Sazuna/UAT_keywords huggingface dataset:
Hydrogen-poor Superluminous Supernovae with Bumpy Light Curves Powered by Precessing Magnetars. Recent observations and statistical studies have revealed that a significant fraction of hydrogen-poor superluminous supernovae (SLSNe-I) exhibit light curves that deviate from the smooth evolution predicted by the magnetar-powered model, instead showing one or more bumps after the primary peak. However, the formation mechanisms of these postpeak bumps remain a matter of debate. Furthermore, previous studies employing the magnetar-powered model have typically assumed a fixed magnetic inclination angle and neglected the effects of magnetar precession. However, recent research has shown that the precession of newborn magnetars forming during the collapse of massive stars causes the magnetic inclination angle to evolve over time, thereby influencing magnetic dipole radiation. In this paper, therefore, we incorporate the effects of magnetar precession into the magnetar-powered model to develop the precessing magnetar-powered model. Using this model, we successfully reproduce the multiband light curves of six selected representative SLSNe-I with postpeak bumps. Moreover, the derived model parameters fall within the typical parameter range for SLSNe-I. By combining the precessing magnetars in SLSNe-I and long gamma-ray bursts, we find that the ellipticity of magnetars is related to the dipole magnetic field strength, which may suggest a common origin for the two phenomena. Our work provides a potential explanation for the origin of postpeak bumps in SLSNe-I and offers evidence for the early precession of newborn magnetars formed in supernova explosions.

Keywords: Magnetars, Light curves, Supernovae
Gotta Go Fast: A Generalization of the Escape Speed to Fluid-dynamical Explosions and Implications for Astrophysical Transients. A star's ability to explode in a core-collapse supernova is correlated with its density profile, ρ(r), such that compact stars with shallow density profiles preferentially "fail" and produce black holes. This correlation can be understood from a mass perspective, as shallower density profiles enclose ∼3M⊙ (i.e., the maximum neutron-star mass) at relatively small radii, but could also be due to the fact that a shockwave (driving the explosion) inevitably stalls if the density profile into which it propagates is shallower than ρ(r) ∝ r‑2. Here, we show that this condition—the density profile being steeper than ρ ∝ r‑2—is necessary, but not sufficient, for generating a strong explosion. In particular, we find solutions to the fluid equations that describe a shockwave propagating at a fixed fraction of the local freefall speed into a temporally evolving, infalling medium, the density profile of which scales as ρ ∝ r‑n at large radii. The speed of the shock diverges as n → 2 and declines (eventually to below the Keplerian escape speed) as n increases, while the total energy contained in the explosion approaches zero as the shock recedes to large distances. These solutions therefore represent fluid-dynamical analogs of marginally bound orbits, and yield the "shock escape speed" as a function of the density profile. We also suggest that stellar explodability is correlated with the power-law index of the density at ∼109 cm, where the neutrino diffusion time equals the local dynamical time for most massive stars, which agrees with supernova simulations.

Keywords: Analytical mathematics, Hydrodynamics, Shocks, Core-collapse supernovae
Galaxy Rest-frame UV Colors at z ∼ 2–4 with HST UVCANDELS. We present an analysis of rest-frame ultraviolet (UV) colors of 17,243 galaxies at z ∼ 2–4 in the Hubble Space Telescope UVCANDELS fields: GOODS-N, GOODS-S, COSMOS, and EGS. Here, we study the rest-frame UV spectral slope, β, measured via model spectra obtained via spectral energy distribution (SED) fitting, βSED, and explore its correlation with various galaxy parameters—photometric redshift, UV magnitude, stellar mass, dust attenuation, star formation rate (SFR), and specific SFR—obtained via SED fitting with DENSE BASIS. We also obtain measurements for β via photometric power-law fitting and compare them to our SED-fit-based results, finding good agreement on average. While we find little evolution in β with redshift from z = 2–4 for the full population, there are clear correlations between β (and related parameters) when binned by stellar mass. For this sample, lower-stellar-mass galaxies (log[M*] = 7.5–8.5 M⊙) are typically bluer ( βSED=‑2.0‑0.2+0.2  /  βPL=‑2.1‑0.4+0.4 ), fainter ( MUV=‑17.8‑0.6+0.7 ), and less dusty ( Av=0.4‑0.1+0.1  mag), and they exhibit lower rates of star formation (log[SFR]= 0.1‑0.2+0.2M⊙yr‑1 ) and higher specific star formation rates (log[sSFR] =  ‑8.2‑0.2+0.2yr‑1 ) than their high-mass counterparts. Higher-mass galaxies (log[M*] = 10.0–12.0 M⊙) are on average redder ( βSED=‑0.9‑0.5+0.8 / βPL=‑1.0‑0.5+0.8 ), brighter ( MUV=‑19.6‑1.2+1.0 ), and dustier ( Av=0.9‑0.4+0.5  mag), and they have higher SFRs (log[SFR] =  1.2‑1.1+0.6M⊙yr‑1 ) and lower sSFRs (log[sSFR] =  ‑9.1‑1.1+0.5yr‑1 ). This study's substantial sample size provides a benchmark for demonstrating that the rest-frame UV spectral slope correlates with stellar-mass-dependent galaxy characteristics at z ∼ 2–4, a relationship less discernible with the smaller data sets typically available at higher redshifts.

Keywords: Galaxy environments, Active galaxies, Ultraviolet color, Galaxy photometry, Extragalactic astronomy
The First Systematically Identified Repeating Partial Tidal Disruption Event. Tidal disruption events (TDEs) occur when a star enters the tidal radius of a supermassive black hole. If the star only grazes the tidal radius, a fraction of the stellar mass will be accreted in a partial TDE (pTDE). The remainder can continue orbiting and may be redisrupted at pericenter, causing a repeating pTDE. pTDEs may be as or more common than full TDEs, yet few are known. In this work, we present the discovery of the first repeating pTDE from a systematically selected sample, AT 2020vdq. AT 2020vdq was originally identified as an optically and radio-flaring TDE. Around 947 days after its discovery, it rebrightened dramatically in the optical. The optical flare was remarkably fast and luminous given its black hole mass compared to previous TDEs. It was accompanied by extremely broad (∼0.1c) optical/UV spectral features and faint X-ray emission (LX ∼ 3 × 1041 erg s‑1), but no new radio-emitting component. Based on the transient optical/UV spectral features and the broadband lightcurve, we show that AT 2020vdq is a repeating pTDE. We then use it to constrain TDE models; in particular, we favor a star originally in a very tight binary system that is tidally broken apart by the Hills mechanism. We also constrain the repeating pTDE rate to be 10‑6–10‑5 yr‑1 galaxy‑1, with uncertainties dominated by the unknown distribution of pTDE repeat timescales. In the Hills framework, this means the binary fraction in the galactic nucleus is of the order of a few percent.

Keywords: Accretion, Supermassive black holes, Tidal disruption
Periodic Low-amplitude Radial Velocity Variations in the Supergiant α Persei. α Per (HD 20902) is one of the brightest F5 supergiants, located at the blue edge of the instability strip. Several studies reported ∼100 day periods in the radial velocity (RV) variations in α Per, but the reported periods and amplitudes were all different, and the origins of these periodic RV variations remained unknown. We obtained 884 spectra for α Per from 2005 to 2020 using the Bohyunsan Observatory Echelle Spectrograph. We found a significant 130.6 day period in RV variations in the generalized Lomb–Scargle periodogram. In addition, the primary 130.6 day period has changed into 66.0 days during the observational duration. The line bisectors, stellar activity indices, such as Ca II H &amp; K lines and Hα equivalent widths, and Hipparcos photometric data were analyzed to establish the origins and the periodicity change of the RV variations. We found ∼130 day periods in line bisector variations, which also changed into ∼66 days as in RV variations, with a time delay of ∼400 days leading the RV variations. Either nonradial oscillations or rotational modulation of surface features can affect both RV and line bisector variations. However, nonradial oscillations are more likely to be the origin of RV variations in α Per, considering the characteristics of the periodogram of RV variations. The change of the periodicities and the time delay between RV and line bisector variations as observed in this work may provide interesting clues to the ongoing physical processes in α Per.

Keywords: Stellar oscillations, Stellar activity, Spectroscopy, Supergiant stars, Radial velocity
Comparing Optical Variability of Type 1 and Type 2 AGN from the BAT 9 Month Sample Using ASAS-SN and TESS Surveys. We present an optical variability analysis and comparison of the samples of Seyfert 1 (Sy1) and Seyfert 2 (Sy2) galaxies, selected from the Swift 9 month BAT catalog, using the light curves from Transiting Exoplanet Survey Satellite (TESS) and All-Sky Automated Survey for SuperNovae (ASAS-SN). We measured the normalized excess variance of TESS and ASAS-SN light curves for each target and performed a Kolmogorov–Smirnov test between the two samples, where our results showed significant differences. This is consistent with predictions from the unification model, where Seyfert 2s are obscured by the larger scale dust torus and their variability is suppressed. This variability difference is independent of the luminosity, Eddington ratio, or black hole mass, further supporting geometrical unification models. We searched the dependence of the normalized excess variance of Sy1s on absolute magnitudes, Eddington ratio, and black hole mass, where our results are consistent with relations found in the literature. Finally, a small subsample of changing-look (CL) active galactic nuclei (AGNs) that transitioned during the time frame of the ASAS-SN light curves, with their variability amplitudes changing according to the classification, have larger variability as type 1s and smaller as 2s. The change of variability amplitudes can be used to better pinpoint when the type transition occurred. The consistency trend of the variability amplitude differences between Sy1s and Sy2s and between CL AGNs in 1 or 2 stages suggests that variability can be a key factor in shedding light on the CL AGN or the dichotomy between Sy1 or Sy2 populations.

Keywords: Supermassive black holes, Seyfert galaxies, Active galactic nuclei, Galaxy accretion disks
MACER3D—An Upgrade of MACER2D with Enhanced Subgrid Models and Gas Physics—and Its Application to Simulating AGN Feedback in a Massive Elliptical Galaxy. We present Multiscale AGN-regulated Cosmic Ecosystem Resolver in 3D (MACER3D), a new suite of three-dimensional hydrodynamic simulations that study active galactic nuclei (AGN) feedback on galactic scales over gigayears in duration, with major enhancements in subgrid models and gas physics over its predecessor—Massive AGN Controlled Ellipticals Resolved (MACER), which is in two dimensions (hereafter MACER2D). MACER3D resolves gas dynamics from within the Bondi radius (∼25 pc) to halo scales. Combined with black hole accretion theory, it enables an accurate calculation of AGN outputs and subsequently their large-scale feedback effects. We present results from simulating an isolated elliptical galaxy with different feedback configurations. In the fiducial model with both AGN and supernova (SN) feedback, the temporal evolution of AGN luminosity and star formation rate are strongly correlated, suggesting shared dependence on the availability of gas supply for SMBH accretion and star formation. AGN duty cycles of several percent with a single-cycle timescale of ∼102 Myr agree with observations, while models with only AGN or SN feedback fail to reproduce observed cycles. While all models maintain a quiescent galaxy state, the fiducial AGN+SN feedback model results in higher star formation than no-SN feedback, suggesting SN feedback, when acting synergistically with AGN feedback, may positively impact star formation. Combined AGN and SN feedback enhances halo-scale metal enrichment compared to single-feedback models. The simulated X-ray properties match observations and predict transient cavities produced by cold-mode AGN winds from past burst events. The differences between the results obtained by MACER2D and MACER3D are also discussed.

Keywords: Hydrodynamical simulations, Galaxy formation, Galaxy evolution
The High-redshift Blazar MG3 J163554+3629: Physical Properties and the Enigma of Its Unexpected Supermassive Black Hole Growth. There is general consensus that active galactic nuclei (AGNs) derive their radiating power from a supermassive black hole (SMBH) that accretes matter. Yet, their precise powering mechanisms and the resulting growth of the SMBH are poorly understood, especially for AGNs at high redshift. Blazars are AGNs pointing their jet toward the observer, thus being detectable from radio through gamma rays at high redshift due to Doppler boosting. The blazar MG3 J163554+3629 is located at redshift z = 3.65 and it is a flat spectrum radio quasar (FSRQ). In this work, we show the results of the modeling of its spectral energy distribution (SED) from radio to gamma rays with a one-zone leptonic model. We estimate the uncertainties through a Markov Chain Monte Carlo approach. As a result, we infer the black hole mass  MBH=1.1−0.1+0.2×109M⊙  and a modest magnetic field of  B=6.56−0.09+0.13×10−2G  in line with the Compton dominance observed in high-redshift FSRQs. The emitting region is outside the broad line region but within the region of the dust torus radius. The rather small accretion efficiency of η = 0.083 is not solely inferred through the SED modeling but also through the energetics. An evolution study suggests that in an Eddington-limited accretion process the SMBH did not have time enough to grow from an initial seed mass of ∼106M⊙ at z ≍ 30 into a mass of MBH ≍ 109M⊙ at z = 3.65. Faster mass growth might be obtained in a super-Eddington process throughout frequent episodes. Alternative scenarios propose that the existence of the jet itself can facilitate a more rapid growth.

Keywords: Supermassive black holes, Cosmological evolution, Blazars, Flat-spectrum radio quasars, Active galactic nuclei, High-redshift galaxies
Constraints on the Evolution of an Overluminous Blue Supergiant from its Parent Open Cluster, vdBH 245. In this paper, we constrain the properties of an overluminous blue supergiant star (BSG) in the open cluster vdBH 245. We confirm the cluster membership of a sample of early-to-mid B-type stars using their proper motions, parallaxes, and radial velocities. We measure the stellar parameters through a spectrophotometric analysis of their optical spectra and near-infrared photometry. We correct for the effects of extinction of the cluster's light and estimate a most likely age range for vdBH 245 of 31.6 −13.8+13.1  Myr using the Binary Population and Spectral Synthesis (or BPASS) Python software hoki and models from the Geneva group. We find a distance of 2.0 ± 0.2 kpc for the cluster, consistent with the value estimated by Gaia of 2.6 ± 0.5 kpc. However, the new age estimate does not agree with previous studies that have found much younger ages. We find that single-star evolution alone is unable to explain the BSG in that age range, even when considering the impact of rotation on stellar evolution. Instead, we find that the overluminous B8─B9 Ia BSG could be interpreted as a merger between two stars with initial masses ranging from 8.5─12.0 M⊙ and 1.1─10.8 M⊙, with a current mass in the range of 13.4─20.6 M⊙. The merger would have occurred somewhere between 5.0 and 21.0 Myr after the cluster's formation. The discovery of such a BSG appearing too young (≍10 Myr in the single-star paradigm) for its population hints at the importance of considering binary interactions to explain the observed population of Galactic BSGs.

Keywords: Open star clusters, Interacting binary stars, Stellar mergers, B supergiant stars
The Abundance and Properties of Barred Galaxies out to z ∼ 4 Using JWST CEERS Data. We present the first estimate of the observed fraction and properties of bars out to z ∼ 4 using JWST CEERS NIRCam images. We analyze 1770 galaxies with M⋆ &gt; 1010 M⊙ at 0.5 ≤ z ≤ 4 and identify barred galaxies from 839 moderately inclined disk galaxies via ellipse fits and visual classification of both F200W and F444W images. Our results apply mainly to bars with projected semimajor axis abar &gt; 1.5 kpc (∼2× point-spread function in F200W images) that can be robustly traced by ellipse fits. For such bars, the observed bar fraction at z ∼ 2–4 is low (≲10%), and they appear to be emerging at least as early as z ∼ 4. Our observed bar fraction at z ∼ 0.5–4 is consistent with the bar fraction predicted by TNG50 simulations for large bars with abar &gt; 1.5 kpc at z ∼ 0.5–4 and with the bar fraction from Auriga simulations out to z ∼ 1.5. However, TNG50 simulations predict a large population of smaller bars that our data cannot robustly detect. If such bars exist, the true bar fraction at z ∼ 2–4 may be significantly higher than our results. At z ≥ 1.5, many barred galaxies show nearby neighbors, suggesting bars may be tidally triggered. From z ∼ 4 to 0.5, the observed bar fraction, average projected bar length, and projected bar strength rise. Our results highlight the early emergence and evolution of barred galaxies and the rising importance of bar-driven secular evolution from z ∼ 4 to today.

Keywords: Barred spiral galaxies, Galaxy evolution
The Chicago–Carnegie Hubble Program: The JWST J-region Asymptotic Giant Branch Extragalactic Distance Scale. The J-region asymptotic giant branch (JAGB) method is a new standard candle based on the constant luminosities of carbon-rich AGB stars in the J band. The JAGB method is independent of the Cepheid and tip of the red giant branch (TRGB) distance indicators. Therefore, we can leverage it to both cross-check Cepheid and TRGB distances for systematic errors and use it to measure an independent local H0. The JAGB method also boasts a number of advantages in measuring distances relative to the TRGB and Cepheids, several of which are especially amplified when combined with JWST's revolutionary resolving power. First, JAGB stars are 1 mag brighter in the near-IR (NIR) than the TRGB and can be discovered from single-epoch NIR photometry, unlike Cepheids, which require congruent optical imaging in at least 12 epochs. Thus, JAGB stars can be used to measure significantly farther distances than both the TRGB stars and Cepheids using the same amount of observing time. Dust extinction is also reduced in NIR observations and JAGB stars are ubiquitous in all galaxies with intermediate-age populations. We present a novel algorithm that identifies the optimal location in a galaxy for applying the JAGB method, so as to minimize the effects from crowding. We then deploy this algorithm in JWST NIRCam imaging of seven SN Ia host galaxies, to measure their JAGB distances, undertaking a completely blind analysis. In our Chicago–Carnegie Hubble Program H0 results paper, by W. L. Freedman et al., we apply the JAGB distances measured in this paper to the Carnegie Supernova Program type Ia supernova sample, measuring a Hubble constant of H0 = 67.80 ±2.17 (stat) ± 1.64 (sys) km s‑1 Mpc‑1. *Based on observations made with the NASA/ESA/CSA James Webb Space Telescope and obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. These observations are associated with program 1995.

Keywords: Galaxy distances, Asymptotic giant branch, Cosmological parameters, Carbon stars, Observational cosmology, Distance indicators, Hubble constant, Asymptotic giant branch stars, James Webb Space Telescope
Search for Gravitational Waves Emitted from SN 2023ixf. We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19, during the LIGO─Virgo─KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered ∼14% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz, where we assume the gravitational-wave emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1 × 10−4 M⊙c2 and luminosity 2.6 × 10−4 M⊙c2 s−1 for a source emitting at 82 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.08, at frequencies above 1200 Hz, surpassing past results.

Keywords: Gravitational waves
Modeling the Ages and Chemical Abundances of Elliptical Galaxies. Spectroscopic studies of elliptical galaxies show that their stellar population ages, mean metallicity, and α enhancement traced by [Mg/Fe] all increase with galaxy stellar mass or velocity dispersion. We use one-zone galactic chemical evolution (GCE) models with a flexible star formation history (SFH) to model the age, [Mg/H], and [Mg/Fe] inferred from simple stellar population (SSP) fits to observed ellipticals at z ∼ 0 and z ∼ 0.7. We show that an SSP fit to the spectrum computed from a full GCE model gives ages and abundances close to the light-weighted, logarithmically averaged values of the composite stellar population, &lt;age&gt;, &lt;[Mg/H]&gt;, and &lt;[Mg/Fe]&gt;. With supernova Mg and Fe yields fixed to values motivated by Milky Way stellar populations, we find that predicted &lt;[Mg/H]&gt;–&lt;age&gt; and &lt;[Mg/Fe]&gt;–&lt;age&gt; relations are surprisingly insensitive to SFH parameters: Older galaxies have higher &lt;[Mg/Fe]&gt;, but the detailed form of the SFH has limited impact. The star formation efficiency (SFE) and outflow efficiency affect the early and late evolution of &lt;[Mg/H]&gt;, respectively; explaining observed trends requires higher SFE and lower outflows in more massive galaxies. With core-collapse supernova yields calibrated to the plateau [Mg/Fe]cc ≈ 0.45 observed in many Milky Way studies, our models underpredict the observed &lt;[Mg/Fe]&gt; ratios of ellipticals by 0.05–0.1 dex. Increasing the core-collapse yield ratio to [Mg/Fe]cc = 0.55 improves the agreement, though the models remain below the data. We discuss potential resolutions of this discrepancy, including the possibility that many ellipticals terminate their star formation with a self-enriching, terminating burst that reduces the light-weighted age and boosts &lt;[Mg/Fe]&gt;.

Keywords: Galaxy abundances, Elliptical galaxies, Galaxy evolution, Galaxy chemical evolution