Sazuna/UAT_keywords huggingface dataset:
Low [O/Fe] Ratio in a Luminous Galaxy at the Early Cosmic Epoch (z &gt; 10): Signature of Short Delay Time or Bright Hypernovae/Pair-instability Supernovae?. We present an [O/Fe] ratio of a luminous galaxy GN-z11 at z = 10.60 derived with the deep public JWST/NIRSpec data. We fit the medium-resolution grating (G140M, G235M, and G395M) data with the model spectra consisting of BPASS-stellar and CLOUDY-nebular spectra in the rest-frame UV wavelength ranges with Fe absorption lines, carefully masking the other emission and absorption lines in the same manner as previous studies conducted for lower-redshift (z ∼ 2–6) galaxies with oxygen abundance measurements. We obtain an Fe-rich abundance ratio  [O/Fe]=‑0.37‑0.22+0.43 , which is confirmed with the independent deep prism data as well as by the classic 1978 index method. This [O/Fe] measurement is lower than that measured for star-forming galaxies at z ∼ 2–3. Because z = 10.60 is an early epoch after the Big Bang (∼430 Myr) and the first star formation (likely ∼200 Myr), it is difficult to produce Fe by Type Ia supernovae (SNe Ia), which requires sufficient delay time for white-dwarf formation and gas accretion. The Fe-rich abundance ratio in GN-z11 suggests that the delay time is short or that the major Fe enrichment is not accomplished by SNe Ia but by bright hypernovae (BrHNe) and/or pair-instability supernovae (PISNe), where the yield models of BrHNe and PISNe explain Fe, Ne, and O abundance ratios of GN-z11. The [O/Fe] measurement is not too low to rule out the connection between GN-z11 and globular clusters (GCs) previously suggested by the nitrogen abundance but rather supports the connection with a GC population at high [N/O] if a metal dilution process exists.

Keywords: Galaxy formation, Galaxy chemical evolution, Star formation, Galaxy evolution, High-redshift galaxies
Bright in the Black: Searching for Electromagnetic Counterparts to Gravitational-wave Candidates in LIGO-Virgo-KAGRA Observation Runs with AstroSat-CZTI. GW150914 marked the start of the gravitational wave (GW) era with the direct detection of a binary black hole (BBH) merger by the LIGO-Virgo GW detectors. The event was tentatively associated with a signal detected by the Fermi Gamma-ray Burst Monitor (GBM), which hinted toward electromagnetic emission associated with compact object coalescence. The detection of a short gamma-ray burst (GRB) associated with GW170817, along with several multiwavelength detections, truly established that compact object mergers are indeed multimessenger events. The CadmiumZincTelluride Imager (CZTI) on board AstroSat can search for X-ray counterparts of the GW events and has detected over 650 GRBs in the 8.5 yr since it was launched. We present results from our searches for counterparts coincident with GW triggers from the first three LIGO-Virgo-KAGRA (LVK) GW Transient Catalogs. For 71 out of 90 GW events for which AstroSat-CZTI data was available, we undertook a systematic search for temporally coincident transients in the 20–200 keV band and detected no X-ray counterparts. We evaluate the upper limits on the maximum possible flux from the source in a 100 s window centered around each trigger, consistent with the GW localization of the event. Thanks to the sensitivity of CZTI, these upper limits are competitive with those from other spacecraft. We use these upper limits to constrain theoretical models that predict high-energy counterparts to BBH mergers. We also discuss the probability of nondetections of BBH mergers at different luminosities and the implications of such nondetections from the ongoing fourth observing run of the LVK detectors.

Keywords: Gamma-ray bursts, Black holes, Stellar mass black holes, Gravitational waves, Compact objects
The Oscillation in Evolution of Changing-look Blazar OQ 334. We investigate the evolution of a changing-look blazar (CLB) on long timescales and expect to trace the state change of a CLB. Three morphological types, including a flat spectrum radio quasar (FSRQ) state, transition state, and BL Lacertae (BL Lac) state, are classified according to the criteria proposed by analyzing the relationship between the equivalent width of the emission line and the γ-ray photon spectral index Γ γ . The multiwavelength light curves and spectral energy distributions corresponding to different epochs are obtained. The efforts found that Γ γ  satisfy the relationships with Γ γ  ≳ 2.2 for the FSRQ state, 2.0 &lt; Γ γ  &lt; 2.2 for the transition state, and Γ γ  ≲ 2.0 for the BL Lac state. We apply the criteria to the photon spectrum evolution of CLB OQ 334 during MJD 58678–60387. The evolution is subdivided into five FSRQ states, nine transition states, and four BL Lac states. Moreover, we use the model spectra parameters of each state epoch to test the reliability of subdivided morphological types. The result shows that: (1) the accretion rate parameter is consistent with our earlier research; and (2) there is an increasing trend in the epochs of the BL Lac states, even if there is not an obvious decreasing trend in epochs of the FSRQ states. We issue strong evidence that a CLB is an especial epoch in the evolution of blazars that could be obtained from the oscillation phenomenon in the CLB evolution.

Keywords: Blazars, Flat-spectrum radio quasars, BL Lacertae objects
Kinematic Insights into Luminous Blue Variables and B[e] Supergiants. Recent work suggests that many luminous blue variables (LBVs) and B[e] supergiants (sgB[e]) are isolated, implying that they may be products of massive binaries, kicked by partner supernovae. However, the evidence is somewhat complex and controversial. To test this scenario, we measure the proper-motion velocities for these objects in the LMC and SMC, using Gaia Data Release 3. Our LMC results show that the kinematics, luminosities, and IR properties point to LBVs and sgB[e] stars being distinct classes. We find that Class 1 LBVs, which have dusty nebulae, and sgB[e] stars both show velocity distributions comparable to that of SMC field OBe stars, which are known to have experienced SN kicks. The sgB[e] stars are faster, plausibly due to their lower average masses. However, Class 2 LBVs, which are luminous objects without dusty nebulae, show no signs of acceleration, therefore suggesting that they are single stars, pre-SN binaries, or perhaps binary mergers. The candidate LBV Class 3 stars, which are dominated by hot dust, are all confirmed sgB[e] stars; their luminosities and velocities show that they simply represent the most luminous and massive of the sgB[e] class. There are very few SMC objects, but the sgB[e] stars are faster than their LMC counterparts, which may be consistent with expectations that lower-metallicity binaries are tighter, causing faster ejections. We also examine the distinct class of dust-free, weak-lined sgB[e] stars, finding that the SMC objects have the fastest velocities of the entire sample.

Keywords: Late stellar evolution, Close binary stars, Massive stars, Stellar dynamics, Luminous blue variable stars, Field stars, Circumstellar matter, Runaway stars, B(e) stars, Stellar evolution
Study of Evolution and Geo-effectiveness of Coronal Mass Ejection–Coronal Mass Ejection Interactions Using Magnetohydrodynamic Simulations with SWASTi Framework. The geo-effectiveness of coronal mass ejections (CMEs) is a critical area of study in space weather, particularly in the lesser-explored domain of CME–CME interactions and their geomagnetic consequences. This study leverages the Space Weather Adaptive SimulaTion framework to perform 3D MHD simulation of a range of CME–CME interaction scenarios within realistic solar wind conditions. The focus is on the dynamics of the initial magnetic flux, speed, density, and tilt of CMEs, and their individual and combined impacts on the disturbance storm time (Dst) index. Additionally, the kinematic, magnetic, and structural impacts on the leading CME, as well as the mixing of both CMEs, are analyzed. Time-series in situ studies are conducted through virtual spacecraft positioned along three different longitudes at 1 au. Our findings reveal that CME–CME interactions are nonuniform along different longitudes, due to the inhomogeneous ambient solar wind conditions. A significant increase in the momentum and kinetic energy of the leading CME is observed due to collisions with the trailing CME, along with the formation of reverse shocks in cases of strong interaction. These reverse shocks lead to complex wave patterns inside CME2, which can prolong the storm recovery phase. Furthermore, we observe that the minimum Dst value decreases with an increase in the initial density, tilt, and speed of the trailing CME.

Keywords: Interplanetary shocks, Space weather, Solar wind, Solar coronal mass ejections, Solar storm, Magnetohydrodynamical simulations
A Hierarchical Bayesian Approach to Point-source Analysis in High-energy Neutrino Telescopes. We propose a novel approach to the detection of point-like sources of high-energy neutrinos. Motivated by evidence for emerging sources in existing data, we focus on the characterization and interpretation of these sources rather than the rejection of the background-only hypothesis. The hierarchical Bayesian model is implemented in the Stan platform, enabling computation of the posterior distribution with a Hamiltonian Monte Carlo algorithm. We simulate a population of weak neutrino sources detected by the IceCube experiment and use the resulting data set to demonstrate and validate our framework. We show that even for the challenging case of sources at the threshold of detection and using limited prior information, it is possible to correctly infer the source properties. Additionally, we demonstrate how modeling flexible connections between similar sources can be used to recover the contribution of sources that would not be detectable individually. While a direct comparison of our method to existing approaches is challenged by the fundamental differences in frequentist and Bayesian frameworks, we draw parallels where possible. In particular, we highlight how including more complexity into the source modeling can increase the sensitivity to sources and their populations.

Keywords: Bayesian statistics, High energy astrophysics, Neutrino astronomy, Astrostatistics, Hierarchical models, Astronomical methods, Particle astrophysics
Estimating the Total Energy Content in Escaping Accelerated Solar Electron Beams. Quantifying the energy content of accelerated electron beams during solar eruptive events is a key outstanding objective that must be constrained to refine particle acceleration models and understand the electron component of space weather. Previous estimations have used in situ measurements near the Earth, and consequently suffer from electron-beam propagation effects. In this study, we deduce properties of a rapid sequence of escaping electron beams that were accelerated during a solar flare on 2013 May 22 and produced type III radio bursts, including the first estimate of energy density from remote-sensing observations. We use extreme-ultraviolet observations to infer the magnetic structure of the source active region NOAA 11745, and Nançay Radioheliograph imaging spectroscopy to estimate the speed and origin of the escaping electron beams. Using the observationally deduced electron-beam properties from the type III bursts and cotemporal hard X-rays, we simulate electron-beam properties to estimate the electron number density and energy in the acceleration region. We find an electron density (above 30 keV) in the acceleration region of 102.5 cm‑3 and an energy density of 2 × 10‑5 erg cm‑3. Radio observations suggest the particles travelled a very short distance before they began to produce radio emission, implying a radially narrow acceleration region. A short but plausibly wide slab-like acceleration volume of 1026–1028 cm3 atop the flaring loop arcade could contain a total energy of 1023–1025 erg (∼100 beams), which is comparable to energy estimates from previous studies.

Keywords: Solar physics, Solar flares, Radio bursts
Identifying the Host Galaxies of Supermassive Black Hole Binaries Found by Pulsar Timing Arrays. Supermassive black hole binaries (SMBHBs) are thought to form in galaxy mergers, possessing the potential to produce electromagnetic (EM) radiation as well as gravitational waves (GWs) detectable with pulsar timing arrays (PTAs). Once GWs from individually resolved SMBHBs are detected, the identification of the host galaxy will be a major challenge due to the ambiguity in possible EM signatures and the poor localization capability of PTAs. To aid EM observations in choosing follow-up sources, we use NANOGrav's galaxy catalog to quantify the number of plausible hosts in both realistic and idealistic scenarios. We outline a host identification pipeline that injects a single-source GW signal into a simulated PTA data set, recovers the signal using production-level techniques, quantifies the localization region and number of galaxies contained therein, and finally imposes cuts on the galaxies using parameter estimates from the GW search. In an ideal case, the 90% credible areas span 29–241 deg2, containing about 14–341 galaxies. After cuts, the number of galaxies remaining ranges from 22 at worst to one true host at best. In a realistic case, these areas range from 287 to 530 deg2 and enclose about 285–1238 galaxies. After cuts, the number of galaxies is 397 at worst and 27 at best. While the signal-to-noise ratio is the primary determinant of the localization area of a given source, we find that the area is also influenced by the proximity to nearby pulsars on the sky and the binary chirp mass.

Keywords: Supermassive black holes, Pulsar timing method, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Galaxy mergers
Why Are Optical Coronal Lines Faint in Active Galactic Nuclei?. Forbidden collisionally excited optical atomic transitions from high-ionization-potential (IP ≥ 54.8 eV) ions, such as Ca4+, Ne4+, Fe6+, Fe10+, Fe13+, Ar9+, and S11+, are known as optical coronal lines (CLs). The spectral energy distributions (SEDs) of active galactic nuclei (AGNs) typically extend to hundreds of electron volts and above, which should be able to produce such highly ionized gas. However, optical CLs are often not detected in AGNs. Here we use photoionization calculations with the CLOUDY spectral synthesis code to determine possible reasons for the rarity of these optical CLs. We calculate CL luminosities and equivalent widths from radiation-pressure-confined photoionized gas slabs exposed to an AGN continuum. We consider the role of dust, metallicity, and ionizing SED in the formation of optical CLs. We find that (i) dust reduces the strength of most CLs by ∼3 orders of magnitude, primarily as a result of depletion of metals onto the dust grains; (ii) in contrast to the CLs, the more widely observed lower-IP optical lines such as [O III] 5007 Å are less affected by depletion, and some are actually enhanced in dusty gas; and (iii) many optical CLs become detectable in dustless gas, and are particularly strong for a hard ionizing SED. This implies that prominent CL emission likely originates in dustless gas. Our calculations also suggest optical CL emission is enhanced in galaxies with low-mass black holes characterized by a harder radiation field and a low dust-to-metals ratio. The fact that optical CLs are not widely observed in the early Universe with JWST may point to rapid dust formation at high redshift.

Keywords: Active galaxies, Line intensities, Quasars
Revealing the Elusive Companion of the Red Giant Binary 2MASS J05215658+4359220 from UV HST and Astrosat/UVIT Data. Black hole (BH) demographics in different environments is critical in view of recent results on massive star binarity, and of the multimessenger detectability of compact object mergers. But the identification and characterization of noninteracting BHs are elusive, especially in the sparse field stellar population. A candidate noninteractive BH + red giant (RG) binary system, 2MASS J05215658+4359220, was identified by T. A. Thompson et al. We obtained Astrosat/UVIT far-ultraviolet (FUV) imaging and Hubble Space Telescope (HST) UV‑optical imaging and spectroscopy of the source to test possible scenarios for the optically elusive companion. HST/STIS spectra from ≈1600 to 10230 Å are best fit by the combination of two stellar sources, a RG with T eff = 4250 ± 150 K, log g = 2.0, R RG ∼ 27.8 R ⊙ (assuming a single-temperature atmosphere), and a subgiant companion with T eff = 6000 K, R comp = 2.7 R ⊙, or T eff = 5270 K, R comp = 4.2 R ⊙ using models with one-tenth or one-third solar metallicity, respectively, log g = 3.0, extinction E  B‑V  = 0.50 ± 0.2, adopting the Data Release 3 Gaia distance D = 2463 ± 120 pc. No FUV data existed prior to our programs. STIS spectra give an upper limit of 10‑17 erg cm‑2 s‑1 Å‑1 shortwards of 2300 Å; an upper limit of ≳25.7 ABmag was obtained in two UVIT FUV broad bands. The nondetection of FUV flux rules out a compact companion such as a hot white dwarf. The STIS spectrum shows strong Mg II λ2800 Å emission, typical of chromospherically active RGs. The masses inferred by comparison with evolutionary tracks, ∼1M ⊙ for the RG and between 1.1 and 1.6 M ⊙ for the subgiant companion, suggest past mass transfer, although the RG currently does not fill its Roche lobe. WFC3 imaging in F218W, F275W, F336W, F475W, and F606W shows an unresolved source in all filters.

Keywords: Subgiant stars, Binary stars, Close binary stars, Stellar mass black holes, Ultraviolet spectroscopy, Spectroscopic binary stars, Companion stars, Red giant stars, Ultraviolet photometry
High-resolution ALMA Observations of Richly Structured Protoplanetary Disks in σ Orionis. The Atacama Large Millimeter/submillimeter Array (ALMA) has detected substructures in numerous protoplanetary disks at radii from a few to over 100 au. These substructures are commonly thought to be associated with planet formation, either by serving as sites fostering planetesimal formation or by arising as a consequence of planet–disk interactions. Our current understanding of substructures, though, is primarily based on observations of nearby star-forming regions with mild UV environments, whereas stars are typically born in much harsher UV environments, which may inhibit planet formation in the outer disk through external photoevaporation. We present high-resolution (∼8 au) ALMA 1.3 mm continuum images of eight disks in σ Orionis, a cluster irradiated by an O9.5 star. Gaps and rings are resolved in the images of five disks. The most striking of these is SO 1274, which features five gaps that appear to be arranged nearly in a resonant chain. In addition, we infer the presence of gap or shoulder-like structures in the other three disks through visibility modeling. These observations indicate that substructures robustly form and survive at semimajor axes of several tens of au or less in disks exposed to intermediate levels of external UV radiation as well as in compact disks. However, our observations also suggest that disks in σ Orionis are mostly small, and thus millimeter continuum gaps beyond a disk radius of 50 au are rare in this region, possibly due to either external photoevaporation or age effects.

Keywords: Radio interferometry, Protoplanetary disks, Planet formation
Exploring the Small-scale Magnetic Fields of the Solar Analog KIC 8006161 Using Asteroseismology. The magnetic field is a significant and universal physical phenomenon in modern astrophysics. Small-scale magnetic fields are very important in the stellar atmosphere. They are ubiquitous and strongly couple with acoustic waves. Therefore, their presence affects the properties of acoustic waves in the stellar outer layer. In the present work, under the assumption that small-scale magnetic features are the cause of the asteroseismic surface term (the frequency-dependent frequency offset between stars and their models), we explore the strength of such fields in the solar analog KIC 8006161. By considering the effect of small-scale magnetic fields in the stellar photosphere, we use the observed oscillation frequencies to constrain the inner structures and surface small-scale magnetic fields of solar-like star KIC 8006161. To agree with the existing observations, such as oscillation frequencies, and their frequency separation ratios, the theoretical model requires a small-scale magnetic field to form a magnetic-arch splicing layer in the stellar outer atmosphere. The small-scale magnetic field strengths for KIC 8006161 obtained from best-fit model with Y init = 0.249 + 1.33 Z init and Y init as a free parameter are approximately 96 and 89 G, respectively. The corresponding locations of the magnetic-arch splicing layer are about 522 and 510 km, respectively.

Keywords: Stellar magnetic fields
Photospheric Hot Spots at Solar Coronal Loop Footpoints Revealed by Hyperspectral Imaging Observations. Poynting flux generated by random shuffling of photospheric magnetic footpoints is transferred through the upper atmosphere of the Sun where the plasma is heated to over 1 MK in the corona. High spatiotemporal resolution observations of the lower atmosphere at the base of coronal magnetic loops are crucial to better understand the nature of the footpoint dynamics and the details of magnetic processes that eventually channel energy into the corona. Here, we report high spatial resolution (∼0.″1) and cadence (1.33 s) hyperspectral imaging of the solar Hα line, acquired by the Microlensed Hyperspectral Imager prototype installed at the Swedish 1-m Solar Telescope, that reveal photospheric hot spots at the base of solar coronal loops. These hot spots manifest themselves as Hα wing enhancements, occurring on small spatial scales of ∼0.″2, and timescales of less than 100 s. By assuming that the Hα wings and the continuum form under the local thermodynamic equilibrium condition, we inverted the Hα line profiles and found that the hot spots are compatible with a temperature increase of about 1000 K above the ambient quiet-Sun temperature. The Hα wing integrated Stokes V/I maps indicate that hot spots are related to magnetic patches with field strengths comparable to or even stronger that the surrounding network elements. But they do not show the presence of parasitic polarity magnetic field that would support the interpretation that these hot spots are reconnection-driven Ellerman bombs. Therefore, we interpret these features as proxies of locations where convection-driven magnetic field intensification in the photosphere can lead to energy transfer into higher layers. We suggest that such hot spots at coronal loop footpoints may be indicative of the specific locations and onset of energy flux injection into the upper atmosphere.

Keywords: Magnetohydrodynamics, Solar magnetic reconnection, Solar photosphere, Solar extreme ultraviolet emission, Solar coronal loops, Solar coronal heating, Solar magnetic fields