Sazuna/UAT_keywords huggingface dataset:
ULTRASAT: A Wide-field Time-domain UV Space Telescope. The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is scheduled to be launched to geostationary orbit in 2027. It will carry a telescope with an unprecedentedly large field of view (204 deg2) and near-ultraviolet (NUV; 230–290 nm) sensitivity (22.5 mag, 5σ, at 900 s). ULTRASAT will conduct the first wide-field survey of transient and variable NUV sources and will revolutionize our ability to study the hot transient Universe. It will explore a new parameter space in energy and timescale (months-long light curves with minutes cadence), with an extragalactic volume accessible for the discovery of transient sources that is &gt;300 times larger than that of the Galaxy Evolution Explorer (GALEX) and comparable to that of the Vera Rubin Observatory's Legacy Survey of Space and Time. ULTRASAT data will be transmitted to the ground in real time, and transient alerts will be distributed to the community in &lt;15 minutes, enabling vigorous ground-based follow up of ULTRASAT sources. ULTRASAT will also provide an all-sky NUV image to &gt;23.5 AB mag, over 10 times deeper than the GALEX map. Two key science goals of ULTRASAT are the study of mergers of binaries involving neutron stars, and supernovae. With a large fraction (&gt;50%) of the sky instantaneously accessible, fast (minutes) slewing capability, and a field of view that covers the error ellipses expected from gravitational-wave (GW) detectors beyond 2026, ULTRASAT will rapidly detect the electromagnetic emission following binary neutron star/neutron star–black hole mergers identified by GW detectors, and will provide continuous NUV light curves of the events. ULTRASAT will provide early (hour) detection and continuous high-cadence (minutes) NUV light curves for hundreds of core-collapse supernovae, including for rarer supernova progenitor types.

Keywords: Cosmology, Gamma-ray bursts, Near ultraviolet astronomy, Exoplanets, Tidal disruption, Gravitational wave sources, Active galactic nuclei, Time domain astronomy, Space telescopes, Supernovae, Galaxies, Solar system astronomy
Multiwavelength Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using Hα and EUV Spectra Taken by SMART/SDDI and SDO/EVE. This paper presents a multiwavelength Sun-as-a-star analysis of the M8.7 flare on 2022 October 2, which was associated with a filament eruption and the subsequent coronal mass ejection. The Sun-as-a-star analysis was performed using Hα data taken by Solar Dynamics Doppler Imager on board the Solar Magnetic Activity Research Telescope at Hida Observatory, Kyoto University, and full-disk integrated extreme ultraviolet (EUV) spectra taken by the Extreme ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory. The Sun-as-a-star Hα spectra showed blueshifted absorption corresponding to the filament eruption. Furthermore, the EVE O V 629.7 Å spectra showed blueshifted brightening, which can also be attributed to the filament eruption. Even when the blueshifted absorption became almost invisible in the Sun-as-a-star Hα spectra, the O V blueshifted brightening up to ‑400 km s‑1 was still clearly visible. This result indicates that even when the shifted components—which are expected to originate from stellar eruptions—become almost invisible in the spatially integrated stellar Hα spectra, the erupting materials may still be present and observable in EUV spectra. Additionally, the Sun-as-a-star Hα and O V spectra exhibited redshifted absorption and brightening, respectively, during the decay phase of the flare. These components probably originate from the post-flare loops, providing clues to the multitemperature nature of the post-flare loops in the spatially integrated observation. Our Sun-as-a-star results suggest that the combination of Hα and EUV lines allows the investigation of the multitemperature structure and temporal development of stellar active phenomena even in spatially integrated spectra.

Keywords: Solar flares, Solar prominences, Solar coronal mass ejections, Stellar flares, Solar filament eruptions, Solar chromosphere
Can Supernovae Quench Star Formation in High-z Galaxies?. JWST is providing a unique opportunity to directly study the feedback processes regulating star formation (SF) in early galaxies. The two z &gt; 5 quiescent systems (JADES-GS-z7-01-QU and MACS0417-z5BBG) detected so far show a recent starburst after which SF is suppressed. To clarify whether such quenching is due to supernova (SN) feedback, we have developed a minimal physical model. We derive a condition on the minimum star formation rate, ${\mathrm{SFR}}_{\min }$ , lasting for a time interval Δt  b , required to quench SF in a galaxy at redshift z, with gas metallicity Z, and hosted by a halo of mass M  h . We find that lower (z, Z, M  h ) systems are more easily quenched. We then apply the condition to JADES-GS-z7-01-QU (z = 7.3, M ⋆ = 108.6 M ⊙) and MACS0417-z5BBG (z = 5.2, M ⋆ = 107.6 M ⊙) and find that SN feedback largely fails to reproduce the observed quenched SF history. Alternatively, we suggest that SF is rapidly suppressed by radiation-driven dusty outflows sustained by the high specific star formation rates (43 and 25 Gyr‑1, respectively) of the two galaxies. Our model provides a simple tool to interpret the SF histories of post-starburst galaxies and unravel quenching mechanisms from incoming JWST data.

Keywords: Cosmology, Galaxy quenching, High-redshift galaxies, Galaxy evolution
X-Ray Polarization of the Black Hole X-Ray Binary 4U 1630─47 Challenges the Standard Thin Accretion Disk Scenario. A large energy-dependent X-ray polarization degree is detected by the Imaging X-ray Polarimetry Explorer (IXPE) in the high-soft emission state of the black hole X-ray binary 4U 1630─47. The highly significant detection (at ≈50σ confidence level) of an unexpectedly high polarization, rising from ∼6% at 2 keV to ∼10% at 8 keV, cannot be easily reconciled with standard models of thin accretion disks. In this work, we compare the predictions of different theoretical models with the IXPE data and conclude that the observed polarization properties are compatible with a scenario in which matter accretes onto the black hole through a thin disk covered by a partially ionized atmosphere flowing away at mildly relativistic velocities.

Keywords: X-ray astronomy, Accretion, Polarimetry, Stellar mass black holes
One-dimensional General Relativistic Particle-in-cell Simulations of Stellar-mass Black Hole Magnetospheres: A Semianalytic Model of Gamma-Rays from Gaps. In the absence of a sufficient amount of plasma injection into the black hole (BH) magnetosphere, the force-free state of the magnetosphere cannot be maintained, leading to the emergence of strong, time-dependent, longitudinal electric fields (i.e., spark gaps). Recent studies of supermassive BH magnetospheres using analytical methods and particle-in-cell (PIC) simulations propose the possibility of efficient particle acceleration and consequent gamma-ray emission in the spark gap. In this work, we perform 1D general relativistic PIC simulations to examine the gamma-ray emission from stellar-mass BH magnetospheres. We find that intermittent spark gaps emerge and particles are efficiently accelerated in a similar manner to the supermassive BH case. We build a semianalytic model of the plasma dynamics and radiative processes, which reproduces the maximum electron energies and peak gamma-ray luminosities of the simulation results. Based on this model, we show that the gamma-ray signals from stellar-mass BHs wandering through the interstellar medium could be detected by gamma-ray telescopes such as the Fermi Large Area Telescope or the Cherenkov Telescope Array.

Keywords: Accretion, Gamma-ray sources, Plasma astrophysics, Black holes
Jets with a Twist: The Emergence of FR0 Jets in a 3D GRMHD Simulation of Zero-angular-momentum Black Hole Accretion. Spinning supermassive black holes (BHs) in active galactic nuclei magnetically launch relativistic collimated outflows, or jets. Without angular momentum supply, such jets are thought to perish within 3 orders of magnitude in distance from the BH, well before reaching kiloparsec scales. We study the survival of such jets at the largest scale separation to date, via 3D general relativistic magnetohydrodynamic simulations of rapidly spinning BHs immersed into uniform zero-angular-momentum gas threaded by a weak vertical magnetic field. We place the gas outside the BH sphere of influence, or the Bondi radius, chosen to be much larger than the BH gravitational radius, R B = 103 R g. The BH develops dynamically important large-scale magnetic fields, forms a magnetically arrested disk (MAD), and launches relativistic jets that propagate well outside R B and suppress BH accretion to 1.5% of the Bondi rate, ${\dot{M}}_{{\rm{B}}}$ . Thus, low-angular-momentum accretion in the MAD state can form large-scale jets in Fanaroff–Riley (FR) type I and II galaxies. Subsequently, the disk shrinks and exits the MAD state: barely a disk (BAD), it rapidly precesses, whips the jets around, globally destroys them, and lets 5%–10% of ${\dot{M}}_{{\rm{B}}}$ reach the BH. Thereafter, the disk starts rocking back and forth by angles 90°–180°: the rocking accretion disk (RAD) launches weak intermittent jets that spread their energy over a large area and suppress BH accretion to ≲2% ${\dot{M}}_{{\rm{B}}}$ . Because the BAD and RAD states tangle up the jets and destroy them well inside R B, they are promising candidates for the more abundant, but less luminous, class of FR0 galaxies.

Keywords: Black hole physics, High energy astrophysics, Relativistic jets, General relativity, Active galactic nuclei
Correlating Intrinsic Stellar Parameters with Mg II Self-reversal Depths. The Mg II h&k emission lines (2803, 2796 Å) are a useful tool for understanding stellar chromospheres and transition regions due to their intrinsic brightness, relatively low interstellar medium (ISM) absorption interference, and abundance of archival spectra available. Similar to other optically thick chromospheric emission lines such as H I Lyα, Mg II emissions commonly present with a self-reversed line core, the depth and shape of which vary from star to star. We explore the relationship between self-reversal and the stellar atmosphere by investigating the extent to which fundamental stellar parameters affect self-reversal. We present a search for correlations between photospheric parameters such as effective temperature, surface gravity, and metallicity with the Mg II k self-reversal depth for a group of 135 FGKM main-sequence stars with high-resolution near-ultraviolet spectra from the Hubble Space Telescope. We modeled the observed Mg II k line profiles to correct for ISM attenuation and recover the depth of the emission line's self-reversal in relation to the intensity of the line. We used the PHOENIX atmosphere code to homogeneously determine the stellar parameters by computing a suite of stellar atmosphere models that include a chromosphere and transition region, and using archival photometry to guide the models of each star. We quantify the sensitivity of the visible and near-infrared photometry to chromospheric and photospheric parameters. We find weak trends between Mg II k self-reversal depth and age, rotation period, Mg II luminosity, temperature, and mass. All stars in our sample older than ∼2 Gyr or rotating slower than ∼10 days exhibit self-reversal.

Keywords: Stellar spectral types
Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14. Parker Solar Probe is a mission designed to explore the properties of the solar wind closer than ever before. Detailed particle observations from the Solar Probe Cup (SPC) have primarily focused on examining the proton population in the solar wind. However, several periods throughout the Parker mission have indicated that SPC has observed a pronounced and distinctive population of fully ionized helium, He2+. Minor ions are imprinted with properties of the solar wind's source region, as well as mechanisms active during outflow, making them sensitive markers of its origin and formation at the Sun. Through a detailed analysis of the He2+ velocity distributions functions, this work examines periods where significant and persistent He2+ peaks are observed with SPC. We compute the helium abundance and examine the stream's bulk speed, density, temperature, magnetic field topology, and electron strahl properties to identify distinctive solar-wind features that can provide insight to their solar source. We find that nearly all periods exhibit an elevated mean helium composition (8.34%) compared to typical solar wind and a majority (∼87%) of these periods are connected to coronal mass ejections (CMEs), with the highest abundance reaching 23.1%. The helium abundance and number of events increases as the solar cycle approaches maximum, with a weak dependence on speed. Additionally, the events not associated with a CME are clustered near the heliospheric current sheet, suggesting they are connected to streamer belt outflows. However, there are currently no theoretical explanations that fully describe the range of depleted and elevated helium abundances observed.

Keywords: Solar abundances, Solar physics, Solar wind, Solar coronal mass ejections
Nonlinear Feedback of the Electrostatic Instability on the Blazar-induced Pair Beam and GeV Cascade. Relativistic pair beams produced in the cosmic voids by TeV gamma-rays from blazars are expected to produce a detectable GeV-scale cascade that is missing in the observations. The suppression of this secondary cascade implies either the deflection of the pair beam by intergalactic magnetic fields or, alternatively, an energy loss of the beam due to the beam-plasma instability. Here, we study how the beam-plasma instability feeds back on the beam, using a realistic two-dimensional beam distribution. We find that the instability broadens the beam opening angles significantly without any significant energy loss, thus confirming a recent feedback study on a simplified one-dimensional beam distribution. However, narrowing diffusion feedback of the beam particles with Lorentz factors less than 106 might become relevant, even though initially it is negligible. Finally, when considering the continuous creation of TeV pairs, we find that the beam distribution and the wave spectrum reach a new quasi-steady state, in which the scattering of beam particles persists and the beam opening angle may increase by a factor of hundreds. Understanding the implications on the GeV cascade emission requires accounting for inverse-Compton cooling.

Keywords: Blazars, Gamma-rays
A Triple Scenario for the Formation of Wide Black Hole Binaries Such as Gaia BH1. Recently, several noninteracting black hole–stellar binaries have been identified in Gaia data—for example, Gaia BH1, where a Sun-like star is in a moderately eccentric (e = 0.44) 185 days orbit around a black hole. This orbit is difficult to explain through binary evolution. The present-day separation suggests the progenitor system would have undergone an episode of common-envelope evolution, but a common envelope should shrink the period below the observed one. Since the majority of massive stars form in higher-multiplicity systems, a triple evolution scenario is more likely for the progenitors of BH binaries. Here we show that such systems can indeed be more easily explained via evolution in hierarchical triple systems. von Zeipel–Lidov–Kozai oscillations or instabilities can delay the onset of the common-envelope phase in the inner binary of the triple, so that the black hole progenitor and low-mass star are more widely separated when it begins, leading to the formation of wider binaries. There are also systems with similar periods but larger eccentricities, where the BH progenitor is a merger product of the inner binary in the triple. Such mergers lead to a more top-heavy black hole mass function.

Keywords: Multiple star evolution, Astrophysical black holes, Common envelope binary stars
Circumgalactic Environments Around Distant Quasars 3C 9 and 4C 05.84. We present results from the Quasar hosts Unveiled by high Angular Resolution Techniques survey studying the circumgalactic medium (CGM) by observing rest-frame UV emission lines Lyα, C IV, and He II around two radio-loud quasars, 3C 9 (z = 2.02) and 4C 05.84 (z = 2.32), using the Keck Cosmic Web Imager. We detect large-scale Lyα nebulae around both quasars with projected diameters ∼100 kpc, with spatially resolved, embedded 15–30 kpc He II and C IV nebulae around both quasars as well as kinematically distinct He II and C IV nebulae at a physical separation of ∼15 kpc from both quasars. Observations of Hα, Hβ, and [O III] emission using Keck MOSFIRE spectroscopically confirm that the Lyα nebulae extend to companion galaxies and that these quasars are in a protogroup/protocluster environment. We confirm that the He II and C IV emission is kinematically and spatially coincident with the companion galaxies. We estimate the virial masses of the companion galaxies, their metallicities, and star formation rates, and investigate the sources of ionization. We measure the dynamical mass of the host dark matter halos and estimate that the dark matter halos of these systems will grow to a mass of 2 × 1014 M ⊙ (3C 9) and 2 × 1013 M ⊙ (4C 05.84) by z = 0. The combined CGM and companion galaxies observations indicate Lyα substructure can indicate the presence of companion galaxies in the CGM.

Keywords: Radio jets, Quasars, Protoclusters, Active galaxies, Companion galaxies, Radio loud quasars, Active galactic nuclei, High-redshift galaxies, Galaxies
Almost Optically Dark Galaxies in DECaLS (I): Detection, Optical Properties, and Possible Origins. We report the discovery of eight optical counterparts of ALFALFA extragalactic objects from DECaLS, five of which are discovered for the first time. These objects were flagged as H I emission sources with no optical counterparts in SDSS before. Multiband data reveal their unusual physical properties. They are faint and blue (g ‑ r = ‑0.35 ∼ 0.55), with quite low surface brightness ( ${\mu }_{{\rm{g}},\mathrm{peak}}\,=\,24.88\sim 26.41\,\mathrm{mag}/{\mathrm{arcsec}}^{2}\;$ ), irregular morphologies, low stellar masses ( ${\mathrm{log}}_{10}\,({M}_{* }/{M}_{\odot })=5.27\sim 7.15$ ), low star formation rates (SFR = 0.21 ∼ 9.24 × 10‑3 M ⊙ yr‑1), and remarkably high H I-to-stellar mass ratios ( ${\mathrm{log}}_{10}\,({M}_{\mathrm{HI}}/{M}_{* })=1.72\sim 3.22$ , except AGC 215415). They deviate from the scaling relations between H I and optical properties defined by the ALFALFA sample and the baryonic Tully–Fisher relation. They agree well with the main sequence of star-forming galaxies but exhibit low star-forming efficiency. Based on their physical properties and environments, we speculate that six of these objects may have originated from tidal processes, while the remaining two appear to have isolated origins. They may have had a relatively calm evolutionary history and only begun to form stars recently.

Keywords: Optical identification, Galaxy photometry, Galaxy stellar content, Low surface brightness galaxies
TYC 3340-2437-1: A Quadruple System with a Massive Star. Hierarchical massive quadruple systems are ideal laboratories for examining the theories of star formation, dynamical evolution, and stellar evolution. The successive mergers of hierarchical quadruple systems might explain the mass gap between neutron stars and black holes. Looking for light curves of O-type binaries identified by LAMOST, we find a (2+2) quadruple system: TYC 3340-2437-1, located in the stellar bow-shock nebula (SBN). It has a probability of over 99.99% being a quadruple system derived from the surface density of the vicinity stars. Its inner orbital periods are 3.390602(89) days and 2.4378(16) days, respectively, and the total mass is about (11.47 + 5.79) + (5.2 + 2.02) = 24.48 M ⊙. The line-of-sight inclinations of the inner binaries, B1 and B2, are 55.°94 and 78.°2, respectively, indicating that they are not coplanar. Based on observations spanning 34 months and the significance of the astrometric excess noise (D &gt; 2) in Gaia Data Release 3 data, we guess that its outer orbital period might be a few years. If it were true, the quadruple system might form through the disk fragmentation mechanism with outer eccentric greater than zero. This eccentricity could be the cause of both the arc-like feature of the SBN and the noncoplanarity of the inner orbit. The outer orbital period and outer eccentric could be determined with the release of future epoch astrometric data of Gaia.

Keywords: Close binary stars, Massive stars, Spectroscopic binary stars, Interstellar clouds, Eclipsing binary stars
Can Chameleon Fields Be the Source of the Dark Energy Dipole and the Cosmic Microwave Background Dipole?. Recent research reveals that the Local Group is in motion toward (l, b) = (276, 30) relative to the cosmic background radiation, manifesting a velocity of 600 km s‑1, a phenomenon recognized as the cosmic background radiation dipole or cosmic microwave background dipole. Despite its well-documented nature, the precise cause of this peculiar motion remains elusive. High mass–density regions, such as galactic superclusters, stand out among the potential contributors to this cosmic flow. This paper employs chameleon fields to investigate anisotropies on both small and large scales. The data utilized in this study comprise Type Ia supernovae from the Pantheon catalog, totaling 1048 supernovae within the redshift range of 0.015 &lt; z &lt; 2.3. The analysis of the bulk flow at various redshifts has yielded noteworthy discoveries. On a smaller scale (less than 150 Mpc), the movement direction of the Local Group coincides with that of the bulk flow. On a larger scale, the bulk flow direction corresponds to the direction of the dark energy dipole. This implies that the anisotropy at the local scale originates from the same source as the anisotropy observed on a larger scale.

Keywords: Virgo Supercluster, Dark energy
Further Development of Event-based Analysis of X-Ray Polarization Data. An event-based maximum likelihood method for handling X-ray polarimetry data is extended to include the effects of background and nonuniform sampling of the possible position angle space. While nonuniform sampling in position angle space generally introduces cross terms in the uncertainties of polarization parameters that could create degeneracies, there are interesting cases that engender no bias or parameter covariance. When including background in Poisson-based likelihood formulation, the formula for the minimum detectable polarization has nearly the same form as for the case of Gaussian statistics derived by Elsner et al. in the limiting case of an unpolarized signal. A polarized background is also considered, which demonstrably increases uncertainties in source polarization measurements. In addition, a Kolmogorov-style test of the event position angle distribution is proposed that can provide an unbinned test of models where the polarization angle in Stokes space depends on event characteristics such as time or energy.

Keywords: X-ray astronomy, Analytical mathematics, Polarimetry, Astronomical methods