Sazuna/UAT_keywords huggingface dataset:
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. III. Aperture Masking Interferometric Observations of the Star HIP 65426 at 3.8 μm. We present aperture masking interferometry (AMI) observations of the star HIP 65426 at 3.8 μm, as part of the JWST Direct Imaging Early Release Science program, obtained using the Near Infrared Imager and Slitless Spectrograph instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of 0.5λ/D for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST's unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a 5σ contrast of ΔmF380M ∼ 7.62 ± 0.13 mag relative to the host star at separations ≳0 07, and the contrast deteriorates steeply at separations ≲0 07. However, we detect no additional companions interior to the known companion HIP 65426b (at separation ∼0 82 or  ). Our observations thus rule out companions more massive than 10–12 MJup at separations ∼10–20 au from HIP 65426, a region out of reach of ground- or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (≳0 07), even for thousands of more distant stars at ∼100 pc, in addition to the stars in the nearby young moving groups and associations, as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space.

Keywords: High contrast techniques, Exoplanet astronomy, James Webb Space Telescope, Direct detection interferometry
Lack of Rest-frame Ultraviolet Variability in Little Red Dots Based on HST and JWST Observations. Variability is a fundamental signature for active galactic nuclei (AGN) activity and serves as an unbiased indicator for rapid instability happening near the center of supermassive black holes (SMBHs). Previous studies showed that AGN variability does not have strong redshift evolution, and scales with their bolometric luminosity and BH mass, making it a powerful probe to identify low-mass, low-luminosity AGNs at high redshift. JWST has discovered a new population of high-redshift galaxies likely hosting moderate accreting BHs (&gt;106M⊙)—the little red dots (LRDs; z ∼ 4–10). In this Letter, we study the variability of a sample of 22 LRDs with V-shaped spectral energy distributions in three JWST deep fields that also have reliable Hubble Space Telescope observations in closely paired filters at 1–2 μm (rest-frame UV), with the time difference between 6 and 11 yr. This LRD sample covers a redshift range of 3 &lt; z &lt; 8 with ‑21.3 &lt; MUV &lt; ‑18.4. Based on both photometry and imaging difference analyses, we find a mean magnitude difference of ∼0.15 ± 0.26 mag, with none of the LRDs showing photometric variability at 3σ significance. Extrapolation of Sloan Digital Sky Survey quasar variability predicts a magnitude change of order 0.3 mag for our LRD sample. This suggests an upper limit of about ∼30% AGN contribution to the total observed UV light in our sample of LRDs.

Keywords: Supermassive black holes, Active galactic nuclei, Quasars
Uniting the Observed Dynamical Dark Energy Preference with the Discrepancies in Ω<SUB>m</SUB> and H<SUB>0</SUB> across Cosmological Probes. Recent results from Type Ia supernovae, baryon acoustic oscillations (BAOs), and the cosmic microwave background (CMB) indicate (1) potentially discrepant measurements of the matter density Ωm and Hubble constant H0 in the ΛCDM model when analyzed individually and (2) hint of dynamical dark energy in a w0waCDM model when data are combined in a joint analysis. We examine whether underlying dynamical dark energy cosmologies favored by data would result in biases in Ωm and H0 for each probe when analyzed individually under ΛCDM. We generate mock data sets in w0waCDM cosmologies, fit the individual probes under the ΛCDM model, and find that expected biases in Ωm are ∼0.03. Notably, the Ωm differences between probes are consistent with values observed in real data sets. We also observe that mock DESI-BAO data sets generated in the w0wa CDM cosmologies will lead to a biased measurement of H0 higher by ∼1.2 km s‑1 Mpc‑1 when fitted under ΛCDM, appearing to mildly improve the Hubble tension, but as the true underlying H0 is lower, the tension is in fact worsened. We find that the Ωm discrepancies, the high BAO H0 relative to the CMB, and the joint dynamical dark energy signal are all related effects that could be explained simultaneously with either new physics or new systematics. While it is possible to unite many of the discrepancies seen in recent analyses along a single axis, our results underscore the importance of understanding systematic differences in data sets, as they have unique impacts in different cosmological parameter spaces.

Keywords: Cosmology, Cosmological parameters, Cosmic microwave background radiation, Dynamical evolution, Type Ia supernovae, Cosmological constant, Baryon acoustic oscillations, Dark energy
Eruptivity of Flaring Active Regions Based on Electric Current Neutralization and Torus Instability Analysis. Solar flares are frequently accompanied by coronal mass ejections (CMEs) that release a significant amount of energetic plasma into interplanetary space, potentially causing geomagnetic disturbances on Earth. However, many solar flares have no association with CMEs. The relationship between solar flare and CME occurrences remains unclear. Therefore, it is valuable to distinguish between active regions (ARs) that potentially produce flares and CMEs and those that do not. It is believed that the eruptivity of a flare can be characterized by the properties of the AR from which it originates. In this study, we analyzed selected ARs that produced solar flares with and without CMEs during solar cycle 24. We carefully calculated the electric current neutralization of each AR by selecting relevant magnetic fluxes based on their connectivities using nonlinear force-free field models. Additionally, we analyzed their stabilities against the torus instability by estimating the proxies of critical heights of the ARs. We found that several noneruptive ARs, which lacked clear signatures of neutral electric currents, exhibited a more apparent relationship with high critical heights of torus instability. Furthermore, we introduced a new nondimensional parameter that incorporates current neutralization and critical height. We found that analyzing ARs based on this new parameter can better discriminate eruptive and noneruptive flare events compared to analysis that relied solely on current neutralization or torus instability. This indicates that torus instability analysis is necessary to complement electric current neutralization in characterizing the eruptivity of solar flares.

Keywords: Solar flares, Solar photosphere, Solar active regions, Solar corona, Solar coronal mass ejections
Unveiling Galaxy Chemical Enrichment Mechanisms Out to z ∼ 8 from Direct Determination of O and Ar Abundances from JWST/NIRSPEC Spectroscopy. Galaxy chemical enrichment mechanisms have primarily been constrained by [α/Fe] and [Fe/H] measurements of individual stars and integrated light from stellar populations. However, such measurements are limited at higher redshifts (z &gt; 1). Recently, we proposed an analogous diagram of the oxygen-to-argon abundance ratio, log(O/Ar), versus Ar abundance, 12+log(Ar/H), as a new diagnostic window for emission nebulae. In this Letter, using line flux measurements including temperature-sensitive auroral lines, we present direct determination of O and Ar abundances in nine star-forming galaxies (SFGs) from JWST/NIRSPEC spectra at z ∼ 1.3–7.7 and two more with Keck/MOSFIRE spectra at z ∼ 2.2. Utilizing their positions on the log(O/Ar) versus 12+log(Ar/H) plane, we present the first inference of galaxy chemical enrichment mechanisms from an ensemble of galaxies. Seven SFGs at z ∼ 1.3–4 are consistent with the Milky Way solar neighborhood galactic chemical enrichment models that are driven by core-collapse and Type Ia supernovae in a self-regulated manner. Such enrichment mechanisms thus occur at least out to z ∼ 4. However, four higher-redshift SFGs (z ∼ 3.6–7.7) have lower log(O/Ar) values, revealing potentially different enrichment paths becoming important at z &gt; 3.6. Such log(O/Ar) values may be caused by physical mechanisms such as rapid but intermittent star formation and/or additional enrichment sources. This new diagnostic window for SFGs enables us to reveal the unique fingerprints of galaxy chemical enrichment out to cosmic dawn.

Keywords: Galaxy formation, Galaxy chemical evolution, Chemical abundances, James Webb Space Telescope, Supernovae, Milky Way Galaxy
A New Age─Activity Relation For Solar Analogs that Accounts for Metallicity. Determining stellar ages is challenging, particularly for cooler main-sequence (MS) stars. Magnetic evolution offers an observational alternative for age estimation via the age─chromospheric activity (AC) relation. We evaluate the impact of metallicity on this relation using near one-solar-mass stars across a wide metallicity range. We analyze a sample of 358 solar-type stars with precise spectroscopic parameters determined through a line-by-line differential technique and with ages derived using Yonsei─Yale isochrones. We measured chromospheric activity (S-index) using high-quality High Accuracy Radial Velocity Planet Searcher spectra, calibrated to the Mount Wilson system and converted to the   index with a temperature-based photospheric correction. Our findings show that the AC relation for   is strongly influenced by metallicity. We propose a new age─activity─metallicity relation for solar-type MS stars ( ) with temperatures 5370 ≲ Teff ≲ 6530 K and metallicities from −0.7 to +0.3 dex. We show that taking metallicity into account significantly enhances chromospheric ages' reliability, reducing the residuals' rms relative to isochronal ages from 2.6 to 0.92 Gyr. This reflects a considerable improvement in the errors of chromospheric ages, from 53% to 15%. The precision level achieved in this work is also consistent with previous age─activity calibration from our group using solar twins.

Keywords: Observational astronomy, Stellar ages, Stellar properties, Fundamental parameters of stars, Stellar activity, Spectroscopy, Stellar evolution
Recent Star Formation in 0.5 &lt; z &lt; 1.5 Quiescent Galaxies. Observations of massive, quiescent galaxies reveal a relatively uniform evolution: following prolific star formation in the early Universe, these galaxies quench and transition to their characteristic quiescent state in the local Universe. The debate on the relative role and frequency of the process(es) driving this evolution is robust. In this Letter, we identify 0.5 ≲ z ≲ 1.5 massive, quiescent galaxies in the Hubble Space Telescope/UVCANDELS extragalactic deep fields using traditional color selection methods and model their spectral energy distributions, incorporating novel UV images. This analysis reveals ∼15% of massive, quiescent galaxies have experienced minor, recent star formation (&lt;10% of total stellar mass within the past ∼1 Gyr). We find only a marginal, positive correlation between the probability for recent star formation and a measure of the richness of the local environment from a statistical analysis. Assuming the recent star formation present in these quiescent galaxies is physically linked to the local environment, these results suggest only a minor role for dynamic external processes (galaxy mergers and interactions) in the formation and evolution of these galaxies at this redshift.

Keywords: Ultraviolet astronomy, Galaxy evolution
A Neutron Capture Explanation for the 10 MeV Emission Line Seen in GRB 221009A. The brightest ever gamma-ray burst (GRB) 221009A displays a significant emission line component around 10 MeV. As the GRB central engine is neutron rich, we propose that the emission line could be originally due to the 2.223 MeV gamma rays following neutron capture with protons. The measured line profile can be adequately fitted with a neutron capture model that involves thermal broadening and a bulk Doppler shift. The spectral modeling reveals a Doppler factor varying from 5.1 to 2.1 for the neutron-rich component, along with a temperature increase from 300 keV to about 900 keV, during the time interval of 280–360 s since the trigger, with about 10‑2 M⊙ deuteriums produced in the process. We argue that the neutron capture can take place in the outer shell of a structured jet, and the disk wind could be another possible site.

Keywords: Gamma-ray bursts, Nuclear astrophysics, Gamma-ray lines
A Constraint on Superheavy Elements of the GRB─Kilonova AT 2023vfi. The discovery of the kilonova (KN) AT 2017gfo, accompanying the gravitational wave event GW170817, provides crucial insight into the synthesis of heavy elements during binary neutron star (BNS) mergers. Following this landmark event, another KN was detected in association with the second-brightest gamma-ray burst (GRB) observed to date, GRB 230307A, and subsequently confirmed by observations of the James Webb Space Telescope (JWST). In this work, we conduct an end-to-end simulation to analyze the temporal evolution of the KN AT 2023vfi associated with GRB 230307A and constrain the abundances of superheavy elements produced. We find that the temporal evolution of AT 2023vfi is similar to AT 2017gfo in the first week post-burst. Additionally, the r-process nuclide abundances of lanthanide-rich ejecta, derived from numerical relativity simulations of BNS mergers, can also successfully interpret the temporal evolution of the KN with the lanthanide-rich ejecta mass of 0.02M⊙, which is consistent with the mass range of dynamical ejecta from numerical simulations in the literature. Both findings strongly suggest the hypothesis that GRB 230307A originated from a BNS merger, similar to AT 2017gfo. Based on the first-time observation of the KN for JWST, we are able to constrain the superheavy elements of another KN following AT 2017gfo. The pre-radioactive-decay abundances of the superheavy nuclides 222Rn, 223Ra, 224Ra, and 225Ac are estimated to be at least on the order of 1 × 10−5. These abundance estimates provide valuable insight into the synthesis of superheavy elements in BNS mergers, contributing to our understanding of astrophysical r-process nucleosynthesis.

Keywords: Neutron stars, Nuclear abundances, Gamma-ray bursts, Nucleosynthesis
Effects of Ion Temperature Anisotropy on Ion-scale Waves' Generation in the Near-Sun Solar Wind: Parker Solar Probe Observations. The ion-scale electromagnetic waves are observed frequently within 0.3 au. Their generation and dissipation driven by wave–particle interaction are very important energy transfer processes in the weak collision corona and solar wind and may be one of the important factors driving the evolution of ion velocity distribution functions therein. In this Letter, we statistically analyze the possible effects of ion temperature anisotropy on the generation of the observed ion-scale waves within 0.3 au. The statistical results indicate that the ion-scale waves' occurrence rate is proportional to ion temperature anisotropy. Moreover, the high occurrence rate of left-handed (LH) waves is closely related to EMIC and firehose instabilities driven by ion temperature anisotropy. However, we only find the close connection between right-handed (RH) waves' high occurrence rate with the proton firehose instability. Besides, for LH waves in the regions with Tp⊥/Tp∥ &gt; 1, their high occurrence rate is usually accompanied by the higher ion temperature (Tp, Tα), larger ion temperature ratio (Tα/Tp), and weaker collision effect. The RH waves are usually accompanied by a relatively lower ion temperature, smaller ion temperature ratio, and stronger collision effect than the LH waves. This Letter suggests that the ion temperature anisotropy is one of the important energy sources for generating ion-scale waves within 0.3 au.

Keywords: Space plasmas, Solar wind, Plasma physics
TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf. We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day─night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.

Keywords: Exoplanet structure, Radial velocity, Exoplanet astronomy, Exoplanets
The Convergence of Heavy and Light Seeds to Overmassive Black Holes at Cosmic Dawn. The James Webb Space Telescope has revealed low-luminosity active galactic nuclei at redshifts of z ≳ 4–7, many of which host accreting massive black holes (BHs) with BH-to-galaxy mass (MBH/M⋆) ratios exceeding the local values by more than an order of magnitude. The origin of these overmassive BHs remains unclear but requires potential contributions from heavy seeds and/or episodes of super-Eddington accretion. We present a growth model coupled with dark matter halo assembly to explore the evolution of the MBH/M⋆ ratio under different seeding and feedback scenarios. Given the gas inflow rates in protogalaxies, BHs grow episodically at moderate super-Eddington rates, and the mass ratio increases early on, despite significant mass loss through feedback. Regardless of seeding mechanisms, the mass ratio converges to a universal value ∼0.1–0.3, set by the balance between gas feeding and star formation efficiency in the nucleus. This behavior defines an attractor in the MBH–M⋆ diagram, where overmassive BHs grow more slowly than their hosts, while undermassive seeds experience rapid growth before aligning with the attractor. We derive an analytical expression for the universal mass ratio, linking it to feedback strength and halo growth. The convergence of evolutionary tracks erases seeding information from the mass ratio by z ∼ 4–6. Detecting BHs with ∼105‑6 M⊙ at higher redshifts that deviate from the convergence trend would provide key diagnostics of their birth conditions.

Keywords: Supermassive black holes, Quasars, Scaling relations, Active galactic nuclei, High-redshift galaxies
Angular Momentum Transport by Internal Gravity Waves across Age. We present 2D numerical simulations of convection and waves in a 7M⊙ star across stellar ages ranging from zero age to terminal age main sequence. We show that waves efficiently transport angular momentum across the stellar radiative envelope at young ages. However, as the core recedes, leaving behind a "spike" in the Brunt–Väisälä frequency at the convective–radiative interface, the waves are severely attenuated. This, coupled with the changing stratification throughout the radiation zone, leads to significantly reduced angular momentum transport at later stages on the main sequence. Indeed the angular momentum transport at mid–main sequence is typically 3–4 orders of magnitude lower than at zero age, though we expect this to be somewhat mitigated by the chemical mixing also induced by such waves. We provide measures of the angular momentum transport, both in terms of the divergence of the Reynolds stress and a typical "wave luminosity." However, we caution that the angular momentum transport drives shear flows, resulting in both slowing and speeding up of radiative interiors. While the values of Reynolds stress and angular momentum transport are only within the context of these limited simulations, they are not significantly different to those found previously using simpler prescriptions, providing some confidence in their applicability.

Keywords: Main sequence stars, Internal waves, Stellar convective zones
Discovery of Quasiperiodic Eruptions in the Tidal Disruption Event and Extreme Coronal Line Emitter AT2022upj: Implications for the QPE/TDE Fraction and a Connection to ECLEs. Quasiperiodic eruptions (QPEs) are recurring soft X-ray transients emerging from the vicinity of supermassive black holes in nearby, low-mass galaxy nuclei; about 10 QPE hosts have been identified thus far. Here we report the NICER discovery of QPEs in the optically selected tidal disruption event (TDE) and extreme coronal line emitter (ECLE) AT2022upj, exhibiting a large spread in recurrence times from 0.5–3.5 days, durations from 0.3–1 days, peak luminosities from 1042.5‑43.0 erg s‑1, and erratic flare profiles. A wealth of evidence now links at least some QPEs to the newly formed accretion flows emerging from TDEs; AT2022upj is the third QPE reported in an optically discovered TDE. Marginalizing over the uncertain distributions of QPE peak luminosity, recurrence time, delay after TDE peak, and lifetime, we use the burgeoning sample to make a Bayesian estimate that the fraction of optical TDEs resulting in QPEs within 5 yr post-disruption is  %. Along with AT2019qiz, AT2022upj also marks the second of the three optical TDE+X-ray QPEs showing coronal line emission, suggesting ECLEs may represent a subset of TDEs particularly efficient at forming QPEs and/or that sustained QPE X-ray emission contributes to coronal line emission in some galactic nuclei.

Keywords: X-ray astronomy, Supermassive black holes, Transient sources, High energy astrophysics
New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI. The sub-Neptune frontier has opened a new window into the rich diversity of planetary environments beyond the solar system. The possibility of hycean worlds, with planet-wide oceans and H2-rich atmospheres, significantly expands and accelerates the search for habitable environments elsewhere. Recent JWST transmission spectroscopy of the candidate hycean world K2-18 b in the near-infrared led to the first detections of the carbon-bearing molecules CH4 and CO2 in its atmosphere, with a composition consistent with predictions for hycean conditions. The observations also provided a tentative hint of dimethyl sulfide (DMS), a possible biosignature gas, but the inference was of low statistical significance. We report a mid-infrared transmission spectrum of K2-18 b obtained using the JWST MIRI LRS instrument in the ∼6–12 μm range. The spectrum shows distinct features and is inconsistent with a featureless spectrum at 3.4σ significance compared to our canonical model. We find that the spectrum cannot be explained by most molecules predicted for K2-18 b, with the exception of DMS and dimethyl disulfide (DMDS), also a potential biosignature gas. We report new independent evidence for DMS and/or DMDS in the atmosphere at 3σ significance, with high abundance (≳10 ppmv) of at least one of the two molecules. More observations are needed to increase the robustness of the findings and resolve the degeneracy between DMS and DMDS. The results also highlight the need for additional experimental and theoretical work to determine accurate cross sections of important biosignature gases and identify potential abiotic sources. We discuss the implications of the present findings for the possibility of biological activity on K2-18 b.

Keywords: Biosignatures, Habitable planets, Exoplanets