Sazuna/UAT_keywords huggingface dataset:
Multiwavelength Observations of Multiple Eruptions of the Recurrent Nova M31N 2008-12a. We report the optical, UV, and soft X-ray observations of the 2017–2022 eruptions of the recurrent nova M31N 2008-12a. We find a cusp feature in the   $r^{\prime} $  - and   $i^{\prime} $  -band light curves close to the peak, which could be related to jets. The geometry of the nova ejecta based on morpho-kinematic modeling of the Hα emission line indicates an extended jet-like bipolar structure. Spectral modeling indicates an ejecta mass of 10‑7–10‑8 M ⊙ during each eruption and an enhanced helium abundance. The supersoft source phase shows significant variability, which is anticorrelated to the UV emission, indicating a common origin. The variability could be due to the reformation of the accretion disk. We infer a steady decrease in the accretion rate over the years based on the intereruption recurrence period. A comparison of the accretion rate with different models on the   ${M}_{\mathrm{WD}}\mbox{--}\dot{M}$   plane yields the mass of a CO white dwarf, powering the H-shell flashes every ∼1 yr, to be &gt;1.36 M ⊙ and growing with time, making M31N 2008-12a a strong candidate for the single degenerate scenario of the Type Ia supernovae progenitor.

Keywords: X-ray astronomy, Transient sources, Ultraviolet astronomy, Photometry, Recurrent novae, Spectroscopy, Cataclysmic variable stars, Andromeda Galaxy
Sun-as-a-star Study of an X-class Solar Flare with Spectroscopic Observations of CHASE. Sun-as-a-star spectroscopic characteristics of solar flares can be used as a benchmark for the detection and analysis of stellar flares. Here, we study the Sun-as-a-star properties of an X1.0 solar flare, using high-resolution spectroscopic data obtained by the Chinese Hα Solar Explorer (CHASE). A noise reduction algorithm based on discrete Fourier transformation is first employed to enhance the signal-to-noise ratio of the space-integral Hα spectrum, with a focus on its typical characteristics. For the flare of interest, we find that the average Hα profile displays a strong emission at the line center and an obvious line broadening. It also presents a clear red asymmetry, corresponding to a redshift velocity of around 50 km s‑1 that slightly decreases with time, consistent with previous results. Furthermore, we study how the size of the space-integral region affects the characteristics of the flare's Sun-as-a-star Hα profile. It is found that although the redshift velocity calculated from the Hα profile remains unchanged, the detectability of the characteristics weakens as the space-integral region becomes larger. An upper limit on the size of the target region where the red asymmetry is detectable is estimated. It is also found that the intensity in Hα profiles, measured by the equivalent widths of the spectra, are significantly underestimated if the Hα spectra are further averaged in the time domain.

Keywords: Stellar flares, The Sun, Solar flares, Solar flare spectra
The Relativistic Spin Precession in the Compact Double Neutron Star System PSR J1946+2052. We observe systematic profile changes in the visible pulsar of the compact double neutron star system PSR J1946+2052 using observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The interpulse of PSR J1946+2052 changed from a single-peak to a double-peak shape from 2018–2021. We attribute this evolution as the result of the relativistic spin precession of the pulsar. With the high sensitivity of FAST, we also measure significant polarization for the first time, allowing us to model this with the precessional rotating vector model. Assuming, to the first order, a circular hollow-cone-like emission beam pattern and taking the validity of general relativity (GR), we derive the binary's orbital inclination angle (  ${{63}^{\circ }}_{-{3}^{\circ }}^{+{5}^{\circ }}$  ) and pulsar's spin geometry. The pulsar's spin vector and the orbital angular momentum vector are found to be only slightly misaligned (  ${{0.}^{\circ }21}_{-{0.}^{\circ }10}^{+{0.}^{\circ }28}$  ). The quoted uncertainties do not reflect the systematic uncertainties introduced by our model assumptions. By simulating future observations of profile and polarization evolution, we estimate that we could constrain the precession rate within a 43% uncertainty in 9 yr. Hence, we suggest that the system's profile evolution could be combined with precise pulsar timing to test GR in the future.

Keywords: General relativity
Magnetic Flux Plays an Important Role during a Black Hole X-Ray Binary Outburst in Radiative Two-temperature General Relativistic Magnetohydrodynamic Simulations. Black hole (Bh) X-ray binaries cycle through different spectral states of accretion over the course of months to years. Although persistent changes in the Bh mass accretion rate are generally recognized as the most important component of state transitions, it is becoming increasingly evident that magnetic fields play a similarly important role. In this article, we present the first radiative two-temperature general relativistic magnetohydrodynamics simulations in which an accretion disk transitions from a quiescent state at an accretion rate of   $\dot{M}\sim {10}^{-10}{\dot{M}}_{\mathrm{Edd}}$   to a hard-intermediate state at an accretion rate of   $\dot{M}\sim {10}^{-2}{\dot{M}}_{\mathrm{Edd}}$  . This huge parameter space in mass accretion rate is bridged by artificially rescaling the gas density scale of the simulations. We present two jetted BH models with varying degrees of magnetic flux saturation. We demonstrate that in "standard and normal evolution" models, which are unsaturated with magnetic flux, the hot torus collapses into a thin and cold accretion disk when   $\dot{M}\gtrsim 5\times {10}^{-3}{\dot{M}}_{\mathrm{Edd}}$  . On the other hand, in "magnetically arrested disk" models, which are fully saturated with vertical magnetic flux, the plasma remains mostly hot with substructures that condense into cold clumps of gas when   $\dot{M}\gtrsim 1\times {10}^{-2}{\dot{M}}_{\mathrm{Edd}}$  . This suggests that the spectral signatures observed during state transitions are closely tied to the level of magnetic flux saturation.

Keywords: Accretion, Hydrodynamical simulations, Black holes, Relativistic jets, Magnetohydrodynamical simulations
A Consistent Explanation for the Unusual Initial Mass Function and Star Formation Rate in the Central Molecular Zone (CMZ). We examine various physical processes that may explain the shallow high-mass slope of the initial mass function (IMF), as well as the low star formation rate (SFR) in star-forming molecular clouds (MCs) in the Central Molecular Zone (CMZ). We show that the strong tidal field and shear experienced by the CMZ have opposite effects on the collapse of density fluctuations and cannot explain these properties. Similarly, we show that the intense magnetic field in the CMZ provides a negligible pressure support and, for the high densities at play, should not modify the probability density function of the turbulent gas flow, thus affecting negligibly the IMF. However, we show that, in contrast to the MCs in the Galactic disk, the ones in the CMZ experience only one single episode of turbulence cascade. Indeed, their rather short lifetime, due to their high mean densities, is similar to one typical turbulence crossing time. Consequently, according to the Hennebelle–Chabrier theory of star formation, within this "single turbulence cascade episode," the cloud experiences one single field of turbulence-induced density fluctuations, leading eventually to gravitationally unstable cores. As shown in Hennebelle &amp; Chabrier (2013), this yields a shallower IMF than usual and leads to the correct observed slope for the CMZ star-forming clouds. Similarly, this single large-scale turbulence event within the cloud lifetime yields a 5–6 times lower SFR than under usual conditions, in agreement with the observed values. Therefore, we suggest that this "single turbulence cascade" scenario can explain both the shallow IMF and low SFR of clouds in the CMZ.

Keywords: Milky Way Galaxy
A New Dissociative Galaxy Cluster Merger: RM J150822.0+575515.2. Galaxy cluster mergers that exhibit clear dissociation between their dark matter, intracluster gas, and stellar components are great laboratories for probing dark matter properties. Mergers that are binary and in the plane of the sky have the additional advantage of being simpler to model, allowing for a better understanding of the merger dynamics. We report the discovery of a galaxy cluster merger with all these characteristics and present a multiwavelength analysis of the system, which was found via a search in the redMaPPer optical cluster catalog. We perform a galaxy redshift survey to confirm the two subclusters are at the same redshift (0.541, with 368 ± 519 km s−1 line-of-sight velocity difference between them). The X-ray morphology shows two surface brightness peaks between the brightest cluster galaxies (BCGs). We construct weak-lensing mass maps that reveal a mass peak associated with each subcluster. Fitting Navarro─Frenk─White profiles to the lensing data, we find masses of M 200c = 36 ± 11 × 1013 and 38 ± 11 × 1013 M ⊙ h −1 for the southern and northern subclusters, respectively. From the mass maps, we infer that the two mass peaks are separated by   ${520}_{-125}^{+162}$   kpc along the merger axis, whereas the two BCGs are separated by 697 kpc. We also present deep GMRT 650 MHz data to search for a radio relic or halo and find none. Using the observed merger parameters, we find analog systems in cosmological n-body simulations and infer that this system is observed between 96 and 236 Myr after pericenter, with the merger axis within 28° of the plane of the sky.

Keywords: Galaxy clusters, Weak gravitational lensing, Hubble Space Telescope, Galaxy spectroscopy, Dark matter
Probing the Stellar Populations and Star Formation History of Early-type Galaxies at 0 &lt; z &lt; 1.1 in the Rest-frame Ultraviolet. We measure the evolution of the rest-frame near-ultraviolet (NUV)‑V colors for early-type galaxies in clusters at 0 &lt; z &lt; 1.1 using data from the Hyper Suprime-Cam Subaru Strategic Program, CFHT Large Area U-band Deep Survey, and local Sloan Digital Sky Survey clusters observed with Galaxy Evolution Explorer. Our results show that there is an excess in the ultraviolet spectrum in most quiescent galaxies (compared to the expectations from models fitting their optical/infrared colors and spectra) below z ∼ 0.6, beyond which the excess UV emission fades rapidly. This evolution of the UV color is only consistent with the presence of a highly evolved, hot horizontal branch subpopulation in these galaxies (among the majority of cool and optically bright stars), comprising on average 10% of the total stellar mass and forming at z &gt; 3. The blue UV colors of early-type galaxies at low–intermediate redshifts are likely driven by this subpopulation being enriched in helium up to ∼44%. At z &gt; 0.8 (when the extra UV component has not yet appeared) the data allow us to constrain the star formation histories of galaxies by fitting models to the evolution of their UV colors: we find that the epoch at which the stellar populations formed lies in the range 3 &lt; z form &lt; 10 (corresponding to 0.5–2.2 Gyr after the Big Bang) with a star formation e-folding timescale of τ = 0.35–0.7 Gyr, suggesting that these galaxies formed the majority of stars at very high redshift, with a brief yet intense burst of star formation activity. The star formation history and chemical evolution of early-type galaxies resemble those of globular clusters, albeit on much larger scales.

Keywords: Galaxy formation, Horizontal branch stars, Galaxy evolution, Extreme horizontal branch stars
The Size–Linewidth Relation and Signatures of Feedback from Quiescent to Active Star Forming Regions in the LMC. To investigate the effects of stellar feedback on the gravitational state of giant molecular clouds (GMCs), we study 12CO and 13CO Atacama Large Millimeter/submillimeter Array maps of nine GMCs distributed throughout the Large Magellanic Cloud (LMC), the nearest star-forming galaxy to our own. We perform noise and resolution matching on the sample, working at a common resolution of 3.″5 (0.85 pc at the LMC distance of 50 kpc), and we use the Spectral Clustering for Molecular Emission Segmentation clustering algorithm to identify discrete substructure, or "clumps." We supplement these data with three tracers of recent star formation: 8 μm surface brightness, continuum-subtracted Hα flux, and interstellar radiation field energy density inferred from dust emission. The 12CO clumps identified cover a range of 3.6 dex in luminosity-based mass and 2.4 dex in average 8 μm surface brightness, representative of the wide range of conditions of the interstellar medium in the LMC. Our observations suggest evidence for increased turbulence in these clouds. While the turbulent linewidths are correlated with clump surface density, in agreement with previous observations, we find even better correlation with the three star formation activity tracers considered, suggesting stellar energy injection plays a significant role in the dynamical state of the clumps. The excess linewidths we measure do not appear to result from opacity broadening. 12CO clumps are found to be typically less gravitationally bound than 13CO clumps, with some evidence of the kinetic-to-gravitational potential energy ratio increasing with star formation tracers. Further multiline analysis may better constrain the assumptions made in these calculations.

Keywords: Giant molecular clouds, Magellanic Clouds, Radio sources, Interstellar medium
Turbulence, and Proton and Electron Heating Rates in the Solar Corona: Analytical Approach. Analytical solutions for 2D and slab turbulence energies in the solar corona are presented, including a derivation of the corresponding correlation lengths, with implications for the proton and electron temperatures in the solar corona. These solutions are derived by solving the transport equations for 2D and slab turbulence energies and their correlation lengths, as well as proton and electron pressures. The solutions assume background profiles for the solar wind speed, solar wind mass density, and Alfvén velocity. Our analytical solutions can be related to those obtained from joint Parker Solar Probe and Solar Orbiter Metis coronagraph observations, as reported in Telloni et al. We find that the solution for 2D turbulence energy in the absence of nonlinear dissipation decreases more slowly compared to the dissipative solution. The solution for slab turbulence energy with no dissipation exhibits a more rapid increase compared to the dissipative solution. The proton heating rate is found to be about 82% of the total plasma heating rate at 6.3 R ⊙, which gradually decreases with increasing distance, eventually becoming ∼80% of the total plasma heating rate at ∼13 R ⊙, consistent with that found by Bandyopadhyay et al. (2023). These analytical solutions provide valuable insight for our understanding of turbulence, and its effect on proton and electron heating rates, in the solar corona. We compare the numerically solved turbulent transport equations for the 2D and slab turbulence energies, correlation lengths, and proton and electron pressures with the analytical solutions, finding good agreement between them.

Keywords: Interplanetary turbulence, Solar wind, The Sun, Solar coronal heating
Mid-infrared Properties of Narrow-line Seyfert 1 Galaxies Detected by LoTSS DR2. Narrow-line Seyfert 1 galaxies (NLS1s), a subclass of active galactic nuclei (AGNs) in an early stage of the accretion process, are also found to host relativistic jets. However, currently known jetted NLS1s are rare. The majority of NLS1s are undetected at the radio band. The radio detection rate of NLS1s increases with the LOFAR Two-metre Sky Survey (LoTSS), which provides a good opportunity for finding more jetted NLS1s. The better sensitivity raises the question whether the radio emission of NLS1s with a low radio luminosity originates from the jet activity. In order to clarify the origin of the radio emission for NLS1s and search for more jetted NLS1s, we explore the mid-infrared properties of LoTSS-detected NLS1s by comparing them with known jetted AGNs and star-forming galaxies (SFGs), which are located above and on the well-studied radio/far-infrared correlation, respectively. The majority of NLS1s show mid-infrared (MIR) excess compared with SFGs. Their radio emission shows a significant correlation with the MIR emission. In the MIR color–color diagram, NLS1s overlap flat spectrum radio quasars, but they are well separated from SFGs and optically selected radio galaxies. The flux ratio of the radio and MIR emission of these NLS1s is also similar to that of a radio-quiet quasar with a weak jet. These results imply substantial contributions from the AGN activities for both the radio and MIR emission of NLS1s. A small fraction of NLS1s with relatively higher radio luminosities are located in a similar region as blazars in the radio-MIR diagram, which suggests that the radio emission of these NLS1s is dominated by the jet. We obtain a sample of jetted NLS1 candidates through their radio excess in the radio-MIR diagram.

Keywords: Radio active galactic nuclei, Low-luminosity active galactic nuclei, Active galactic nuclei
Mass Assembly in Massive Star Formation: A Fragmentation Study of ATLASGAL Clumps. The mass assembly in star-forming regions arises from the hierarchical structure in molecular clouds in tandem with fragmentation at different scales. In this paper, we present a study of the fragmentation of massive clumps covering a range of evolutionary states, selected from the ATLASGAL survey, using the compact configuration of the Submillimeter Array. The observations reveal a wide diversity in the fragmentation properties with about 60% of the sources showing limited to no fragmentation at the 2″ scale, or a physical scale of 0.015─0.09 pc. We also find several examples where the cores detected with the Submillimeter Array are significantly offset from the clump potential, suggesting that initial fragmentation does not result in the formation of a large number of Jeans mass fragments. The fraction of the clump mass that is in compact structures is seen to increase with source evolution. We also see a significant correlation between the maximum mass of a fragment and the bolometric luminosity of the parent clump. These suggest that massive star formation proceeds through clump fed core accretion, with the initial fragmentation being dependent on the density structure of the clumps and/or magnetic fields.

Keywords: Submillimeter astronomy, Protostars, Star formation, Molecular clouds
ROME. IV. An Arecibo Search for Substellar Magnetospheric Radio Emissions in Purported Exoplanet-hosting Systems at 5 GHz. Plasma flow–obstacle interactions, such as those between an exoplanet's magnetosphere and the host star's stellar wind, may lead to detectable radio emissions. Despite many attempts to detect magnetospheric (auroral) radio emissions from exoplanets, a reproducible, unambiguous detection remains elusive. This fourth paper of the Radio Observations of Magnetized Exoplanets (ROME) series presents the results of a targeted radio survey of nine nearby systems that host exoplanet, brown dwarf, or low-mass-stellar companions conducted with the Arecibo radio telescope at ∼5 GHz. This search for magnetospheric radio emissions has the greatest sensitivity (∼1 mJy during &lt;1 s integration times) and collected full Stokes parameters over the largest simultaneous bandpass of any survey to date. It is also the first survey to search for radio emission from brown dwarfs of spectral class Y, which may illuminate open questions regarding their magnetism, interior and atmospheric structure, and formation histories. No magnetospheric radio emissions from substellar companions were detected. These results are examined within the context of recent theoretical work on plasma flow–obstacle interactions, and radio emissions observed from the solar system planets and ultracool dwarfs.

Keywords: Brown dwarfs, Spectropolarimetry, Magnetospheric radio emissions, Exoplanets, Natural satellites (Extrasolar), Y dwarfs, Aurorae, Non-thermal radiation sources, Planetary magnetospheres, Magnetic fields
Comprehensive High-resolution Chemical Spectroscopy of Barnard's Star with SPIRou. Determination of fundamental parameters of stars impacts all fields of astrophysics, from galaxy evolution to constraining the internal structure of exoplanets. This paper presents a detailed spectroscopic analysis of Barnard's star (otherwise known as Gl 699) that compares an exceptionally high-quality (an average signal-to-noise ratio of ∼1000 in the entire domain), high-resolution near-infrared (NIR) spectrum taken with Canada-France-Hawaii Telescope/SPIRou to PHOENIX-ACES stellar atmosphere models. The observed spectrum shows thousands of lines not identified in the models with a similarly large number of lines present in the model but not in the observed data. We also identify several other caveats, such as continuum mismatch, unresolved contamination, and spectral lines significantly shifted from their expected wavelengths; all of these can be a source of bias for the determination of abundance. Out of &gt;104 observed lines in the NIR that could be used for chemical spectroscopy, we identify a short list of a few hundred lines that are reliable. We present a novel method for determining the effective temperature (T eff) and overall metallicity of slowly rotating M dwarfs that uses several groups of lines as opposed to bulk spectral fitting methods. With this method, we infer T eff = 3231 ± 21 K for Barnard's star, consistent with the value of 3238 ± 11 K inferred from the interferometric method. We also provide measurements of the abundance of 15 different elements for Barnard's star, including the abundances of four elements (K, O, Y, Th) never reported before for this star. This work emphasizes the need to improve current atmosphere models to fully exploit the NIR domain for chemical spectroscopy analysis.

Keywords: M dwarf stars, Abundance ratios, Stellar abundances, Molecular spectroscopy, Chemical abundances, Astronomical techniques, Atomic spectroscopy, Low mass stars, Metallicity, Stellar atmospheres
Test for Echo: X-Ray Reflection Variability in the Seyfert-2 Active Galactic Nucleus NGC 4388. We report on a study of the narrow Fe Kα line and reflection spectrum in the well-known Seyfert-2 active galactic nucleus (AGN), NGC 4388. X-ray spectra summed from two extensive NICER monitoring campaigns, separated by years, show strong evidence of variation in the direct continuum and reflected emission, but only small variations in the obscuring gas. Fits to the spectra from individual NICER observations find a strong, positive correlation between the power-law photon index, Γ, and direct flux that is commonly observed in unobscured AGN. A search for a reverberation lag between the direct and reflected spectra—dominated by the narrow Fe Kα emission line—measures a timescale of   $t={16.37}_{-0.38}^{+0.46}$   days, or a characteristic radius of   $r={1.374}_{-0.032}^{+0.039}\,\times {10}^{-2}$   pc   $={\,3.4}_{-0.1}^{+0.1}\times {10}^{4}\,{GM}/{c}^{2}$  . Only one cycle of this tentative lag is observed, but it is driven by a particularly sharp drop in the direct continuum that leads to the subsequent disappearance of the otherwise prominent Fe Kα line. Physically motivated fits to high-resolution Chandra spectra of NGC 4388 measure a line production radius of   $r={2.9}_{-0.7}^{+1.2}\,\times {10}^{4}\,{GM}/{c}^{2}$  , formally consistent with the tentative lag. The line profile also prefers a Compton-thick reflector, indicating an origin in the disk and/or thick clumps within a wind. We discuss the strengths and weaknesses of our analysis and methods for testing our results in future observations, and we note the potential for X-ray reverberation lags to constrain black hole masses in obscured Seyferts wherein the optical broad line region is not visible.

Keywords: Active galactic nuclei, X-ray active galactic nuclei, Black holes