Sazuna/UAT_keywords huggingface dataset:
Extensive Intrusive Magmatism in the Lunar Farside Apollo and South Pole–Aitken Basins, Chang'e-6 Landing Site. Lunar igneous activities, including intrusive magmatism and extrusive volcanism, and their products contain significant information about the lunar interior and its thermal state. Their distribution is asymmetrical on the nearside and farside, reflecting the global dichotomy. Samples from the South Pole–Aitken (SPA) basin on the farside hold the key to disclosing the dichotomy conundrum and rebalancing the asymmetrical understandings of the Moon, in addition to previously returned nearside samples (Apollo, Luna, Chang'e-5). For the first time, the Chang'e-6 mission obtained ∼1935.5 g of lunar soils from the farside in the southern Apollo basin, northeast of SPA, opening a window to solve this long-standing question. However, compared with the well-known mare/cryptomare volcanism in SPA, intrusive activity has a much more obscure presence and origin, due to its unclear surface expression, thus impeding the ongoing Chang'e-6 sample analysis, which is therefore emphasized here. We found evidence that intrusive magmatism is extensive across SPA, including Mg-suite intrusions, floor-modified craters, and linear/ring dikes, consistent with its intermediate crustal thickness, where dike intrusion is favored. Intrusive magmatism is abundant in the Apollo basin, where Chang'e-6 landed. Two obscure craters were discovered (Apollo X and Q) with evidence for subsurface intrusions, strongly suggesting the intensive intrusion in the region. Plutonic materials are very likely to be obtained by Chang'e-6, especially the Mg-suite from the western peak ring of the Apollo basin that delivered and mixed in the soils by the Chaffee S crater, whose components might provide critical new insights into their petrogenesis, early lunar evolution, and the origin of dichotomy.

Keywords: Lunar petrology, Lunar interior, Lunar science, Lunar mineralogy, Lunar features
Obliquity Constraints for the Extremely Eccentric Sub-Saturn Kepler-1656 b. The orbits of close-in exoplanets provide clues to their formation and evolutionary history. Many close-in exoplanets likely formed far out in their protoplanetary disks and migrated to their current orbits, perhaps via high-eccentricity migration (HEM), a process that can also excite obliquities. A handful of known exoplanets are perhaps caught in the act of HEM, as they are observed on highly eccentric orbits with tidal circularization timescales shorter than their ages. One such exoplanet is Kepler-1656 b, which is also the only known nongiant exoplanet (&lt;100 M ⊕) with an extreme eccentricity (e = 0.84). We measured the sky-projected obliquity of Kepler-1656 b by observing the Rossiter─McLaughlin effect during a transit with the Keck Planet Finder. Our data are consistent with an aligned orbit but are also consistent with moderate misalignment with λ &lt; 50° at 95% confidence, with the most likely solution of  35.0−21.6+14.9  deg. A low obliquity would be an unlikely outcome of most eccentricity-exciting scenarios, but we show that the properties of the outer companion in the system are consistent with the coplanar HEM mechanism. Alternatively, if the system is not relatively coplanar (≲20° mutual inclination), Kepler-1656 b may be presently at a rare snapshot of long-lived eccentricity oscillations that do not induce migration. Kepler-1656 b is only the fourth exoplanet with e &gt; 0.8 to have its obliquity constrained; expanding this population will help establish the degree to which orbital misalignment accompanies migration. Future work that constrains the mutual inclinations of outer perturbers will be key for distinguishing plausible mechanisms.

Keywords: Exoplanet dynamics, Exoplanet migration, Elliptical orbits, Prograde orbit
Coexistence of Antisunward and Sunward Ion Cyclotron Waves in the Near-Sun Solar Wind: Excitation by the Proton Cyclotron Instability. Based on observations from the Parker Solar Probe in the near-Sun solar wind, this study identifies an ion-scale wave event characterized by two distinct frequency bands. The lower-band waves exhibit right-hand polarization, while the upper-band waves have left-hand polarization. Alongside these waves, there are clear indications of the existence of both proton core and beam components, with the perpendicular temperature being higher than the parallel temperature in the measured proton velocity distribution functions (VDFs). Utilizing the plasma parameters derived from typical proton VDFs, instability analyses are conducted to investigate the mode nature of the observed waves and their excitation mechanism. The lower-band waves are identified as sunward ion cyclotron waves (ICWs), generated through the proton beam cyclotron instability; the upper-band waves are recognized as antisunward ICWs, induced by the proton core cyclotron instability. This study provides the first direct observational evidence confirming the presence of counterpropagating ICWs and proton cyclotron instability in the solar wind.

Keywords: Space plasmas, Solar wind, Plasma physics
Multiple Subscale Magnetic Reconnection Embedded inside a Heliospheric Current Sheet Reconnection Exhaust: Evidence for Flux Rope Merging. We report observations of multiple subscale reconnecting current sheets embedded inside a large-scale heliospheric current sheet (HCS) reconnection exhaust. The discovery was made possible by the unusual skimming trajectory of Parker Solar Probe through a sunward-directed HCS exhaust, sampling structures convecting with the exhaust outflows for more than 3 hr during Encounter 14, at a radial distance of ∼17 solar radii. A large number of subscale current sheets (SCSs) were detected inside the HCS exhaust. Remarkably, five SCSs showed direct evidence for reconnection, displaying near-Alfvénic outflow jets and bifurcated current sheets. The reconnecting SCSs all had small magnetic shears (27°–81°), i.e., strong guide fields. The thickness of the subscale reconnecting current sheets ranged from ∼60 km to ∼5000 km (∼20–2000 ion inertial lengths). The SCS exhausts were directed predominantly in the normal or out-of-plane direction of the HCS, i.e., nearly orthogonal to the HCS exhaust direction. The presence of multiple low-magnetic-shear reconnecting current sheets inside a large-scale exhaust could be associated with coalescence of multiple large flux ropes inside the HCS exhaust. The orientation of some SCS exhausts was partly in the ecliptic plane of the HCS, which may indicate that the coalescence process is highly three-dimensional. Since the coalescence process is likely short-lived, the detection of five such events inside a single HCS crossing could imply the common occurrence of flux rope coalescence in large-scale HCS reconnection exhausts.

Keywords: Solar physics
PO and PN in the Envelope of VY Canis Majoris: Elucidating the Chemistry and Origin of Phosphorus. The J = 5.5 → 4.5 and J = 5 → 4 transitions of PO and PN, respectively, have been imaged in the envelope of hypergiant star VY Canis Majoris (VY CMa) using the Atacama Large Millimeter/submillimeter Array with angular resolutions of 0.″2 and 1.″5 and data from the Submillimeter Telescope of the Arizona Radio Observatory. These maps are the first high-fidelity images of PO and PN in a circumstellar envelope. Both molecules are primarily present in a spherical, star-centered region with a radius ∼60 R * (0.″5), indicating formation by LTE chemistry and then condensation into grains. PN, however, shows additional, fan-shaped emission 2″ southwest of the star, coincident with dust features resolved by Hubble Space Telescope (HST), as well as four newly identified distinct structures 1″–2″ toward the north, east, and west (Cloudlets I–IV), not visible in HST images. The "SW Fan" and the cloudlets are also prominent in the J = 5.5 → 4.5 transition of NS. The correlation of PN with NS, SiO, and dust knots in the SW Fan suggests a formation in shocked gas enhanced with nitrogen. Excess nitrogen is predicted to favor PN synthesis over PO. Abundances for PN and PO in the spherical source are f ∼ 4.4 × 10‑8 and 1.4 × 10‑7, respectively, relative to H2. Given a cosmic abundance of phosphorus, an unusually high fraction (∼35%) is contained in PO and PN. Alternatively, the stellar winds may be enriched in P (and N) by dredge-up from the interior of VY CMa.

Keywords: Interstellar molecules, Circumstellar envelopes, Millimeter astronomy, Chemical abundances, Astrochemistry, Hypergiant stars
Star Formation by Supernova Implosion. Recent hydrodynamical simulations of the late stages of supernova remnant (SNR) evolution have revealed that as they merge with the ambient medium, SNRs implode, leading to the formation of dense clouds in their center. While being highly chemically enriched by their host SNR, these clouds appear to have similar properties as giant molecular clouds, which are believed to be the main site of star formation. Here, we develop a simple model in order to estimate the efficiency of the star formation that might be triggered by the implosion of SNRs. We separately consider two cases: cyclic star formation, maintained by the episodic driving of feedback from new generations of stars, and a single burst of star formation, triggered by a single explosion. We find that in the cyclic case, star formation is inefficient, with implosion-triggered star formation contributing a few percent of the observed star formation efficiency per freefall timescale. In the single-burst case, higher star formation efficiencies can be obtained. However, while the implosion-triggered process might not contribute much to the overall star formation, due to the high chemical enrichment of the birth clouds, it can explain the formation of a significant fraction of metal-rich stars.

Keywords: Supernova remnants, Star formation, Interstellar medium, Dense interstellar clouds
Discovery of Very High Energy Gamma-Ray Emissions from the Low-luminosity AGN NGC 4278 by LHAASO. The first source catalog of the Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a very high energy gamma-ray source, 1LHAASO J1219+2915. This Letter presents a further detailed study of the spectral and temporal behavior of this pointlike source. The best-fit position of the TeV source (R.A. = 185.°05 ± 0.°04, decl. = 29.°25 ± 0.°03) is compatible with NGC 4278 within ∼0.°03. Variation analysis shows an indication of variability on a timescale of a few months in the TeV band, which is consistent with low-frequency observations. Based on these observations, we report the detection of TeV γ-ray emissions from this low-luminosity active galactic nucleus. The observation by LHAASO's Water Cherenkov Detector Array during the active period has a significance level of 8.8σ with a best-fit photon spectral index Γ = 2.56 ± 0.14 and a flux f 1–10 TeV = (7.0 ± 1.1sta ± 0.35syst) × 10‑13 photons cm‑2 s‑1, or approximately 5% of the Crab Nebula. The discovery of VHE gamma-ray emission from NGC 4278 indicates that compact, weak radio jets can efficiently accelerate particles and emit TeV photons.

Keywords: High energy astrophysics, Blazars, LINER galaxies, Low-luminosity active galactic nuclei, Fanaroff-Riley radio galaxies, Gamma-ray astronomy
Eddington Envelopes: The Fate of Stars on Parabolic Orbits Tidally Disrupted by Supermassive Black Holes. Stars falling too close to massive black holes in the centers of galaxies can be torn apart by the strong tidal forces. Simulating the subsequent feeding of the black hole with disrupted material has proved challenging because of the range of timescales involved. Here we report a set of simulations that capture the relativistic disruption of the star, followed by 1 yr of evolution of the returning debris stream. These reveal the formation of an expanding asymmetric bubble of material extending to hundreds of au—an outflowing Eddington envelope with an optically thick inner region. Such outflows have been hypothesized as the reprocessing layer needed to explain optical/UV emission in tidal disruption events but never produced self-consistently in a simulation. Our model broadly matches the observed light curves with low temperatures, faint luminosities, and line widths of 10,000–20,000 km s‑1.

Keywords: Supermassive black holes, Black hole physics, High energy astrophysics, Tidal disruption, Transient sources, X-ray transient sources, Active galactic nuclei, General relativity, Ultraviolet transient sources
Can Solar Limb Flare Prediction Be Properly Made by Extreme-ultraviolet Intensities?. We address the question of whether the solar limb flare prediction can be properly made by EUV intensity, which has less projection effects than solar white light and magnetogram data. We develop empirical and multilayer perceptron (MLP) models to forecast the probability of a major solar limb flare within a day. We use Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 94 and 131 Å that have high correlations and large slopes with X-ray flare fluxes from 2010 to 2022. We select 240 flares stronger than or equal to the M1.0 class and located near the limb region (60° or more in heliographic longitude). For input data, we use the limb intensity as the sum of SDO/AIA intensities in the limb region and the total intensity of the whole image. We compare the model performances using metrics such as the receiver operating characteristic—area under the curve. Our major results are as follows. First, we can forecast major solar limb flare occurrences with only SDO/AIA 94 and/or 131 Å intensities. Second, our models show better probability prediction than the climatological model. Third, both empirical (AUC = 0.85) and MLP (AUC = 0.84) models have similar performances, which are much better than a random forecast (AUC = 0.50). Finally, it is interesting to note that our model can forecast the flaring probability of all 52 events during the test period, while the models in the NASA/CCMC flare scoreboard can forecast only 22 events. From the above results, we can answer that the solar limb flare prediction using EUV intensity can be properly made.

Keywords: The Sun, Solar flares, Solar extreme ultraviolet emission, Neural networks
Chemical Mapping of Temperate Sub-Neptune Atmospheres: Constraining the Deep Interior H<SUB>2</SUB>O/H<SUB>2</SUB> Ratio from the Atmospheric CO<SUB>2</SUB>/CH<SUB>4</SUB> Ratio. Understanding the planetary envelope composition of sub-Neptune-type exoplanets is challenging due to the inherent degeneracy in their interior composition scenarios. Particularly, the planetary envelope's H2O/H2 ratio, which can also be expressed as the O/H ratio, provides crucial insights into its original location relative to the ice line during planetary formation. Using self-consistent radiative transfer modeling and a rate-based automatic chemical network generator combined with 1D photochemical kinetic-transport atmospheric modeling, we investigate various atmospheric scenarios of temperate sub-Neptunes, ranging from H2-dominated to H2O-dominated atmospheres with equilibrium temperatures (T eq) of 250—400 K. This study includes examples such as K2-18 b (T eq = 255 K), LP 791-18 c (T eq = 324 K), and TOI-270 d (T eq = 354 K). Our models indicate that the atmospheric CO2/CH4 ratio can be used to infer the deep interior H2O/H2 ratio. Applying this method to recent JWST observations, our findings suggest that K2-18 b likely has an interior that is 50% highly enriched in water, exceeding the water content in a 100 × Z ⊙ scenario and suggesting a planetary formation mechanism involving substantial accretion of ices. In contrast, our model suggests that approximately 25% of TOI-270 d's interior is composed of H2O, which aligns with the conventional metallicity framework with a metallicity higher than 100 × Z ⊙. Furthermore, our models identify carbonyl sulfide (OCS) and sulfur dioxide (SO2) as strong indicators for temperate sub-Neptunes with at least 10% of their interior composed of water. These results provide a method to delineate the internal composition and formation mechanisms of temperate sub-Neptunes (T eq &lt; ∼ 500 K) via atmospheric characterization through transmission spectroscopy.

Keywords: Exoplanet atmospheric composition , Theoretical models, Exoplanet atmospheres, Astrochemistry, James Webb Space Telescope, Mini Neptunes, Exoplanet formation, Planet formation
Toward Spectrum Coexistence: First Demonstration of the Effectiveness of Boresight Avoidance between the NRAO Green Bank Telescope and Starlink Satellites. NRAO and SpaceX have been engaged in coordinated testing efforts since Fall 2021, including conducting experiments on different interference avoidance schemes for the Karl G. Jansky Very Large Array in New Mexico, and the Green Bank Telescope (GBT) inside the National Radio Quiet Zone in West Virginia. The Starlink system is capable of avoiding direct illumination of telescope sites with their adaptive tasking to place downlink beams far away. Nevertheless, even satellites operating in this mode can potentially present strong signals into the telescope's receiver system if they pass close to the telescope's main beam at the boresight. For additional protection, Starlink satellites can either momentarily redirect or completely disable their downlink channels while they pass within some minimum angular separation threshold from the telescope's boresight, methods that are referred to as "telescope boresight avoidance." In two separate experiments conducted since Fall 2023, NRAO and SpaceX arranged to have the GBT observe a fixed R.A./decl. position in the sky, chosen to have a large number of close-to-boresight Starlink passages. Preliminary analysis from these two experiments illustrates the feasibility of these avoidance methods to significantly reduce, if not eliminate, the negative impact of close-to-boresight satellite passages. Importantly, these experiments demonstrate the value of continuing cooperative efforts between NRAO and SpaceX, and expanding cooperation between the radio astronomy and satellite communities more generally.

Keywords: Observational astronomy, Microwave spectroscopy, Polarimetry, Artificial satellites, Single-dish antennas, Radio interferometers, Radio astronomy
Revealing the Fate of Exoplanet Systems: Asteroseismic Identification of Host Star in the Red Clump or Red Giant Branch. Determining the evolutionary stage of stars is crucial for understanding the evolution of exoplanetary systems. In this context, red giant branch (RGB) and red clump (RC) stars, which formed at stages in the later evolution of stars situated before and after the helium flash, harbor critical clues to unveiling the evolution of planets. The first step in revealing these clues is to confirm the evolutionary stage of the host stars through asteroseismology. However, up to now, host stars confirmed to be RGB or RC stars are extremely rare. In this investigation, we present a comprehensive asteroseismic analysis of two evolved stars, HD 120084 and HD 29399, known to harbor exoplanets, using data from the Transiting Exoplanet Survey Satellite. We have discovered for the first time that HD 120084 is an RC star in the helium-core-burning phase, and confirmed that HD 29399 is an RGB star in the hydrogen-shell burning phase. Through the precise measurement of asteroseismic parameters such as  νmax , Δν, and ΔΠ1, we have determined the evolutionary states of these stars and derived their fundamental stellar parameters. The significance of this study lies in the application of automated techniques to measure asymptotic period spacings in red giants, which provides critical insights into the evolutionary outcomes of exoplanet systems. We demonstrate that asteroseismology is a potent tool for probing the internal structures of stars, thereby offering a window into the past and future dynamics of planetary orbits. The presence of a long-period giant planet orbiting HD 120084, in particular, raises intriguing questions about the potential engulfment of inner planets during the host star's expansion, a hypothesis that warrants further investigation.

Keywords: Red giant branch, Exoplanets, Red giant clump, Planet hosting stars, Asteroseismology
Host Galaxies for Four Nearby CHIME/FRB Sources and the Local Universe FRB Host Galaxy Population. We present the host galaxies of four apparently nonrepeating fast radio bursts (FRBs), FRB 20181223C, FRB 20190418A, FRB 20191220A, and FRB 20190425A, reported in the first Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB) catalog. Our selection of these FRBs is based on a planned hypothesis testing framework where we search all CHIME/FRB Catalog-1 events that have low extragalactic dispersion measure (&lt;100 pc cm−3), with high Galactic latitude (∣b∣ &gt; 10°) and saved baseband data. We associate the selected FRBs with galaxies with moderate to high star formation rates located at redshifts between 0.027 and 0.071. We also search for possible multimessenger counterparts, including persistent compact radio and gravitational-wave sources, and find none. Utilizing the four FRB hosts from this study, along with the hosts of 14 published local Universe FRBs (z &lt; 0.1) with robust host association, we conduct an FRB host demographics analysis. We find all 18 local Universe FRB hosts in our sample to be spirals (or late-type galaxies), including the host of FRB 20220509G, which was previously reported to be elliptical. Using this observation, we scrutinize proposed FRB source formation channels and argue that core-collapse supernovae are likely the dominant channel to form FRB sources. Moreover, we infer no significant difference in the host properties of repeating and apparently nonrepeating FRBs in our local Universe FRB host sample. Finally, we find the burst rates of these four apparently nonrepeating FRBs to be consistent with those of the sample of localized repeating FRBs observed by CHIME/FRB. Therefore, we encourage further monitoring of these FRBs with more sensitive radio telescopes.

Keywords: Neutron stars, Spiral galaxies, Transient sources, Pulsars, Radio bursts, Supernovae, Radio transient sources
Magnetization Factors of Gamma-Ray Burst Jets Revealed by a Systematic Analysis of the Fermi Sample. The composition of gamma-ray burst (GRB) jets remained a mystery until recently. In practice, we usually characterize the magnetization of the GRB jets (σ 0) through the ratio between the Poynting flux and matter (baryonic) flux. With the increasing value of σ 0, magnetic energy gradually takes on a dominant role in the acceleration and energy dissipation of the jet, causing the proportion of thermal component in the prompt-emission spectrum of GRBs to gradually decrease or even be completely suppressed. In this work, we conducted an extensive analysis of the time-resolved spectrum for all Fermi GRBs with known redshift, and we diagnose σ 0 for each time bin by contrasting the thermal and nonthermal radiation components. Our results suggest that most GRB jets should contain a significant magnetic energy component, likely with magnetization factors σ 0 ≥ 10. The value of σ 0 seems to vary significantly within the same GRB. Future studies with more samples, especially those with lower-energy spectral information coverage, will further verify our results.

Keywords: Gamma-ray bursts