal pressure profile (UPP), incorporating a temperature profile for a 'typical' self-similar atmosphere described by only one parameter: M500. We compare our simulated polarization products with current observational data from Very Large Array (VLA) and LOw Frequency ARay (LOFAR), as well as continuing investigations from our previous work, such as the detectability of the Laing Garrington effect. We also studied the variation of mean fractional polarization with cluster mass and jet power. We produce simulated Stokes Q and U channel images and using the Rotation Measure (RM) synthesis technique we create RM maps. These data provide insight into what we should expect of current and future high-resolution polarimetric studies of active galactic nucleus (AGN) outflows as we were able to probe the limitations of the RM synthesis technique by comparing it with the RM map direct from our simulations. Highlights of our study include clear reproduction of polarization enhancements towards the edges of radio lobes for suitable conditions and a demonstration that complex lobe morphologies with multiple emission and Faraday active regions interspersed as might be expected in some pole-on or perhaps precessing sources should be distinguishable in observations with current technology. Given that the UPP is our most representative general cluster atmosphere, these numerical simulations, and the polarimetric properties derived from them, represent the most realistic yet for spherically symmetric atmospheres.

Aims. We report the discovery of periodic maser variability of an unusual pattern in the high-mass young stellar object G26.598-0.024. Methods. A ten-year monitoring of the 6.7 GHz methanol maser was carried out with the Torun 32 m radio telescope. The archival data collected so far were also used to characterize the target with high angular resolution and examine its infrared variability. Results. We found anticorrelated flux variations of the opposite blueshifted and redshifted emission features with a period of 70.1 (2.2) d and the relative amplitude of 1.3 and 0.6, respectively. The light curves are best fit with a sinusoidal function modulated by mild changes in the average flux density on 3-5 yr timescales. The emission of the middle parts of the spectrum shows only long-term variability. High-angular-resolution data indicate that the maser is associated with one of the two 1.3 mm dust emission cores, while the periodic comes from two extended regions ~1500 au apart. We discuss several possible causes of the peculiar variability.

Polarization observations of tidal disruption events offer unique insights into the accretion processes around supermassive black holes. Here, we present optical polarization observations of the nearby event AT 2023clx, obtained using the Nordic Optical Telescope. Our observations reveal a rise and subsequent decay in the polarization degree, temporally offset from the peak of the optical light curve, reaching maximum intrinsic polarization degree of $\sim$5 per cent. In addition, the polarization angle shifts by $\sim60^\circ-100^\circ$ between 6 to 20 days after the optical peak, remaining stable thereafter. Remarkably, the observed polarization variability closely resembles that of AT 2020mot, strongly suggesting a common mechanism for accretion disk formation in these events. The variability in both polarization degree and angle supports models in which tidal stream shocks drive the optical outburst during the accretion disk formation.

Detecting Population III (Pop. III) stars remains a major observational challenge. Their Balmer series recombination line emission, redshifted into the infrared at $z \sim 5-11$, is a potential tracer. JWST/NIRSpec offers the first opportunity to detect such lines, provided fluxes exceed instrumental sensitivity. This study aims to model the expected luminosities of the first four Balmer series transitions from Pop. III star-forming halos and assess their detectability with JWST/NIRSpec across $5 \leq z \leq 11$. We use the semi-analytical code A-SLOTH with merger trees constructed from the extended Press-Schechter (EPS) formalism and cosmological N-body simulations targeting Milky Way-like halos and the halo population in a 8~Mpc$/h$ box. Predicted fluxes are compared to JWST detection limits derived from the Exposure Time Calculator (ETC) assuming a 10,000 s NIRSpec exposure at a signal-to-noise ratio of 5. For our default model parameters, Pop. III H$\alpha$ fluxes peak at $\sim10^{-21}$ erg s$^{-1}$ cm$^{-2}$, 2-3 orders of magnitude below the JWST detection threshold ($\sim6 \times 10^{-19}$ erg s$^{-1}$ cm$^{-2}$). The fluxes in the other Balmer series lines are weaker than H$\alpha$ and hence are also not detectable. Among the model parameters that we explore, the ionizing photon escape fraction $f_{\mathrm{esc,III}}$ has the strongest effect on Pop. III Balmer series fluxes when changed: reducing $f_\mathrm{esc,III}$ from 0.9 to 0.1 increases the fluxes by $\gtrsim$1 order of magnitude. However, even in this case, the lines remain undetectable. Balmer series lines powered by emission from Pop. III stars will be undetectable by JWST without strong lensing ($\mu \gtrsim 10$). A-SLOTH provides a useful tool to predict emission strengths and assess the detectability of Pop. III stars across cosmic history.

The fate of the remnant following the merger of two neutron stars initially on quasicircular orbits depends primarily on the mass of the initial neutron stars, the mass ratio, and the still-uncertain dense-matter equation of state (EoS). Previous works studying the threshold mass for prompt collapse to a black hole have primarily focused on the uncertainties in the zero-temperature EoS, which are parametrized by a macroscopic quantity such as the characteristic neutron star radius. However, prompt collapse can take place either with or without a core bounce during the merger. In the bounce-collapse scenario, shocks can produce additional thermal support, potentially altering the threshold for collapse. In this work, we investigate the impact of the uncertainties in the finite-temperature part of the nuclear EoS on the threshold mass for prompt collapse in equal mass mergers. Using two cold EoSs, combined with four parametrizations of the finite-temperature part of the EoS, we find that the threshold mass is insensitive to realistic variations of the thermal prescription, at sub-percent accuracy. We report on the thermal properties and ejecta of mergers with masses just above the threshold mass, i.e., which experience a single core-bounce before collapsing. During the bounce, the thermal pressure can reach )(1-10)% of the cold pressure at supranuclear densities, depending on the thermal treatment, leading to modest differences in the dynamical ejecta that are launched and in the remnant disk mass as a result.

Over decades of solar wind observations, heavy ions have been observed to have a higher temperature and flow faster than protons in the solar corona and heliosphere. Remote observations have largely been limited to the low corona ($< 4R_{\odot}$), while in situ observations for heavy ions ($Z>2$) have only been sampled at 1 au and beyond. As a result, theories that address heavy ion heating and acceleration remain largely unconstrained. With the launch of Solar Orbiter, heavy ion kinetics can be probed closer to the Sun, as close as the orbit of Mercury ($65R_{\odot}$), to examine their radial behavior. Through a statistical analysis of O$^{6+}$, this work provides a comprehensive analysis of the velocity and temperature of O$^{6+}$ from 0.3 au to 1 au. The study finds that the O$^{6+}$ relative drift, normalized to the local Alfvén speed, and its temperature compared to protons, both decrease with distance from the Sun and show some speed dependence. The O$^{6+}$ temperature is well fit by a single temperature adiabatic profile across all wind speeds, suggesting there is no significant heating at these heliocentric distances. This is in contrast to what is observed for protons and He$^{2+}$. Alfvénic fluctuations, with full 180$^{\circ}$ field rotation, create momentary negative differential streaming where the speed of O$^{6+}$ trails the protons. The amount of negative differential streaming gradually increases at larger distances. These results provide critical constraints to the proposed mechanisms seeking to describe ion heating and acceleration in the solar wind.

We present the first high-resolution XRISM spectrum of the neutron star low-mass X-ray binary GX 340+0, revealing unprecedented detail in its emission and absorption features. The spectrum reveals a rich and complex Fe XXV He$\alpha$ line profile and a P-Cygni profile from Ca XX. We use the state-of-the-art spectral synthesis code Cloudy to model the emission and absorption features in detail. Our analysis reveals multi-ionization and multi-velocity structures, where the combination of broad ($\sim$ 800 km/s) and narrow ($\sim$ 360 km/s) line components, along with rest-frame and blueshifted emission and absorption lines, accounts for the observed line profile complexity. We identify a modest $\sim$ 2735 km/s accretion disk wind exhibiting both absorption and emission features. We also detect a relativistic reflection feature in the spectrum, which we model using relxillNS - specifically designed to characterize X-ray reprocessing in accretion disks around neutron stars. Furthermore, we examine the detailed physics of the Fe XXV He$\alpha$ complex, focusing on the forbidden-to-resonance line ratio under the influence of continuum pumping and optical depth effects.

Low-mass stars and brown dwarfs -- spectral types (SpTs) M0 and later -- play a significant role in studying stellar and substellar processes and demographics, reaching down to planetary-mass objects. Currently, the classification of these sources remains heavily reliant on visual inspection of spectral features, equivalent width measurements, or narrow-/wide-band spectral indices. Recent advances in machine learning (ML) methods offer automated approaches for spectral typing, which are becoming increasingly important as large spectroscopic surveys such as Gaia, SDSS, and SPHEREx generate datasets containing millions of spectra. We investigate the application of ML in spectral type classification on low-resolution (R $\sim$ 120) near-infrared spectra of M0--T9 dwarfs obtained with the SpeX instrument on the NASA Infrared Telescope Facility. We specifically aim to classify the gravity- and metallicity-dependent subclasses for late-type dwarfs. We used binned fluxes as input features and compared the efficacy of spectral type estimators built using Random Forest (RF), Support Vector Machine (SVM), and K-Nearest Neighbor (KNN) models. We tested the influence of different normalizations and analyzed the relative importance of different spectral regions for surface gravity and metallicity subclass classification. Our best-performing model (using KNN) classifies 95.5 $\pm$ 0.6% of sources to within $\pm$1 SpT, and assigns surface gravity and metallicity subclasses with 89.5 $\pm$ 0.9% accuracy. We test the dependence of signal-to-noise ratio on classification accuracy and find sources with SNR $\gtrsim$ 60 have $\gtrsim$ 95% accuracy. We also find that zy-band plays the most prominent role in the RF model, with FeH and TiO having the highest feature importance.

Within the molecular clouds of the Camelopardis OB1 association exists a region previously noted as one subgroup. However, bulk clustering from Gaia astrometry has recently shown three distinctive kinematically coherent groups, all found in a similar location in the sky ($137 \lessapprox l\lessapprox145$ and $-2\lessapprox b \lessapprox5$) and at a similar distance ($\sim$1kpc). In this work, we derive from first principles the three proposed clusters in this region, refine the membership list and cluster ages, and, for the first time, examine the 3D structure, motion, and origin of the clusters. Using clustering of Gaia data in 3D position + 2D velocity space, supplemented by available SDSS-V radial velocities, we find the clusters of ages 10, 15.8, and 20 Myr with members numbering 140, 469, and 184, respectively. All three clusters overlap currently in 3D space. Tracing their previous location, based on present-day motions, shows that each cluster originated in its own distinct region and exhibited no influence on each other's formation. Two of the clusters trace their origin to different areas within the Cam OB1 association, with the oldest cluster tracing its origins to the near edge of the Perseus arm, in the direction of the Per OB1 or Cas 0B6 associations. Overall, this work illustrates how different stellar groups, even those originating in a different spiral arm, can visit and pass through each other as they travel through the Galaxy.

We report a candidate repeating tidal disruption event (TDE), AT2022sxl, found from large-field optical survey data. Two flares with a separation time of $\sim$7.2\,yr between the two optical peaks are observed. Related mid-infrared (MIR) flares, with delay times of $\sim$200\,day are also seen. We analyze two optical spectra of the TDE source, onenear the optical peak of the second flare from the Transient Name Server and one at the quiescent flux level after the second flare. The latter was taken by us with the 10.4-m Gran Telescopio Canarias. Comparing the features of the two spectra, we identify that the host is likely a composite galaxy at redshift 0.23 and the TDE event, probably an H+He type, mainly powered broad components in the emission lines of H$\alpha$, H$\beta$, and He~I $\lambda$5876. More interestingly, we find that two Bronze-type neutrino events, detected by the IceCube neutrino observatory, match the TDE in position and the second flare, especially the delayed MIR flare, in time. We discuss the MIR luminosity properties of the currently reported (candidate) neutrino-emitting TDEs and suggest that luminous MIR emission is a prerequisite for neutrino production in TDEs.

The magnetic fields of terrestrial planets are generated in their liquid cores through dynamo action driven by thermal and compositional convection. The coexistence of these two buoyancy sources gives rise to double-diffusive convection (DDC) due to the contrast between thermal and compositional diffusivities. However, most dynamo simulations adopt the co-density model, where the two diffusivities are assumed to be equal. In this study, we performed both hydrodynamic and dynamo simulations of top-heavy DDC in a rotating spherical shell with the Lewis number $Le=100$, and compared them with corresponding co-density models. In the hydrodynamic regime, the convective flow morphology is strongly influenced by the nature of the buoyancy sources. However, our dynamo simulations in the strong-field regime demonstrate that the co-density and DDC models yield qualitatively similar magnetic fields at comparable magnetic Reynolds numbers, albeit with some differences in detail. These numerical models further justify the use of the co-density model in planetary dynamo simulations. Finally, we demonstrate that dynamo models based on DDC and co-density produce similar magnetic fields and secular variations at the core-mantle boundary. This suggests that it may not be possible to distinguish the buoyancy sources responsible for planetary dynamos based solely on magnetic field observations.

A key science goal of large sky surveys such as those conducted by the Vera C. Rubin Observatory and precursors to the Square Kilometre Array is the identification of variable and transient objects. One approach is the statistical analysis of the time series of the changing brightness of sources, that is, their light curves. However, finding adequate statistical representations of light curves is challenging because of data quality issues such as sparsity of observations, irregular sampling, and other nuisance factors inherent in astronomical data collection. The wide diversity of objects that a large-scale survey will observe also means that making parametric assumptions about the shape of light curves is problematic. We present a Gaussian process (GP) regression approach for characterising light curve variability that addresses these challenges. Our approach makes no assumptions about the shape of a light curve and, therefore, is general enough to detect a range of variable source types. In particular, we propose using the joint distribution of GP amplitude hyperparameters to distinguish variable and transient candidates from nominally stable ones and apply this approach to 6394 radio light curves from the ThunderKAT survey. We compare our results with two variability metrics commonly used in radio astronomy, namely $\eta_\nu$ and $V_\nu$, and show that our approach has better discriminatory power and interpretability. Finally, we conduct a rudimentary search for transient sources in the ThunderKAT dataset to demonstrate how our approach might be used as an initial screening tool. Computational notebooks in Python and R are available to help facilitate the deployment of this framework to other surveys.

We present a joint analysis of high-resolution $K$- and $L$-band observations of the benchmark hot Jupiter \hdb\ from the Keck Planet Imager and Characterizer (KPIC). One half night of observations were obtained in each bandpass covering similar pre-eclipse phases. The two epochs were then jointly analyzed using our atmospheric retrieval pipeline based on \petit\ to constrain the atmospheric pressure-temperature profile and chemical composition. Consistent with recent results from \textit{JWST} observations at lower spectral resolution, we obtain an oxygen-rich composition for \hdb\ ($\rm C/O < 10^{-3}$ at 95\% confidence) and a lower limit on the volatile metallicity similar to the solar value ($\rm [(C+O)/H] > -0.2$ at 95\% confidence). Leveraging the large spectral grasp of the multi-band observations, we constrain the H$_2$O mixing ratio to $\rm \log H_2O_{VMR} > -3.1$ at 95\% confidence, and obtain 95\% upper limits on the atmospheric mixing ratios of CO ($<10^{-4.8}$), CH$_4$ ($<10^{-4.5}$), NH$_3$ ($<10^{-5.8}$), H$_2$S ($<10^{-3.3}$), and HCN ($<10^{-5.6}$). The limits on CH$_4$, NH$_3$, and HCN are consistent with recent results from \textit{JWST} transmission spectroscopy, demonstrating the value of multi-band ground-based high resolution spectroscopy for precisely constraining trace species abundances in exoplanet atmospheres. The retrieved low-C/O, moderate-metallicity composition for \hdb\ is consistent with formation scenarios involving late accretion of substantial quantities of oxygen-rich refractory solids and/or ices.

The lowest mass at which the third dredge-up (TDU) occurs for thermally-pulsing asymptotic giant branch (TP-AGB) stars remains a key uncertainty in detailed stellar models. S-type AGB stars are an important constraint on this uncertainty as they have C/O ratios between 0.5 and 1, meaning they have only experienced up to a few episodes of TDU. AGB stars are also long-period variable stars, pulsating in low order radial pulsation modes. In this paper we estimate the initial masses of a large literature sample of intrinsic S-type AGB stars, by analysing their visual light curves, estimating their luminosities with Gaia DR3 parallax distances and finally comparing to a grid of detailed stellar models combined with linear pulsation models. We find that the initial mass distribution of intrinsic S-type stars peaks at 1.3 to 1.4 \Msun, depending on model assumptions. There also appear to be stars with initial masses down to 1 solar mass, which is in conflict with current detailed stellar models. Additionally, we find that though the mass estimates for semiregular variable stars pulsating in higher order radial modes are precise, the Mira variables pulsating in the fundamental mode present challenges observationally from uncertain parallax distances, and theoretically from the onset of increased mass-loss and the necessity of non-linear pulsation models.

We present the discovery of two extended, low surface brightness radio continuum sources, each consisting of a near-circular body and an extended tail of emission, nicknamed Stingray 1 (ASKAP J0129-5350) and Stingray 2 (ASKAP J0245-5642). Both are found in the direction of the Magellanic Stream (MS) and were discovered in the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey at 944 MHz. We combine the ASKAP data with low-frequency radio observations from the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) to conduct a radio continuum analysis. We explore both Galactic/near Galactic scenarios, including runaway or circumgalactic supernova remnants (SNRs) and parentless pulsar-wind nebulae (PWNe), and extragalactic scenarios including radio active galactic nuclei (AGNs), dying radio galaxies, galaxy clusters, galaxy pairs or groups, head-tail radio galaxies, and Odd Radio Circles (ORCs), as well as the possibility that the morphology is due to a chance alignment. The Stingrays exhibit non-thermal emission with spectral indices of $\alpha$ = -0.89 $\pm$ 0.09 for Stingray 1 and $\alpha$ = -1.77 $\pm$ 0.06 for Stingray 2. We find that none of the proposed scenarios can explain all of the observed properties, however we determine it most likely that their shape is caused by some kind of complex environmental interaction. The most likely scenario from the available data is that of a head-tail radio galaxy, but more data is required for a definitive classification.

We measure thermal Sunyaev-Zel'dovich (tSZ) Effect in the circumgalactic medium (CGM) of $\approx$2.5 million $\rm M_{200}$=$\rm 10^{12-14}\,M_\odot$ WISE$\times$DESI galaxies out to $z$=1.2. We split the sample into quiescent (0.7 million) and star-forming (1.8 million) galaxies, exploring the relation between the thermal pressure of the CGM and star formation for the first time. We develop and implement a novel probabilistic approach to cross-correlate the galaxy catalog with the Atacama Cosmology Telescope+Planck data by taking into account the uncertainties in redshift, mass, and star formation rate. The S/N of the stacked Compton-$y$ value in the CGM varies from 4.9 to 18.5, depending on the sample size and the CGM signal strength within the relevant mass bin. We detect the CGM signal down to $\rm M_{200}=10^{12.3}\,M_\odot$, and provide stringent upper limit at $\rm M_{200}<10^{12.3}\,M_\odot$. The data fit well with the standard GNFW profile of thermal pressure and do not require a flatter or steeper profile. This suggests a significant impact of cooling and the absence of dominant feedback. In galaxies with $\rm M_{200}\approx10^{12.3-12.8}\,M_\odot$ halos, the volume filling CGM is likely the largest contributor to the $galactic$ baryons at their virial temperatures of $\sim$10$^{6-6.4}\rm\,K$. For $\rm M_{200}>10^{12.8}\,M_\odot$ halos, the most massive phase of the CGM is likely at a sub-virial temperature of $\rm\gtrsim 10^6\,K$. The thermal energy of the CGM of quiescent galaxies follows the self-similar relation with mass, but the star-forming galaxies deviate from this relation. This indicates that the impact of non-gravitational factors varies among halos of different degrees of star-forming activity.

We report the RAD@home citizen science discovery of two rare spiral-host radio galaxies (NGC 3898 and WISEA J221656.57-132042434.1 or RAD-"Thumbs up" galaxy), both exhibiting asymmetric radio lobes extending over 30 to 220 kiloparsec scales. We present a multi-wavelength image analysis of these two sources using radio, optical, and ultraviolet data. Both host galaxies are young, star-forming systems with asymmetric or distorted stellar disks. These disks show similarities to those in galaxies undergoing ram pressure stripping, and the radio morphologies resemble those of asymmetric or bent FR-II and wide-angle-tailed radio galaxies. We suggest that non-uniform gas density in the environment surrounding the ram pressure-stripped disks may contribute to the observed asymmetry in the size, shape, and brightness of the bipolar radio lobes. Such environmental effects, when properly accounted for, could help explain many of the non-standard radio morphologies observed in Seyfert galaxies and in recently identified populations of galaxies with galaxy-scale radio jets, now being revealed through deep and sensitive radio surveys with uGMRT, MeerKAT, LOFAR, and, in the future, the SKAO. These findings also underscore the potential of citizen science to complement professional research and data-driven approaches involving machine learning and artificial intelligence in the analysis of complex radio sources.

We present a GPU-accelerated implementation of a magnetohydrodynamic (MHD) solver using directive-based programming with OpenMP target offloading. The solver is integrated into the DISPATCH framework, which organises the computational domain into a collection of asynchronously updated patches. To reduce GPU kernel launch overhead, patches are grouped into "bunches" that are updated collectively. While porting the particular solver required a complete code refactoring, it yielded performance gains on both GPU and CPU. A stand-alone mini-app achieved a 7.3x speed-up compared to a single NVIDIA A100 GPU to seven AMD 7F72 Rome CPU cores. Within the full DISPATCH framework, the GPU-accelerated MHD Bunch solver showed excellent agreement with the CPU-based reference implementation on standard test problems such as the Sod shock tube and Orszag-Tang vortex. In large-scale 3D tests, the GPU implementation achieved a 9.8x overall speedup, comparing one GPU to 12 CPU cores, with the core MHD update routine being two orders of magnitude faster on the GPU than on a single CPU core. These results demonstrate that OpenMP offloading can provide substantial performance improvements for astrophysical codes while maintaining portability and accuracy. The work also demonstrates how new codes should be structured to allow simple and efficient directive-based GPU offloading.

Gas-giant exoplanets are test cases for theories of planet formation as their atmospheres are proposed to carry signatures of their formation within the protoplanetary disk. The metallicity and C/O are key diagnostics, allowing to distinguish formation location within the disk (e.g., relative to snowlines), and mechanism (e.g., core accretion versus gravitational instability). We can now probe the composition of the planet-forming regions of disks, and that in gas-giant exoplanets, to scrutinise these theories and diagnostics. So far, ALMA has revealed that the outer disk regions are typically metal-depleted and O-poor, whereas JWST is showing that the inner disk regions around Sun-like stars are mostly O-rich. Further, JWST is showing that most transiting gas-giant planets are typically metal-enriched and O-rich, consistent with formation at/within the water snowline and pollution by icy bodies. There is emerging an arguably "conventional" picture of gas-giant planet formation for transiting planets, to be confirmed, of course, with future data.

The discovery of exoplanets has expanded our understanding of planetary systems and opened new avenues for astronomical research. In this study, we present a machine learning (ML) framework for exoplanet identification using a time-series photometric dataset from the Kepler Space Telescope, comprising 3,198 flux measurements across 5,074 stars. We investigate the performance of four supervised classification algorithms, namely Random Forest, k-Nearest Neighbors (KNN), Decision Tree, and Logistic Regression, using a comprehensive set of evaluation metrics such as accuracy, precision, recall, F1-score, Area Under the Receiver Operating Characteristic Curve (AUC-ROC), confusion matrices, and learning curves. Among the models, Random Forest achieves the highest accuracy (99.8\%) and near-perfect F1-scores, demonstrating superior generalization and robustness. KNN also performs strongly, achieving 99.3\% accuracy, while Decision Tree demonstrates moderate performance with 97.1\% accuracy, and Logistic Regression trails behind with the lowest accuracy and generalization at 95.8\%. Notably, the application of the Synthetic Minority Over-sampling Technique (SMOTE) significantly improves performance across all models by addressing class imbalance. These findings underscore the effectiveness of ensemble-based machine learning techniques, particularly Random Forest, in handling large volumes of photometric data for automated exoplanet detection. This approach holds significant potential for implementation at ground-based facilities, such as the Iranian National Observatory (INO), where such extensive and precise datasets can further advance exoplanet discovery and characterization efforts.

We present a new spectro-polarimetric method for estimation of the inclination of X-ray binaries using the linear polarization (LP) value in black hole (BH) sources, based on the early paper by Sunyaev \& Titarchuk (1985, ST85). The X-ray LP arises from multiple scattering of initially soft photons in a hot, optically thick Compton cloud (CC) using a flat geometry. ST85 showed that the LP degree $P$ depends on the binary inclination $i$ and remains independent of the photon energy. Moreover, the $P$ follows a characteristic angular distribution based on the CC optical depth $\tau_0$, in particular for $\tau_0 >$ 10 the LP follows the Chandrasekhar (1950) distribution. In light of the vast number of recent IXPE spectro-polarimetric observations of BHs, testing this approach in combination with spectral analysis of these sources by other missions is desirable. In particular, the BH source, 4U 1957+115 was observed with IXPE in the high/soft state for which $P\sim 2\%$ was found (Marra et al. 2024). To apply the new method, in addition to knowing $P$ for a given source, it is necessary to estimate the CC optical depth $\tau_0$ and then to calculate of the best-fit photon index $\Gamma$ and the plasma temperature $kT_e$. We present the X-ray spectral analysis of 4U~1957+11 using data from IXPE, NuSTAR, NICER, RXTE}, Swift, Suzaku and ASCA. We show that the X-ray source spectra are well described by the Comptonization model with $\Gamma$ varying from 1.5 to 3. We find a monotonic increase in $\Gamma$ with the mass accretion rate, $\dot M$, and a final saturation of the index at $\Gamma\sim3$ for high $\dot M$. We determine a BH mass by the scaling method: $M_{1957}=4.8 \pm 1.8~M_{\odot}$, assuming a source distance of 22 kpc, using H 1743-322, 4U 1630-47, and GRS 1915+105 as reference sources.

We study the cooling of isolated dark-matter-admixed neutron stars, employing a realistic nuclear equation of state and realistic nuclear pairing gaps, together with fermionic dark matter of variable particle mass and dark-matter fraction. The related parameter space is scanned for the stellar structural and cooling properties. We find that a consistent description of all current cooling data requires fast direct Urca cooling and reasonable proton 1S0 gaps. but no neutron 3P2 pairing. Dark matter affects the cooling properties by a modification of the nuclear density profiles, but also changes stellar radius and maximum mass. Possible signals of a large dark matter content could be a very massive but slow-cooling star or a very light but fast-cooling star.

Recent analyses combining Atacama Cosmology Telescope (ACT) data with other cosmological datasets report a higher scalar spectral index $n_s$, creating tension with a wide range of inflationary models. Since a Gauss-Bonnet term with a coupling function $\xi(\phi) = 3\lambda/[4V(\phi)]$ leaves $n_s$ nearly unchanged (up to a field rescaling) while reducing the tensor-to-scalar ratio $r$ by a factor $(1-\lambda)$, so choosing $(1-\lambda)$ sufficiently small effectively removes $r$ as a limiting observable, making it easier for inflationary models to satisfy the latest observational constraints and alleviating this tension. Applying this mechanism to chaotic inflation, E-models, T-models, and hilltop inflation, we find that broad regions of parameter space become consistent with the latest ACT-based CMB constraints. These results demonstrate that Gauss-Bonnet couplings can help bring a broad class of inflationary models into agreement with current CMB measurements.

Ground-based Cherenkov telescopes, although typically inoperative during moonlit nights for gamma-ray observations, offer a valuable opportunity for secondary scientific applications through Intensity Interferometry (II). Recent developments and observations suggest that implementing II instrumentation on existing Imaging Atmospheric Cherenkov Telescopes (IACTs) or the Cherenkov Telescope Array (CTA) can significantly advance optical stellar measurements. Motivated by the resurgence of II efforts over the past two decades, this work presents simulations demonstrating the estimation of stellar parameters for a radially pulsating star, such as Polaris, using either a single telescope or multiple telescopes. For single-telescope simulations, we assume that the photon pixels in the camera are mapped onto four distinct regions of the aperture, generating multiple baselines and enabling enhanced observational plane coverage. These results highlight the potential of Cherenkov telescopes in India for high-resolution optical astronomy during otherwise inoperative periods and offer promising insights into the characterization of bright stellar objects with unprecedented precision.

Predictions from current theories and simulations suggest that dual AGN systems are exceedingly rare at high redshifts. The intense radiation and powerful outflows from AGNs regulate star formation, heat the interstellar medium, and drive massive gas outflows that shape the host galaxy and its surroundings. One manifestation of AGN feedback is the creation of extended Ly$\alpha$ nebulae. However, identifying these systems at high-$z$ is challenging. Here, we report a remarkable dual AGN candidate at $z \sim 5.4$ using JWST NIRCam and NIRSpec, with a separation of $\sim1.7$ arcseconds ($\sim10.4$ pkpc). This is one of the highest spectroscopically confirmed redshift dual AGNs discovered. Photometric SED fitting shows excellent agreement with AGN templates, strongly suggesting a rare dual AGN system. BPT diagrams and high ionisation lines further support the presence of AGNs. VLT/MUSE observations reveal strong extended Ly$\alpha$ emission, extending to $>22$ kpc, making it one of the most extended Ly$\alpha$ nebulae at $z \sim 6$. This provides observational evidence of anisotropic AGN-driven photoionization or shocks. The high Ly$\alpha$ escape fraction also indicates an AGN outflow. This dual AGN candidate is also associated with a well-defined overdensity, potentially at the center of a $z \sim 5.4$ protocluster or filamentary structure node. Further analysis indicates the fraction of dual AGNs is significantly higher than theoretically expected at high redshifts. This discovery provides a new opportunity to study dual AGN interactions and their impact on the circumgalactic medium and cosmic structure evolution.

The discrepancy between the predictions of primordial nucleosynthesis and the observed lithium abundance in Spite plateau stars has been attributed either to a challenge to the standard model of nucleosynthesis or to stellar processes occurring after the stars formed. To understand the origin of this discrepancy, it is crucial to link the cosmic star formation rate with a chemical enrichment model that incorporates the yields of both Population (Pop) III and II stars. It is within this framework that the evolution of lithium can be determined. The primary goal is to demonstrate that there is no discrepancy between the predictions of primordial nucleosynthesis and the observed lithium abundance. By combining a standard chemical evolution model with the hierarchical structure formation scenario, it is possible to determine the lithium abundance as a function of $[\mathrm{Fe/H}]$. The model's results are compared with observational data, including two extremely iron-poor stars: J0023+0307 and SMSS J0313-6708. The Spite plateau is naturally established in the range $-8.0 \lesssim [\mathrm{Fe/H}] \lesssim -2.0$ with $^{7}\mathrm{Li/H}$ $\sim 1.81 \times 10^{-10}$. We find that J0023+0307 could have formed $\sim 4.4 \times 10^{5} - 1.3 \times 10^{6}$ years after the explosion of the first Pop III star in the Universe, whereas for SMSS J0313-6708 this event would have occurred $\sim 2.2 \times 10^{5} - 4.4 \times 10^{5}$ years later. The Spite plateau serves as an observational signature of the formation of Pop III stars. The abundances observed in J0023+0307 and SMSS J0313-6708 are consistent with Pop III progenitor stars in the mass range $10-100 M_{\odot}$. However, if some high-redshift star formation occurs within subhalo-like structures, the contribution of stars in the mass range $140-260 M_{\odot}$ to the formation of the extended Spite plateau cannot be ruled out.

Astronomical surveys and the growing involvement of amateur astronomers are producing more sky images than ever before, and this calls for automated processing methods that are accurate and robust. Detecting Deep Sky Objects -- such as galaxies, nebulae, and star clusters -- remains challenging because of their faint signals and complex backgrounds. Advances in Computer Vision and Deep Learning now make it possible to improve and automate this process. In this paper, we present the training and comparison of different detection models (YOLO, RET-DETR) on smart telescope images, using High-Performance Computing (HPC) to parallelise computations, in particular for robustness testing.

Aims. OH 231.8+4.2 , also known as the Rotten Egg or Calabash nebula is a protoplanetary nebula which is seen in the direction of the open cluster M 46. While an association of the nebula with the cluster has been suggested in the past, this has been never confirmed. Here, we present accurate trigonometric parallax and proper motion measurements using VLBI observations of masers in the nebula and Gaia DR3 data for the cluster. Methods. We observed 22 GHz H2O and 43 GHz SiO masers around OH 231.8+4.2 using the Very Long Baseline Array at 4 epochs over 1 year. We also calculated the parallax and proper motion of the open star cluster M 46 using Gaia DR3 data. Results. Based on astrometric monitoring for 1 year, we measured an annual parallax of OH 231.8+4.2 to be 0.65 +\- 0.01 mas (stat.) +\- 0.02 mas (syst.), corresponding to a distance of 1.54 +\- 0.05 kpc. This agrees well with the parallax of M 46 from the Gaia DR3 data, which is 0.639 +\- 0.001 mas (stat.) +\- 0.010 mas (syst.). We re-estimated the luminosity of OH 231.8+4.2 to be 1.4 x 10^4 L_sol. However, there is a 15 km/s velocity difference between OH 231.8+4.2 and M 46 which could be caused by a past merger event.

Multi-channel aperiodic fiber Bragg grating (FBG) based hydroxyl (OH) line filters have attracted significant interest in ground-based near-infrared (NIR) astronomical observations. In this paper, we present the performance of a new self-compensating enclosure for the filters, that can be used in non-temperature-controlled environments. Our prototype encloses a 110 mm long single-mode photosensitive optical fiber with three 10 mm filter gratings. A fourth grating was used as a reference outside the package to measure the uncompensated wavelength shift. The prototype was tested over three thermal cycles, and showed a maximum wavelength deviation of 12 pm, a wavelength drift of only 0.37 pm/$^{\circ}$C, over the temperature range of -17$^{\circ}$C to 15$^{\circ}$C. The athermalization factor, i.e., the ratio of the maximum wavelength shift of the compensated grating to the uncompensated reference filter grating was $\frac{1}{22}$. The results demonstrate the capability of the prototype for stabilizing multi-channel long-length FBGs or chirped FBGs, particularly for astronomical applications that require sub-picometer stability.

We investigate the stellar structure of neutron stars in the framework of Starobinsky gravity, characterized by a quadratic correction to the Einstein-Hilbert action, $f(R) = R + \alpha R^2$. In order to {\em preserve causality throughout\/} the star, we adopt a two-phase hybrid construction for the stellar matter, in which the core region consists of deconfined quark matter described by the MIT bag model, while the outer layers are composed of hadronic matter represented by unified equations of state such as SLy4, BSk20, and BSk21. Within this framework, we derive the modified field equations with static spherical symmetry, and numerically integrate the corresponding Tolman-Oppenheimer-Volkoff (TOV) equations with the chosen hybrid equations of state. Our analyses show that, unlike in general relativity, the Ricci scalar remains nonzero outside the stellar surface, and gradually falls to zero beyond 50 km, while the stellar surface remains within 10--12 km for the hybrid equations of state considered. This extended Ricci scalar profile arises from the extra degree of freedom (scalaron) inherent in Starobinsky gravity, which also contributes to the gravitational mass outside the star, causing the ADM mass measured at infinity to exceed the stellar mass at the surface. Nevertheless, the key physical relationships, such as the mass-central density and mass-radius curves, remain consistent with what is expected physically. Notably, we find that the maximum stable mass of neutron stars increases with the Starobinsky parameter $\alpha$, with the combined MIT-BSk21 model supporting an ADM mass of up to $2.07 \, M_\odot$ for $\alpha = 10\,r_g^2$. This theoreical limit for a nonrotating neutron star suggests that a rotating configuration could reach mass thresholds in the range of $2.48$ to $2.59 \, M_\odot$, considering that rapid rotation can enhance the maximum mass by approximately 20--25\%.

Powerful jetted radio sources for which the luminosity in directed kinetic energy has been empirically determined, independent of assumptions, are considered. The total outflow lifetime of each source determined in the context of detailed cosmological studies was found to depend only upon the luminosity in directed kinetic energy ($L$). The distributions of $L$, total outflow lifetime, and total outflow energy each have a broad range of values, as do the supermassive black hole masses. The total outflow energy relative to the black hole mass is a small number with a small dispersion. Three explanations of these remarkable results are considered. This could indicate (1) the efficiencies with which black hole irreducible mass is increased and spin mass energy is extracted during the outflow event, (2) that the merger of two supermassive black holes occurs over a timescale commensurate with the independently determined outflow lifetime and that these mergers lead to the production of the low-frequency gravitational wave background, or (3) that feedback shuts off black hole accretion due to energy injected into the ambient medium.

Searching for radio pulsars orbiting around the Galactic centre black hole (BH), Sagittarius A$^\star$ (Sgr A$^\star$), represents a holy grail goal for large-area radio telescopes, in particular for the Square Kilometre Array. Follow-up timing observation of such a PSR-Sgr A$^\star$ binary system with an orbital period $\lesssim O(1\,{\rm year})$ will bring forward a handful of new tests on different aspects of fundamental physics that are barely accessible with other means. However, mass perturbation in the Galactic centre harms the gravitational cleanness of PSR-Sgr A$^\star$ systems. In order to flexibly account for perturbations, a numerical pulsar timing model is gradually being built, which can be used to probe the spacetime around Sgr A$^\star$ BH and study the nature of dark matter.

The V883 Ori system is a rapidly accreting young stellar object that has been used as a laboratory for studying the molecular inventory of young circumstellar disks with high luminosity. We simultaneously fit high resolution spectroscopy and medium resolution spectrophotometry of the system to constrain the physical conditions in the inner au. Using our thin viscous accretion disk model, we find $\dot{M} = 10^{-3.9 \pm 0.2} \ M_\odot$ yr$^{-1}$, $R_\mathrm{inner} = 5.86 \pm 1 \ R_\odot$, $i = 38.2 \pm 3$ degrees and $A_V = 20.8 \pm 0.7$ mag, resulting in an accretion luminosity of 458 $L_\odot$ and maximum disk temperature of 7045 K. The optical portion of the SED greatly exceeds the flux level expected for a highly extincted accretion disk. We propose that the excess emission arises from a contribution due to scattering of the accretion disk spectrum off nearby envelope material that is viewed along a less-extincted line of sight. Additionally, we use photometric observations spanning 137 years to demonstrate that the source has accreted at least 18 $M_\mathrm{Jup}$ of disk material to date. Finally, we discuss the importance of considering both the viscous heating from the midplane and the consequent irradiation effects on the outer disk when modeling the temperature structure to reproduce millimeter-wavelength observations.

Stochastic $\delta N$ formalism is a powerful tool to calculate the cosmological correlators non-perturbatively. However, it requires the initial data for the amplitude of the noise on the initial flat hypersurface which for a free theory during inflation is fixed to be $\frac{H}{2 \pi}$. In this work, we study the setups where the underlying theory involves interactions and the stochastic noises inherit these interactions. We extend the stochastic $\delta N$ formalism to these setups and rewrite the corresponding Langevin and Fokker-Planck equations in which the QFT corrections in the amplitude of the noises are taken into account. As an example, in the three-phase SR-USR-SR setup which is employed for PBHs formation, the modification in the amplitude of noise is calculated from the one-loop corrections in power spectrum via in-in formalism. We show that in these setups the amplitude of the stochastic noise is modified to $\frac{H}{2 \pi} \Big(1+ \frac{ \Delta {\cal P}_{\cal R} }{ {\cal P}^{(0)}_{ {\cal R} } }\Big)^{\frac{1}{2}}$ in which $ \frac{\Delta {\cal P}_{\cal R} }{ {\cal P}^{(0)}_{{\cal R} } }$ is the fractional one-loop correction in power spectrum.

The detection of gamma-ray burst GRB~221009A has attracted significant attention due to its record brightness and the first-ever detection of multi-TeV $\gamma$-rays from a GRB. Located at redshift $z=0.151$, this event is relatively nearby by GRB standards yet remains cosmologically distant, making the survival of multi-TeV photons surprising. The Large High Altitude Air Shower Observatory detected photons with energies up to $\sim 13$~TeV during the early afterglow phase, challenging standard EBL models. We investigate whether several theoretical frameworks can explain this anomalous emission: reduced EBL opacity due to cosmic voids along the line of sight, novel emission mechanisms within the GRB environment, secondary $\gamma$-ray production through cosmic-ray cascades, and new-physics scenarios involving Lorentz-invariance violation or axion-like particles. Our analysis highlights the exceptional nature of this event and ongoing theoretical tensions about the dominant physical processes. We discuss the limitations of current models and identify specific observational signatures that future multiwavelength and multi-messenger observations could provide to discriminate between competing explanations. Continued study of similar events with next-generation facilities will be crucial for resolving these challenges and advancing our understanding of extreme particle acceleration in astrophysical environments.

Context. Cold molecular gas tracers, such as CI and CO lines, have been widely used to infer specific characteristics of the ISM and to derive star-formation relations among galaxies. Aims. However, there is still a lack of systematic studies of the star-formation scaling relation of CO and [CI] lines across cosmic time on multiple physical scales. Methods. We used observations of the ground state transitions of [CI], CO, and [CII], for 885 sources collected from the literature, to infer possible correlations between line luminosities of $\rm L^{'}_{[CI](1-0)}, \rm L^{'}_{CO(1-0)}$, and $\rm L^{'}_{[CII]}$ with star formation rates (SFR). With linear regression, we fit the relations between SFR and molecular mass derived from CO, CI, and CII lines. Results. The relation between [CI] and CO-based total molecular masses is weakly superlinear. Nevertheless, they can be calibrated against each other. For $\rm \alpha_{CO} = 0.8$ and $4.0\ \rm {M}_{\odot}\,({K}\,{km}\,{s}^{-1}\,{pc}^2)^{-1}$ we derive $\alpha_{\rm [CI]} = 3.9$ and $\sim$$17\ \rm {M}_{\odot}\,({K}\,{km}\,{s}^{-1}\,{pc}^2)^{-1}$ , respectively. Using the \emph{lmfit} package, we derived relation slopes of SFR--$\rm L^{'}_{[CI](1-0)}$, SFR--$\rm L^{'}_{CO(1-0)}$, and SFR--$\rm L^{'}_{[CII](1-0)}$ to be $\rm \beta$ = 1.06 $\pm$ 0.02, 1.24 $\pm$ 0.02, and 0.74 $\pm$ 0.02, respectively. With a Bayesian-inference \emph{linmix} method, we find consistent results. Conclusions. Our relations for [CI](1-0) and CO(1-0) indicate that they trace similar molecular gas contents, across different redshifts and different types of galaxies. This suggests that these correlations do not have strong evolution with cosmic time.

GW231123, the heaviest binary black hole merger detected by the LIGO-Virgo-KAGRA collaboration to date, lies in the pair-instability mass gap and exhibits unusually high component spins. In this letter, we show that both merging black holes may have a primordial origin with smaller initial masses. The observed masses and, crucially, the spins of GW231123 are naturally accommodated within the most vanilla primordial black hole framework, once cosmological accretion is taken into account. Interestingly, the parameter space needed to explain the inferred GW231123 rate is at the edge of the exclusion region from Xray and CMB observations, suggesting that this interpretation can be either confirmed or ruled out. The upcoming O5 observing run by the collaboration should detect ${\cal O}(20)$ similar events, testing their mass-spin correlation, while next-generation detectors would be capable of observing high redshift events, as predicted in this scenario.

Bulge globular clusters(BGCs) are exceptional tracers of the formation and chemodynamical evolution of this oldest Galactic this http URL, until now, observational difficulties have prevented us from taking full advantage of these powerful Galactic archeological tools. CAPOS, the bulge Cluster APOgee Survey, addresses this key topic by observing a large number of BGCs, most of which have been poorly studied. We aim to obtain accurate mean values for metallicity,[alpha/Fe],and radial velocity, as well as abundances for 11 other elements. We present final parameters based on ASPCAP for all 18 CAPOS BGCs. We carry out a stringent membership selection, finding 303 with SNR>70 and 125 with lower SNR. We reinforced the finding that stars with high [N/Fe] abundances show higher [Fe/H] than their lower [N/Fe] counterparts. Mg,Ca and global alpha abundances show similar trends, while Si is well-behaved. The [Fe/H] value of these 2nd population stars is corrected to derive the mean metallicity. Mean metallicities are determined to a precision of 0.05 dex,[alpha/Fe] to 0.06 dex, and radial velocity to 3.4 km/s. No clusters show strong evidence for internal metallicity variation, including M22. Abundances for 11 other elements using only 1st population stars are calculated and are generally in good agreement with the literature. We develope a new chemodynamical GC classification scheme, synthesizing several recent studies. We also compile up-to-date metallicities. The BGC metallicity distribution is bimodal, with peaks at [Fe/H]=-0.45 and -1.1, with the metal-poor peak strongly dominant, while exsitu GCs are unimodal, with a peak at -1.6. Surprisingly, we find only a small, statistically insignificant difference in the mean [Si/Fe] of in and exsitu GCs. The 4 GCs with the lowest [Si/Fe] values are all exsitu, relatively young, and 3 belong to Sagittarius, but no other correlations are evident.

We present a study of neutron-capture element abundances (Sr, Y, Zr, Ba, La, Ce, Nd, Pr, and Eu) in a large and homogeneous sample of 160 F-, G-, and K-type planet-host stars located in the northern hemisphere, including 32 stars in multi-planetary systems. The sample hosts a total of 175 high-mass planets and 47 Neptunian and super-Earth planets. High-resolution spectra were obtained with the 1.65-metre telescope at the Molėtai Astronomical Observatory using a fibre-fed spectrograph covering 4000-8500 Å. Elemental abundances were determined by differential line-by-line spectrum synthesis with the TURBOSPECTRUM code and MARCS model atmospheres. The analysis of $[\mathrm{El}/\mathrm{Fe}]$ ratios shows that most elements in PHSs follow the Galactic chemical evolution, but $[\mathrm{Zr}/\mathrm{Fe}]$, $[\mathrm{La}/\mathrm{Fe}]$, and $[\mathrm{Ce}/\mathrm{Fe}]$ are overabundant in PHSs relative to reference stars at a given $[\mathrm{Fe}/\mathrm{H}]$. Correlations between $[\mathrm{El}/\mathrm{Fe}]$ and planet mass are generally positive, except for Sr, Y, and Ba, which show no significant trends. The distribution of $\Delta[\mathrm{El}/\mathrm{H}]$ versus condensation temperature ($T_{\mathrm{cond}}$) slopes is positively skewed for PHSs, indicating enrichment in refractory elements compared to analogues. While no strong correlations are found between $\Delta[\mathrm{El}/\mathrm{H}]$-$T_{\mathrm{cond}}$ slopes and stellar or planetary parameters, older dwarf stars with multiple planets tend to have smaller or negative slopes, whereas younger dwarf stars exhibit larger positive slopes. Our results also confirm that multi-planetary systems are more frequent around metal-rich stars.

Recent developments have yielded significant progress towards systematically understanding loop corrections to de Sitter (dS) correlators. In close analogy with physics in Anti-de Sitter (AdS), large logarithms can result from loops that can be interpreted as corrections to the dimensions of operators. In contrast with AdS, these dimensions are not manifestly real. This implies that the theoretical constraints on the associated correlators are less transparent, particularly in the presence of light scalars. In this paper, we revisit these issues by performing and comparing calculations using the spectral representation approach and the Soft de Sitter Effective Theory (SdSET). We review the general arguments that yield positivity constraints on dS correlators from both perspectives. Our particular focus will be on vertex operators for compact scalar fields, since this case introduces novel complications. We will explain how to resolve apparent disagreements between different techniques for calculating the anomalous dimensions for principal series fields coupled to these vertex operators. Along the way, we will offer new proofs of positivity of the anomalous dimensions, and explain why renormalization group flow associated with these anomalous dimensions in SdSET is the same as resumming bubble diagrams in the spectral representation.

A very few three-dimensional (3D) periodic orbits of general three-body problem (with three finite masses) have been discovered since Newton mentioned it in 1680s. Using a high-accuracy numerical strategy we discovered 10,059 three-dimensional periodic orbits of the three-body problem in the cases of $m_{1}=m_{2}=1$ and $m_{3}=0.1n$ where $1\leq n\leq 20$ is an integer, among which 1,996 (about 20\%) are linearly stable. Note that our approach is valid for arbitrary mass $m_{3}$ so that in theory we can gain an arbitrarily large amount of 3D periodic orbits of the three-body problem. In the case of three equal masses, we discovered twenty-one 3D ``choerographical'' periodic orbits whose three bodies move periodically in a single closed orbit. It is very interesting that, in the case of two equal masses, we discovered 273 three-dimensional periodic orbits with the two bodies ($m_{1}=m_{2}=1$) moving along a single closed orbit and the third ($m_{3}\neq 1$) along a different one: we name them ``piano-trio'' orbits, like a trio for two violins and one piano. To the best of our knowledge, all of these 3D periodic orbits have never been reported, indicating the novelty of this work. The large amount of these new 3D periodic orbits are helpful for us to have better understandings about chaotic properties of the famous three-body problem, which ``are, so to say, the only opening through which we can try to penetrate in a place which, up to now, was supposed to be inaccessible'', as pointed out by Poincaré, the founder of chaos theory.

The Vera C. Rubin Observatory is expected to increase interstellar object (ISO) detections from a few over the past decade to potentially one per few months, demanding a systematic classification scheme. We present the Loeb Scale, formally the Interstellar Object Significance Scale (IOSS), a 0-10 classification system extending the proven Torino Scale framework, to address ISOs' unique anomalies, including potential technosignatures. The scale provides quantitative thresholds for natural phenomena (Levels 0-3) and graduated protocols for increasingly anomalous characteristics (Levels 4-7), with Levels 8-10 reserved for confirmed artificial origin. Each level specifies observable criteria and response protocols. We demonstrate the scale's application using 1I/'Oumuamua (Level 4), 2I/Borisov (Level 0), and 3I/ATLAS (Level 4) as test cases. The Loeb Scale provides the astronomical community with a standardized framework for consistent, evidence-based and dynamic evaluation while maintaining scientific rigor across the full spectrum of possibilities as we enter an era of routine ISO encounters.

Dense nucleonic matter is of vital importance for understanding compact stars and inferring the transition into deconfined quark phase. We present the $\textit{ab initio}$ exact calculations of infinite nucleonic matter with the state-of-the-art full configuration-interaction quantum Monte Carlo (FCIQMC) method, enabling us to rigorously benchmark many-body methods and assess the degree to which the nucleonic matter is strongly correlated. This method has been numerically testified to exact diagonalization within a small basis. Calculations of nucleonic matter using the chiral nuclear forces reveal that the symmetric nuclear matter is strikingly strongly correlated than expected, raising questions on previous $\textit{ab initio}$ calculations of nuclear matter with truncations and offering insights into simultaneous descriptions of finite nuclei and infinite nucleonic matter from first principles.

Parameterizing radiative transfer in means navigating trade-offs between physical accuracy and conceptual clarity. However, currently available schemes sit at the extremes of this spectrum: correlated-k schemes are fast and accurate but rely on lookup tables which obscure the underlying physics and make such schemes difficult to modify, while gray radiation schemes are conceptually straightforward but introduce significant biases in atmospheric circulation. Here we introduce a Simple Spectral Model (SSM) for clear-sky longwave radiative transfer which bridges this `clarity-accuracy' gap. The SSM accomplishes this by representing the spectral structure of H$_{2}$O and CO$_{2}$ absorption using analytic fits at reference conditions, then uses simple functional forms to extend these fits to different atmospheric conditions. This, coupled to a simple, two-stream solver, yields a system of six equations and ten physically-meaningful parameters which can solve for clear-sky longwave fluxes given atmospheric profiles of temperature and humidity. When implemented in an idealized aquaplanet GCM, the SSM produces zonal-mean climate states which accurately mimic the results using a benchmark correlated-k code. The SSM also alleviates the significant zonal-mean climate biases associated with using gray radiation, including an improved representation of radiative cooling profiles, tropopause structure, jet dynamics, and Hadley Cell characteristics both in control climates and in response to uniform warming. This work demonstrates that even a simple spectral representation of atmospheric absorption suffices to capture the essential physics of longwave radiative transfer, and the SSM promises to be a valuable tool both for idealized climate modeling, and for teaching radiative transfer in the classroom.

Gravitational Waves (GWs) provide a powerful means for cosmological distance estimation, circumventing the systematic uncertainties associated with traditional electromagnetic (EM) indicators. This work presents a model for estimating distances to binary black hole (BBH) mergers using only GW data, independent of EM counterparts or galaxy catalogs. By utilizing the intrinsic properties of the GW signal, specifically the strain amplitude and merger frequency, our model offers a computationally efficient preliminary distance estimation approach that could complements existing Bayesian parameter estimation pipelines. In this work, we examine a simplified analytical expression for the GW luminosity distance derived from General Relativity (GR), based on the leading-order quadrupole approximation. Without incorporating post-Newtonian (PN) or numerical relativity (NR) corrections, or modeling spin, eccentricity, or inclination, we test how closely this expression can reproduce distances reported by full Bayesian inference pipelines. We apply our model to 87 events from the LIGO-Virgo-Kagra (LVK) Gravitational Wave Transient Catalogues (GWTC), computing distances for these sources. Our results demonstrate consistent agreement with GWTC-reported distances, further supported by graphical comparisons that highlight the model's performance across multiple events.

Building on the feasibility study in CERN-PBC Report-2018-002 (Arduini et al. 2018), this report supported by the Physics Beyond Colliders (PBC) Study Group describes the technical implementation of modifications to the PX46 shaft at LHC Point 4 during LS3 (June 2026 - June 2030) that would enable it to accommodate the installation and operation of a vertical long-baseline Atom Interferometer during Run 4 without affecting LHC operations. We specify in detail the necessary civil-engineering work, installation of bespoke radiation shielding, deployment of access-control systems and safety alarms, and design of a mobile elevator platform. Our comprehensive technical assessment identifies no fundamental obstacles or showstoppers to implementation. Refined cost estimates and a critical-path schedule confirm that, from formal approval, all interventions can be completed within a 1.5-year window. These preparations would ensure seamless, concurrent operation of the Atom Interferometer experiment and the HL-LHC, with all technical challenges successfully addressed through established engineering solutions.

This study investigates the modeling of anisotropic magnetized static neutron stars within the framework of five-dimensional Einstein-Gauss-Bonnet (5D EGB) gravity. While Einstein's gravity has traditionally been employed to examine neutron stars, recent observational advancements have revealed its limitations in accurately describing high-mass astronomical objects-particularly in predicting or explaining certain observed neutron star masses. In response, this research seeks to address the limitations of Einstein's gravity in characterizing high-mass neutron stars by modifying the gravitational action and incorporating the Gauss-Bonnet term. This term holds significant dynamical relevance in higher dimensions, particularly within the context of five-dimensional Einstein-Gauss-Bonnet (EGB) gravity explored in this study, thereby providing a more realistic description of gravitational phenomena under extreme conditions. By deriving the generalized Tolman-Oppenheimer-Volkoff equations for five-dimensional Einstein-Gauss-Bonnet gravity and utilizing the AV18 potential, we analyze the profiles of metric functions, density and pressure, gradients of density and pressure, the anisotropic function and its trace, mass-function and compactness, the mass-radius curve, surface redshift function, equation of state parameters, and radial and tangential sound speeds. Additionally, stability factors, adiabatic indices, and energy conditions are examined. The results indicate that all conditions are satisfied for specific values of the coupling constant, confirming the physical stability of the model. Furthermore, higher dimensions enhance resistance to gravitational collapse, resulting in an increase in the maximum mass predicted by the proposed model. Ultimately, calculations show that the modified Buchdahl inequality is satisfied as well.

The Standard Model (SM) leaves several fundamental questions unanswered, including the origin of neutrino masses, the baryon asymmetry of the Universe, and the nature of dark matter. Motivated by these gaps, we investigate an extension of the SM with an additional local $U(1)_X$ gauge symmetry and a complex scalar singlet that spontaneously breaks this symmetry via its vacuum expectation value. The extended framework naturally accommodates three right-handed neutrinos (RHNs) to ensure anomaly cancellation and implements a type-I seesaw mechanism for active neutrino masses. We perform a detailed numerical analysis demonstrating consistency with current neutrino oscillation data, including predictions for the effective Majorana mass parameter relevant to neutrinoless double beta decay. Furthermore, we estimate the key parameters of the first-order phase transition and compute the resulting stochastic gravitational wave spectrum, demonstrating that it can lie within the reach of forthcoming experiments such as LISA, DECIGO, BBO, and the Einstein Telescope. The right-handed neutrinos also open a viable path for thermal leptogenesis, providing a unified link between neutrino mass generation, baryogenesis, and gravitational wave signatures. Our results demonstrate that this minimal $U(1)_X$ scenario remains a promising probe for physics beyond the Standard Model, accessible through upcoming gravitational wave and neutrino experiments.

In this paper, we investigate the strong gravitational lensing effects around the Reissner-Nordstr{ö}m-like black hole (RN-like BH) in bumblebee gravity. We calculate the lensing quantities such as deflection angle, radius of the photon sphere, angular separation, relativistic image characteristics, Einstein ring and time delay. By taking the supermassive black holes (SMBHs) like Sgr A*, M87*, NGC 1332, NGC 4649 etc. as RN-like BH, we compute the lensing observables and compare with the observables associated with the Reissner-Nordström black hole (RNBH). The quasinormal modes (QNMs) of massless Dirac field perturbation of Reissner-Nordstr{ö}m-de Sitter-like (RNdS-like) BH are also calculated. We discuss the behaviour of both real and imaginary parts of QNM frequencies with varying of $Q$ and $L$. It shows the damping rate and the oscillation frequency decrease with increasing $L$ but it has the opposite effect for the increase of $Q$. We further explore the detectability of QNMs by LIGO and LISA, and study the impact of $L$ and $Q$ on the detectable BH mass range. Further, we investigate the behaviour of greybody factor (GF) of RNdS-like BH in bumblebee gravity and find that the probability of wave transmission increases with increasing $L$ but decreases with the increase of $Q$. The behaviour of absorption cross section and sparsity of Hawking radiation for different values of $L$ and $Q$ are also analysed graphically.

We report measurements of the K$\alpha$ emission from the astrophysically very abundant Ca XIX (He-like ion) and its satellite lines resonantly excited by dielectronic recombination (DR). We achieve an electron-energy resolution of 8 eV in a cryogenic electron beam ion trap, and determine the energies of the exciting electrons and the emitted photons up to the KLn ($n\le 8$) manifold with $0.05\%$ and $0.1\%$ respective uncertainties. For the KLL satellites, energies agree very well with our predictions using the Flexible Atomic Code (FAC) and previous state-of-the-art calculations. Our calculations also agree with our experimental direct excitation cross-sections for K$\alpha$ within their $10\%$ uncertainty. We extract DR coefficient rates and find good agreement with values tabulated in the OPEN-ADAS database. As an application, we experimentally benchmark Ca XIX atomic data used to model high-temperature astrophysical plasmas by comparing FAC synthetic spectra with recent XRISM observations revealing the contributions of DR satellites to the Ca XIX lines.

The origin of the universal asymmetry between matter and antimatter remains a mystery. Electroweak baryogenesis is a well-motivated mechanism for generating the asymmetry dynamically, using interesting features of the Standard Model. In addition, it relies on beyond-the-Standard Model physics active around the electroweak scale: new physics coupling to the Higgs to make the electroweak phase transition first order, and a new mechanism of CP violation. The relatively low energy scale at which electroweak baryogenesis occurs makes certain aspects of the mechanism testable through collider experiments, electric dipole moment measurements, and gravitational wave observations. However, scenarios of electroweak baryogenesis are increasingly challenged by results from contemporary experiments. The developing experimental programs will play a crucial role in either falsifying or detecting the new physics responsible for electroweak baryogenesis. To achieve this, it is essential to make precise predictions for the baryon asymmetry and the corresponding experimental signatures within specific scenarios. This review aims to provide a comprehensive overview of the rich physics involved in these predictions. Our goal is to offer a practical computational guide, with a focus on recent developments in the field.