Sazuna/UAT_keywords huggingface dataset:
Multiscale Periodic Variations of Solar Active Regions during the Time Interval 1996–2023. Solar active regions are believed to provide significant information on the mutual conversion of the poloidal and toroidal components of the global magnetic field. However, the multiscale periodic variations, in particular the quasi-biennial oscillations (QBOs), of solar active regions are not fully understood. In the present study, the flux, area, and number of solar active regions, as well as the sunspot number data in the period from 1996 May to 2023 November, are studied in detail. The multiscale periodic components in the above four data sets are investigated by the techniques of ensemble empirical mode decomposition and cross-correlation analysis. The main results are as follows. (1) The four data sets exhibit similar periodic components, including the 11 yr Schwabe cycle, the QBOs, and a Rieger-type period. (2) The multiscale periodicity of solar active regions shows different physical characteristics. Under different periodic scales, the highest correlation is between active region flux and area, indicating that active region flux and area better reflect the evolution of active regions. (3) By superimposing the QBOs on the 11 yr Schwabe cycle, the Gnevyshev gap phenomenon was clearly observed, implying that the Gnevyshev gap may be caused by the modulation of the 11 yr Schwabe cycle. (4) The active region flux in both hemispheres shows similar periodic components to the full disk, but the periodic variations are uneven between the northern and southern hemispheres. The results of our analysis could be beneficial for the understanding of the spatiotemporal distribution of solar active regions, and could also provide statistical constraints on solar dynamo theories.

Keywords: Solar cycle, Solar active regions, Solar magnetic fields, Solar oscillations, Solar activity
ALMA Reveals an Eccentricity Gradient in the Fomalhaut Debris Disk. We present evidence of a negative eccentricity gradient in the debris disk of the nearby A-type main-sequence star, Fomalhaut. Fitting to the high-resolution, archival ALMA 1.32 mm continuum data for Fomalhaut (with a synthesized angular resolution of 0 .″ 76 × 0 .″ 55; 4─6 au), we present a model that describes the bulk properties of the disk (semimajor axis, width, and geometry) and its asymmetric morphology. The best-fit model incorporates a forced eccentricity gradient that varies with semimajor axis,  ef∝anpow , a generalized form of the parametric models of E. M. Lynch &amp; J. B. Lovell, with npow = −1.75 ± 0.16. We show that this model is statistically preferred to models with constant forced and free eccentricities. In comparison to disk models with constant forced eccentricities, negative eccentricity gradient models broaden disk widths at pericenter versus apocenter, and increase disk surface densities at apocenter versus pericenter, both of which are seen in the Fomalhaut disk, and which we collectively term "Eccentric Velocity Divergence." We propose single-planet architectures consistent with the model and investigate the stability of the disk over 440 Myr to planet─disk interactions via N-body modeling. We find that Fomalhaut's ring eccentricity plausibly formed during the protoplanetary disk stage, with subsequent planet─disk interactions responsible for carving the disk morphology.

Keywords: Planetary system evolution, Planetary-disk interactions, Circumstellar disks, Debris disks, Eccentricity
Transient LoBALs at High Velocities: A Case of Extreme Broad Absorption Line Variability in J115636.82+085628.9. We present a multiepoch spectroscopic study of the broad absorption line (BAL) quasar J115636.82+085628.9 (zem = 2.1077), based on five spectra spanning nearly two decades in the observer's frame. This source exhibits remarkable variability in both low-ionization (LoBAL: Al III and Mg II) and high-ionization (HiBAL: C IV and Si IV) absorption features. For the first time, we detect the emergence and subsequent disappearance of LoBAL troughs at high velocities (∼20,000 km s‑1), coinciding with the strengthening and weakening of the corresponding HiBAL absorption. The C IV BAL profile extends from ∼6700 km s‑1 to a conservative upper limit of 30,000 km s‑1 and is composed of narrow, variable absorption features embedded within a broad, smooth envelope. Both C IV and Si IV BAL troughs exhibit dramatic equivalent width (EW) changes—among the most extreme reported to date. Notably, these EW variations are strongly anticorrelated with continuum flux changes inferred from optical photometric light curves. We interpret this variability as the result of a new absorbing flow transiting into our line of sight, increasing the shielding of a more distant, preexisting outflow and giving rise to transient LoBAL absorption. This scenario supports a unified picture in which LoBAL and HiBAL features arise from similar outflow structures, with observed differences governed primarily by line-of-sight column densities consistent with previous findings. *Based on observations collected at Southern African Large Telescope (SALT; Programme IDs 2015-1-SCI-005, 2018-1-SCI-009, 2019-1-SCI-019, and 2020-1-SCI-011) and the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 093.A-0255.

Keywords: Quasars
Structure and Skewness of the Effective Inspiral Spin Distribution of Binary Black Hole Mergers. The detection of gravitational waves has brought to light a population of binary black holes that merge within a Hubble time. Multiple formation channels can contribute to this population, making it difficult to definitively associate particular population features with underlying stellar physics. Black hole spins are considered an important discriminator between various channels, but they are less well measured than masses, making conclusive astrophysical statements using spins difficult thus far. In this paper, we consider the distribution of the effective inspiral spin χeff—a quantity much better measured than individual component spins. We show that non-Gaussian features like skewness, asymmetry about zero, and multimodality can naturally arise in the χeff distribution when multiple channels contribute to the population. Searching for such features, we find signs of skewness and asymmetry already in the current catalogs, but no statistically significant signs of bimodality. These features provide robust evidence for the presence of a subpopulation with spins preferentially aligned to the binary's orbital angular momentum; and we conservatively estimate the fraction of this subpopulation to be at least 12%–17% (at 90% credibility). Our models do not find a sharp excess of nonspinning systems and instead find that at least ∼20% of the binaries have some degree of negative χeff. The data also suggest that, if preferentially aligned mergers form a significant fraction of the population, they must have small spins.

Keywords: Gravitational wave astronomy, Black holes, Gravitational wave sources
One Year of SN 2023ixf: Breaking through the Degenerate Parameter Space in Light-curve Models with Pulsating Progenitors. We present and analyze the extensive optical broadband photometry of the Type II SN 2023ixf up to 1 yr after explosion. We find that, when compared to two preexisting model grids, the bolometric light curve is consistent with drastically different combinations of progenitor and explosion properties. This may be an effect of known degeneracies in Type IIP light-curve models. We independently compute a large grid of MESA+STELLA single-star progenitor and light-curve models with various zero-age main-sequence masses, mass-loss efficiencies, and convective efficiencies. Using the observed progenitor variability as an additional constraint, we select stellar models consistent with the pulsation period and explode them according to previously established scaling laws to match plateau properties. Our hydrodynamic modeling indicates that SN 2023ixf is most consistent with a moderate-energy ( Eexp≈7×1050  erg) explosion of an initially high-mass red supergiant progenitor (≳16.5 M⊙) that lost a significant amount of mass in its prior evolution, leaving a low-mass hydrogen envelope (≲3 M⊙) at the time of explosion, with a radius ≳950 R⊙ and a synthesized 56Ni mass of ≈0.068 M⊙. We posit that previous mass transfer in a binary system may have stripped the envelope of SN 2023ixf's progenitor. The analysis method with pulsation period presented in this work offers a way to break degeneracies in light-curve modeling in the future, particularly with the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time, when a record of progenitor variability will be more common.

Keywords: Red supergiant stars, Core-collapse supernovae, Type II supernovae, Massive stars, Stellar mass loss, Supernovae
JWST Discovery of a High-redshift Tidal Disruption Event Candidate in COSMOS-Web. The rates and properties of tidal disruption events (TDEs) provide valuable insights into their host galaxy central stellar densities and the demographics of their central supermassive black holes. TDEs have been observed only at low redshifts (z ≲ 1), due to the difficulty in conducting deep time-domain surveys. In this work, we present the discovery of a high-redshift TDE candidate, HZTDE-1, in the COSMOS-Web survey with JWST's NIRCam, using a novel selection technique based on color and morphology. We outline a methodology for identifying high-z TDEs in deep infrared imaging surveys, leveraging the unique spectral energy distributions and morphologies of these transients. While focused on TDEs, this methodology could also be applied to find other UV-bright transients, such as superluminous supernovae (SLSNe). We apply this technique to COSMOS-Web in filters F115W, F150W, F277W, and F444W, and identify HZTDE-1, a transient point source relative to archival UltraVISTA infrared observations. If we assume it is a TDE, we estimate a photometric redshift of  z=5.02−1.11+1.32 . HZTDE-1 cannot be explained by reasonable supernova or active galactic nuclei models. However, an SLSN at z ≳ 3 can also plausibly explain this transient and would be the highest-redshift SLSN yet known. If confirmed with follow-up observations, HZTDE-1 would represent the highest-redshift TDE discovery to date, and suggest an enhancement of the TDE rate in the high-redshift Universe. Our method, which can be applied to future deep surveys with the JWST and Nancy Grace Roman Space Telescope, offers a pathway to identify TDEs at z &gt; 4 and probe black hole demographics at early cosmic times.

Keywords: Supermassive black holes, Tidal disruption, James Webb Space Telescope
PEACHES. IV. Tracing the Formation and Evolution of C<SUB>2</SUB>H in Perseus Low-mass Protostars. The radical hydrocarbon molecule C2H is widely detected in various stages of star and planet formation, and has emerged as a useful tracer of high-C/O gas within the photochemically active surface layers of mature (Class II) protoplanetary disks. However, the chemistry and evolution of C2H within younger (Class 0/I) protostars remains much more poorly understood. Here, using data observed as part of the PEACHES survey along with new Atacama Large Millimeter/submillimeter Array Atacama Compact Array observations, we investigate the C2H emission toward an unbiased sample of 35 Class 0/I low-mass protostars in Perseus. With this large sample, we identify a clear association between C2H emission and the protostellar outflow cavity walls, and a consistent spatial anticorrelation between C2H and SO emission. Together, these trends confirm that C2H is tracing photochemically active, O-poor gas in these younger sources. We fitted the C2H spectra with a simple LTE model to yield column density maps, and find values ranging from 1014 to 1015 cm‑2 in these sources. We also looked for trends in the C2H emission morphology as a function of various protostellar evolutionary metrics, but find no clear patterns; the C2H emission remains spatially extended in most sources, independent of age. This indicates that the transition to the compact C2H emission observed on the surfaces of Class II disks must happen rapidly, sometime just after the embedded stage.

Keywords: Interstellar molecules, Protostars, Millimeter astronomy
The Cosmic Evolution of C IV Absorbers at 1.4 &lt; z &lt; 4.5: Insights from 100,000 Systems in DESI Quasars. We present the largest catalog to date of triply ionized carbon (C IV) absorbers detected in quasar spectra from the Dark Energy Spectroscopic Instrument. Using an automated matched-kernel convolution method with adaptive signal-to-noise thresholds, we identify 101,487 C IV systems in the redshift range 1.4 &lt; z &lt; 4.5 from 300,637 quasar spectra. Completeness is estimated via Monte Carlo simulations, and the catalog is 50% complete at EWC IV ≥ 0.4 Å. The differential equivalent width frequency distribution declines exponentially and shows weak redshift evolution. The absorber incidence per unit comoving path increases by a factor of 2–5 from z ≈ 4.5 to z ≈ 1.4, with stronger redshift evolution for strong systems. Using column densities derived from the apparent optical depth method, we constrain the cosmic mass density of C IV, ΩC IV, which increases by a factor of ∼3.8 from (0.82 ± 0.05) × 10‑8 at z ≈ 4.5 to (3.16 ± 0.2) × 10‑8 at z ≈ 1.4. From ΩC IV, we estimate a lower limit on intergalactic medium metallicity  log(ZIGM/Z⊙)≳‑3.25  at z ∼ 2.3, with a smooth decline at higher redshifts. These trends trace the cosmic star formation history and He II photoheating rate, suggesting a link between C IV enrichment, star formation, and UV background over ∼3 Gyr. The catalog also provides a critical resource for future studies connecting circumgalactic metals to galaxy evolution, especially near cosmic noon.

Keywords: Astronomy software, Redshift surveys, Quasar absorption line spectroscopy, Intergalactic medium
Massive Extremely High-velocity Outflow in the Quasar J164653.72+243942.2. We present analysis of one of the most extreme quasar outflows found to date in our survey of extremely high-velocity outflows (EHVOs). J164653.72+243942.2 (zem ∼ 3.04) shows variable C IVλλ1548,1551 absorption at speeds larger than 0.1c, accompanied by Si IV, N V, and Lyα, and disappearing absorption at lower speeds. We perform absorption measurements using the apparent optical depth method and SimBAL. We find the absorption to be very broad (Δv ∼ 35,100 km s‑1 in the first epoch and 13,000 km s‑1 in the second one) and fast (vmax ∼ –50,200 km s‑1 and ‑49,000 km s‑1, respectively). We measure large column densities ( logNH&gt;  21.6 (cm‑2)) and are able to place distance estimates for the EHVO (5 ≲ R ≲ 28 pc) and the lower-velocity outflow (7 ≲ R ≲ 540 pc). We estimate a mass outflow rate for the EHVO to be  Ṁout∼50–290M⊙yr‑1  and a kinetic luminosity of  logLKE∼46.5–47.2(ergs‑1)  in both epochs. The lower-velocity component has a mass outflow rate  Ṁout∼10–790M⊙yr‑1  and a kinetic luminosity of  logLKE∼45.3–47.2(ergs‑1) . We find that J164653.72+243942.2 is not an outlier among EHVO quasars in regard to its physical properties. While its column density is lower than typical BAL values, its higher outflow velocities drive most of the mass outflow rate and kinetic luminosity. These results emphasize the crucial role of EHVOs in powering quasar feedback, and failing to account for these outflows likely leads to underestimating the feedback impact on galaxies.

Keywords: Active galactic nuclei, Quasars, Broad-absorption line quasar
A Time-domain Study of Repeat and Nonrepeat Fast Radio Bursts. Fast radio bursts (FRBs) are extremely energetic radio transients, typically classified as repeat or nonrepeat, but their origins remain uncertain. In this work, we focus on the timing characteristics of the pulses in 536 FRBs observed by CHIME with improved pulse-finding and fitting algorithms. The results show that the fitted mean of rise time, decay time, FWHM, and minimum variable timescale distributions for the repeat FRBs are larger. Furthermore, the Kolmogorov–Smirnov test reveals significant differences (&gt;5σ) for some parameters between repeat and nonrepeat FRBs, implying that the former may have more stable and longer-lived sources (e.g., magnetars). However, we do not find significant differences in waiting times, which may be a limitation of the sample. We also investigate the relationship between these parameters, identifying some correlations, e.g., a negative power-law correlation between pulse amplitude and FWHM. Our findings suggest that the repeat and nonrepeat FRBs originate from different progenitors, environments, and/or emission mechanisms. Interestingly, both of their observations do not contradict that they originate from within the magnetosphere of a magnetar.

Keywords: Radio transient sources
Tracing the Light: Identification for the Optical Counterpart Candidates of Binary Black Holes during O3. The accretion disks of active galactic nuclei (AGN) are widely considered the ideal environments for binary black hole mergers and the only plausible sites for their electromagnetic counterparts. M. J. Graham et al. (2023) identified seven AGN flares that are potentially associated with gravitational wave (GW) events detected by the LIGO─Virgo─KAGRA Collaboration during the third observing run. In this article, utilizing an additional three years of Zwicky Transient Facility public data after their discovery, we conduct an updated analysis and find that only three flares can be identified. By implementing a joint analysis of optical and GW data through a Bayesian framework, we find two flares exhibit a strong correlation with GW events, with no secondary flares observed in their host AGN up to 2024 October 31. Combining these two most robust associations, we derive a Hubble constant measurement of  H0=72.1−23.1+23.9kms−1Mpc−1  and incorporating the multimessenger event GW170817 improves the precision to  H0=73.5−6.9+9.8kms−1Mpc−1 . Both results are consistent with existing measurements reported in the literature.

Keywords: Active galactic nuclei, Stellar mass black holes, Gravitational wave sources
Unraveling the Feedback-regulated Star Formation Activities around the Expanding Galactic Mid-infrared Bubble [HKS2019] E71. We explore the physical environment of the Galactic mid-infrared (MIR) bubble [HKS2019] E71 (hereafter E71) through a multiwavelength approach. E71 is located at the edge of a filamentary structure, as traced in Herschel images (250─500 μm), Herschel column density map, and molecular maps in the velocity range [−20, −14] km s−1. It hosts a stellar cluster (radius ∼ 1.26 pc, distance ∼1.81 ± 0.15 kpc) associated with radio continuum emission, including a centrally positioned B1.5-type massive star (hereafter "m2"), along with an enhanced population of evolved low-mass stars and young stellar objects. MIR images and molecular line maps reveal a photodissociation region surrounding "m2," exhibiting an arc-like structure along the edges of E71. Regularly spaced molecular and dust condensations are identified along this structure. The position─velocity map of 12CO (1─0) emission suggests an expansion of molecular gas concentrated at the periphery of E71. Near-infrared spectroscopic observations with TANSPEC confirm the presence of the accretion process in a massive young stellar object (MYSO) located near the edge of the bubble. High-resolution uGMRT radio continuum maps uncover substructures in the ionized emission, both toward the MYSO and the center of E71. These findings support that "m2" has shaped an arc-like morphology through its feedback processes. The pressure exerted by "m2" and the velocity structure of the 12/13CO (1─0) emission suggest that the stellar feedback has likely driven out molecular material, leading to the formation of the expanding E71 bubble. Our overall investigation infers that the "collect and collapse" process might be a possible mechanism that can describe the ongoing star formation activities around the E71 bubble.

Keywords: Stellar feedback, Stellar wind bubbles, Star forming regions, Young stellar objects, Star formation, Interstellar medium, H II regions
Theoretical Radio Signals from Radio-band Gravitational Waves Converted from the Neutron Star Magnetic Field. Gravitational waves (GWs) can convert into electromagnetic waves in the presence of a magnetic field via the Gertsenshtein–Zeldovich effect. The characteristics of the magnetic field substantially affect this conversion probability. This paper confirms that strong magnetic fields in neutron stars significantly enhance the conversion probability, facilitating detectable radio signatures of very high-frequency (VHF,  106–1011Hz ) GWs. We theoretically identify two distinct signatures using single-dish telescopes (FAST, TMRT, QTT, GBT) and interferometers (SKA1/2-MID): transient signals from burst-like GW sources and persistent signals from cosmological background GW sources. These signatures are mapped to graviton spectral lines derived from quantum field theory by incorporating spin-2 and mass constraints, resulting in smooth, featureless profiles that are critical for distinguishing GW signals from astrophysical foregrounds. FAST attains a characteristic strain bound of hc &lt; 10‑23, approaching 10‑24 in the frequency range of 1–3 GHz with a 6 hr observation period. This performance exceeds the 5σ detection thresholds for GWs originating from primordial black holes and nears the limits set by Big Bang nucleosynthesis. Additionally, projections for SKA2-MID indicate even greater sensitivity. Detecting such GWs would improve our comprehension of cosmological models, refine the parameter spaces for primordial black holes, and function as a test for quantum field theory. This approach addresses significant deficiencies in VHF GW research, improving detection sensitivity and facilitating the advancement of next-generation radio telescopes such as FASTA and Square Kilometre Array, which feature larger fields of view and enhanced gain.

Keywords: Early universe, Magnetic stars, Observational cosmology, Pulsars, Gravitational waves, Radio astronomy, Radio sources
Shear Particle Acceleration in Structured Gamma-Ray Burst Jets. III. The Radiation Physics of Bright Prompt Optical Flash. The radiation physics of bright prompt optical emission of gamma-ray bursts (GRBs) remains a puzzle. Assuming that the GRB ejecta is structured, we investigated this issue by characterizing the ejecta as an ultrarelativistic uniform jet core surrounded by a mild-relativistic cocoon. The mixed jet-cocoon (MJC) region can accelerate particles through the shear acceleration mechanism. Parameterizing the radial velocity profile of the MJC region with an exponential function and assuming a uniform magnetic field configuration, we show that the synchrotron radiation of the shear-accelerated electrons can produce a bright optical flash. Emission of the self-synchrotron Compton process of the electron population can result in an X-ray excess and an extra MeV–GeV gamma-ray flash relative to the Band function component in the keV–MeV band, which is attributed to the synchrotron radiation of the shock-accelerated electrons in the jet core. Our model reasonably represents the extremely bright optical flash and spectral characteristics of GRBs 990123, 080319B, and 130427A. The inferred magnetic field strength of the MJC region is above 105 G, potentially suggesting that the jets of these GRBs are highly magnetized.

Keywords: Gamma-ray bursts, Non-thermal radiation sources