Sazuna/UAT_keywords huggingface dataset:
Hydrogen-poor Superluminous Supernovae in the Nebular Phase: Spectral Diversity Due to Ejecta Ionization as a Probe of the Power Source. We present a large sample of 39 nebular-phase optical spectra of 25 hydrogen-poor superluminous supernovae (SLSNe-I) and jointly analyze them with previously published spectra of 12 events. We measure the properties of key emission features, namely, those at 6300, 7300, and 7774 Å (associated with [O I], [Ca II]/[O II], and O I, respectively), and find that SLSNe exhibit much wider spectral diversity than normal SNe Ic, primarily in the line ratio L7300/L6300, which is highly sensitive to ejecta ionization. Some events exhibit weak [O I] and a clear [O II] contribution to the 7300 Å feature, enhancing the ratio, along with [O III] lines at 4363 and 5007 Å. Other SLSNe show weak or no lines of ionized oxygen. Moreover, we find that the population exhibits decreasing L7300/L6300 over time, while a few outliers instead display sustained high or increasing ratios for extended periods. The ratio L7300/L6300 is also correlated with the rise and decline times of the light curves, with slower events exhibiting higher ionization, the first robust connection between early light-curve and late-time spectral properties, likely due to the magnetar's impact: slower-evolving SLSNe are generally powered by engines with longer spin-down timescales, which deposit more energy at later phases. Among the events with decreasing L7300/L6300, SLSNe with high ionization are on average powered by magnetars with higher thermalized spin-down power, a correlation that is most significant for events with Mej ≲ 12 M⊙. The ionization in the outliers with increasing L7300/L6300 may be due to late circumstellar medium interaction. L7300/L6300 and its evolution are therefore key diagnostics of SLSN engines and progenitor mass loss.

Keywords: Supernovae, Core-collapse supernovae
The First Quantitative Study of Cometary Tail Regrowth following a Coronal Mass Ejection-driven Disconnection Event. Comet C/2023 P1 (Nishimura) was observed by the Solar Orbiter Heliospheric Imager (SoloHI), on board the Solar Orbiter spacecraft, from 2023 September 1 to 14. During this period, the ion tail of the comet exhibited continual fluctuations and four tail disconnection events (TDEs), each coinciding with the passage of a coronal mass ejection (CME). In this work, we report on the ion tail dynamics of the best observed TDE, which occurred on September 11. The SoloHI white-light images reveal an abrupt bending, subsequent kinks, and severing of a downstream portion of the preexisting ion tail. The onset of disconnection occurred ∼6.5 hr after the projected passage of the CME leading edge in the images, consistent with a CME flank encounter. After the disconnection, the ion tail reformed in over ∼24 hr, with a regrowth rate of ∼86 ± 7 km s−1, indicating the rate at which newly ionized material forms along the magnetic field draped around the comet's coma. After the TDE, the detached tail drifted anti-sunward at an estimated speed of ∼295 ± 20 km s−1, comparable to the local CME flank's speed, suggesting that the severed plasma was most likely carried away from the comet by the CME. This study provides the first direct, quantitative characterization of comet─CME interactions and the subsequent regrowth phase of a cometary TDE. These measurements were achievable by SoloHI's unique inner-heliospheric coverage, thanks to a combination of high photometric sensitivity, short exposure times, and a wide field of view that preserves the fine-scale tail dynamics.

Keywords: Comet ion tails, Near-sun comets, Heliosphere, Comet dynamics, Long period comets, Solar physics, Solar observatories, Solar coronal mass ejections, Solar magnetic fields, Solar activity
Sigmoid Formation, Filament Destabilization, and Initiation of Weak Flare by Tether Cutting Reconnection. We have studied a B-class solar flare and an associated filament eruption through multiwavelength observations. The flare is triggered at 16:24 UT on 2017 June 7 from Active Region(AR) 12661, and it maximizes at 16:54 UT. Magnetic flux cancellation occurs near the polarity inversion line preceding the flare, and ultraviolet (UV) brightenings occur in the preflare phase at the flux cancellation sites, suggesting reconnection occurs in the lower atmosphere, initially. An S-shaped sigmoid forms through successive steps in the corona, i.e., small-scale brightenings, helical/twisted field lines, bright patches, and finally, a developed sigmoid. This observation justifies that runaway reconnection within the coronal arcades forms the sigmoid within the filament. Differential emission measure analysis reveals the existence of plasma at a temperature of more than 10 MK within the sigmoid. The initial magnetic reconnection reorganizes the field overlying the filament as per the tether cutting model. Therefore, it enables the filament to rise slowly, and around 16:41 UT, the eruption phase of the filament begins. The filament eruption removes the overlying coronal field, including the sigmoid. During the eruption phase, we have found the intersecting/crossing of coronal loops and jet-like structures far away from the sigmoid─filament system. In conclusion, all the observational findings (e.g., magnetic flux convergence, cancellation, UV brightenings, and spatial and temporal correlation between formation/evolution of the sigmoid and rise/eruption of the filament) suggest that the formation of a solar flare and the eruption of the filament are consistent with the tether cutting model of solar eruptions.

Keywords: Solar flares, Solar filament eruptions, Solar filaments
HOPS-288: A Laboratory for Complex Organics in Proto-binary/Proto-multiple Systems. Complex organic molecules (COMs) in young stellar objects have attracted significant attention in recent years due to their potential connection to prebiotic chemistry and their utility as tracers of warm or shocked gas components. Proto-binary and multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. We present Atacama Large Millimeter/submillimeter Array observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system consisting of HOPS-288-A and HOPS-288-B due to the limited spatial resolutions, with a separation of 200 au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members traced by CH3OH and tentatively by CH3CHO. The hot corino in HOPS-288-A exhibits rotational features and might trace a disk. The hot corino in HOPS-288-B is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs, including 13CH3OH, CH2DOH, CH3CHO, HCOOCH3, C2H5OH, 13CH3CN, and NH2CHO, are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

Keywords: Binary stars, Astrochemistry, Star formation, Protostars, Complex organic molecules
Unipolarity of the Solar Magnetic Field in Equatorial Coronal Holes. A study of the unbalanced magnetic polarity distribution of 70 coronal holes was performed. Data from the Helioseismic and Magnetic Imager were used to examine the photospheric line-of-sight magnetic field (BLOS) beneath these coronal holes. The skewness (S) values of the BLOS distributions revealed significant asymmetry, characterized by the dominance of one magnetic polarity, with ∼88% of the coronal holes exhibiting a skewness value ranging from ±(0.20 to 0.40). The corresponding magnetic flux imbalance (Φimb) ranges from 20% to 45%. In contrast, quiet-Sun regions show symmetric magnetic field distributions with skewness values less than 0.11 and flux imbalance less than 11.0%. A study of a coronal hole as it traverses across the disk shows that the magnetic field distribution does not evolve significantly over this time, remaining stable across half a solar rotation. A moderate correlation (r = 0.60) between the magnetic flux imbalance and the speed of associated HSSs (vHSS) suggests that flux imbalance may contribute to the generation of these faster solar wind streams. These results imply that regions with higher flux imbalance (Φimb), indicative of more open magnetic field structures, present more favorable conditions for plasma acceleration as compared to closed bipolar field, but the moderate correlation indicates that other factors may also play important roles.

Keywords: Solar coronal holes
The Collision and Merger Products of Stars Do Not Look Alike: A Magnetohydrodynamics Comparison. A significant fraction of stars experience close interactions, including collisions resulting from gravitational encounters and mergers within close binary systems. These processes can produce more massive stars that may give rise to relatively rare objects such as blue stragglers. Distinguishing the outcomes of collisions and mergers is challenging yet essential for interpreting observations. This study utilizes the magnetohydrodynamics code AREPO to simulate collisions and mergers of 5─10 M⊙ main-sequence stars, systematically comparing the properties of the resulting products. Both collisions and mergers yield more massive, strongly magnetized, rapidly and differentially rotating stars with cores enriched in hydrogen, but notable quantitative differences emerge. Merger products exhibit core hydrogen fractions up to 10% higher than those of collision products. In both scenarios, turbulent mixing amplifies magnetic field energies by 9─12 orders of magnitude. However, magnetic fields in small-impact-parameter collision products display small-scale reversals that may dissipate over time, whereas merger products and large-impact-parameter collision products develop large-scale ordered, potentially long-lived magnetic fields. Additionally, only merger products display magnetically driven, bipolar outflows with radial velocities up to 300 km s−1. These distinctions may result in different long-term evolutionary outcomes, which warrant further investigation in future studies.

Keywords: Binary stars, Hydrodynamics, Stellar mergers, Stellar dynamics, Stellar evolution
A Single-pulse Study of Three CRAFTS Pulsars Discovered with FAST. We present a comprehensive single-pulse study of three pulsars, namely PSRs J1854─0036, J2159+0202, and J2112+0740, discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey (CRAFTS). We observe that these pulsars display different kinds of single-pulse phenomena, bearing implications for pulse emission mechanisms and geometry. PSR J1854─0036 exhibits quasiperiodic nulling with a nulling fraction of 31% ± 1% and a periodicity of (127.4 ± 0.4)P (where P is the spin period of the pulsar). We identified a weak emission in the null profile, suggesting either a global magnetospheric state switching or a change in geometric orientation rather than complete cessation of emission. PSR J2159+0202 exhibits complex subpulse drifting or intensity modulations with periodicities ranging from P3 = (7.0 ± 0.2)P to (10.9 ± 0.1)P. PSR J2112+0740 exhibits burst-like radiation without evidence of nulling or coherent subpulse drifting, potentially associated with stochastic pair production or plasma instabilities within the pulsar's emission region. These results highlight the multiscale nature of the pulsar emission, potentially linking nulling, drifting, and erratic radiation to different magnetospheric processes.

Keywords: Radio pulsars
Herringbone Structures during an X-class Eruptive Flare. In this paper, we report quasiperiodic herringbone structures during the impulsive phase of an X-class flare, coinciding with the distinct acceleration phase of eruptive prominence ejection on 2023 December 31. The prominence propagates nonradially in the southeast direction with an inclination angle of ∼35 .° 4. The fast coronal mass ejection (CME) at a speed of ∼2852 km s−1 drives a shock wave and a coronal extreme-ultraviolet wave. The herringbone structures lasting for ∼4 minutes take place at the initial stage of a group of type II radio bursts. The herringbones in the frequency range 20−70 MHz are characterized by simultaneous forward-drift and reverse-drift bursts with average durations of ∼2.5 and ∼3.1 s. The frequency drift rates of these bursts fall in a range of 1.3−9.4 MHz s−1 with average values of ∼3.6 and ∼4.1 MHz s−1, respectively. The speeds of electron beams producing the herringbones are estimated to be 0.04c−0.41c, with average values of ∼0.23c and ∼0.11c for forward-drifting and reverse-drift bursts, respectively. The heights of particle acceleration regions are estimated to be 0.64−0.78 R⊙ above the photosphere, which are consistent with the height of the CME front (∼0.75 R⊙) when the shock forms. Quasiperiodic pulsations with periods of 17.5−21.3 s are found in the radio fluxes of herringbones, suggesting that electrons are accelerated by the CME-driven shock intermittently.

Keywords: Solar radio emission, Solar coronal mass ejections, Solar flares, Solar prominences
Properties and Possible Physical Origins of γ-Ray Emission in Extreme Synchrotron Blazars. Extreme synchrotron blazars, characterized by a first peak in their broadband spectral energy distributions (SEDs) at frequencies exceeding 1017 Hz, often exhibit a second peak beyond 1 TeV. These sources serve as ideal laboratories for studying particle acceleration and radiation mechanisms in relativistic jets. In this work, we systematically analyze the ∼16 yr Fermi-LAT observational data for 25 extreme high-synchrotron-peaked BL Lacertae (EHBL) objects. The results indicate that the majority of these sources display stable or low flux levels in the GeV band, with only six sources showing significant variability at a confidence level exceeding 5σ. The time-averaged spectra over the 16 yr period for most EHBLs are well described by a hard power-law model, with photon indices predominantly clustered between 1.7 and 1.8. Using Fermi-LAT data in conjunction with multiwavelength observations compiled from the literature, we construct broadband SEDs for these EHBLs and fit them with a one-zone synchrotron and synchrotron self-Compton (SSC) model. We find that this simplified theoretical framework is sufficient for modeling the observed SEDs of most of these EHBLs, albeit requiring relatively higher electron energies compared to other γ-ray emitting HBLs, and at times under-representing the UV emission. Based on the SED fitting results, we investigate the physical properties of the emission regions in these EHBLs and compare them with those of other γ-ray emitting HBLs. Consistent with other GeV─TeV γ-ray-emitting BL Lacertae objects, the jets in these EHBLs are marked by low radiation efficiency and low magnetization.

Keywords: BL Lacertae objects, Blazars, Relativistic jets, Non-thermal radiation sources, Gamma-rays
JWST Discovery of High-velocity Mid-infrared Ionized Outflows in Ultraluminous Infrared Galaxies F11119+3257 and F05189-2524. Ultrafast outflows (UFOs) are thought to be a driving mechanism of large-scale winds driven by active galactic nuclei (AGN), which cause significant galactic feedback through quenching star formation and regulating supermassive black hole growth. We present James Webb Space Telescope (JWST) Mid-Infrared Instrument Medium-Resolution Spectrometer observations of two nearby ultraluminous infrared galaxies, F11119+3257 and F05189-2524, with nuclear X-ray detected UFOs and kiloparsec-scale outflow. These galaxies show remarkably similar mid-infrared continuum and emission line features, notably including a high-velocity v90 ∼ 4000 km s−1 outflow detected in highly ionized neon emission lines, e.g., [Ne VI]. In F05189-2524, we see a slightly slower biconical outflow extending up to ∼2 kpc in the same neon emission lines. Both sources show evidence of AGN-driven radiative feedback through a deficit of rotational molecular hydrogen lines in the nuclear region, &lt;1 kpc from the central quasar, but no clear evidence of any molecular gas entrained in the quasar-driven outflow. Energetic analysis shows that the warm ionized gas in both of these sources contributes minimally (∼0.1%─5%) to the momentum outflow rate of these sources and leaves the conclusions of previous literature unchanged: the energetics of these sources are broadly consistent with a momentum-conserving outflow.

Keywords: AGN host galaxies, Active galaxies, Galaxy winds, Quasars
HR-GO. II. Chemical Abundances of Low-E Retrograde Dynamically Tagged Groups: Revealing Thamnos as a Very Metal-poor Substructure. Milky Way halo substructures identified in dynamical space are known to suffer from contamination from the Milky Way in situ stars, which makes their accreted origins uncertain. We present detailed chemical abundances of 35 stars belonging to two sets of dynamically tagged groups, Rg8 and Rg9, to investigate their accreted nature. Both groups are composed of stars with low orbital energy and very retrograde orbits. We find that Rg8 and Rg9 are chemically indistinguishable across 20 elements, from C to Eu, strongly indicating that they belong to the same structure. The iron-abundance distribution of this low-E retrograde group has a prominent peak at [Fe/H] ≍ ─2.1, revealing that its main population is very metal-poor (VMP), and a secondary peak at [Fe/H] ≍ ─1.5, very likely due to contamination from Milky Way in situ stars. These groups also heavily overlap with the Thamnos substructure in dynamical space, and we thus use them to investigate the chemical properties of Thamnos. The dominant, low-metallicity population provides strong evidence for the ex situ origin of Thamnos, as does its VMP nature. We do not see any evidence of an α-knee in our sample, which is consistent with previous studies. Comparison with the Cetus-Palca stream in the chemical space shows similar abundance distributions, and thus it suggests that the Thamnos progenitor dwarf galaxy had a truncated star formation history due to its early merger with the Milky Way.

Keywords: Milky Way stellar halo, Milky Way dynamics, Milky Way formation, Chemical abundances
The Dichotomy in the Nuclear and Host-galaxy Properties of High-redshift Quasars. The early growth of high-redshift quasars and their host galaxies raises critical questions about their cosmic evolution. We exploit the angular resolution and sensitivity of NIRCam to investigate the host galaxies of 31 quasars at 4 ≲ z ≲ 7 drawn from multiple JWST surveys. Using a new multiband forward-modeling code (GALFITS) that incorporates physically motivated priors, we securely detect and quantify the host emission in 30 objects, while simultaneously characterizing the nuclear spectral energy distribution. The host galaxies of high-redshift quasars are ∼0.3 dex more compact than star-forming galaxies of comparable mass. A striking dichotomy emerges: luminous "blue" quasars (L5100 ≳ 1045 erg s−1) reside in bulge-dominated galaxies (Sérsic index n ≍ 5) and exhibit a narrow range of ultraviolet nuclear slopes (median βUV ≍ −1.4), while fainter "red" quasars inhabit disklike hosts (n ≍ 1) and display a broad range of slopes (βUV ≍ −2─4). These two populations differ markedly in their black hole-to-stellar mass ratios, with high-luminosity quasars showing MBH/M* = 1.2% compared to 4.7% for lower-luminosity sources, placing them collectively ∼0.6 dex above the local MBH─M* relation. This offset likely reflects rapid black hole growth in early gas-rich environments, where feedback from the active galactic nucleus becomes effective only after substantial gas depletion. Our findings suggest that the observed dichotomy, whether due to intrinsic spectral differences or dust extinction, fundamentally shapes the coevolution of supermassive black holes and their host galaxies in the early Universe.

Keywords: Active galaxies, High-redshift galaxies, Quasars
The Lyα and Continuum Origins Survey. II. The Connection between the Escape of Ionizing Radiation and Lyα Halos in Star-forming Galaxies. One of the current challenges in galaxy evolution studies is to establish the mechanisms that govern the escape of ionizing radiation from galaxies. Here, we investigate the connection between Lyman continuum (LyC) escape and the conditions of the circumgalactic medium (CGM), as probed by Lyα halos (LAHs) in emission. We use Lyα and UV continuum imaging data from the Lyα and Continuum Origins Survey (LaCOS), targeting 42 nearby (z≃0.3), star-forming galaxies with LyC observations (escape fractions of  fescLyC≃0.01−0.49 ). LaCOS galaxies show extended Lyα emission ubiquitously, with LyC emitters (LCEs) having more compact Lyα morphologies than non-LCEs, and Lyα spatial offsets that do not exceed the extent of the UV continuum. We model the diffuse LAHs using a combined Sérsic plus exponential 2D profile, and find that the characteristic scale length of the Lyα halo is 10 times larger than the UV, on average. We unveil a significant anticorrelation between  fescLyC  and the Lyα halo fraction (HF; or contribution of the halo to the total Lyα luminosity), which we propose as a new LyC indicator. Our observations show that halo scale lengths and HFs both scale positively with the optical depth of the neutral gas in the interstellar medium, revealing a picture in which Lyα and LyC photons in LCEs either emerge directly from the central starbursts or escape isotropically, and in the case of Lyα, minimize the number of scattering interactions in a less-extended CGM.

Keywords: Emission line galaxies, Ultraviolet astronomy, Interstellar absorption, Circumgalactic medium, Lyman-alpha galaxies, Reionization
Solving Milky Way─sized Systems with HASKAP PIE: A Halo Finding Algorithm with Efficient Sampling, K-means Clustering, Tree-assembly, Particle Tracking, Python Modules, Intercode Applicability, and Energy Solving. We describe a new Python-based stand-alone halo finding algorithm, HASKAP PIE, that combines several methods of halo finding and tracking into a single calculation. Our halo-finder flexibly solves halos for simulations produced by eight simulation codes (ART-I, ENZO, RAMSES, CHANGA, GADGET- 3, GEAR, AREPO, and GIZMO) and for both zoomed-in or full-box N-body or hydrodynamical simulations and includes a unified, robust set of pretuned parameters. When compared to ROCKSTAR (P. S. Behroozi et al.) and CONSISTENT TREES, our halo-finder tracks subhalos for much longer and more consistently, produces halos with better constrained physical parameters, and returns a much denser halo mass function for halos with more than 100 particles. Our results also compare favorably to recently described specialized particle-tracking extensions to ROCKSTAR. HASKAP PIE is well suited to a variety of studies of simulated galaxies and is particularly robust for a new generation of studies of merging and satellite galaxies. For our initial paper, we focus on describing our algorithm's ability to find and track halos and subhalos in complex Milky Way─sized halo systems.

Keywords: Cosmology, Galaxy dark matter halos, Galaxy evolution