Sazuna/UAT_keywords huggingface dataset:
The Primary Flare Following a Stellar Collision in a Galactic Nucleus. High-velocity stellar collisions near supermassive black holes may result in a complete disruption of the stars. The initial disruption can have energies on par with supernovae and power a very fast transient. In this work, we examine the primary flare that follows the initial transient, which arises when streams of gas from the disrupted stars travel around the central black hole and collide with each other on the antipodal side with respect to the original collision. We present a simple analytic estimate for the properties of the flare, which depends on the distance of the collision from the central black hole and on the center of mass velocity of the colliding stars. We also present the first-of-their-kind radiation-hydrodynamics simulations of a few examples of stellar collisions and postcollision flow of the ejected gas and calculate the expected bolometric light curves. We find that such postcollision flares are expected to be similar to flares that arise in tidal disruptions events of single stars.

Keywords: Supermassive black holes, Computational astronomy, Galactic center, Stellar dynamics, Transient sources
The Discovery of Three Pulsars in the Globular Cluster M15 with FAST. We present the discovery of three pulsars in the globular cluster (GC) M15 (NGC 7078) by the Five-hundred-meter Aperture Spherical Radio Telescope. PSR J2129+1210J (M15J) is a millisecond pulsar with a spin period of 11.84 ms and a dispersion measure of 66.68 pc cm‑3. Both PSR J2129+1210K and L (M15K and L) are long-period pulsars with spin periods of 1928 ms and 3961 ms, respectively. M15L is the GC pulsar with the longest spin period known. We update the timing solutions of M15A to M15H. As predicted by A. Ridolfi et al., the flux density of M15C keeps decreasing, and the latest detection in our data set was on 2022 December 20. We have also detected M15I's signal for the first time since its discovery. Current timing suggests that it is an isolated pulsar.

Keywords: Globular star clusters, Radio astronomy, Radio pulsars
The Clearing Timescale for Infrared-selected Star Clusters in M83 with HST. We present an analysis of Hubble Space Telescope data from Wide Field Camera 3 (WFC3)/Ultraviolet Imaging Spectrometer, WFC3/IR, and the Advanced Camera for Surveys, investigating the young stellar cluster (YSC) population in the face-on spiral galaxy M83. Within the field of view of the IR pointings, we identify 454 sources with compact F814W continuum and Paβ line emission with a S/N ≥ 3 as possible YSC candidates embedded in dust. We refine this selection to 97 candidates based on their spectral energy distributions, multiwavelength morphology, and photometric uncertainties. For sources that are detected in all bands and have mass &gt;102.8 M ⊙ (53 sources), we find that by 2 Myr 75% of IR-selected star clusters have an A  V  ≤ 1 and that by 3 Myr the fraction rises to ∼82%. This evidence of early clearing implies that presupernova (pre-SN) feedback from massive stars is responsible for clearing the majority of the natal gas and dust that surround IR-selected star clusters in M83. Further, this result is consistent with previous estimates based on WFC3 observations and adds to the growing body of literature suggesting pre-SN feedback to be crucial for YSC emergence in normal star-forming galaxies. Finally, we find a weak correlation between the YSC concentration index and age over the first 10 Myr, which matches previous studies and indicates little or no change in the size of YSCs in M83 during their early evolution.

Keywords: Barred spiral galaxies, Young star clusters, Interstellar medium
Asymmetric Dust Accumulation of the PDS 70 Disk Revealed by ALMA Band 3 Observations. The PDS 70 system, hosting two planets within its disk, is an ideal target for examining the effect of planets on dust accumulation, growth, and ongoing planet formation. Here, we present high-resolution (0.″07 = 8 au) dust continuum observations of the PDS 70 disk in ALMA Band 3 (3.0 mm). While previous Band 7 observations showed a dust ring with slight asymmetry, our Band 3 observations reveal a more prominent asymmetric peak in the northwest direction, where the intensity is 2.5 times higher than in other directions and the spectral index is at the local minimum with α SED ∼ 2.2. This indicates that a substantial amount of dust is accumulated both radially and azimuthally in the peak. We also detect point-source emission around the stellar position in the Band 3 image, which is likely to be free–free emission. We constrain the eccentricity of the outer ring to be e &lt; 0.04 from the position of the central star and the outer ring. From the comparison with numerical simulations, we constrain the mass of PDS 70c to be less than 4.9  MJupiter  if the gas turbulence strength α turb = 10‑3. Then, we discuss the formation mechanism of the disk structures and further planet formation scenarios in the disk.

Keywords: Dust continuum emission, Protoplanetary disks, Submillimeter astronomy, Exoplanet formation, Planet formation
Stacking X-Ray Observations of "Little Red Dots": Implications for Their Active Galactic Nucleus Properties. Recent James Webb Space Telescope observations have revealed a population of compact extragalactic objects at z ≳ 4 with red near-infrared colors, which have been dubbed as "Little Red Dots" (LRDs). The spectroscopically selected LRDs exhibit broad Hα emission lines, which likely indicate that type I active galactic nuclei (AGNs) are harbored in the galaxies' dust-reddened cores. However, other mechanisms, like strong outflowing winds, could also produce broad Hα emission lines, and thus, the nature of LRDs is still under debate. We test the AGN hypothesis for LRDs by stacking the archival Chandra observations of 34 spectroscopically selected LRDs. We obtain tentative detections in the soft (0.5─2 keV) and hard (2─8 keV) X-ray bands with 2.9σ and 3.2σ significance, and with 4.1σ significance when combining the two bands. Nevertheless, we find that the soft (hard) band 3σ upper limit is ∼1 dex (∼0.3 dex) lower than the expected level from the L X─L Hα  relation for typical type I AGNs. Our results indicate that AGN activity is indeed likely present in LRDs though these objects have significantly different properties compared to previously identified type I AGNs, i.e., LRDs may have intrinsically weak X-ray emissions. We find it difficult to explain the low L X/L Hα  ratios observed in LRDs solely by absorption. It is also unlikely that fast outflows have major contributions to the broad Hα lines. Our findings indicate that empirical relations (e.g., for black hole mass measurements) established for typical type I AGNs should be used with caution when analyzing the properties of LRDs.

Keywords: Active galactic nuclei
GOALS-JWST: Constraining the Emergence Timescale for Massive Star Clusters in NGC 3256. We present the results of a James Webb Space Telescope NIRCam and NIRSpec investigation into the young massive star cluster (YMC) population of NGC 3256, the most cluster-rich luminous infrared galaxy in the Great Observatories All Sky LIRG Survey. We detect 3061 compact YMC candidates with a signal-to-noise ratio ≥3 at F150W, F200W, and F335M. Based on yggdrasil stellar population models, we identify 116/3061 sources with F150W – F200W &gt; 0.47 and F200W – F355M &gt; ‑1.37 colors, suggesting that they are young (t ≤ 5 Myr), dusty (A  V  = 5‑15), and massive (M ⊙ &gt; 105). This increases the sample of dust-enshrouded YMCs detected in this system by an order of magnitude relative to previous Hubble Space Telescope studies. With NIRSpec integral field unit pointings centered on the northern and southern nucleus, we extract the Paα and 3.3 μm polycyclic aromatic hydrocarbon (PAH) equivalent widths for eight bright and isolated YMCs. Variations in both the F200W – F335M color and 3.3 μm PAH emission with the Paα line strength suggest a rapid dust clearing (&lt;3‑4 Myr) for the emerging YMCs in the nuclei of NGC 3256. Finally, with both the age and dust emission accurately measured, we use yggdrasil to derive the color excess (E(B ‑ V)) for all eight YMCs. We demonstrate that YMCs with strong 3.3 μm PAH emission (F200W – F335M &gt; 0) correspond to sources with E(B ‑ V) &gt; 3, which are typically missed in UV-optical studies. This underscores the importance of deep near-infrared imaging for finding and characterizing these very young and dust-embedded sources.

Keywords: Starburst galaxies, Stellar feedback, Star forming regions, Young star clusters, Luminous infrared galaxies
JWST Reveals Bulge-dominated Star-forming Galaxies at Cosmic Noon. Hubble Space Telescope imaging shows that most star-forming galaxies at cosmic noon—the peak of cosmic star formation history—appear disk-dominated, leaving the origin of the dense cores in their quiescent descendants unclear. With the James Webb Space Telescope's high-resolution imaging to 5 μm, we can now map the rest-frame near-infrared emission, a much closer proxy for stellar mass distribution, in these massive galaxies. We selected 70 star-forming galaxies with 10 &lt; log(M) &lt; 12 and 1.5 &lt; z &lt; 3 in the CEERS survey and compare their morphologies in the rest-frame optical to those in the rest-frame near-IR. While the bulk of these galaxies are disk-dominated in 1.5 μm (rest-frame optical) imaging, they appear more bulge-dominated at 4.4 μm (rest-frame near-infrared). Our analysis reveals that in massive star-forming galaxies at z ∼ 2, the radial surface brightness profiles steepen significantly, from a slope of ∼0.3 dex‑1 at 1.5 μm to ∼1.4 dex‑1 at 4.4 μm within radii &lt;1 kpc. Additionally, we find their total flux contained within the central 1 kpc is approximately 7 times higher in F444W than in F150W. In rest-optical emission, a galaxy's central surface density appears to be the strongest indicator of whether it is quenched or star-forming. Our most significant finding is that at redder wavelengths, the central surface density ratio between quiescent and star-forming galaxies dramatically decreases from ∼10 to ∼1. This suggests the high central densities associated with galaxy quenching are already in place during the star-forming phase, imposing new constraints on the transition from star formation to quiescence.

Keywords: Galaxy formation, Quenched galaxies, Galaxy structure, Galaxy bulges, Galaxy evolution
Nearby Supernova and Cloud Crossing Effects on the Orbits of Small Bodies in the Solar System. Supernova (SN) blasts envelop many surrounding stellar systems, transferring kinetic energy to small bodies in the systems. Geologic evidence from 60Fe points to recent nearby SN activity within the past several Myr. Here, we model the transfer of energy and resulting orbital changes from these SN blasts to the Oort Cloud, the Kuiper Belt, and Saturn's Phoebe ring. For the Oort Cloud, an impulse approximation shows that a 50 pc SN can eject approximately half of all objects less than 1 cm while altering the trajectories of larger ones, depending on their orbital parameters. For stars closest to SNe, objects up to ∼100 m can be ejected. Turning to the explored solar system, we find that SNe closer than 50 pc may affect Saturn's Phoebe ring and can sweep away Kuiper Belt dust. It is also possible that the passage of the solar system through a dense interstellar cloud could have a similar effect; a numerical trajectory simulation shows that the location of the dust grains and the direction of the wind (from an SN or interstellar cloud) has a significant impact on whether or not the grains will become unbound from their orbit in the Kuiper Belt. Overall, nearby SNe sweep micron-sized dust from the solar system, though whether the grains are ultimately cast toward the Sun or altogether ejected depends on various factors. Evidence of SN-modified dust grain trajectories may be observed by New Horizons, though further modeling efforts are required.

Keywords: Kuiper belt, Saturn, Oort cloud, Supernovae
Discovery of the Binarity of Gliese 229B, and Constraints on the System's Properties. We present two epochs of radial velocities of the first imaged T dwarf Gliese 229 B obtained with Keck/NIRSPEC. The two radial velocities are discrepant with one another and with the radial velocity of the host star, at ≈11σ significance. This points to the existence of a previously postulated, but as-yet undetected, massive companion to Gl 229 B; we denote the two components as Gl 229 Ba and Gl 229 Bb. We compute the joint likelihood of the radial velocities to constrain the period and mass of the secondary companion. Our radial velocities are consistent with an orbital period between a few days and ≈60 days, and a secondary mass of at least ≈15 M Jup and up to nearly half the total system mass of Gl 229 B. With a significant fraction of the system mass in a faint companion, the strong tension between Gl 229 B's dynamical mass and the predictions of evolutionary models is resolved.

Keywords: Close binary stars, Radial velocity, High resolution spectroscopy, T dwarfs
Very High-energy Gamma-Ray Episodic Activity of Radio Galaxy NGC 1275 in 2022–2023 Measured with MACE. The radio galaxy NGC 1275, located at the central region of Perseus cluster, is a well-known very high-energy (VHE) gamma-ray emitter. The Major Atmospheric Cherenkov Experiment Telescope has detected two distinct episodes of VHE (E &gt; 80 GeV) gamma-ray emission from NGC 1275 during 2022 December and 2023 January. The second outburst, observed on 2023 January 10, was the more intense of the two, with flux reaching 58% of the Crab Nebula flux above 80 GeV. The differential energy spectrum measured between 80 GeV and  1.5ṪeV  can be described by a power law with a spectral index of Γ = ‑2.90 ± 0.16stat for both flaring events. The broadband spectral energy distribution derived from these flares, along with quasisimultaneous low-energy counterparts, suggests that the observed gamma-ray emission can be explained using a homogeneous single-zone synchrotron self-Compton model. The physical parameters derived from this model for both flaring states are similar. The intermediate state observed between two flaring episodes is explained by a lower Doppler factor or magnetic field, which subsequently returned to its previous value during the high-activity state observed on 2023 January 10.

Keywords: Gamma-ray astronomy
Coherence of Multidimensional Pair Production Discharges in Polar Caps of Pulsars. We report on the first self-consistent multidimensional particle-in-cell numerical simulations of nonhomogeneous pair discharges in polar caps of rotation-powered pulsars. By introducing strong inhomogeneities in the initial plasma distribution in our simulations, we analyze the degree of self-consistently emerging coherence of discharges across magnetic field lines. In 2D, we study discharge evolution for a wide range of physical parameters and boundary conditions corresponding to both the absent and free escape of charged particles from the surface of a neutron star. We also present the results of the first 3D simulations of discharges in a polar cap with a distribution of the global magnetospheric current appropriate for a pulsar with 60° inclination angle. For all parameters, we find the coherence scale of pair discharges across magnetic field lines to be of the order of the gap height. We also demonstrate that the popular "spark" model of pair discharges is incompatible with the universally adopted force-free magnetosphere model: intermittent discharges fill the entire zone of the polar cap that allows pair cascades, leaving no space for discharge-free regions. Our findings disprove the key assumption of the spark model about the existence of isolated distinct discharge columns.

Keywords: High energy astrophysics, Plasma physics, Plasma astrophysics, Pulsars, Radio pulsars
Possible Carbon Dioxide above the Thick Aerosols of GJ 1214 b. Sub-Neptune planets with radii smaller than Neptune (3.9 R ⊕) are the most common type of planet known to exist in the Milky Way, even though they are absent in the solar system. These planets can potentially have a large diversity of compositions as a result of different mixtures of rocky material, icy material, and gas accreted from a protoplanetary disk. However, the bulk density of a sub-Neptune, informed by its mass and radius alone, cannot uniquely constrain its composition; atmospheric spectroscopy is necessary. GJ 1214 b, which hosts an atmosphere that is potentially the most favorable for spectroscopic detection of any sub-Neptune, is instead enshrouded in aerosols (thus showing no spectroscopic features), hiding its composition from view at previously observed wavelengths in its terminator. Here, we present a JWST NIRSpec transmission spectrum from 2.8 to 5.1 μm that shows signatures of CO2 and CH4, expected at high metallicity. A model containing both these molecules is preferred by 3.3σ and 3.6σ as compared to a featureless spectrum for two different data analysis pipelines, respectively. Given the low signal-to-noise of the features compared to the continuum, however, more observations are needed to confirm the CO2 and CH4 signatures and better constrain other diagnostic features in the near-infrared. Further modeling of the planet's atmosphere, interior structure and origins will provide valuable insights about how sub-Neptunes like GJ 1214 b form and evolve.

Keywords: Exoplanet atmospheric composition , Transmission spectroscopy, James Webb Space Telescope, Mini Neptunes, Exoplanet atmospheres
On the 1/f Spectrum in Slow Solar Wind Turbulence: The Role of Alfvénicity. The slow solar wind has been recently observed to have a number of intervals that are dominated by large-scale Alfvénic fluctuations, especially within 1 au, with similar turbulence characteristics to those found in fast wind streams, including a 1/f range. These results suggest that the slow solar wind exists in at least two flavors: the typical slow wind that generally does not exhibit a 1/f range and an Alfvénic wind that is more similar to fast wind streams. The Alfvénic slow wind is usually differentiated from the typical slow wind (not dominated by Alfvénic fluctuations) by the normalized cross helicity, σ  c . Values of ∣σ  c ∣ near unity are associated with Alfvénic fluctuations, whereas values near zero are typically thought of as non-Alfvénic. This classification by cross helicity excludes the case of solar wind fluctuations dominated by balanced Alfvénic turbulence, i.e., the turbulence regime where there is equal energy flux of counterpropagating fluctuations propagating along the mean field. We use a large statistical analysis to isolate intervals of slow wind at 1 au in a 20 yr period of Wind data. These intervals are sorted into subsets corresponding to the type of slow wind via the mean values of their magnetic compressibility and cross helicity. Our analysis finds several intervals of low-cross-helicity slow wind dominated by balanced Alfvénic turbulence, which possess similar characteristics found in high-cross-helicity streams. Our results support the conclusion that a 1/f spectrum may be a property associated with streams dominated by Alfvénic turbulence, whether the turbulence is balanced or imbalanced.

Keywords: Slow solar wind, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Solar physics, Alfven waves
Linking High-z and Low-z: Are We Observing the Progenitors of the Milky Way with JWST?. The recent JWST observation of the Firefly Sparkle at z = 8.3 offers a unique opportunity to link the high- and the low-z Universe. Indeed, the claim of it being a Milky Way (MW) type of assembly at the cosmic dawn opens the possibility of interpreting the observation with locally calibrated galaxy-formation models. Here, we use the a state-of-the-art MW-evolution model to perform forward modeling of our Galaxy's progenitors at high-z. We build a set of mock spectra for the MW building blocks to make predictions for JWST and to interpret the Firefly Sparkle observation. First, we find that the most massive MW progenitor becomes detectable in a deep survey like JADES from z ≈ 8.2, meaning that we could have already observed MW analogs that still need interpretation. Second, we provide predictions for the number of detectable MW progenitors in lensed surveys like the CAnadian NIRISS Unbiased Cluster Survey, and interpret the Firefly Sparkle as a group of MW building blocks. Both the number of detections and the observed NIRCam photometry are consistent with our predictions. By identifying the MW progenitors whose mock photometry best fits the data, we find bursty and extended star formation histories, lasting &gt;150–300 Myr, and estimate their properties: M  h  ≈ 108‑9 M ⊙, M ⋆ ≈ 106.2‑7.5 M ⊙, SFR ≈ 0.04–0.20 M ⊙ yr‑1, and Z gas ≈ 0.04–0.24 Z ⊙. Uncovering the properties of MW analogs at cosmic dawn by combining JWST observations and locally constrained models will allow us to understand our Galaxy's formation, linking the high- and low-z perspectives.

Keywords: Galaxy formation, James Webb Space Telescope, Galaxy evolution, High-redshift galaxies, Milky Way Galaxy
AT2023vto: An Exceptionally Luminous Helium Tidal Disruption Event from a Massive Star. We present optical/UV observations and the spectroscopic classification of the transient AT2023vto as a tidal disruption event (TDE) at z = 0.4846. The spectrum is dominated by a broad blueshifted He II λ4686 emission line, classifying it as a member of the TDE-He class. The light curve exhibits a persistent blue color of g ‑ r ≈ ‑0.4 mag, long rise, and decline timescale, with a large peak absolute magnitude of M  g  ≈ ‑23.2, making it the most luminous of the classical optical TDEs (H, H+He, He) discovered to date by about 1.5 mag. We identify the host galaxy of AT2023vto in archival Pan-STARRS images and find that the transient is located at the galaxy center. Modeling the light curves of AT2023vto, we find that it resulted from the disruption of a ≈8 M ⊙ star by a ≈107 M ⊙ supermassive black hole. The star mass is about 5 times larger than the highest star masses previously inferred in TDEs, and the black hole mass is at the high end of the distribution. AT2023vto is comparable in luminosity and timescale to some putative TDEs (blue featureless continuum), as well as to the mean of a recently identified population of ambiguous nuclear transients (ANTs). ANTs have been speculated to arise from tidal disruptions of massive stars, perhaps in active galactic nuclei, and AT2023vto may represent a similar case to ANTs but in a dormant black hole, thereby bridging the TDE and ANT populations. We anticipate that the Rubin Observatory/LSST will uncover similar luminous TDEs to z ∼ 3.

Keywords: AB photometry, Optical astronomy, Tidal disruption, Transient sources, Time domain astronomy
The Production Population of Impact Craters in the Chang'E-6 Landing Mare. The Chang'E-6 mission accomplished the first sample return from the lunar farside. Earlier crater population measurements estimated the model age of the landing mare to range from the Eratosthenian to Late Imbrian, both of which are underrepresented by earlier returned samples. Establishing a new calibration point for lunar impact flux based on isotopic ages of the samples is promising, but the representative crater density for the landing mare (i.e., spatial density of craters with D ≥ 1 km; N (1)) is equally important for this purpose, which lacks good constraints. After excluding the effects of background secondaries, crater equilibrium, and observational uncertainties on crater statistics, this work extracts production populations in different diameter ranges (∼200 m–2 km) from multiple subareas of the landing mare. Cross-validation of the production populations verifies that N (1) derived from direct measurements of craters with D ≥ 1 km in sketched areas are reliable, which is (2.01 ± 0.90) × 10‑3 and (6.05 ± 2.71) × 10‑3 km2 for the western and eastern mare, respectively.

Keywords: Lunar craters, Lunar maria, The Moon, Lunar science, Lunar geochronology, Lunar impacts, Lunar surface, Lunar evolution