Sazuna/UAT_keywords huggingface dataset:
Kinetic Simulations of the Kruskal─Schwarzschild Instability in Accelerating Striped Outflows: Dynamics and Energy Dissipation. Astrophysical relativistic outflows are launched as Poynting-flux dominated, yet the mechanism governing efficient magnetic dissipation, which powers the observed emission, is still poorly understood. We study magnetic energy dissipation in relativistic "striped" jets, which host current sheets separating magnetically dominated regions with opposite field polarity. The effective gravity force g in the rest frame of accelerating jets drives the Kruskal─Schwarzschild instability (KSI), a magnetic analog of the Rayleigh─Taylor instability. By means of 2D and 3D particle-in-cell simulations, we study the linear and nonlinear evolution of the KSI. The linear stage is well described by linear stability analysis. The nonlinear stages of the KSI generate thin (skin-depth-thick) current layers, with length comparable to the dominant KSI wavelength. There, the relativistic drift-kink mode and the tearing mode drive efficient magnetic dissipation. The dissipation rate can be cast as an increase in the effective width ∆eff of the dissipative region, which follows  . Our results have important implications for the location of the dissipation region in gamma-ray burst and active galactic nuclei jets.

Keywords: Magnetic fields, Plasma astrophysics, High energy astrophysics, Compact objects
Characterizing Magnetic Properties of Young Protostars in Orion. The B-field Orion Protostellar Survey (BOPS) recently obtained polarimetric observations at 870 μm toward 61 protostars in the Orion molecular clouds with ∼1″ spatial resolution using the Atacama Large Millimeter/submillimeter Array. From the BOPS sample, we selected the 26 protostars with extended polarized emission within a radius of ∼6″ (2400 au) around the protostar. This allows us to have sufficient statistical polarization data to infer the magnetic field strength. The magnetic field strength is derived using the Davis–Chandrasekhar–Fermi method. The underlying magnetic field strengths are approximately 2.0 mG for protostars with a standard hourglass magnetic field morphology, which is higher than the values derived for protostars with rotated hourglass, spiral, and complex magnetic field configurations (≲1.0 mG). This suggests that the magnetic field plays a more significant role in envelopes exhibiting a standard hourglass field morphology, and a value of ≳2.0 mG would be required to maintain such a structure at these scales. Furthermore, most protostars in the sample are slightly supercritical, with mass-to-flux ratios ≲3.0. In particular, the mass-to-flux ratios for all protostars with a standard hourglass magnetic field morphology are lower than 3.0. However, these ratios do not account for the contribution of the protostellar mass, which means they are likely significantly underestimated.

Keywords: Circumstellar envelopes, Star forming regions, Interstellar magnetic fields, Star formation, Protostars
Correlations between the Neutron Star Mass–Radius Relation and the Equation of State of Dense Matter. We develop an analytic method of inverting the Tolman–Oppenheimer–Volkoff relations to high accuracy. In principle, a specified energy density–pressure relation gives a unique mass–radius (M–R) relation and vice versa. Our method is developed from the strong correlations that are shown to exist between the neutron star mass–radius curve and the equation of state (EOS) or pressure–energy density relation. Selecting points that have masses equal to fixed fractions of the maximum mass, we find a semi-universal power-law relation between the central energy densities, pressures, sound speeds, chemical potentials, and number densities of those stars, with the maximum mass and the radii of one or more fractional maximum mass points. Rms fitting accuracies, for EOSs without large first-order phase transitions, are typically 0.5% for all quantities at all mass points. The method also works well, although less accurately, in reconstructing the EOS of hybrid stars with first-order phase transitions. These results permit, in effect, an analytic method of inverting an arbitrary M–R curve to yield its underlying EOS. We discuss applications of this inversion technique to the inference of the dense matter EOS from measurements of neutron star masses and radii as a possible alternative to traditional Bayesian approaches.

Keywords: Neutron stars, Bayesian statistics
NICER Spectral and Timing Analysis of 4U 1630-47 and Its Heartbeat State. We present a spectral and timing analysis of NICER observations of the black hole X-ray binary 4U 1630-47 from 2018 to 2024. We find relativistic reflection features in the hard and soft intermediate states, and disk wind absorption features in the soft intermediate state and soft state. We fit the reflection features with relxillCP and find a stable and untruncated disk in the intermediate states; we fit the wind features with XSTAR and find a stable, highly ionized wind with high column density across different outbursts. Specifically, the heartbeat state is seen in two observations in 2021 and 2023, respectively. Through the phase-resolved spectral fitting, we find the flux of the source to be correlated with the disk parameters while no strong correlation with the coronal parameters is observed, consistent with the scenario given by the inner disk radiation pressure instability. A hard lag on a timescale of 1 s and high coherence are observed near the characteristic frequency of the heartbeat, which can be explained by the viscous propagation of mass accretion fluctuations in the disk. The positive relationship between the heartbeat fractional rms and energy can possibly be explained by a disk-originated oscillation that is then magnified by the coronal scattering.

Keywords: X-ray astronomy, X-ray binary stars, Accretion, Astrophysical black holes
Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. V. The Expanded Sample. We present spatially resolved measurements of the ionized gas masses and mass outflow rates for six low-redshift (z ≤ 0.02) active galaxies. In this study, we expand our sample to galaxies with more complex gas kinematics modeled as outflows along a galactic disk that is ionized by the active galactic nucleus (AGN) bicone. We use Hubble Space Telescope Space Telescope Imaging Spectrograph spectroscopy, Wide Field Camera 3 narrow-band imaging, and the photoionization modeling technique that we developed in M. Revalski et al. (Paper IV in this series) to calculate ionized gas masses using the [O III]/Hβ ratios at each radius. We combine these with existing kinematic models to derive mass and energy outflow rates, which exhibit substantial radial variations due to changes in the outflow velocities. The full sample of 12 galaxies from this series of studies spans 103 in bolometric luminosity, and we find that the outflows contain ionized gas masses of M ≈ 104.6–107.2 M⊙, reach maximum mass outflow rates of  M⊙ yr‑1, and encompass kinetic energies of E ≈ 1052–1056 erg. These energetic properties positively correlate with AGN luminosity. The outflow energetics are less than benchmarks for effective feedback from theoretical models, but the evacuation of gas and injection of energy may still generate long-term effects on star formation in these nearby galaxies. These results highlight the necessity of high spatial resolution imaging and spectroscopy for accurately modeling ionized outflows in active galaxies.

Keywords: AGN host galaxies, Supermassive black holes, Galactic winds, Active galaxies, Emission line galaxies, Seyfert galaxies, Active galactic nuclei, Galaxy kinematics, Interstellar medium wind
Search for Fast Radio Bursts and Radio Pulsars from Pulsing Ultraluminous X-Ray Sources. We conducted targeted fast radio burst (FRB) and pulsar searches on eight pulsing ultraluminous X-ray sources (PULXs) using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and the Parkes 64 m Radio Telescope (Murriyang) to investigate whether PULXs could be progenitors of FRBs. FAST carried out 12 observations of four PULXs, totaling 8 hr, while Parkes conducted 12 observations of the remaining four PULXs, totaling 11 hr. No significant signals were detected through single-pulse and periodic searches, covering a dispersion measure range of 0–5000 pc cm‑3, placing stringent upper limits on the radio flux density from these sources. The results imply that accretion processes and dense stellar winds in PULXs likely suppress or attenuate potential coherent emission in the radio band. Additionally, the beaming factor and luminosity of FRBs associated with PULXs, as well as the highly relativistic and magnetized nature of their outflows, may limit detectability. Nondetection yielded from the observations covering the full orbital phases of PULXs can also constrain the theoretical models that link FRB emission to highly magnetized neutron stars in binary systems.

Keywords: Pulsars
Using Nebular Near-infrared Spectroscopy to Measure Asymmetric Chemical Distributions in 2003fg-like Thermonuclear Supernovae. We present an analysis of three near-infrared (NIR; 1.0–2.4 μm) spectra of the SN 2003fg–like/"super-Chandrasekhar" Type Ia supernovae (SNe Ia) SN 2009dc, SN 2020hvf, and SN 2022pul at respective phases of +372, +296, and +294 days relative to the epoch of B-band maximum. We find that all objects in our sample have asymmetric, or "tilted," [Fe II] 1.257 and 1.644 μm profiles. We quantify the asymmetry of these features using five methods: velocity at peak flux, profile tilts, residual testing, velocity fitting, and comparison to deflagration–detonation transition models. Our results demonstrate that, while the profiles of the [Fe II] 1.257 and 1.644 μm features are widely varied between 2003fg-likes, these features are correlated in shape within the same SNe. This implies that line blending is most likely not the dominant cause of the asymmetries inferred from these profiles. Instead, it is more plausible that 2003fg-like SNe have aspherical chemical distributions in their inner regions. These distributions may come from aspherical progenitor systems, such as double white dwarf mergers, or off-center delayed-detonation explosions of near-Chandrasekhar mass carbon–oxygen white dwarfs. Additional late-phase NIR observation of 2003fg-like SNe and detailed 3D non-LTE modeling of these two explosion scenarios are encouraged.

Keywords: Supernovae, Core-collapse supernovae
Limb-brightened Jet in M87 from Anisotropic Nonthermal Electrons. Very long baseline interferometry observations reveal that relativistic jets like the one in M87 have a limb-brightened, double-edged structure. Analytic and numerical models struggle to reproduce this limb-brightening. We propose a model in which we invoke anisotropy in the distribution function of synchrotron-emitting nonthermal electrons such that electron velocities are preferentially directed parallel to magnetic field lines, as suggested by recent particle-in-cell simulations of electron acceleration and the effects of synchrotron cooling. We assume that the energy injected into nonthermal electrons is proportional to the jet Poynting flux, and we account for synchrotron cooling via a broken power-law energy distribution. We implement our emission model in both general relativistic magnetohydrodynamic (GRMHD) simulations and axisymmetric force-free electrodynamic (GRFFE) jet models and produce simulated jet images at multiple scales and frequencies using polarized general relativistic radiative transfer. We find that the synchrotron emission is concentrated parallel to the local helical magnetic field and that this feature produces limb-brightened jet images on scales ranging from tens of microarcseconds to hundreds of milliarcseconds in M87. We present theoretical predictions for horizon-scale M87 jet images at 230 and 345 GHz that can be tested with next-generation instruments. Due to the scale-invariance of the GRMHD and GRFFE models, our emission prescription can be applied to other targets and serve as a foundation for a unified description of limb-brightened synchrotron images of extragalactic jets.

Keywords: Black hole physics, Plasma jets, Active galactic nuclei, Radiative transfer, Particle astrophysics
Localized Heating and Dynamics of the Solar Corona due to a Symbiosis of Waves and Reconnection. The Sun's outer atmosphere, the corona, is maintained at mega-Kelvin temperatures and fills the heliosphere with a supersonic outflowing wind. The dissipation of magnetic waves and direct electric currents are likely to be the most significant processes for heating the corona, but a lively debate exists on their relative roles. Here, we suggest that the two are often intrinsically linked, since magnetic waves may trigger current dissipation, and impulsive reconnection can launch magnetic waves. We present a study of the first of these processes by using a 2D physics-based numerical simulation using the Adaptive Mesh Refined Versatile Advection Code. Magnetic waves such as fast magnetoacoustic waves are often observed to propagate in the large-scale corona and interact with local magnetic structures. The present numerical simulations show how the propagation of magnetic disturbances toward a null point or separator can lead to the accumulation of the electric currents. Lorentz forces can laterally push and vertically stretch the magnetic fields, forming a current sheet with a strong magnetic field gradient. The magnetic field lines then break and reconnect and so contribute toward coronal heating. Numerical results are presented that support these ideas and support the concept of a symbiosis between waves and reconnection in heating the solar corona.

Keywords: Magnetohydrodynamics, Solar magnetic reconnection, Solar coronal waves, Solar corona, Active solar corona
Strong Near-infrared Emission Following the Long-duration GRB 211211A: Dust Heating as an Alternative to a Kilonova. The prolonged near-infrared (NIR) emission observed following the long-duration GRB 211211A is inconsistent with afterglow emission from the shock being driven into the circumstellar medium (CSM) as well as with emission from a possible underlying supernova. It has therefore been suggested that the observed NIR flux is the signature of a kilonova—a radioactive ejecta that is similar to the outcome of the binary neutron star merger GW170817. We propose here an alternative plausible explanation. We show that the NIR flux is consistent with thermal emission from dust, heated by UV and soft-X-ray radiation produced by the interaction of the gamma-ray-burst (GRB) jet plasma with the CSM. This NIR emission was predicted by Waxman &amp; Draine for GRBs residing near or within massive molecular clouds. The dust NIR emission scenario is consistent with a GRB at z ≲ 1. Inspection of the environment of GRB 211211A suggests that there are at least two host galaxy candidates, one at z = 0.076 and the other at z = 0.459. The z = 0.459 possibility is also consistent with the nondetection of a supernova signature in the light curve of the GRB afterglow as well as with the typical GRB gamma-ray energy for the fluence of GRB 211211A.

Keywords: Neutron stars, Gamma-ray bursts, Dust destruction
The Temperature and First Ionization Potential Bias of Active Regions and Their Relations to In Situ Solar Wind. Active regions (ARs) are important sources of the slow solar wind. Connecting the properties of ARs and their associated solar wind can improve our understanding of the origin and generation mechanisms of the slow solar wind. In this study, we compare the physics properties of the AR upflow regions and nonupflow regions. The relationships between the properties of these regions and the associated solar wind parameters are analyzed. We find that the electron densities of the upflow regions are significantly lower than those of the nonupflow regions. The temperatures of the upflow regions are generally close to those of the nonupflow regions. The first ionization potential (FIP) bias varies significantly among different ARs. The FIP bias of upflow regions and that of nonupflow regions are generally similar for the same AR. The FIP bias of both upflow and nonupflow regions positively correlates with their associated solar wind. There is no relationship between the solar wind O7+/O6+ and the temperature of the source regions. The results suggest that in the upflow regions, the magnetic reconnection between closed loops and open field lines may be important for generating the nascent slow solar wind. We conclude that it is unreliable to infer the temperatures of ARs directly from the O7+/O6+ ratios of the in situ solar wind.

Keywords: Solar abundances, Solar surface, Solar active regions, Solar wind
Dynamic Motion of Microwave Bursts during a Solar Limb Flare. The SOL2013-10-28T02:02:58L133C110 flare occurred on the western limb, acquiring the GOES class of X1.0, and we focus on an oscillatory phenomenon detected at 34 GHz by the Nobeyama Radioheliograph (NoRH) during this flare. The oscillation is less obvious at 17 GHz and is unseen for a hard X-ray source detected by the RHESSI. In the 94 Å images from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we traced the evolution of the extreme ultraviolet (EUV) images capturing an eruption around 01:58 UT over the location of the RHESSI 50–100 keV source. We located the microwave emitting loop inferred from the 17/34 GHz maps within the complex EUV loop systems, and performed a model calculation of the dynamic evolution of the microwave brightness, including the radiative transfer in a magnetically asymmetric loop and evolving nonthermal electrons. The results demonstrate that a quasiperiodic injection of energetic electrons at a fixed spatial point is sufficient to reproduce such an oscillatory motion, without an actual shift of the nonthermal electron injection point, and that the magnetic environment required for the microwave loop model is consistent with the observed EUV activities related to the overall reconnection geometry.

Keywords: Solar flares
The AstroSat UV Deep Field South. II. A Diverse Set of Lyman-continuum Leakers at z ∼ 1. We report the detection of five newly identified Lyman-continuum (LyC) leaker candidates at redshifts 0.99─1.42 in the AstroSat UV Deep Field South F154W image. We derive physical properties of these galaxies using a combination of spectral-energy distribution fitting and information from publicly available spectra. The estimated escape fraction of these objects varies from 14% to 85% after accounting for the intergalactic medium attenuation. With only about a dozen known leakers at these redshifts, these detections significantly raise the fraction of LyC leakers in this redshift-range. High-resolution Hubble Space Telescope UV imaging reveals that a subset of the galaxies in our sample have blue star-forming structures that are likely associated with harder ionizing sources. We find tentative evidence that the LyC emission is spatially offset from the nonionizing UV-continuum centers of these galaxies. The integrated properties of these galaxies, such as the UV-continuum slope, dust attenuation, stellar mass, and [O III]λ5007/[O II]λ3727 ratios, make them atypical compared to known LyC leakers. The leakage of LyC photons from these systems presents a compelling challenge.

Keywords: Ultraviolet astronomy, Reionization
A Multimessenger Mass Determination Method for LISA Neutron Star–White Dwarf Binaries. Determining the masses of neutron stars (NSs) accurately improves our understanding of the NS interior and complicated binary evolution. However, the masses of the systems are degenerate with the orbital inclination angle when using solely gravitational waves (GWs) or electromagnetic measurements, especially for face-on binaries. Taking advantage of both GWs and optical observations for LISA NS–white dwarf (WD) binaries, we propose a mass determination method utilising multimessenger observational information. By combining the binary mass function obtained from optical observations and a GW mass function, which we introduce, derived from GW observations, we demonstrate how we can set improved constraints on the NS mass and break the degeneracy in the mass and viewing inclination determination. We further comment on the universal relation of the error bar of the GW mass function versus the GW signal-to-noise ratio and propose a simple method for estimating the capability of using GW observations for mass determination with LISA. We show that for ultracompact NS–WD binaries within our Galaxy, the mass of the NS can be constrained to within an accuracy of ±0.2 M⊙ with the proposed method.

Keywords: Neutron stars, Compact binary stars, Gravitational waves
LAMOST J101356.33+272410.7: A Detached White Dwarf–Main-sequence Binary with a Massive White Dwarf within the Period Gap. We report the analysis of the detached eclipsing spectroscopic binary system LAMOST J101356.33+272410.7, which features a massive white dwarf and has an orbital period of 185.82 minutes. Using Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Sloan Digital Sky Survey spectra, we determined the stellar parameters, radial velocity semiamplitudes, and orbital periods of both components. Spectral energy distribution fitting of photometric data from the Galaxy Evolution Explorer, the Two Micron All Sky Survey, and Pan-STARRS1 yielded the effective temperatures and photometric radii. Eclipsing analysis of high-speed photometric data from the Liverpool Telescope provided orbital inclination, masses, radii, and related physical parameters. The white dwarf in this system has a mass of 1.05 ± 0.09 M⊙ and a radius of 0.0090 ± 0.0008 R⊙, while the main-sequence star has a mass of 0.299 ± 0.045 M⊙ and a radius of 0.286 ± 0.018 R⊙. Emission lines observed in the spectra indicate the likely presence of stellar magnetic activity in this system. The relatively cool temperature of the white dwarf suggests that the system could be a post-common-envelope binary (PCEB) that has not undergone mass transfer, while the presence of a massive white dwarf indicates that the system might also represent a detached cataclysmic variable crossing the period gap. We suggest that the system is more likely to be a PCEB, and it is predicted to evolve into a cataclysmic variable and begin mass transfer in approximately 0.27 Gyr.

Keywords: M dwarf stars, White dwarf stars, Detached binary stars, Eclipsing binary stars, Cataclysmic variable stars
Atmospheric Absorption of Dark Matter. Typically, the interaction between dark matter and ordinary matter is assumed to be very small. Nevertheless, in this article, I show that the effective resonant absorption of dark photon dark matter in the atmosphere is definitely possible. This might also be associated with the alleged temperature anomalies observed in our upper stratosphere. By allowing a small amount of additional energy deposition to our upper stratosphere, a narrow dark matter mass range mA ∼ 0.0001–0.001 eV and the corresponding range of the mixing parameter ɛ are constrained for the first time. This proposal might overturn our usual assumption of extremely weak interaction between dark matter and ordinary matter and revive the hope of detecting dark matter directly. Some important implications of this proposal, such as the heating of planets and supermassive dark stars, would also be discussed.

Keywords: Dark matter, Particle astrophysics