Sazuna/UAT_keywords huggingface dataset:
RR Lyrae Stars Belonging to the Candidate Globular Cluster Patchick 99. Patchick 99 is a candidate globular cluster located in the direction of the Galactic bulge, with a proper motion almost identical to the field and extreme field star contamination. A recent analysis suggests it is a low-luminosity globular cluster with a population of RR Lyrae stars. We present new spectra of stars in and around Patchick 99, targeting specifically the three RR Lyrae stars associated with the cluster as well as the other RR Lyrae stars in the field. A sample of 53 giant stars selected from proper motions and a position on the color–magnitude diagram are also observed. The three RR Lyrae stars associated with the cluster have similar radial velocities and distances, and two of the targeted giants also have radial velocities in this velocity regime and [Fe/H] metallicities that are slightly more metal-poor than the field. Therefore, if Patchick 99 is a bona fide globular cluster, it would have a radial velocity of ‑92 ± 10 km s‑1, a distance of 6.7 ± 0.4 kpc (as determined from the RR Lyrae stars), and an orbit that confines it to the inner bulge.

Keywords: Galactic center, Stellar populations, Galactic archaeology, Galaxy bulges, Milky Way dynamics, Galactic bulge, Stellar astronomy, Milky Way Galaxy physics, RR Lyrae variable stars, Milky Way evolution, Milky Way Galaxy, Star clusters
A Fast Radio Burst in a Compact Galaxy Group at z ∼ 1. FRB 20220610A is a high-redshift fast radio burst (FRB) that has not been observed to repeat. Here, we present rest-frame UV and optical Hubble Space Telescope observations of the field of FRB 20220610A. The imaging reveals seven extended sources, one of which we identify as the most likely host galaxy with a spectroscopic redshift of z = 1.017. We spectroscopically confirm three additional sources to be at the same redshift and identify the system as a compact galaxy group with possible signs of interaction among group members. We determine the host of FRB 20220610A to be a star-forming galaxy with a stellar mass of ≈109.7 M ☉, mass-weighted age of ≈2.6 Gyr, and star formation rate (integrated over the last 100 Myr) of ≈1.7 M ☉ yr−1. These host properties are commensurate with the star-forming field galaxy population at z ∼ 1 and trace their properties analogously to the population of low-z FRB hosts. Based on estimates of the total stellar mass of the galaxy group, we calculate a fiducial contribution to the observed dispersion measure from the intragroup medium of ≈90─182 pc cm−3 (rest frame). This leaves a significant excess of ${515}_{-272}^{+122}$ pc cm−3 (in the observer frame); further observation will be required to determine the origin of this excess. Given the low occurrence rates of galaxies in compact groups, the discovery of an FRB in one demonstrates a rare, novel environment in which FRBs can occur. As such groups may represent ongoing or future mergers that can trigger star formation, this supports a young stellar progenitor relative to star formation.

Keywords: Interacting galaxies, Galaxy groups, Galaxies, Radio transient sources
Bridging the Gap between Luminous Red Novae and Common Envelope Evolution: The Role of Recombination Energy and Radiation Force. Luminous red novae and their connection to common envelope evolution (CEE) remain elusive in astrophysics. Here, we present a radiation hydrodynamic model capable of simulating the light curves of material ejected during a CEE. For the first time, the radiation hydrodynamic model incorporates complete recombination physics for hydrogen and helium. The radiation hydrodynamic equations are solved with Guangqi. With time-independent ejecta simulations, we show that the peaks in the light curves are attributed to radiation-dominated ejecta, while the extended plateaus are produced by matter-dominated ejecta. To showcase our model's capability, we fit the light curve of AT 2019zhd. The central mass object of 6 M ⊙ is assumed based on observations and scaling relations. Our model demonstrates that the ejecta mass of AT 2019zhd falls within the range of 0.04–0.1 M ⊙. Additionally, we demonstrate that recombination energy and radiation force acceleration significantly impact the light curves, whereas dust formation has a limited effect during the peak and plateau phases.

Keywords: Common envelope evolution, Transient sources
Radial Evolution of the Near-Sun Solar Wind: Parker Solar Probe Observations. A statistical study of the radial evolution of the solar wind within 0.3 au is shown in this Letter based on Parker Solar Probe observations. We show the radial distribution of the main solar wind parameters, including the solar wind speed V sw, magnetic field ∣B∣, the number density of electrons N  e , protons N  p , and α particles N  α , and the temperature of protons T  p  and α particles T  α . The power-law fitting results of these parameters in the near-Sun solar wind are compared with previous radial models. We also show the radial distribution of the angle between the magnetic field B , solar wind V sw, and radial vector R . In the solar wind within 0.3 au, ${\theta }_{{\mathrm{BV}}_{\mathrm{sw}}}$ , and θ BR mainly concentrate around 135°, and ${\theta }_{{\mathrm{RV}}_{\mathrm{sw}}}$ almost concentrates in the region less than 20°. Furthermore, we also present the radial distribution of the relative values between the solar wind parameters, including the electric neutrality estimation ((2 × N  α  + N  p )/N  e  ≃ 1 within 0.2 au), relative number density ratio (N  α /N  p  ≃ 0.02 in slow solar wind and N  α /N  p  ≃ 0.04 in faster solar wind), relative temperature ratio (T  α /T  p  decreases with the increase of heliocentric distance and its decay rate is larger in faster solar wind), and differential speed (both V  α  ‑ V  p  and (V  α  ‑ V  p )/V  A  are larger in the faster solar wind and decrease as heliocentric distance increases).

Keywords: Space plasmas, Solar wind, Solar evolution
Using JWST Transits and Occultations to Determine ∼1% Stellar Radii and Temperatures of Low-mass Stars. Using JWST observations of a primary transit and two secondary eclipses for GJ 1214b, we determine an eccentricity that is more precise than a decade of HARPS data, which enables us to measure the stellar density to 2.62%. Coupled with a prior on the stellar mass from a dynamically calibrated K S–M * relation, we determine R * to 1.13%—3 times more precise than any other published analysis of this system. Then, using the bolometric flux from a spectral energy distribution model, we determine T eff to 1.39%—40% more precise than systematic floors from spectroscopy. Within the global model, these also improve the planetary radius and insolation. This is a proof of concept for a new method to determine accurate R * and T eff to a precision currently achieved for only a small number of low-mass stars. By applying our method to all high signal-to-noise ratio planetary transits and occultations, we can expand the sample of precisely measured stars without assuming tidal circularization and calibrate new relations to improve our understanding of all low-mass stars.

Keywords: Eclipses, Super Earths, Exoplanet astronomy, Occultation, Low mass stars
Unveiling Luminous Lyα Emitters at z ≈ 6 through JWST/NIRCam Imaging in the COSMOS Field. We study a sample of 14 spectroscopically confirmed Lyα emitters (LAEs) in the late era of reionization (at redshift z ≈ 6) based on the JWST/NIRCam imaging data set. These LAEs with high Lyα luminosity of L(Lyα) ∼1042.4–1043.4 erg s‑1 have been covered by the (ongoing) COSMOS-Web survey over 0.28 deg2 in four NIRCam bands (F115W, F150W, F277W, and F444W). With JWST/NIRCam imaging, we determine the UV continua with M UV ranging from ‑20.5 to ‑18.5 mag. The UV slopes have a median value of β ≈ ‑2.35, and the steepest slopes can reach β &lt; ‑3. Under the excellent spatial resolution of JWST, we identify three objects in the sample as potential merging/interacting systems. The 14 LAEs (and their components) are compact in morphology, residing substantially below the mass–size relation of high-z galaxies. We further investigate their physical properties, including the stellar mass (M *) and star formation rates (SFRs). Most of the LAEs lie on the SFR–M * main-sequence relation, while two of them, featured as "little red dots," likely host active galactic nuclei (AGNs), implying a ∼10% AGN fraction. Moreover, we reveal that a new correlation may exist between Lyα equivalent width and the offset between Lyα and UV emission (Δd Lyα ), with a median Δd Lyα  ∼ 1 kpc. This could be explained by the Lyα radiative transfer process in both the interstellar medium and circumgalactic medium. The results usher in a new era of detailed analysis on high-z LAEs with the JWST capability.

Keywords: Galaxy properties, Active galactic nuclei, Galaxy mergers, Lyman-alpha galaxies, Reionization, High-redshift galaxies
Modeling the Radial Distribution of Pulsars in the Galaxy. The Parkes 20 cm multibeam pulsar surveys have discovered nearly half of the known pulsars and revealed many distant pulsars with high dispersion measures. Using a sample of 1301 pulsars from these surveys, we have explored the spatial distribution and birth rate of normal pulsars. The pulsar distances used to calculate the pulsar surface density are estimated from the YMW16 electron-density model. When estimating the impact of the Galactic background radiation on our survey, we projected pulsars in the galaxy onto the Galactic plane, assuming that the flux density distribution of pulsars is uniform in all directions, and utilized the most up-to-date background temperature map. We also used an up-to-date version of the ATNF Pulsar Catalogue to model the distribution of pulsar flux densities at 1400 MHz. We derive an improved radial distribution for the pulsar surface density projected onto the Galactic plane, which has a maximum value at ∼4 kpc from the Galactic center. We also derive the local surface density and birth rate of pulsars, obtaining 47 ± 5 kpc‑2 and ∼4.7 ± 0.5 kpc‑2 Myr‑1, respectively. For the total number of potentially detectable pulsars in the galaxy, we obtain (1.1 ± 0.2) × 104 and (1.1 ± 0.2)×105 before and after applying the Tauris &amp; Manchester beaming correction model. The radial distribution function is used to estimate the proportion of pulsars in each spiral arm and the Galactic center.

Keywords: Milky Way disk, Radio pulsars
Jupiter's Metastable Companions. Jovian co-orbitals share Jupiter's orbit and exhibit 1:1 mean-motion resonance with the planet. This includes &gt;10,000 so-called Trojan asteroids surrounding the leading (L4) and trailing (L5) Lagrange points, viewed as stable groups dating back to planet formation. A small number of extremely transient horseshoe and quasi-satellite co-orbitals have been identified, which only briefly (&lt;1,000 yr) exhibit co-orbital motions. Via an extensive numerical study, we identify for the first time some Trojans that are certainly only "metastable"; instead of being primordial, they are recent captures from heliocentric orbits into moderately long-lived (10 kyr–100 Myr) metastable states that will escape back to the scattering regime. We have also identified (1) the first two Jovian horseshoe co-orbitals that exist for many resonant libration periods and (2) eight Jovian quasi-satellites with metastable lifetimes of 4–130 kyr. Our perspective on the Trojan population is thus now more complex as Jupiter joins the other giant planets in having known metastable co-orbitals that are in steady-state equilibrium with the planet-crossing Centaur and asteroid populations; the 27 identified here are in agreement with theoretical estimates.

Keywords: Celestial mechanics, Jupiter trojans, N-body simulations
X-Ray Polarization Variability of High Spectral Peak BL Lacertaes: Cases of 1ES 1959+650 and PKS 2155–304. The high-energy-peaked BL Lacertae objects (HBLs) are the main targets of the Imaging X-ray Polarimetry Explorer (IXPE) for investigating the mechanisms of radiation and particle acceleration in jets. In this Letter, we report the first IXPE observations of two HBLs, 1ES 1959+650 and PKS 2155–304. Both sources exhibit X-ray polarization with a confidence level exceeding 99%, as well as significant variability in polarization across different time intervals and energy ranges. Notably, PKS 2155–304 demonstrates the highest X-ray polarization among all blazars detected by IXPE within its entire energy band (2–8 keV), with a polarization degree of ΠX = 21.9% ± 1.9% (MDP99 ∼ 6.0%). An even higher polarization is observed in the 3–4 keV band, reaching ΠX = 28.6% ± 2.7% (MDP99 ∼ 8.1%) with a confidence level of 10.8σ. Furthermore, no polarization is detected above the 5 keV energy band. For 1ES 1959+650, the highest detected polarization degree in the 2–8 keV band is ΠX = 12.4% ± 0.7% (MDP99 ∼ 2.2%), with an electric vector position angle (EVPA) of ψ X = 19.°7 ± 1.°6. The X-ray polarization of 1ES 1959+650 exhibits evident variability, accompanied by the variations of ψ X, flux, spectrum, and energy bin. We discuss possible implications of these observational findings, including the variability in polarization, rotation of EVPA, and transition between synchrotron and synchrotron–self-Compton. We speculate that the X-rays observed during different IXPE observations originate from distinct regions in the jet and may involve diverse mechanisms for particle acceleration.

Keywords: Blazars, X-ray active galactic nuclei, Active galactic nuclei, Polarimetry
Evidence for Evolved Stellar Binary Mergers in Observed B-type Blue Supergiants. Blue supergiants are the brightest stars in their host galaxies, and yet their evolutionary status has been a long-standing problem in stellar astrophysics. In this pioneering work, we present a large sample of 59 early B-type supergiants in the Large Magellanic Cloud with newly derived stellar parameters and identify the signatures of stars born from binary mergers among them. We simulate novel 1D merger models of binaries consisting of post main-sequence giants with helium-rich cores (primaries) and main-sequence companions (secondaries), and consider the effects of interaction of the secondary with the core of the primary along with the mixing induced by the merger in the envelope. Thereafter, the evolution of the newborn 17─43 $\,{{\rm{M}}}_{\odot }$ stars is followed until core-carbon depletion, close to their final pre-explosion stage. Unlike stars born alone with comparable masses, stars born from mergers of evolved binaries are blue throughout their core helium-burning phase and replicate the surface gravities and Hertzsprung─Russell diagram positions of most of our sample, thus indicating that B-type supergiants structurally resemble stars born from such mergers. Moreover, the large nitrogen-to-carbon and nitrogen-to-oxygen number ratios, coupled with helium enhancements exhibited by at least half our data sample, is uniquely reproduced by our merger models. Collectively, these findings provide compelling evidence toward the important role of binary mergers in producing the currently observed population of blue supergiants in our Universe.

Keywords: Binary stars, B supergiant stars, Stellar mergers, Type II supernovae, Massive stars, Stellar abundances, Stellar evolutionary models, Large Magellanic Cloud, Spectroscopy, Magellanic Clouds
Small-amplitude Red Giants Elucidate the Nature of the Tip of the Red Giant Branch as a Standard Candle. The tip of the red giant branch (TRGB) is an important standard candle for determining luminosity distances. Although several 105 small-amplitude red giant stars (SARGs) have been discovered, variability was previously considered irrelevant for the TRGB as a standard candle. Here, we show that all stars near the TRGB are SARGs that follow several period–luminosity sequences, of which sequence A is younger than sequence B as predicted by stellar evolution. We measure apparent TRGB magnitudes, m TRGB, in the Large Magellanic Cloud (LMC) using Sobel filters applied to photometry from the Optical Gravitational Lensing Experiment and the ESA Gaia mission, and we identify several weaknesses in a recent LMC-based TRGB calibration used to measure the Hubble constant. We consider four samples: all red giants (RGs), SARGs, and sequences A and B. The B sequence is best suited for measuring distances to old RG populations, with M F814W,0 = ‑4.025 ± 0.014(stat.) ± 0.033(syst.) mag assuming the LMC's geometric distance. Control of systematics is demonstrated using detailed simulations. Population diversity affects m TRGB at a level exceeding the stated precision: the SARG and A-sequence samples yield 0.039 and 0.085 mag fainter (at 5σ significance) m TRGB values, respectively. Ensuring equivalent RG populations is crucial to measuring accurate TRGB distances. Additionally, luminosity function smoothing (∼0.02 mag) and edge detection response weighting (as much as ‑0.06 mag) can further bias TRGB measurements, with the latter introducing a tip-contrast relation. We are optimistic that variable RGs will enable further improvements to the TRGB as a standard candle.

Keywords: Red giant tip, Pulsating variable stars, Standard candles, Hubble constant, Stellar distance, Giant stars
Long-term Evolution of Relativistic Unmagnetized Collisionless Shocks. We study a relativistic collisionless electron–positron shock propagating into an unmagnetized ambient medium using 2D particle-in-cell simulations of unprecedented duration and size. The shock generates intermittent magnetic structures of increasingly larger size as the simulation progresses. Toward the end of our simulation, at around 26,000 plasma times, the magnetic coherence scale approaches λ ∼ 100 plasma skin depths, both ahead and behind the shock front. We anticipate a continued growth of λ beyond the time span of our simulation, as long as the shock accelerates particles to increasingly higher energies. The post-shock field is concentrated in localized patches, which maintain a local magnetic energy fraction ɛ  B  ∼ 0.1. Particles randomly sampling the downstream fields spend most of their time in low field regions (ɛ  B  ≪ 0.1) but emit a large fraction of the synchrotron power in the localized patches with strong fields (ɛ  B  ∼ 0.1). Our results have important implications for models of gamma-ray burst afterglows.

Keywords: Gamma-ray bursts, High energy astrophysics, Plasma astrophysics, Non-thermal radiation sources, Shocks
Linking Cause and Effect: Nanoscale Vibrational Spectroscopy of Space Weathering from Asteroid Ryugu. Airless bodies are subjected to space-weathering effects that modify the first few microns of their surface. Therefore, understanding their impact on the optical properties of asteroids is key to the interpretation of their color variability and infrared reflectance observations. The recent Hayabusa2 sample return mission to asteroid Ryugu offers the first opportunity to study these effects, in the case of the most abundant spectral type among the main-asteroid belt, C-type objects. This study employs vibrational electron energy-loss spectroscopy in the transmission electron microscope to achieve the spatial resolution required to measure the distinct mid-infrared spectral signature of Ryugu's space-weathered surface. The comparison with the spectrum of the pristine underlying matrix reveals the loss of structural -OH and C-rich components in the space-weathered layers, providing direct experimental evidence that exposure to the space environment tends to mask the optical signatures of phyllosilicates and carbonaceous matter. Our findings should contribute to rectifying potential underestimations of water and carbon content of C-type asteroids when studied through remote sensing with new-generation telescopes.

Keywords: Small Solar System bodies, Infrared spectroscopy, Space weather, Planetary mineralogy, Remote sensing, Vibrational spectroscopy, Impact gardening, Asteroid surfaces
Stochastic Wave Dark Matter with Fermi-LAT γ-Ray Pulsar Timing Array. Pulsar timing arrays (PTAs) can detect disturbances in the fabric of spacetime on a galactic scale by monitoring the arrival time of pulses from millisecond pulsars (MSPs). Recent advancements have enabled the use of γ-ray radiation emitted by MSPs, in addition to radio waves, for PTA experiments. Wave dark matter (DM), a prominent class of DM candidates, can be detected with PTAs due to its periodic perturbations of the spacetime metric. In response to this development, we perform in this Letter a first analysis of applying the γ-ray PTA to detect the ultralight axion-like wave DM, with the data of Fermi Large Area Telescope (Fermi-LAT). Despite its much smaller collecting area, the Fermi-LAT γ-ray PTA demonstrates a promising sensitivity potential. We show that the upper limits not far from those of the dedicated radio-PTA projects can be achieved. Moreover, we initiate a cross-correlation analysis using the data of two Fermi-LAT pulsars. The cross-correlation of phases, while carrying key information on the source of the spacetime perturbations, has been ignored in the existing data analyses for the wave DM detection with PTAs. Our analysis indicates that taking this information into account can improve the sensitivity to wave DM by ≳50% at masses below 10‑23 eV.

Keywords: Gamma-ray astronomy, Dark matter, Pulsar timing method
Alive but Barely Kicking: News from 3+ yr of Swift and XMM-Newton X-Ray Monitoring of Quasiperiodic Eruptions from eRO-QPE1. Quasiperiodic eruptions (QPEs) represent a novel class of extragalactic X-ray transients that are known to repeat at roughly regular intervals of a few hours to days. Their underlying physical mechanism is a topic of heated debate, with most models proposing that they originate either from instabilities within the inner accretion flow or from orbiting objects. At present, our knowledge of how QPEs evolve over an extended timescale of multiple years is limited, except for the unique QPE source GSN 069. In this study, we present results from strategically designed Swift observing programs spanning the past 3 yr, aimed at tracking eruptions from eRO-QPE1. Our main results are as follows: (1) the recurrence time of eruptions can vary from flare to flare and is in the range of 0.6─1.2 days; (2) there is no detectable secular trend in evolution of the recurrence times; (3) consistent with prior studies, their eruption profiles can have complex shapes; and (4) the peak flux of the eruptions has been declining over the past 3 yr, with the eruptions barely detected in the most recent Swift data set taken in 2023 June. This trend of weakening eruptions has been reported recently in GSN 069. However, because the background luminosity of eRO-QPE1 is below our detection limit, we cannot verify whether the weakening is correlated with the background luminosity (as is claimed to be the case for GSN 069). We discuss these findings within the context of various proposed QPE models.

Keywords: X-ray astronomy, Black hole physics, Supermassive black holes, High energy astrophysics, Tidal disruption, Astronomy data analysis, X-ray sources