adsabs/SciX_UAT_keywords huggingface dataset:
Thermodynamical Description of Hot, Rapidly Rotating Neutron Stars, Protoneutron Stars, and Neutron Star Merger Remnants

The prediction of the equation of state of hot, dense nuclear matter is one of the most complicated and interesting problems in nuclear astrophysics. At the same time, knowledge of it is the basic ingredient for some of the most interesting studies. In the present work, we concentrate our study on the construction of the equation of state of hot, dense nuclear matter, related mainly to the interior of the neutron star. We employ a theoretical nuclear model, which includes momentum-dependent interaction among the nucleons, along with state-of-the-art microscopic calculations. Thermal effects are introduced in a self-consistent way, and a set of isothermal and isentropic equations of state are predicted. The predicted equations of state are used in order to acquire and extend the knowledge of the thermal effect on both nonrotating and rapidly rotating with the Kepler frequency neutron stars. The simultaneous study of thermal and rotation effects provides useful information on some of the most important quantities, including the mass (gravitational and baryon) and radius, the Kepler frequency and Kerr parameter, the moment of inertia, etc. These quantities are directly related to studies of protoneutron stars and mainly the hot and rapidly rotating remnant of a binary neutron star merger. Data from the late observations of binary neutron star mergers and the present study may offer useful tools for investigation and help in providing possible constraints on the equation of state of nuclear matter.

Keywords: neutron stars; nuclear astrophysics; nuclear physics; relativistic binary stars
VODKA-JWST: A 3.8 kpc Dual Quasar at Cosmic Noon in a Powerful Starburst Galaxy with JWST/MIRI Integral Field Unit

Dual quasars—two active supermassive black holes at galactic scales—represent crucial objects for studying the impact of galaxy mergers and quasar activity on the star formation rate (SFR) within their host galaxies, particularly at cosmic noon when SFR peaks. We present JWST/MIRI mid-infrared integral field spectroscopy of J074922.96+225511.7, a dual quasar with a projected separation of 3.8 kpc at a redshift z = 2.17. We detect spatially extended [Fe II] 5.34 μm and polycyclic aromatic hydrocarbon (PAH) 3.3 μm emissions from the star formation activity in its host galaxy. We derive the SFR of 103.0±0.2 M ⊙ yr‑1 using PAH 3.3 μm, which is 5 times higher than that derived from the knee of the infrared luminosity function for galaxies at z ∼ 2. While the SFR of J0749+2255 agrees with that of star-forming galaxies of comparable stellar mass at the same redshifts, its molecular gas content falls short of expectations based on the molecular Kennicutt–Schmidt law. This discrepancy may result from molecular gas depletion due to the longer elevated stage of star formation, even after the molecular gas reservoir is depleted. We do not observe any quasar-driven outflow that impacts PAH and [Fe II] in the host galaxy based on the spatially resolved maps. From the expected flux in PAH-based star formation, the [Fe II] line likely originates from the star-forming regions in the host galaxy. Our study highlights the extreme stardust nature of J0749+2255, indicating a potential connection between the dual quasar phase and intense star formation activities.

Keywords: infrared astronomy; double quasars; active galactic nuclei; galaxy mergers; polycyclic aromatic hydrocarbons; star formation
A Search for Extraterrestrial Technosignatures in Archival FAST Survey Data Using a New Procedure

The search for extraterrestrial intelligence (SETI) commensal surveys aim to scan the sky to find possible technosignatures from an extraterrestrial intelligence (ETI). The mitigation of radio frequency interference (RFI) is an important step, especially for the most sensitive Five-hundred-meter Aperture Spherical radio Telescope (FAST), which can detect more weak RFI. In this paper, we propose several new techniques for RFI mitigation and use our procedure to search for ETI signals from the archival data of FAST's first SETI commensal survey. We detect the persistent narrowband RFI by setting a threshold of the signals' sky separation and detect the drifting RFI (and potentially other types of RFI) using the Hough transform. We also use the clustering algorithms to remove more RFI and select candidates. The results of our procedure are compared to the earlier work on the same FAST data. We find that our methods, though relatively simpler in computation, remove more RFI (99.9912% compared to 99.9063% in the earlier work) but preserve the simulated ETI signals, except for those (5.1%) severely affected by the RFI. We also report more interesting candidate signals, about a dozen of which are new candidates that were not previously reported. In addition, we find that the proposed Hough transform method, with suitable parameters, also has the potential to remove the broadband RFI. We conclude that our methods can effectively remove the vast majority of the RFI while preserving and finding the candidate signals that we are interested in.

Keywords: search for extraterrestrial intelligence; astronomy data analysis; radio astronomy
Mercury's Chaotic Secular Evolution as a Subdiffusive Process

Mercury's orbit can destabilize, generally resulting in a collision with either Venus or the Sun. Chaotic evolution can cause g 1 to decrease to the approximately constant value of g 5 and create a resonance. Previous work has approximated the variation in g 1 as stochastic diffusion, which leads to a phenomological model that can reproduce the Mercury instability statistics of secular and N-body models on timescales longer than 10 Gyr. Here we show that the diffusive model significantly underpredicts the Mercury instability probability on timescales less than 5 Gyr, the remaining lifespan of the solar system. This is because g 1 exhibits larger variations on short timescales than the diffusive model would suggest. To better model the variations on short timescales, we build a new subdiffusive phenomological model for g 1. Subdiffusion is similar to diffusion but exhibits larger displacements on short timescales and smaller displacements on long timescales. We choose model parameters based on the behavior of the g 1 trajectories in the N-body simulations, leading to a tuned model that can reproduce Mercury instability statistics from 1–40 Gyr. This work motivates fundamental questions in solar system dynamics: why does subdiffusion better approximate the variation in g 1 than standard diffusion? Why is there an upper bound on g 1, but not a lower bound that would prevent it from reaching g 5?

Keywords: mercury (planet); planetary dynamics
Estimating AGN Black Hole Masses via Continuum Reverberation Mapping in the Era of LSST

Spectroscopic reverberation mapping (RM) is a direct approach widely used to determine the mass of black holes (BHs) in active galactic nuclei (AGNs). However, it is very time consuming and difficult to apply to a large AGN sample. The empirical relation between the broad-line region size and luminosity (Hβ R BLR-L) provides a practical alternative yet is subject to large scatter and systematic bias. Based on the relation between the continuum emitting region size and luminosity (R CER-L) reported by Netzer (2022), we present a new BH mass estimator via continuum RM (CRM) by comparing R CER and R BLR, assuming that the continuum lags are dominated by the diffuse continuum emission. Using a sample of 21 AGNs, we find a tight R BLR-R CER relation (scatter~0.28 dex) and that R BLR is larger than R CER at 5100 Å by an average factor of 8.1. This tight relation enables the BH mass estimation based on the CRM combined with the velocity information. Applying the relation to rest objects in our CRM sample, we demonstrate that the predicted R BLR,CRM follows the existing Hβ R BLR-L relation well and the estimated CRM BH masses are consistent with the RM/single-epoch BH masses using Hβ. This method will provide significant applications for BH mass estimation thanks to the short continuum lags and the easily accessible high-cadence, large-area photometric data, especially in the era of Legacy Survey of Space and Time.

Keywords: active galactic nuclei; quasars; reverberation mapping
The Last Journey. I. An Extreme-scale Simulation on the Mira Supercomputer

The Last Journey is a large-volume, gravity-only, cosmological N-body simulation evolving more than 1.24 trillion particles in a periodic box with a side length of 5.025 Gpc. It was implemented using the HACC simulation and analysis framework on the BG/Q system Mira. The cosmological parameters are chosen to be consistent with the results from the Planck satellite. A range of analysis tools have been run in situ to enable a diverse set of science projects and, at the same time, keep the resulting data amount manageable. Analysis outputs have been generated starting at redshift z ∼ 10 to allow for construction of synthetic galaxy catalogs using a semianalytic modeling approach in postprocessing. As part of our in situ analysis pipeline, we employ a new method for tracking halo substructures, introducing the concept of subhalo cores. The production of multiwavelength synthetic sky maps is facilitated by generating particle light cones in situ, also beginning at z ∼ 10. We provide an overview of the simulation setup and generated data products; a first set of analysis results is presented. A subset of the data is publicly available.

Keywords: cosmology; large-scale structure of the universe; n-body simulations
Wideband Monitoring Observations of PSR J1803-3002A in the Globular Cluster NGC 6522

We report the first wideband monitoring observations of PSR J1803-3002A, a relatively bright millisecond pulsar (MSP) in the globular cluster NGC 6522 with a spin period of 7.1 ms and no known binary companion. These observations were performed using the Parkes 64 m radio telescope with the Ultra-Wideband Low receiver system, which covers 704-4032 MHz. We confirm that PSR J1803-3002A is an isolated MSP located near the cluster center and probe the emission properties of the pulsar over the wide observed band. The mean pulse profile consists of three components, with the outer components becoming more prominent at higher frequencies, and a mean spectral index for the pulsed emission of -1.66 ± 0.07 over the observed band. The fractional linear and circular polarization increase with increasing frequency, which is unusual for pulsars. We determine a Faraday rotation measure of -107 ± 6 rad m-2 for the pulsar. PSR J1803-3002A is a distant pulsar in the Galactic plane, but our observations show no evidence of pulse broadening due to interstellar scattering. These results demonstrate the power of ultra-wideband receivers and signal processing systems.

Keywords: astronomy data analysis; globular star clusters; pulsars
Covariant Radiative Transfer for Black Hole Spacetimes

It has now become possible to study directly, via numerical simulation, the evolution of relativistic, radiation-dominated flows around compact objects. With this in mind we set out explicitly covariant forms of the radiative transfer equation that are suitable for numerical integration in curved spacetime or flat spacetime in curvilinear coordinates. Our work builds on and summarizes in consistent form earlier work by Lindquist, Thorne, Morita & Kaneko, and others. We give explicitly the basic equations in spherical polar coordinates for Minkowski space and the Kerr spacetime in Kerr-Schild coordinates.

Keywords: radiative transfer; black holes; radiative magnetohydrodynamics
Near-infrared and Optical Continuum Emission Region Size Measurements in the Gravitationally lensed Quasars Q0957+561 and SBS0909+532

We present a microlensing analysis of updated light curves in three filters, the g-band, r-band, and H-band, for the gravitationally lensed quasars Q0957+561 and SBS0909+532. Both systems display prominent microlensing features which we analyze using our Bayesian Monte Carlo technique to constrain the quasar continuum emission region sizes in each band. We report sizes as half-light radii scaled to a 60° inclination angle. For Q0957+561 we measure $\mathrm{log}({r}_{1/2}/\mathrm{cm})={16.54}_{-0.33}^{+0.33}$ , ${16.66}_{-0.62}^{+0.37}$ , and ${17.37}_{-0.40}^{+0.49}$ in g-, r-, and H-band, respectively. For SBS0909+532 we measure $\mathrm{log}({r}_{1/2}/\mathrm{cm})={15.83}_{-0.33}^{+0.33}$ , ${16.21}_{-0.62}^{+0.37}$ , and ${17.90}_{-0.63}^{+0.61}$ in the g-, r-, and H-band respectively. With size measurements in three bands spanning the quasar rest frame ultraviolet to optical, we can place constraints on the scaling of accretion disk size with wavelength, $r\propto {\lambda }^{1/\beta }$ . In a joint analysis of both systems we find a slope shallower than that predicted by thin disk theory, $\beta ={0.35}_{-0.08}^{+0.16}$ , consistent with other constraints from multi-epoch microlensing studies.

Keywords: quasar microlensing; gravitational lensing; gravitational microlensing; quasars
Stellar Evolution in AGN Disks

Active galactic nuclei (AGNs) are powered by geometrically thin accretion disks surrounding a central supermassive black hole. Here we explore the evolution of stars embedded in these extreme astrophysical environments (AGN stars). Because AGN disks are much hotter and denser than most components of the interstellar medium, AGN stars are subject to very different boundary conditions than normal stars. They are also strongly affected by both mass accretion, which can run away given the vast mass of the disk, and mass loss due to super-Eddington winds. Moreover, chemical mixing plays a critical role in the evolution of these stars by allowing fresh hydrogen accreted from the disk to mix into their cores. We find that, depending on the local AGN density and sound speed and the duration of the AGN phase, AGN stars can rapidly become very massive (M > 100 M⊙). These stars undergo core collapse, leave behind compact remnants, and contribute to polluting the disk with heavy elements. We show that the evolution of AGN stars can have a profound impact on the evolution of AGN metallicities, as well as the production of gravitational wave sources observed by LIGO-Virgo. We point to our Galactic Center as a region well suited to testing some of our predictions for this exotic stellar evolutionary channel.

Keywords: stellar evolution; active galactic nuclei; stellar physics; massive stars; compact objects; gravitational waves; stellar mass black holes; chemical enrichment; galaxy chemical evolution; bondi accretion; stellar mass loss; galactic center
A Census of Near-UV M-dwarf Flares Using Archival GALEX Data and the gPHOTON2 Pipeline

M-dwarfs are common stellar hosts of habitable-zone exoplanets. Near-UV (NUV) radiation can severely impact the atmospheric and surface conditions of such planets, making the characterization of NUV flaring activity a key aspect in determining habitability. We use archival data from the Galaxy Evolution Explorer (GALEX) and XMM-Newton telescopes to study the flaring activity of M-dwarfs in the NUV. The GALEX observations form the most extensive data set of M-dwarfs in the NUV to date, with the exploitation of this data possible due to the new gPHOTON2 pipeline. We run a dedicated algorithm to detect flares in the pipeline-produced lightcurves and find some of the most energetic flares observed to date within the NUV bandpass, with energies of ~1034 erg. Using GALEX data, we constrain flare frequency distributions for stars from M0-M6 in the NUV up to 105 s in equivalent duration and 1034 erg in energy, orders of magnitude above any previous study in the UV. We estimate the combined effect of NUV luminosities and flare rates of stars later than M2 to be sufficient for abiogenesis on habitable-zone exoplanets orbiting them. As a counterpoint, we speculate the high frequencies of energetic UV flares and associated coronal mass ejections would inhibit the formation of an ozone layer, possibly preventing the genesis of complex Earth-like life-forms due to sterilizing levels of surface UV radiation. We also provide a framework for future observations of M-dwarfs with ULTRASAT, a wide field-of-view NUV telescope to be launched in 2026.

Keywords: red dwarf flare stars; stellar flares; m dwarf stars; ultraviolet astronomy; near ultraviolet astronomy; habitable planets; pre-biotic astrochemistry
Spectral Variability of the Born-again Ejecta in A 58

Born-again planetary nebulae (PNs) allow investigating stellar evolution, dust production, and nebular shocks in human timescales. Here we present an analysis of multiepoch optical spectroscopic observations of the born-again PN A 58 around V605 Aql, which experienced a very late thermal pulse about a century ago. The H-deficient ejecta has experienced a considerable brightening in the time period considered, from 1996 to 2021, with notable changes also in many emission line ratios. Neither the reduction of the extinction caused by the dilution of the ejecta nor the increase of the ionizing photon flux from the central star seem capable to produce these spectral changes, which are instead attributed to shocks in the bipolar H-poor outflow, dissociating molecular material, and propagating through the outer nebula.

Keywords: interstellar medium; stellar jets; stellar winds; planetary nebulae; low mass stars
J-PLUS: Photometric Recalibration with the Stellar Color Regression Method and an Improved Gaia XP Synthetic Photometry Method

We employ the corrected Gaia Early Data Release 3 photometric data and spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR7 to assemble a sample of approximately 0.25 million FGK dwarf photometric standard stars for the 12 J-PLUS filters using the stellar color regression (SCR) method. We then independently validate the J-PLUS DR3 photometry and uncover significant systematic errors: up to 15 mmag in the results from the stellar locus method and up to 10 mmag primarily caused by magnitude-, color-, and extinction-dependent errors of the Gaia XP spectra as revealed by the Gaia BP/RP (XP) synthetic photometry (XPSP) method. We have also further developed the XPSP method using the corrected Gaia XP spectra by B. Huang et al. and applied it to the J-PLUS DR3 photometry. This resulted in an agreement of 1-5 mmag with the SCR method and a twofold improvement in the J-PLUS zero-point precision. Finally, the zero-point calibration for around 91% of the tiles within the LAMOST observation footprint is determined through the SCR method, with the remaining approximately 9% of the tiles outside this footprint relying on the improved XPSP method. The recalibrated J-PLUS DR3 photometric data establish a solid data foundation for conducting research that depends on high-precision photometric calibration.

Keywords: stellar photometry; astronomy data analysis; calibration
A Highly Collimated Flow from the High-mass Protostar ISOSS J23053+5953 SMM2

We present Very Large Array cm continuum observations, as well as 1.3 mm continuum and CO(2-1) observations taken with the Submillimeter Array toward the high-mass protostellar candidate ISOSS J23053+5953 SMM2. Compact cm continuum emission was detected near the center of the SMM2 dust core, and the 1.3 mm thermal dust emission indicates a core mass of 46 M⊙. The CO(2-1) observation revealed a large, massive molecular flow centered on the SMM2 core. This fast outflow (>50 km s-1) appears highly collimated, with a broader, lower-velocity component. The large values for outflow mass (45 M⊙), and energetics derived are consistent with those of flows driven by high-mass YSOs. The dynamical timescale of the flow is between 1.5-7.2 × 104 yr. Our data confirm previous findings that SMM2 is an emerging high-mass protostar in a very early phase of evolution, with an ionized jet, and a fast, highly collimated, and massive outflow.

Keywords: stellar jets; star formation
Closeby Habitable Exoplanet Survey (CHES). I. Astrometric Noise and Planetary Detection Efficiency Due to Stellar Spots and Faculae

The Closeby Habitable Exoplanet Survey (CHES) is dedicated to the astrometric exploration for habitable-zone Earth-like planets orbiting solar-type stars in close proximity, achieving unprecedented microarcsecond precision. Given the elevated precision, meticulous consideration of photocenter jitters induced by stellar activity becomes imperative. This study endeavors to model the stellar activity of solar-type stars, compute astrometric noise, and delineate the detection limits of habitable planets within the astrometric domain. Simulations were conducted for identified primary targets of CHES, involving the generation of simulated observed data for astrometry and photometry, accounting for the impact of stellar activity. Estimation of activity levels in our sample was achieved through chromospheric activity indices, revealing that over 90% of the stars exhibited photocenter jitters below 1 μas. Notably, certain proximate stars, such as α Cen A and B, displayed more discernible noise arising from stellar activity. Subsequent tests were performed to evaluate detection performance, unveiling that stellar activity tends to have a less pronounced impact on planetary detectability for the majority of the stars. Approximately 95% of the targets demonstrated a detection efficiency exceeding 80%. However, for several cold stars, e.g., HD 32450 and HD 21531, with the habitable zones close to the stars, a reduction in detection efficiency was observed. These findings offer invaluable insights into the intricate interplay between stellar activity and astrometric precision, significantly advancing our understanding in the search for habitable planets.

Keywords: astrometric exoplanet detection; habitable planets; planetary system formation; stellar activity
Chromium Isotopic Constraints on the Origin of the Ureilite Parent Body

We report on the mass-independent Cr isotope compositions of 11 main group ureilites and an ureilitic trachyandesite (ALM-A). The 54Cr/52Cr ratios for main group ureilites vary from -1.06 ± 0.04 to -0.78 ± 0.05 and averaged at -0.91 ± 0.15 (2SD, N = 18) including the data from literature. We argue that this variation reflects primitive mantle heterogeneities within the ureilite parent body (UPB). As such, this body did not experience a global-scale magma ocean, which is consistent with heterogeneous O isotope in ureilites. Furthermore, the ɛ54Cr values, Mn/Cr ratios, C isotope ratios, Mg# values, and Fe/Mn ratios in the olivine cores of ureilites are correlated with each other, which suggests the mixing of ureilite precursors from at least two reservoirs, rather than a smelting process or the oxidation from ice melting. All the ureilite samples (including the ALM-A) fall on a well-defined 53Mn-53Cr isochron corresponding to a 53Mn/55Mn ratio of (6.02 ± 1.59) × 10-6, which translates to an age of 4566.7 ± 1.5 Ma (within 2 Ma after calcium-aluminum-rich inclusions; CAIs) when anchored to the U-corrected Pb-Pb age for the D'Orbigny angrite. This old age indicates early partial melting on the UPB, consistent with the early accretion of the UPB (within 1 Ma after CAIs) predicted by thermal modeling. Furthermore, there is a 4∼5 Ma age difference between the external isochron in this study and internal isochron ages for the feldspathic clasts in polymict ureilites, which likely reflects an impact history during the early evolution of the UPB.

Keywords: astrochemistry; cosmochemistry; cosmochronology; asteroids; small solar system bodies; solar system planets; isotopic abundances; nucleosynthesis