Papers for Monday, Apr 14 2025

Cosmological perturbation theory provides a fundamental framework for analyzing the evolution of density fluctuations and gravitational potentials in the Universe. It plays a crucial role in understanding large-scale structure formation and cosmic microwave background (CMB) anisotropies. In this study, we apply perturbation theory to the minimally extended varying speed of light (meVSL) model to investigate the effects of a varying speed of light on the matter density contrast and the Newtonian gravitational potential. Unlike conventional models with a constant speed of light, the meVSL model introduces modifications to the cosmological evolution equations, leading to potential deviations in structure formation and gravitational interactions. By deriving and analyzing the perturbed equations within this framework, we explore how a varying speed of light affects the growth of density perturbations and the evolution of gravitational potentials. Compared to the standard constant speed of the light model, we find deviations of approximately $2$\% in the subhorizon modes of both quantities. Although detecting these effects observationally remains a significant challenge, our results provide new theoretical insights into the meVSL model and its potential observational signatures, such as the integrated Sachs-Wolfe effect and gravitational lensing of the CMB.

Cosmic filaments form the backbone of the cosmic web, yet their properties and evolution remain uncertain. Using the EAGLE hydrodynamical simulations, we investigate the dark matter density profiles in filaments and their implications for dark matter decay signals. We show that GeV-scale dark matter particles decaying into electron-positron pairs can produce detectable radio synchrotron emission. By leveraging stacked filament radio data, we place stringent constraints on the dark matter decay lifetime, improving existing limits by up to two orders of magnitude for strong filamentary magnetic fields.

We study the luminosity function (LF) and clustering properties of 888 H$\alpha$ emitters (HAEs) at $3.75 < z < 6$ in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans $\sim$62 arcmin$^2$ and reaches $L_{\rm H\alpha} \sim 10^{41.2} {\rm erg s^{-1}}$. We identify two prominent filamentary protoclusters at $z \approx 4.41$ and $z \approx 5.19$, hosting 98 and 144 HAEs, respectively. The observed H$\alpha$ LFs show similar shallow faint-end slopes for both protocluster and field galaxies at $z=3.75-5$, and for the protocluster at $z=5-6$ ($\alpha\approx 1.2$ to $-1.3$). In contrast, the field LF at $z=5-6$ is much steeper ($\alpha=-1.87_{-0.23}^{+0.30}$), suggesting that protocluster galaxies at $z > 5$ are more evolved, resembling those at $z=3.75-5$. The observed star formation rate density from H$\alpha$, integrated down to 0.45 ${\rm M_\odot yr^{-1}}$, is $0.050^{+0.002}_{-0.003}$ and $0.046^{+0.006}_{-0.004} M_\odot {\rm yr}^{-1} {\rm Mpc}^{-3}$ at $z=3.75-5$ and $z=5-6$, with protoclusters contributing $\sim$25% and 55%, respectively. This implies that a large fraction of star formation at $z > 4$ occurs in protoclusters. We conduct the first star-formation-rate-limited 3D clustering analysis at $z > 4$. We find the filamentary protocluster geometry flattens the power-law shape of the HAE auto-correlation functions, with slopes much shallower than typically assumed. The auto-correlation function of field HAEs have correlation lengths of $r_0 = 4.61^{+1.00}_{-0.68} h^{-1}{\rm Mpc}$ at $z \approx 4-5$ and $r_0 = 6.23^{+1.68}_{-1.13} h^{-1}{\rm Mpc}$ at $z=5-6$. Comparing the observed correlation functions with the UniverseMachine simulation, we infer the dark matter (sub-)halo masses of HAEs to be $\log (M_h/M_\odot)=11.0-11.2$ at $z\approx 4-6$, with a scatter of 0.4 dex.

In this paper, we establish and calibrate mid-infrared hydrogen recombination lines observed with JWST as accretion tracers for pre-main-sequence stars that accrete from circumstellar disks. This work is part of a coordinated, multi-observatory effort that monitored the well-known binary system DQ Tau over three orbital periods, capturing its periodic accretion bursts. In this first paper, we present 9 epochs of MIRI-MRS spectra with near-simultaneous LCO photometry and VLT X-Shooter spectroscopy. This program caught exceptional accretion variability, spanning almost two orders of magnitude between the peak of the first periastron accretion burst and the following quiescent phases. The MIRI spectra show H I line luminosities that vary in step with the accretion-luminosity time series measured with LCO and X-Shooter. The tight correlation with accretion and the large line widths, which MIRI resolves for the first time, support an accretion-flow origin for mid-infrared H I transitions. Combining these three exceptional datasets, we derive accurate relations between mid-infrared line and accretion luminosities for three H I transitions (10-7, 7-6, 8-7), and improve upon a previous relation based on Spitzer spectra. These new relations equip the community with a direct measurement of the accretion luminosity from MIRI-MRS spectra. A MIRI-derived accretion luminosity is fundamental for time-domain chemistry studies, as well as for studies of accretion in embedded/distant sources that are currently inaccessible in the optical. With these new relations, we provide accretion luminosities for an archival sample of 38 MRS spectra of protoplanetary disks published to date.

Active galactic nuclei (AGN) have been proposed as environments that can facilitate the capture of extreme-mass-ratio binaries and accelerate their inspiral beyond the rate expected from gravitational wave emission alone. In this work, we explore binaries shortly after capture, focusing on the evolution of the binary parameters when the system is still far from merger. We find that repeated interactions with the AGN disk typically reduce both the inclination and semi-major axis of the orbit. The evolution of the eccentricity is more intricate, exhibiting phases of growth and decay. Nevertheless, as the binary gradually aligns with the disk plane, the system tends to circularize. Interestingly, we also identify scenarios where initially highly eccentric, nearly counter-rotating orbits can undergo a rapid transition to co-rotation while maintaining a constant eccentricity. These dynamical effects could have significant implications for the modeling and interpretation of LISA sources.

A subset of galaxies have dense nuclei, and when these galaxies are accreted and tidally stripped, the nuclei can masquerade as globular clusters in the halos of large galaxies. If these nuclei contain massive central black holes, some may accrete gas and become observable as active galactic nuclei. Previous studies have found that candidate stripped nuclei rarely host luminous X-ray sources, but these studies were typically restricted to both the most massive candidate nuclei and the most luminous X-ray sources. Here we use new and archival Chandra and XMM-Newton data to search for X-ray emission in a near-complete sample of massive globular clusters and candidate stripped nuclei in the nearest accessible elliptical galaxy, NGC 5128. This sample has the unique advantage that the candidate stripped nuclei are identified dynamically via elevated mass-to-light ratios. Our central result is that 5/22 ($23^{+11}_{-6}$%) of the candidate stripped nuclei have X-ray sources down to a typical limit of $L_X \sim 5 \times 10^{36}$ erg s$^{-1}$, a fraction lower than or comparable to that among massive clusters with normal mass-to-light ratios (16/41; $39^{+8}_{-7}$%). Hence we confirm and extend the result that nearly all X-ray sources in stripped nuclei are likely to be X-ray binaries rather than active galactic nuclei. If the candidate stripped nuclei have black holes of typical masses $\sim 2 \times 10^{5} M_{\odot}$ needed to explain their elevated mass-to-light ratios, then they have typical Eddington ratios of $\lesssim 2 \times 10^{-6}$. This suggests that it will be challenging to conduct an accretion census of wandering black holes around even nearby galaxies.

Aims. We study the individual and cumulative impact of stellar feedback processes on massive black hole (MBH) growth in a simulated low-mass dwarf galaxy. Methods. A suite of high-resolution radiation-hydrodynamic simulations called Noctua is performed, using the ArepoNoctua numerical framework for BHs in galaxy simulations. The chemical evolution of the gas is explicitly modelled in a time-dependent non-equilibrium way. Two types of stellar feedback are considered: individually-traced type II supernova (SNII) explosions, and radiatively transferred (on-the-fly) ionising stellar radiation (ISR) from OB stars. As part of the numerical framework, we develop and apply a novel physically-motivated model for MBH gas accretion, taking into account the angular momentum of the gas in the radiatively efficient regime, to estimate the gas accretion rate from the sub-grid accretion disc. Results. Without any stellar feedback, an initial $10^4~\mathrm{M}_\odot$ MBH is able to steadily grow over time, roughly doubling its mass after 800 Myr. Surprisingly, the growth of the MBH is more than doubled when only ISR feedback is considered, compared to the no stellar feedback run. This is due to the star formation rate (SFR) being highly suppressed (to a similar level or slightly above that when SNII feedback is considered), enabling a higher cumulative net gas inflow onto the MBH from not only the cold neutral- and molecular medium phases, but also the unstable- and warm neutral medium phases. With SNII feedback included, the gas accretion onto the MBH is episodic over time, and is suppressed by more than an order of magnitude already during the first 150 Myr. When combining SNII with ISR feedback, the growth of the MBH remains suppressed due to SNII feedback, but to a lesser extent compared to the SNII-only feedback run, due to a slightly lower SFR, and hence a reduced number of SNII events.

We develop a new statistical framework for studying the host galaxies of astrophysical sources that accounts for both redshift evolution and the multi-variate nature of host-galaxy properties. These aspects are critical when dealing with sources that span a wide range of redshifts, and/or with unknown redshift-dependent selection effects. We apply our method to a sample of Fast Radio Burst (FRB) host-galaxies as a means of probing the uncertain progenitor(s) of these events. Using our method we are able to rule out that FRBs track star-formation rate (SFR), as would be expected if FRBs are associated exclusively with young neutron stars born via core-collapse supernovae (SNe). Furthermore, we robustly rule out a recently proposed model whereby FRBs track SFR only above a certain metallicity threshold. Motivated by the fact that at least one FRB has been localized to a globular cluster (GC), we also investigate the hypothesis that that all FRBs occur in GCs and rule out this scenario explicitly for the first time. Alternatively, we find that a `mixed' model whereby FRBs track a linear combination of both SFR and stellar-mass best explains the data. The preferred parameters of such a mixed model are remarkably similar to those inferred for Type Ia SNe, and implies a possible connection between the progenitors of these different transients.

We report the discovery of 13 broad-line AGNs at $z = 5 - 8$ from the first 10% data of the JWST Cycle 3 Treasury Program COSMOS-3D. These AGNs are identified by their broad H$\alpha$ or H$\beta$ emission lines through the NIRCam grism wide-field slitless spectroscopy. One object at $z = 7.646$ with broad H$\beta$ emission has an F444W magnitude of 23.6 mag, making it one of the brightest $z > 7.5$ broad-line AGNs yet known. Among the 13 AGNs, 10 objects have reddened optical continua with slopes $\beta_{\rm opt}>0$. The remaining three objects have their overall SEDs that resemble those of UV-luminous quasars at similar redshifts, but their $\beta_{\rm opt}$, though negative, are not as blue as those of unobscured quasars. We also obtain MIRI photometry at 7.7-18 $\mu$m for two AGNs and place strong constraints on their rest-frame near-IR SED. We find no significant variability in the rest-frame UV by comparing the COSMOS-3D and COSMOS-Web F115W images taken apart by 60 days in the rest-frame. We compute the H$\alpha$ luminosity functions (LFs) for the broad H$\alpha$ emitters at $z \approx 5-6$ and find a potential redshift evolution when compared with that of the $z \approx 4-5$ sample. We also derive the H$\beta$ LF at $z\sim8$ for AGNs and galaxies by combining our sample with those from the literature. The broad H$\beta$ emitters in this work suggest a number density two orders of magnitude higher than that predicted by the quasar LF based on rest-frame UV-selected samples. As a preview, our work showcases the ability of the COSMOS-3D grism survey to provide a complete view of the properties, growth, and evolution of bright broad-line AGNs at $z>5$.

Feedback from active galactic nuclei (AGN) is crucial for regulating galaxy evolution. Motivated by observations of broad absorption line winds from rapidly accreting supermassive black holes (SMBHs), we introduce the Mistral AGN feedback model, implemented in the Arepo code. Mistral comes in two versions: continuous radial (Mistral-continuous) and stochastic bipolar momentum deposition (Mistral-stochastic). Using the framework of the IllustrisTNG simulations, we explore the effect of Mistral on BH and galaxy properties, through an idealized Milky Way-mass galaxy and cosmological zoom simulations run down to $z=2$. Unlike standard thermal AGN feedback prescriptions, Mistral generates galaxy-scale winds that mimic outflows driven by BH accretion. Mistral-continuous produces short-lived galactic fountains, and is inefficient at regulating the growth of massive galaxies at $z=2$. In contrast, Mistral-stochastic efficiently suppresses star formation in massive galaxies, and reproduces the empirical stellar-to-halo mass and ($z=0$) BH-stellar mass relations. By supporting large-scale ($>50\,\rm kpc$) outflows while simultaneously preventing gas inflows, Mistral-stochastic additionally regulates the cold and hot gas fractions at both galaxy and halo scales. Mistral-stochastic therefore works self-consistently across the halo mass range explored $\left(10^{12}-3\times10^{13}\,\rm M_\odot\right)$, without adopting a SMBH-mass dependent AGN feedback scheme such as the one used in IllustrisTNG. Our model is a promising tool for predicting the impact of radiatively efficient AGN winds on galaxy evolution, and interpreting the growing population of high-redshift galaxies and quasars observed by JWST. This work is part of the "Learning the Universe" collaboration, which aims to infer the physical processes governing the evolution of the Universe.

The thermal structure and evolution of protoplanetary disks play a crucial role in planet formation. In addition to stellar irradiation, accretion heating is also believed to significantly affect the disk thermal structure and planet formation processes. We present the long-term evolution (from the beginning of Class II to disk dissipation) of thermal structures in laminar magnetized disks to investigate where and when accretion heating is a dominant heat source. In addition, we demonstrate how the difference in disk structures affects the water content of forming planets. We consider the mass loss by magnetohydrodynamic (MHD) and photoevaporative disk winds to investigate the influence of wind mass loss on the accretion rate profile. Our model includes the recent understanding of accretion heating; that is, the accretion heating in the laminar disks is less efficient than that in turbulent disks because of surface heating at optically thinner altitudes and energy removal by disk winds. We find that the accretion heating is weaker than irradiation heating at around 1--10 au even in the early Class II disk, whereas it can affect the temperature in the inner 1-au region. We also find that the MHD-wind mass loss in the inner region can significantly reduce the accretion rate compared with that in the outer region, in turn reducing accretion heating. Furthermore, using evolving disk structures, we demonstrate that updating accretion heating models impacts the evolution of protoplanets. In particular, we find that our model may produce a dichotomy of the planetary water fraction of 1--10 $M_\oplus$.

To study how massive variable stars effect their environment, we search for variability among Zwicky Transient Facility (ZTF) sources located within the optical extent of a nearby starburst galaxy IC 10. We present the ZTF IC 10 catalog, which classifies 1516 $r$ band sources and 864 $g$ band sources within a $225''$ radius around IC 10 into three categories: 1388 (767) $r$ ($g$) band non-variables, 150 (85) $r$ ($g$) band non-periodic variables, and 37 (12) $r$ ($g$) band periodic variables. Among them 101 (48) $r$ ($g$) band non-periodic variables, and 22 (4) $r$ ($g$) band periodic variables are inside IC 10. We verify our classification by cross-matching with previous variability catalogs and machine learning powered classifications. Various analysis including population demographics, color-magnitude diagrams, and cross matching with a set of different surveys and database such as Gaia, XMM-Newton, Chandra, and SIMBAD are also presented. Based on source density and parallax, we distinguish sources within IC 10 from non-IC 10 sources. For IC 10 sources, we highlight flaring super giants, a source with long secondary period, periodic super giants including possible S Doradus luminous blue variable and candidate Miras. For non-IC 10 sources, we present super red sources and compact objects such as a possible long period subdwarf and a periodic X-ray source. The catalog can serve as a useful database to study the connection between various type of massive stars and their host galaxies.

The Andromeda galaxy is surrounded by a strikingly asymmetrical distribution of satellite dwarf galaxies aligned towards the Milky Way. The standard model of cosmology predicts that most satellite galaxy systems are near-isotropic, and dwarf associations observed in the local Universe are only weakly asymmetric. Here, we characterise the Andromeda system's asymmetry, and test its agreement with expectations from concordance cosmology. All but one of Andromeda's 37 satellite galaxies are contained within 107 degrees of our Galaxy. In standard cosmological simulations, less than 0.3% (0.5% when accounting for possible observational incompleteness) of Andromeda-like systems demonstrate a comparably significant asymmetry. None are as collectively lopsided as the observed satellite configuration. In conjunction with its satellite plane, our results paint the Andromeda system as an extreme outlier in the prevailing cosmological paradigm, further challenging our understanding of structure formation at small scales.

Accurate photometry in astronomical surveys is challenged by image artefacts, which affect measurements and degrade data quality. Due to the large amount of available data, this task is increasingly handled using machine learning algorithms, which often require a labelled training set to learn data patterns. We present an expert-labelled dataset of 1127 artefacts with 1213 labels from 26 fields in ZTF DR3, along with a complementary set of nominal objects. The artefact dataset was compiled using the active anomaly detection algorithm PineForest, developed by the SNAD team. These datasets can serve as valuable resources for real-bogus classification, catalogue cleaning, anomaly detection, and educational purposes. Both artefacts and nominal images are provided in FITS format in two sizes (28 x 28 and 63 x 63 pixels). The datasets are publicly available for further scientific applications.

A complex interplay between mixing and nucleosynthesis is at work in asymptotic giant branch (AGB) stars. In addition to the slow neutron capture process (s-process), the intermediate neutron capture process (i-process) can develop during protons ingestion events (PIEs). In this paper, after quickly reviewing the different modes of production of heavy elements in AGB stars that were identified so far, we investigate the synthesis of actinides and other short-lived radioactive nuclei (SLRs, $^{60}$Fe, $^{107}$Pd, $^{126}$Sn, $^{129}$I, $^{135}$Cs and $^{182}$Hf) during i-process nucleosynthesis. AGB stellar models with initial masses $1 \leq M_{\rm ini}/M_{\odot} \leq 3$, metallicities $-3 \leq $ [Fe/H] $ \leq 0$ and different overshoot strengths were computed with the stellar evolution code STAREVOL. During PIEs, a nuclear network of 1160 isotopes is used and coupled to the transport equations. We found that AGB models with [Fe/H] $<-2$ can synthesize actinides with sometimes abundances greater than solar. The $^{60}$Fe yield scales with the initial metallicity while the $^{107}$Pd, $^{126}$Sn, $^{129}$I, $^{135}$Cs and $^{182}$Hf yields follow a similar pattern as a function of metallicity, with a production peak at [Fe/H] $\simeq -1.3$. At [Fe/H] $<-1$, the fraction of odd Ba isotopes $f_{\rm Ba,odd}$ is predicted to vary between 0.6 and 0.8 depending on the initial mass and metallicity. Nuclear uncertainties on our $1 M_{\odot}$, [Fe/H] $=-2.5$ model lead to $f_{\rm Ba,odd}$ ranging between 0.27 and 0.76, which is clearly above the s-process value. AGB stars experiencing PIEs appear to be potential producers of actinides and SLRs, particularly at low metallicity (except for $^{60}$Fe). Galactic chemical evolution modeling are required to assess their possible contribution to the galactic enrichment.

Accretion flows in both stellar and supermassive black holes show a distinct spectral transition. This is seen directly in binaries and changing look AGN, and also in a recent sample of eROSITA X-ray selected, unobscured AGN where the stacked spectral energy distributions (SEDs) for a single black hole mass bin (log $M/M_{\odot} =8-8.5$) clearly show the UV bright disk appearing as the luminosity increases. In binaries, this transition is associated with a change in radio jet, from coupling to the X-ray hot flow with $L_R \propto L_X^{0.7}$ (Fundamental Plane relation), to collapsing when the X-ray hot flow collapses into a disc. We explore the radio behaviour across the transition in our AGN sample by stacking VLASS images. We significantly detect weak radio emission even after subtracting the contribution from star formation in the host galaxy. The residual radio emission remains relatively constant across the transition, despite the mean mass accretion rate changing by a factor 6 and UV flux changing by a factor 100. However, the X-rays change by only a factor 2, giving a constant radio to X-ray flux ratio as predicted by the 'fundamental plane'. We show that this is consistent with these AGN having the same compact radio jet coupling to the X-ray hot flow (not the disc) as in the binaries. The most significant difference is the persistence of the coronal X-rays across the spectral transition in AGN, whereas in binaries the coronal X-rays can be very weak in the disc dominated state.

We present 0.7-3.3 pc resolution mid-infrared (MIR) JWST images at 7.7 $\mu$m (F770W) and 21 $\mu$m (F2100W) covering the main star-forming regions of two of the closest star-forming low-metallicity dwarf galaxies, NGC6822 and Wolf-Lundmark-Melotte (WLM). The images of NGC6822 reveal filaments, edge-brightened bubbles, diffuse emission, and a plethora of point sources. By contrast, most of the MIR emission in WLM is point-like, with a small amount of extended emission. Compared to solar metallicity galaxies, the ratio of 7.7 $\mu$m intensity ($I_\nu^{F770W}$), tracing polycyclic aromatic hydrocarbons (PAHs), to 21 $\mu$m intensity ($I_\nu^{F2100W}$), tracing small, warm dust grain emission, is suppressed in these low-metallicity dwarfs. Using ALMA CO(2-1) observations, we find that detected CO intensity versus $I_\nu^{F770W}$ at ~2 pc resolution in dwarfs follows a similar relationship to that at solar metallicity and lower resolution, while the CO versus $I_\nu^{F2100W}$ relationship in dwarfs lies significantly below that derived from solar metallicity galaxies at lower resolution, suggesting more pronounced destruction of CO molecules at low metallicity. Finally, adding in Local Group L-Band Survey VLA 21 cm HI observations, we find that $I_\nu^{F2100W}$ and $I_\nu^{F770W}$ vs. total gas ratios are suppressed in NGC6822 and WLM compared to solar metallicity galaxies. In agreement with dust models, the level of suppression appears to be at least partly accounted for by the reduced galaxy-averaged dust-to-gas and PAH-to-dust mass ratios in the dwarfs. Remaining differences are likely due to spatial variations in dust model parameters, which should be an exciting direction for future work in local dwarf galaxies.

The Herschel-SPIRE Dark Field is the deepest field produced by the SPIRE instrument pushing down below the galaxy confusion limit in each of the 250, 350, 500 $\mu$m bands. Standard source extraction techniques inevitably fail because of this, and we must turn to statistical methods. Here, we present a P(D) - probability of deflection - analysis of a 12$'$ diameter region of uniform coverage at the centre of the Herschel-SPIRE Dark Field. Comparing the distribution of pixel fluxes from our observations to the distributions predicted by current literature models, we find that none of the most recent models can accurately recreate our observations. Using a P(D) analysis, we produce a fitted differential source count spline with a bump in the source counts at faint flux densities, followed by a turnover at fainter fluxes, required to fit the observations. This indicates a possible missing component from the current literature models that could be interpreted perhaps as a new population of galaxies, or a missing aspect of galaxy evolution. Taking our best-fitting results, we also calculate the contribution to the cosmic infrared background (CIB) in each of the bands, which all agree with the Planck CIB measurements in this field.

JAX-bandflux is a JAX implementation of critical supernova modelling functionality for cosmological analysis. The codebase implements key components of the established library SNCosmo in a differentiable framework, offering efficient parallelisation and gradient-based optimisation capabilities through GPU acceleration. The package facilitates differentiable computation of supernova light curve measurements, supporting the inference of SALT parameters necessary for cosmological analysis.

In this chapter, we give an overview of the major components of the interstellar medium (ISM) in galaxies at a level appropriate for upper level undergraduates or beginning graduate students. We discuss the major constituents of the the ISM in present-day star forming galaxies and summarize common methods to observe these components. We also review basic aspects of ISM structure accessible to extragalactic observations. Finally, we describe variations in ISM content and star-formation activity among local universe galaxies.

We present tilsotua, a code that calculates sky positions of the slits from Low-Resolution Imaging Spectrograph (LRIS) slitmasks used in multislit observations. Raw data for the Keck/LRIS spectrograph does not include information about the sky positions of the slitmask targets, making it difficult to use beyond the scope of the original programs. tilsotua translates slit coordinates from the mask design files in the mask milling machine frame to sky coordinates. tilsotua also shifts the original input astrometry to modern frames using the objects targeted by mask alignment boxes. This can be applied to the archived mask design files at the Lick Observatory Archive. We demonstrate that the final reconstructed slit positions are accurate to 0."14 (RMS) across the set of archived masks based on a comparison of our calculated mask alignment box coordinates with Gaia astrometric positions of the likely alignment objects. We make available the tilsotua code, archived mask files, and slit positions of the historical masks for the community to maximize the science from Keck/LRIS data in the Keck Observatory Archive.

We present an optical variability analysis and comparison of the samples of Seyfert 1 and 2 galaxies, selected from the \textit{Swift} 9-month BAT catalog, using the light curves from Transiting Exoplanet Survey Satellite (TESS) and All-Sky Automated Survey for SuperNovae (ASAS-SN). We measured the normalized excess variance of TESS and ASAS-SN light curves for each target and performed a Kolmogorov-Smirnov test between the two samples, where our results showed significant differences. This is consistent with predictions from the unification model, where Seyfert 2s are obscured by the larger scale dust torus and their variability is suppressed. This variability difference is independent of the luminosity, Eddington ratio, or black hole mass, further supporting geometrical unification models. We searched the dependence of the normalized excess variance of Seyfert 1s on absolute magnitudes, Eddington ratio, and black hole mass, where our results are consistent with relations found in the literature. Finally, a small sub-sample of changing-look AGNs that transitioned during the time frame of the ASAS-SN light curves, with their variability amplitudes changing according to the classification, larger variability as type 1s and smaller as 2s. The change of variability amplitudes can be used to better pinpoint when the type transition occurred. The consistency trend of the variability amplitude differences between Seyfert 1s and 2s and between changing-look AGNs in 1 or 2 stages suggests that variability can be a key factor in shedding light on the changing-look AGN or the dichotomy between Seyfert 1 or 2 populations.

In this study, we develop a membership identification method and apply it for 30 open clusters (OCs) within 200 pc of the Sun using astrometric data of Gaia DR3. By accounting for projection effects that distort apparent stellar motions, our approach converts astrometric data into accurate five-dimensional positions and velocities. This approach enables better identification of members in nearby open clusters. We then compare our refined membership lists with previous catalogs, revealing more members in most open clusters, but also the identification of elongated structures in Melotte 25 (Hyades), NGC 2632 (Praesepe), Melotte 111 (Coma Berenices), Platais 3, Melotte 22 (Pleiades), NGC 2451A, Platais 9, IC 2391, Platais 8, UPK 640, HSC 2986, which we studied in detail. An analysis of the ages of their members reveals the members within and outside of the tidal radius are distinctly coeval, further validating our methodology. This study suggests that for OCs in the solar neighborhood, correcting for the projection effect is very important for identification of OC members.

$\delta$ Scuti stars are hot, rapid rotators and are a poorly understood class of pulsators. Asteroseismology provides the only means with which to probe their interior dynamics. However, their complex and unexplained oscillation patterns restrict analyses to only a small fraction with interpretable pulsations. Here, we identify 5381 $\delta$ Scuti stars from 63 sectors of TESS observations, of which 300 had interpretable oscillations, with 24 showing rotational splittings. We inferred compositions and ages ($\tau$) for the 300 stars finding them in near-ZAMS states (Bedding et al. 2020), and measured the mean envelope rotation rates ($< f_{rot} >$) for 24 of them. Analyzing their age-dependent rotation, we found these stars essentially exhibit weak-to-no spindown, while evolving past the ZAMS across a narrow time-span during which they show regular pulsations. A quantitative fit to their spin-evolution results in a trend $f_{rot} (d^{-1}) \propto (\tau/{Gyr})^{-0.048 \pm 0.016}$, much slower than the spindown of cooler late-type stars due to magnetic braking (Skumanich's law: $f_{rot} (d^{-1}) \propto (\tau/{Gyr})^{-0.5}$). Based on stellar evolution calculations, we show this weak spindown is consistent with the gradual increase in their moment-of-inertia.

In this study, we investigated the radial variation of the azimuthal propagation of star formation across the spiral arms in the nearby galaxy NGC 5194 (M51a) by analysing the spatial separation between young star clusters and their nearest HII regions. The significant differences in the radial profiles of the mean azimuthal offsets in the M51a arms were found when the southern and northern arms were studied separately. The northern arm analysis showed that its radial profile is consistent with the predictions of stationary density wave theory for trailing spirals, while the explanation of the radial profile for the southern arm required its pattern speed to be higher than the rotation velocity of disc matter within the corotation circle, and lower than that outside of it. At the same time, these different radial profiles of the mean azimuthal offset in the two arms are joined by a common localization of corotation resonances, confirmed by independent studies using different methods.

Over the past decade, stellar rotation has emerged as a key factor in shaping the morphology of color-magnitude diagrams of young and intermediate-age star clusters. In this study, we use MUSE integral-field spectroscopy to investigate the stellar rotation of ~2300 stars in the 1.5 Gyr old cluster NGC 1783 in the Large Magellanic Cloud. The effective temperature, surface gravity, radial velocity, and projected rotational velocity ($v\mathrm{sin}i$) of the entire sample were obtained within a Bayesian framework to derive robust estimates of these parameters along with their associated errors. The analysis shows that stars along the extended main sequence turn-off (eMSTO) cover a wide range of rotational velocities, from values consistent with no/slow rotation up to $v\mathrm{sin}i$ ~ 250 km/s. The distribution of stellar rotation velocities appears to play a crucial role in explaining the broadening of the eMSTO in this cluster, and a correlation is observed between $v\mathrm{sin}i$ and the color of the eMSTO stars, with $v\mathrm{sin}i$ increasing as the color becomes redder. Among the eMSTO stars, we investigate the peculiar population of stars strongly dimmed in the UV (so-called UV-dim stars), recently discovered in NGC 1783. UV-dim stars show clear photometric evidence of self-extinction and mild spectroscopic signatures typically observed in shell stars, thus suggesting that they have likely a decretion disc observed nearly equator-on. Interestingly, the study also shows that a significant fraction of UV-dim stars are slow rotators. We discuss potential implications these results may have on our understanding of the formation and evolution of UV-dim stars and we propose that the rotational properties of the UV-dim stars should vary with cluster age.

A multitude of spectral activity indicators are routinely computed nowadays from the spectra generated as part of planet-hunting radial velocity surveys. Searching for shared periods among them can help to robustly identify astrophysical quantities of interest, such as the stellar rotation period. However, this identification can be complicated due to the fact that many different peaks occurring in the periodograms. This is especially true in the presence of aliasing and spurious signals caused by environmental influences affecting the instrument. Our goal is to test a clustering algorithm to find signals with the same periodicity, (i.e. with the stellar rotation period) in the periodograms of a large number of activity indicators. On this basis, we have looked to evaluate the correlations between activity indicators and fundamental stellar parameters. We used generalised Lomb-Scargle periodograms to find periodic signals in 24 activity indicators, spanning the VIS and NIR channels of the CARMENES spectrograph. Common periods were subsequently determined by a machine learning algorithm for density-based spatial clustering of applications with noise (DBSCAN). The clustering analysis of the signals apparent in the spectral activity indicators is a powerful tool for the detection of stellar rotation periods. It is straightforward to implement and can be easily automated, so that large data sets can be analysed. For a sample of 136 stars, we were able to recover the stellar rotation period in a total of 59 cases, including 3 with a previously unknown rotation period. In addition, we analysed spurious signals frequently occurring at the period of one year and its integer fractions, concluding that they are likely aliases of one underlying signal. Furthermore, we reproduced the results of several previous studies on the relationships between activity indicators and the stellar characteristics.

This paper deals with the formation and evolution of Mars' moons, Phobos and Deimos, assuming the dislocation of a larger progenitor as the origin of these moons. The study by Hyodo et al. (2022) argue that under somewhat simplistic modeling, the post-dislocation orbits of Phobos and Deimos inevitably collide within 10,000 years, leading to their mutual annihilation. These findings are based on $\mathcal{N}$-body simulations, accounting for Mars' $J_2$ and $J_4$ gravitational perturbations and mutual perturbations between the moons. In this paper, we challenge these findings by extending their work. We incorporate important perturbations such as solar perturbations, Mars' axial precession and nutation, and its deformation along three axes. We also extend some of the hypotheses made by Hyodo et al. (2022) concerning the initial distribution of Phobos and Deimos after the dislocation. Our analysis reveals that including these additional perturbations as well as the possibility of having more than two fragments after the dislocation does not alter the ultimate fate of Phobos and Deimos. The moons still converge towards collision within comparable timescales, supporting Hyodo et al. (2022) conclusions that the dislocation hypothesis under the dynamical scenario developed by Bagheri et al. (2021) has, in the best conditions, about 10\% chance of surviving after the first 100,000 years following their formation.

The current generation of millimeter receivers is able to produce cubes of 800 000 pixels by 200 000 frequency channels to cover several square degrees over the 3 mm atmospheric window. Estimating the physical conditions of the interstellar medium (ISM) with an astrophysical model on such datasets is challenging. Common approaches tend to converge to local minima and typically poorly reconstruct regions with low signal-to-noise ratio (S/N). This instrumental revolution thus calls for new scalable data analysis techniques. We present Beetroots, a Python software that performs Bayesian reconstruction of maps of physical conditions from observation maps and an astrophysical model. It relies on an accurate statistical model, exploits spatial regularization to guide estimations, and uses state-of-the-art algorithms. It also assesses the ability of the astrophysical model to explain the observations, providing feedback to improve ISM models. We demonstrate the power of Beetroots with the Meudon PDR code on synthetic data, and then apply it to estimate physical condition maps in the full Orion molecular cloud 1 (OMC-1) star forming region based on Herschel molecular line emission maps. The application to the synthetic case shows that Beetroots can currently analyse maps with up to ten thousand pixels, addressing large variations of S/N, escaping from local minima, and providing consistent uncertainty quantifications. On a laptop, the inference runtime ranges from a few minutes for 100-pixel maps to 28 hours for 8100-pixel maps. The results on the OMC-1 maps are consistent with independent estimations from the literature, and improve our understanding of the region. This work paves the way towards systematic and rigorous analyses of observations produced by current and future instruments.

Filament eruptions are considered to be a common phenomenon on the Sun and other stars, yet they are rarely directly imaged in the meter and decimeter wavebands. Using imaging data from the DAocheng solar Radio Telescope (DART) in the 150-450 MHz frequency range, we present two eruptive filaments that manifest as radio dimmings (i.e., emission depressions). Simultaneously, portions of these eruptive filaments are discernible as dark features in the chromospheric images. The sun-as-a-star flux curves of brightness temperature, derived from the DART images, exhibit obvious radio dimmings. The dimming depths range from 1.5% to 8% of the background level and show a negative correlation with radio frequencies and a positive correlation with filament areas. Our investigation suggests that radio dimming is caused by free-free absorption during filament eruptions obscuring the solar corona. This may provide a new method for detecting stellar filament eruptions.

We report the measurements of low radio frequency spectra of fourteen gigahertz-peaked spectra (GPS) pulsar candidates, between 300~MHz and 700~MHz, using the upgraded Giant Meterwave Radio Telescope. Combining newly collected measurements with archival results the spectral nature of each pulsar was examined using four different physical models: simple power law, broken power law, low-frequency turn-over power law and free-free thermal absorption. Based on this analysis, we confirm the GPS nature of five pulsars, three of them being new detections. In addition, one pulsar can be classified as having a broken power law spectrum, and we found the typical power law spectra in four other cases. In the remaining four pulsars the spectra showed tendencies of low frequency turn-over that require further investigations at lower frequency ranges. These results demonstrate the effectiveness of wideband measurements at low frequencies, below 1 GHz, in characterizing the spectral nature in pulsars. Our results also underline the need for more systematic theoretical studies to refine existing models and better interpret pulsar emission properties.

This paper presents a systematic study of X-ray-selected canonical tidal disruption events (TDEs) discovered in the western Galactic hemisphere of the first two eROSITA all-sky surveys (eRASS1 and eRASS2) performed between Dec 2019 and Dec 2020. We compiled a TDE sample from the catalog of eROSITA's extragalactic transients and variables eRO-ExTra, which includes X-ray sources with a variability significance and fractional amplitude over four between eRASS1 and eRASS2, not associated with known AGNs. Each X-ray source is associated with an optical counterpart from the Legacy Survey DR10. Canonical TDEs were selected based on their X-ray light-curve properties (single flare or decline), soft X-ray spectra ($\Gamma>3$), and the absence of archival X-ray variability and AGN signatures in their host photometry and spectroscopy. The sample includes 31 X-ray-selected TDE candidates with redshifts of $0.02< z<0.34$ and luminosities of $5.7 \times 10^{41}<L_X<5.3 \times 10^{44}$ erg/s in the 0.2-6.0 keV rest frame, of which 30 are canonical TDEs and one is an off-nuclear TDE candidate. The derived X-ray luminosity function is best fit by a double power law with a luminosity break at $10^{44}$ erg/s, corresponding to the Eddington-limiting prediction. This corresponds to a TDE volumetric rate of $ (2.3^{+1.2}_{-0.9})\times10^{-7}\,Mpc^{-3} yr^{-1}$ ($\approx1.2\times 10^{-5}$ events per galaxy per year). TDE host galaxies show a green-valley overdensity. In addition, 20%, 30%, and 15% of the sample exhibit flares in the optical, mid-infrared (mid-IR), or radio bands, respectively. We discuss the differences between X-ray, optical, and mid-IR TDE populations and the origins of multiwavelength flares in the context of the obscuring envelope and stream-stream collision models. Finally, we highlight TDE subpopulations that are not included in the canonical sample and should be explored in the future.

We present a systematic analysis of the radio properties of an X-ray selected sample of tidal disruption event (TDE) candidates discovered by the eROSITA telescope. We find radio sources coincident with half of the transient events (11 TDEs), with 8 radio sources showing statistically significant variability over a 6-month period. We model the radio spectra of 6 sources with sufficiently bright radio emission and find the sources show radio spectra consistent with optically thin synchrotron emission and radio outflow minimum radii of $10^{16}$--$10^{17}$ cm, velocities 0.01--0.05 c, and energies $10^{48}$--$10^{51}$ erg. On comparison with the radio properties of an optically-selected TDE sample at similar late times, we find no significant difference in the radio luminosity range or radio detection rate. We find a tentative positive trend with peak radio and X-ray luminosity, but require further observations to determine if this is real or due to observational bias due to the large range in distances of the events. Interestingly, none of the X-ray selected events show late rising radio emission, compared to 45% of radio-detected sources of an optically-selected sample that showed late rising radio emission. We propose that this may indicate that many TDEs launch radio outflows at or near peak X-ray luminosity, which can be significantly delayed from peak optical luminosity. This study presents the first systematic analysis of the radio properties of an X-ray selected sample of TDEs, and gives insight into the possible link between the physical processes that power X-ray and radio emission in TDEs.

The observation of peta-electronvolt (PeV) $\gamma$-ray photons from the Crab Nebula by LHAASO has revitalised the possibility of a secondary population of hadrons producing the highest energy emission through neutral pion decay. Despite previous studies modelling this population, the origin of such high-energy hadronic particles remains unclear. We consider possible acceleration scenarios for multi PeV particles in the Crab Nebula environment, including one in which high-energy protons produced at the supernova remnant's outer shock diffuse into the pulsar wind nebula. Particles which reach the Crab Pulsar's wind termination shock can be accelerated to the required energies, and subsequently interact with the dense filaments surrounding the nebula. We perform particle transport simulations of this scenario, including the effects of the expansion of the pulsar wind nebula into the surrounding supernova ejecta. We find that this results in PeV photons being produced over the lifetime of the Crab system, without over-estimating the flux at lower energies or exceeding the energy budget of the Crab Pulsar. This results in a reasonable match to the LHAASO data at the highest energies. We also present predictions for the resulting all-flavour neutrino flux, finding it to be approximately an order of magnitude below the sensitivity of current generation instruments.

Stellar obliquities, or spin-orbit angles, prevalent in exoplanet systems, can impose important constraints on their formation and evolution histories. Recent studies suggest that primordial misalignments between protoplanetary disks and stellar spin axes may significantly contribute to these obliquities, as those frequently observed in systems hosting hot Jupiters. In this study, we demonstrate that misaligned protoplanetary disks combined with stellar oblateness drive complex dynamical evolution in planetary systems during their disk dispersal stages. Specifically, we identify bifurcated evolutionary pathways in multi-planet systems: systems with low star-disk misalignment angles ($\psi_{\star0}$) undergo smooth, adiabatic evolution, producing nearly coplanar, low-obliquity configurations; in contrast, systems with high misalignment angles typically experience an abrupt, non-adiabatic transition, leading to large-amplitude libration of mutual planetary inclinations and then triggering chaotic eccentricity excitation. This libration and eccentricity excitation process can propagate inward-outward in compact multi-planet systems, forming an excitation chain that can destabilize the entire system. The non-adiabatic transition arises from the dynamical bifurcation-induced effect, which occurs during disk dissipation when $\psi_{\star0}\gtrsim44.6^\circ$ (for one-planet systems). Our framework predicts that surviving typical compact multi-planet systems originating from misaligned disks evolve toward coplanar, low-obliquity configurations, consistent with observations of Kepler multi-planet systems. These results advance our understanding of planetary dynamics in misaligned disks and their evolutionary outcomes.

The physical mechanism responsible for the photometric period changes in chemically peculiar star 56 Ari was searched. It was previously shown that rate of the star's period increase is few orders of magnitude larger than the rates expected from the evolutionary changes of the angular momentum or due to magnetic braking. Also no secular changes were detected in the surface structure or visibility of chemical spots which are responsible for the rotational modulation of stellar brightness. We hypothesise that period changes in 56 Ari are caused by the drift of surface magnetic and associated abundance structures as a result of the kink-type (Tayler) instability of the background magnetic field in the radiative zone of the star. Results of the numerical simulation presented in the paper yield growth and drift rates of the most rapidly developing non-axisymmetric mode of the instability, consistent with the observed rate of period changes in 56 Ari. The surface geometry of the 56 Ari magnetic field is also reproduces in the calculations. The proposed mechanism may also be used to explain the character of period changes in other Ap/Bp stars demonstrating such an effect.

There is a pressing need to model X-ray Ultra-Violet (XUV: 1-30 nm) stellar irradiances, given the scarcity of current measurements. One of the measurable effects of a stellar cycle is the significant (more than one order of magnitude) variation in XUV irradiance. As a first step in modelling stellar irradiances, we present EUV irradiances in a sample of strong spectral lines formed in different layers and regions of the solar atmosphere, obtained from Solar Dynamics Observatory Extreme Ultraviolet Variability Experiment (SDO EVE). These irradiances span half a solar cycle. We present correlations with several proxies of solar activity, such as the Mg II index, sunspot numbers, and cm radio fluxes. Among these, the sunspot number proves to be the poorest proxy, whereas the Mg II index is a very good proxy for coronal lines (hotter temperature lines). We find a relatively strong linear relationship, which enables us to build a model essential for various applications. Additionally, we compare our results with the previous EUV standard solar irradiances reported by Del Zanna and Andretta 2014, derived from Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer (SOHO CDS) data, as well as historical records from the literature. We have also run a DEM analysis on Quiet Sun (QS) and Active Regions (AR) and list the blends and formation temperatures for the strong lines. Finally we provide a simple routine for deriving the irradiances of the strong lines based on proxy values.

A method for pulsar timing based on monitoring data from the 3-th diagramm of the Large Phased Array (LPA LPI) radio telescope is proposed. In our observations, recorders with quartz clock generators were used as local clocks. Such recorders initially had an accuracy and hardware reference to the UTC time scale insufficient for pulsar timing. We have developed a method for referencing such clocks to the UTC based on observations of known pulsars used as intermediate reference clocks. This allowed us to improve dramatically the accuracy of determining the Time of Arrivals (TOA) of pulsars' pulses. We applied this method to the results of our observations of 24 second period pulsars over a time interval of 10 years. It was shown that the accuracy of the pulsar period, its first derivative ($P$ and $\dot P$) and their coordinates in right ascension and declination ($\alpha, \delta$) allow us to predict the pulsar phase within $\pm 0.5 P$ during several years. The accuracy of determining the coordinates by right ascension and declination was typically better than $10^{\prime \prime}$ with an angular resolution of the radio telescope of about $30^\prime$. That makes it possible to use these parameters for timing using radio telescopes with narrow beam patterns. The accuracy of the calculated period was typically better than $10^{-8}$~s.

We present a weak lensing and multi-wavelength analysis of three galaxy clusters: A115, A2219, and A2261. Weak lensing is performed using shape measurements made in short 60s exposure images obtained using WIYN-ODI. Forced measurement is used to measure low Signal to Noise (SNR) sources in individual exposures. We find the weak lensing significance map recovers the galaxy clusters and most galaxy groups in the wide 40$'$ $\times$ 40$'$ field. Significant parts of the filamentary structures over this field, as indicated by the galaxy number density map, were also successfully recovered in lensing significance maps. We find the amount of structure recovery depends on both the depth and average seeing of the images. In particular, we detect a $>$ 9 Mpc long structure that contains the cluster A2219. We compare our weak lensing maps with Chandra, XMM, and LOFAR observations and find that A115 and A2219 show clear signs of ongoing mergers. In particular, we find a significant separation of hot ICM and the weak lensing contours in A115. On the other hand, while A2261 appears relaxed, based on radio and X-ray analysis, we find that it is likely interacting with a structure 700 kpc SW of the main cluster. We also successfully recovered mass structures in two regions around A2261 indicated by diffuse X-ray emission in XMM images.

We systematically perform numerical-relativity simulations for equal-mass binary neutron star mergers for the models varying the thermal index $\Gamma_{\rm th}$ with 3 different equations of state (EOSs) of the neutron stars (NSs), which are consistent with current multi-messenger observational data and state-of-the-art theoretical calculations, and 2 different binary total mass ($m_0=2.7\ \text{and}\ 2.9~M_\odot$). By varying the value of $\Gamma_{\rm th}$ within the hybrid EOS framework, we investigate the thermal effects on the merger dynamics, gravitational waves (GWs), and the dynamical mass ejection process. We find that the choice of the constant $\Gamma_{\rm th}$ can change the outcome of the remnant for specific EOSs and $m_0$. We also show that the dynamical ejecta mass is affected by the $\Gamma_{\rm th}$ value in a different way for different EOSs: for a stiff EOS the ejecta mass is high when $\Gamma_{\rm th}$ is small, while for softer EOSs the largest ejecta is achieved when $\Gamma_{\rm th} = 1.3$--$1.4$. While the inspiral motion does not depend on the $\Gamma_{\rm th}$, the post merger phase evolution is highly affected by that. We show that the dominant peak frequency $f_2$ of the post merger GW spectrum monotonically decreases as the $\Gamma_{\rm th}$ increases. We find that the universal relations between NS macroscopic properties and post-merger GW frequencies are subject to non-negligible thermal uncertainties, which can obscure the universal relation between the tidal deformability and $f_2$.

We present AstroLLaVA, a vision language model for astronomy that enables interaction with astronomical imagery through natural dialogue. By fine-tuning the LLaVA model on a diverse dataset of $\sim$30k images with captions and question-answer pairs sourced from NASA's `Astronomy Picture of the Day', the European Southern Observatory, and the NASA/ESA Hubble Space Telescope, we create a model capable of answering open-ended questions about astronomical concepts depicted visually. Our two-stage fine-tuning process adapts the model to both image captioning and visual question answering in the astronomy domain. We demonstrate AstroLLaVA's performance on an astronomical visual question answering benchmark and release the model weights, code, and training set to encourage further open source work in this space. Finally, we suggest a roadmap towards general astronomical data alignment with pre-trained language models, and provide an open space for collaboration towards this end for interested researchers.

The interaction of ultra-high-energy cosmic rays with air nuclei triggers extensive air showers that reach their maximal energy deposition at the atmospheric depth $X_{\max}$. The distribution of this shower observable encodes information about the proton-air cross-section via fluctuations of the primary interaction point, $X_1$, and hadron production through $\Delta X_{\max} \equiv X_{\max} - X_1$. We introduce new multiparticle production variables, $\alpha_{\textrm{had}}$, $\zeta_{\textrm{had}}$, and $\zeta_{\mathrm{EM}}$, built from the energy spectra of secondaries in the primary interaction. Their linear combination, $\xi$, predicts over $50 \%$ of the fluctuations in $\Delta X_{\max}$. Moreover, we build a probabilistic mapping based on the causal connection between $\xi$ and $\Delta X_{\max}$ that enables model-independent predictions of $X_{\max}$ moments with biases below $3\,\mathrm{g\,cm^{-2}}$. Therefore, measurements of the distribution of $X_{\max}$ allow a data-driven probing of secondary hadron spectra from the cosmic-ray-air interaction, in proton-induced showers. The distributions of the new multiparticle production variables can be measured in rapidity regions accessible to current accelerators and are strongly dependent on the hadronic interaction model in the kinematic regions exclusive to ultra-high-energy cosmic rays.

The twin star configuration, where two neutron stars share the same mass but exhibit different radii, arises from a strong first-order phase transition within the stellar interior. In widely used equation of state (EoS) meta-models, such as the Polytrope (PP) and Speed-of-Sound (CS) models, this first-order phase transition behavior can be naturally mimicked by tuning some model parameters. Here, we systematically explore the under-explored parameter space within one of a widely adopted CS model that leads to twin stars via a strong first-order phase transition. Within this twin-star subspace, we perform a comprehensive Bayesian analysis that integrates mass--radius (MR) constraints from X-ray observations of rotation-powered millisecond pulsars. The resultant twin star branch, situated within the 1--1.2 $M_{\odot}$ mass range and approximately 7 km in radius, surprisingly coincides with the MR ranges proposed for the recent anomaly in the Accreting Millisecond X-ray Pulsars XTE J1814--338 (J1814), suggesting a hybrid twin star configuration. Moreover, incorporating the J1814 observation as an additional constraint yields an extreme phase transition pressure $P_{\text{trans}} = 108.9_{-4.85}^{+6.46}$ MeV/fm$^3$, a transition density of $\varepsilon_{\text{trans}}/\varepsilon_0 = 4.847_{-0.134}^{+0.271}$(where $\varepsilon_0$ is the nuclear saturation energy density) and an energy density jump $\Delta \varepsilon = 558.7_{-278.7}^{+303.6}$ MeV/fm$^3$, corresponding to $\Delta \varepsilon/\varepsilon_0 = 3.716_{-1.854}^{+2.020}$. Notably, to satisfy all astrophysical constraints, the speed of sound inside of the hybrid twin star core is driven toward the speed of light ($c_s^2/c^2 > 0.9$), indicating the potential presence of strongly interacting, exotic matter in this core region.

The products of stellar mergers between two massive main-sequence (MS) stars appear as seemingly normal MS stars after a phase of thermal relaxation, if not for certain peculiarities. Since these peculiarities are not limited to the merger product's surface, we use asteroseismology to predict how the differences in the internal structure of a merger product and a genuine single star manifest via properties of non-radial stellar pulsations. We mapped the result of a 3D MHD stellar merger simulation between a 9 and an 8 solar-mass MS star to 1D and evolved it through the MS. We compare the predicted pressure (p) and gravity (g) modes for the merger product model with those predicted for a corresponding genuine single-star model. The p-mode frequencies are consistently lower for the merger product than for the genuine single star, and the differences between them are more than a thousand times larger than the current best observational uncertainties for measured mode frequencies of this kind. Even though g-mode period spacing differences vary in value and sign throughout the MS, they, too, are larger than the current best observational uncertainties for such long-period modes. This, combined with additional variability in the merger product's period spacing patterns, shows the potential of identifying merger products in future-forward modelling. We also attempt to replicate the merger product's structure using three widely applied 1D merger prescriptions and repeat the asteroseismic analysis. Although none of the 1D prescriptions reproduces the entire merger product's structure, we conclude that the prescription with shock heating shows the highest potential, provided that it can be calibrated on binary-evolution-driven 3D merger simulations. Our work should be expanded to encompass the various possible merger product structures predicted to exist in the Universe. (abridged)

Extended regions of very high energy $\gamma$-ray emission associated with middle-aged pulsars have been found by $\gamma$-ray observatories. These regions, called TeV halos or pulsar halos, are thought to be created when energetic electrons from a pulsar or pulsar wind nebula transport into interstellar medium and undergo inverse Compton scattering with the cosmic microwave background radiation. The same electrons are expected to emit synchrotron emission in the X-ray band in the interstellar magnetic field. HESS J1813-126 is a pulsar halo candidate from which TeV $\gamma$-ray emission with extension 0.21\degr and a hard $E^{-2}$ spectrum is observed. We searched for the synchrotron component of this pulsar halo with Swift-XRT. In particular, we observed two fields within the region covered by HESS J1813-126 for 35 ksec each and a region nearby as a background reference for 10 ksec. We find no evidence for excess X-ray emission from the two observations near HESS J1813-126 and place an upper limit differential flux of $4.32\times 10^{-4}\, \rm keV^{-1}\, cm^{-2}\,s^{-1} $ and $5.38\times 10^{-4}\, \rm keV^{-1}\, cm^{-2}\,s^{-1} $ at 1 keV assuming an $E^{-2}$ power law spectrum. The non-detection implies that the magnetic field inside the halo is not significantly enhanced compared to the average Galactic magnetic field.

Context. Changes of the rotational period observed in various magnetized accreting sources are generally attributed to the interaction between the in-falling plasma and the large-scale magnetic field of the accretor. A number of models have been proposed to link these changes to the mass accretion rate, based on different assumptions on the relevant physical processes and system parameters. For X-ray binaries with neutron stars, with the help of precise measurements of the spin periods provided by current instrumentation, these models render a way to infer such parameters as the strength of the dipolar field and a distance to the system. Often, the obtained magnetic field strength values contradict those from other methods used to obtain magnetic field estimates. Aims. We want to compare the results of several of the proposed accretion models. To this end an example application of these models to data is performed. Methods. We reformulate the set of disk accretion torque models in a way that their parametrization are directly comparable. The application of the reformulated models is discussed and demonstrated using Fermi/GBM and Swift/BAT monitoring data covering several X-ray outbursts of the accreting pulsar 4U 0115+63. Results. We find that most of the models under consideration are able to describe the observations to a high degree of accuracy and with little indication for one model being preferred over the others. Yet, derived parameters from those models show a large spread. Specifically the magnetic field strength ranges over one order of magnitude for the different models. This indicates that the results are heavily influenced by systematic uncertainties.

ExoMolHR is an empirical, high-resolution molecular spectrum calculator for the high-temperature molecular line lists available from the ExoMol molecular database. Uncertainties, where available, in recommended ExoMol datasets are used to select highly accurate spectral lines. These lines largely rely on empirical energy levels generated through the MARVEL (measured active rotation vibration energy levels) procedure, which is being systematically used to improve the energy and transition data provided by the ExoMol database. The freely accessible ExoMolHR database provides line positions with calculated intensities for a user-specified wavenumber/wavelength range and temperature. Spectra can be plotted on the ExoMolHR website (this https URL) or downloaded as a CSV file. Cross sections can be calculated using the Python program PyExoCross. The ExoMolHR database currently provides 24307135 spectral lines for 33 molecules and 58 isotopologues; these numbers will increase as the ExoMol database is updated.

We investigate the gravitational field of a kinetic gas beyond its usual derivation from the second moment of the one-particle distribution function (1PDF), that serves as energy-momentum tensor in the Einstein equations. This standard procedure raises the question why the other moments of the 1PDF (which are needed to fully characterize the kinematical properties of the gas) do not contribute to the gravitational field and what could be their relevance in addressing the dark energy problem? Using the canonical coupling of the entire 1PDF to Finsler spacetime geometry via the Finsler gravity equation, we show that these higher moments contribute non-trivially. A Finslerian geometric description of our universe allows us to determine not only the scale factor but also of the causal structure dynamically. We find that already a Finslerian vacuum solution naturally permits an exponential expanding universe, without the need for a cosmological constant or any additional quantities. This solution possesses a causal structure which is a mild deformation of the causal structure of Friedmann-Lemaître-Robertson-Walker (FLRW) geometry; close to the rest frame defined by cosmological time (i.e., for slowly moving objects), the causal structures of the two geometries are nearly indistinguishable.

The canonical signal model in continuous gravitational wave searches is deterministic, and stable over the long integration times needed to separate a putative signal from the noise, e.g. with a matched filter. However, there exist plausible physical mechanisms that give rise to "spin-wandering", i.e. small stochastic variations in the frequency of the gravitational wave. Stochastic variations degrade the sensitivity of matched filters which assume a deterministic frequency evolution. Suites of synthetic spin-wandering injections are performed to infer the loss in sensitivity depth $D_{\rm SW}$ when compared to the depth for a canonical signal $D_{\rm det}$. For a fiducial spin-wandering signal that wanders by $\lesssim5 \times 10^{-6}\,$Hz per day, the depth ratio is $D_{\rm det} / D_{\rm SW}=4.39^{+0.23}_{-0.27}$, $1.51^{+0.02}_{-0.03}$, $1.75^{+0.04}_{-0.04}$, and $1.07^{+0.01}_{-0.02}$ for the coherent $F$-statistic, semi-coherent $F$-statistic, CrossCorr, and HMM-Viterbi algorithms respectively. Increasing the coherence time of the semi-coherent algorithms does not necessarily increase their sensitivity to spin-wandering signals.

We present a scheme for numerically solving Maxwell's equations in a weakly perturbed spacetime without introducing the usual geometric optics approximation. Using this scheme, we study light propagation through a spherical perturbation of a stationary metric in the linear limit. Going beyond geometric approximation allows us to explore the wave optics effects that occur when the wavefront propagates through the gravitational potential. We find that the wavefront breaks on the gravitational potential due to the Shapiro time delay, i.e. due to the slowing down of light when propagating in an inhomogeneous spacetime. This again leads to constructive interference, resulting in a persistent frequency dependent amplification of parts of the wave amplitude. When the wave length is shorter than a certain threshold set by the induced gravitational mass, the waves are reflected on the curvature gradient.

Observations have largely ruled out macroscopic dark matter across a wide range of masses, leaving an experimentally interesting window in the asteroid-mass region. Yet, theoretical motivation for this mass window is still insufficient. We initiate a new pattern of nontopological solitons, where a charge asymmetry is inherited from baryogenesis and later trapped by a first-order phase transition. This pattern makes the solitons coincident dark matter that provides new explanations for the coincidence problem between baryon and dark matter energy densities. Coincident soliton dark matter miraculously resides in the asteroid-mass window if strong gravitational waves reach the detection region, providing a strong motivation for macroscopic dark matter within this window. For the first time, we provide a realistic neutrino-ball scenario that solves the baryon asymmetry, dark matter, and neutrino mass problems. New particles are below the electroweak scale, and observable signals are correlated, including lensing effects, gravitational waves, and soliton evaporation/collision.

A density structure within the magnetic cloud of an interplanetary coronal mass ejection impacted Earth and caused significant perturbations in plasma boundaries. We describe the effects of this structure on the magnetosheath plasma downstream of the bow shock using spacecraft observations. During this event, the bow shock breathing motion is evident due to the changes in the upstream dynamic pressure. A magnetic enhancement forms in the inner magnetosheath and ahead of a plasma compression region. The structure has the characteristics of a fast magnetosonic shock wave, propagating earthward and perpendicular to the background magnetic field further accelerating the already heated magnetosheath plasma. Following these events, a sunward motion of the magnetosheath plasma is observed. Ion distributions show that both the high density core population as well as the high energy tail of the distribution have a sunward directed flow indicating that the sunward flows are caused by magnetic field line expansion in the very low $\beta$ magnetosheath plasma. Rarefaction effects and enhancement of the magnetic pressure in the magnetosheath result in magnetic pressure gradient forcing that drives the expansion of magnetosheath magnetic field lines. This picture is supported by a reasonable agreement between the estimated plasma accelerations and the magnetic pressure gradient force.

The Combined Release and Radiation Effects Satellite (CRRES) observed the response of the Van Allen radiation belts to peak solar activity within solar cycle 22. This study analyses the occurrence and loss timescales of relativistic electrons within the CRRES High Energy Electron Fluxometer (HEEF) dataset, including during several large geomagnetic storms that flooded the slot region with multi-MeV electrons and which allow the first definitive multi-MeV lifetimes to be calculated in this region. The HEEF loss timescales are otherwise broadly in agreement with those from later solar cycles but differences include longer-lasting sub-MeV electrons near the inner region of the outer belt and faster decaying multi-MeV electrons near geosynchronous orbit. These differences are associated with higher levels of geomagnetic activity, a phenomenon that enables the spread in the results to be parameterised accordingly. The timescales generally appear well-bounded by Kp-dependent theoretical predictions but the variability within the spread is however not always well-ordered by geomagnetic activity. This reveals the limits of pitch-angle diffusion in accounting for the decay of elevated electron fluxes following geomagnetic storms.

In this article, the potential of water Cherenkov detectors equipped with multi-PMT modules for precision neutrino direction reconstruction is demonstrated. By analyzing signal time traces with transformer-based models, significant improvements in angular resolution are achieved compared to previous designs with larger PMTs. These detectors enable the reconstruction of neutrino directions with resolutions of approximately $10$ degrees in azimuth and $7$ degrees in zenith for high-signal events. This design reduces saturation effects and enhances directional sensitivity, particularly for high-energy neutrinos. The results highlight the potential of WCD arrays as complementary tools for neutrino astronomy, particularly in the context of multimessenger observations of transient astrophysical sources. The nearly continuous operation and wide field of view of these detectors further enhance their suitability for real-time monitoring and alert generation.