Sazuna/UAT_keywords huggingface dataset:
Mapping the Merging Zone of Late Infall in the AB Aur Planet-forming System. Late infall events challenge the traditional view that planet formation occurs without external influence. Here we present deep Atacama Large Millimeter/submillimeter Array 12CO J = 2─1 and SO JN = 56─45 observations toward AB Aurigae (AB Aur), a Class II disk system with strong signs of gravitational instability and ongoing planet formation. By applying Keplerian and anti-Keplerian masks, we separate disk-like and non-disk-like motions of 12CO, considering the two outputs as the "disk" and "exo-disk" (out of disk) emission components, respectively. The disk component of 12CO extends to ∼1600 au in radius and exhibits a stunningly rich architecture of global spiral structure. The exo-disk emission consists predominantly of three spiral structures—S1, S2, and S3—whose projections are cospatial with the disk. We successfully reproduce their trajectories with a ballistic accretion flow model, finding that S1 and S2 (both redshifted) are infalling toward the disk from in front, and S3 (blueshifted) is infalling from behind. Where the terminal ends of S1 and S2 become indistinguishable from the disk, we observe a brightness peak in SO emission 2.5× the azimuthal average of a background SO ring. This merging zone lies within a relatively confined region 15°─100∘ east of north, and between ∼150 and 300 au from the star, at scales relevant to where planet candidates have been previously identified. The AB Aur system provides a unified picture of late infall inducing replenishment of the disk, triggering gravitational instability, and modifying the conditions of forming planets.

Keywords: Gravitational instability, Radio interferometry, Protoplanetary disks, Planet formation
HCN and C<SUB>2</SUB>H<SUB>2</SUB> in the Atmosphere of a T8.5+T9 Brown Dwarf Binary. T-type brown dwarfs present an opportunity to explore atmospheres teeming with molecules such as H2O, CH4, and NH3, which exhibit a wealth of absorption features in the mid-infrared. With JWST, we can finally explore this chemistry in detail, including for the coldest brown dwarfs that were not yet discovered in the Spitzer era. This allows precise derivations of the molecular abundances, which in turn inform our understanding of vertical transport in these atmospheres and can provide clues about the formation of cold brown dwarfs and exoplanets. This study presents the first JWST/MRS mid-IR spectrum (R ∼ 1500–3000) of a T dwarf: the T8.5+T9 brown dwarf binary WISE J045853.90+643451.9. We fit the spectrum using a parameterized P–T profile and free molecular abundances (i.e., a retrieval analysis), treating the binary as unresolved. We find a good fit with a cloud-free atmosphere and identify H2O, CH4, and NH3 features. Moreover, we make the first detections of HCN and C2H2 (at 13.4σ and 9.5σ respectively) in any brown dwarf atmosphere. The detection of HCN suggests intense vertical mixing (Kzz ∼ 1011 cm2 s‑1), challenging previous literature derivations of Kzz values for T-type brown dwarfs. Even more surprising is the C2H2 detection, which cannot be explained with existing atmospheric models for isolated objects. This result challenges model assumptions about vertical mixing and/or our understanding of the C2H2 chemical network, or might hint towards more complex atmospheric processes such as magnetic fields driving aurorae or lightning driving ionization. These findings open a new frontier in studying carbon chemistry within brown dwarf atmospheres.

Keywords: Brown dwarfs, Stellar atmospheres, Extrasolar gaseous giant planets, Exoplanet atmospheres, T dwarfs
A Time-resolved High-resolution Spectroscopic Analysis of Ionized Calcium and Dynamical Processes in the Ultra-hot Jupiter HAT-P-70 b. We present the first transmission spectroscopy study of an exoplanet atmosphere with the high-resolution mode of the new Gemini High-resolution Optical SpecTrograph (GHOST) instrument at the Gemini South Observatory. We observed one transit of HAT-P-70 b—an ultra-hot Jupiter with an inflated radius—and made a new detection of the infrared Ca II triplet in its transmission spectrum. The depth of the strongest line implies that a substantial amount of Ca II extends to at least 47% above the bulk planetary radius. The triplet lines are blueshifted between ∼3 to 5 km s−1, indicative of strong dayside-to-nightside winds common on highly irradiated gas giants. Comparing the transmission spectrum with atmospheric models that incorporate non─local thermodynamic equilibrium effects suggests that the planetary mass is likely between 1 and 2 MJ, much lighter than the upper limit previously derived from radial velocity measurements. Importantly, thanks to the high signal-to-noise ratio achieved by GHOST/Gemini South, we are able to measure the temporal variation of these signals. Absorption depths and velocity offsets of the individual Ca II lines remain mostly consistent across the transit, except for the egress phases, where weaker absorption and stronger blueshifts are observed, highlighting the atmospheric processes within the trailing limb alone. Our study demonstrates the ability of GHOST to make time-resolved detections of individual spectral lines, providing valuable insights into the 3D nature of exoplanet atmospheres by probing different planetary longitudes as the tidally locked planet rotates during the transit.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Hot Jupiters, Exoplanet atmospheric dynamics, Transmission spectroscopy, Exoplanet atmospheres
Bridging Scales: Coupling the Galactic Nucleus to the Larger Cosmic Environment. Coupling black hole (BH) feeding and feedback involves interactions across vast spatial and temporal scales that are computationally challenging to model. Tracking gas inflows and outflows from kiloparsec scales to the event horizon for non-spinning BHs in the presence of strong magnetic fields, H. Cho et al. report strong suppression of accretion on horizon scales and low (2%) feedback efficiency. In this letter, we explore the impact of these findings for the supermassive BHs M87* and Sgr A*, using high-resolution, non-cosmological, magnetohydrodynamic simulations with the FIRE-2 model. Without feedback, we find rapid BH growth due to "cooling flows," with 2% feedback efficiency, while accretion is suppressed, the rates still remain higher than constraints from Event Horizon Telescope (EHT) data for M87* and Sgr A*. To match the EHT observations of M87*, an efficiency greater than 15% is required, suggesting the need to include enhanced feedback from BH spin. Similarly, a feedback efficiency of &gt;15% is needed for Sgr A* to match the observationally estimated star formation rate of ≲2M⊙ yr‑1. Even with 100% feedback efficiency, the simulation-predicted Sgr A* accretion rate remains higher than EHT-inferred levels on average, while only episodically matching it, suggesting that Sgr A* is currently in a temporary quiescent phase. Bridging accretion and feedback across scales, we conclude that higher feedback efficiencies, possibly due to nonzero BH spin, are necessary to suppress "cooling flows" and match both the observed accretion and star formation rates in M87* and Sgr A*.

Keywords: Accretion, Supermassive black holes, Schwarzschild black holes, Bondi accretion, Active galactic nuclei, Magnetohydrodynamical simulations
Identification of a Turnover in the Initial Mass Function of a Young Stellar Cluster Down to 0.5 M<SUB>J</SUB>. A successful theory of star formation should predict the number of objects as a function of their mass produced through star-forming events. Previous studies in star-forming regions and the solar neighborhood have identified a mass function increasing from the hydrogen-burning limit down to about 10 MJ. Theory predicts a limit to the fragmentation process, providing a natural turnover in the mass function down to the opacity limit of turbulent fragmentation, thought to be near 1–10 MJ. Programs to date have not been sensitive enough to probe the hypothesized opacity limit of fragmentation. We present the first identification of a turnover in the initial mass function below 12 MJ within NGC 2024, a young star-forming region. With JWST/NIRCam deep exposures across 0.7–5 μm, we identified several free-floating objects down to roughly 3 MJ with sensitivity to 0.5 MJ. We present evidence for a double power-law model increasing from about 60 MJ to roughly 12 MJ, consistent with previous studies, followed by a decrease down to 0.5 MJ. Our results support the predictions of star and brown dwarf formation theory, identifying the theoretical turnover in the mass function and suggesting the fundamental limit of turbulent fragmentation to be near 3 MJ.

Keywords: Brown dwarfs, Initial mass function, Star forming regions, Free floating planets, James Webb Space Telescope, Star formation, Infrared photometry
A Novel q-PED Method: Precise Physical Properties of a Merger-origin Binary Cepheid OGLE-LMC-CEP-1347. Recently, a double-lined binary classical Cepheid, OGLE-LMC-CEP-1347, was discovered with the orbital period (Porb = 59 days), 5 times shorter than that of any binary Cepheid known before. The expected mass of the Cepheid was below 3.5 M⊙, which, if confirmed, would also probe uncharted territory. The system configuration also pointed to the Cepheid being a merger. We present a novel method for determining precise physical parameters of binary Cepheids using both theory and observations. This q-PED method combines the measured mass ratio (q), pulsation (P), and evolutionary (E) models and the known distance (D), supplemented with multiband photometry. Applying it, we determined the mass of the Cepheid to be 3.41 ± 0.08 M⊙ and its radius to be 13.65 ± 0.27 R⊙, and the companion's mass to be 1.89 ± 0.04 M⊙ and radius to be 12.51 ± 0.62 R⊙. With the current configuration, the apparent evolutionary age difference of almost 1 Gyr between the components strongly favors the Cepheid merger origin scenario. If so, the actual age of the Cepheid would be 1.09 Gyr, on the edge of Population II stars, indicating that a significant fraction of Cepheids may be much older than typically assumed. We also applied our method to an eclipsing binary Cepheid OGLE-LMC-CEP-1812 with accurately determined physical parameters, obtaining a close agreement, which confirmed our method's reliability.

Keywords: Spectroscopic binary stars, Double-mode Cepheid variable stars, Cepheid variable stars
Isolated Black Holes as Potential PeVatrons and Ultrahigh-energy Gamma-Ray Sources. The origin of PeV cosmic rays (CRs) is a long-standing mystery, and ultrahigh-energy gamma-ray observations would play a crucial role in identifying it. Recently, LHAASO reported the discovery of "dark" gamma-ray sources that were detected above 100 TeV without any GeV–TeV gamma-ray counterparts. The origins of these dark gamma-ray sources are unknown. We propose isolated black holes (IBHs) wandering in molecular clouds as the origins of PeV CRs and LHAASO dark sources. An IBH accretes surrounding dense gas, which forms a magnetically arrested disk (MAD) around the IBH. Magnetic reconnection in the MAD can accelerate CR protons up to PeV energies. CR protons of GeV–TeV energies fall to the IBH, whereas CR protons at sub-PeV energies can escape from the MAD, providing PeV CRs into the interstellar medium. The sub-PeV CR protons interact with the surrounding molecular clouds, producing TeV–PeV gamma rays without emitting GeV–TeV gamma rays. This scenario can explain the dark sources detected by LHAASO. Taking into account the IBH and molecular cloud distributions in our Galaxy, we demonstrate that IBHs can provide a significant contribution to the PeV CRs observed on Earth. Future gamma-ray detectors in the southern sky and neutrino detectors would provide a concrete test to our scenario.

Keywords: Gamma-ray sources, Bondi accretion, Stellar mass black holes, Galactic cosmic rays, Astrophysical black holes
An Unexplained Origin for the Unusual Globular Cluster System in the Ultradiffuse Galaxy FCC 224. We study the quiescent ultradiffuse galaxy FCC 224 in the Fornax cluster using Hubble Space Telescope (HST) imaging, motivated by peculiar properties of its globular cluster (GC) system revealed in shallower imaging. The surface brightness fluctuation distance of FCC 224 measured from HST is 18.6 ± 2.7 Mpc, consistent with the Fornax cluster distance. We use Prospector to infer the stellar population from a combination of multiwavelength photometry (HST, ground-based, Wide-field Infrared Survey Explorer) and Keck Cosmic Web Imager spectroscopy. The galaxy has a mass-weighted age of ∼10 Gyr, metallicity [M/H] of ∼‑1.25 dex, and a very short formation e-folding time of τ ∼ 0.3 Gyr. Its 12 candidate GCs exhibit highly homogeneous g475 ‑ I814 colors, merely 0.04 mag bluer than the diffuse starlight, which supports a single-burst formation scenario for this galaxy. We confirm a top-heavy GC luminosity function, similar to the two dark matter deficient galaxies NGC 1052-DF2 and DF4. However, FCC 224 differs from those galaxies with relatively small GC sizes of ∼3 pc (∼35% smaller than typical for other dwarfs), and with radial mass segregation in its GC system. We are not yet able to identify a formation scenario to explain all of the GC properties in FCC 224. Follow-up measurements of the dark matter content in FCC 224 will be crucial because of the mix of similarities and differences among FCC 224, DF2, and DF4.

Keywords: Globular star clusters, Galaxy formation, Dwarf galaxies
Analytical Insights into Inaccurate Normal Vector Determination by Minimum Variance Analysis of Magnetic Fields. It has been widely recognized that the minimum variance analysis of magnetic fields (MVAB) often fails to accurately predict the direction normal to a discontinuity or current sheet, compared with multiple-spacecraft methods. However, there is a lack of analytical proof to support this claim. In this paper, the accuracy of MVAB is tested using an analytical tangential and rotational discontinuity, where the exact normal is known. To evaluate the performance of MVAB, random fluctuations generated from a normal distribution, with varying magnitudes of variance ( ), are imposed on the   component. Results show that the MVAB normal is misaligned with the exact normal when   is comparable to or larger than  . Here,   is the eigenvalue of the intermediate variance direction at   = 0. To achieve good accuracy, it is required that   &gt; 4.0,   &lt; 0.3, and   0.3, where   and   are the eigenvalues of the intermediate and minimum variance directions, and   and   are the variances of the magnetic field components along the normals, predicted from the MVAB with the constraint   = 0 and the cross-product method, respectively, within the MVAB interval. Notably,   and   closely match the designated  . These two variance ratios,   and  , are introduced for the first time as measures to assess the accuracy of MVAB. Two event studies are presented: one demonstrates an accurate MVAB normal, while the other shows an unreliable one. The accuracy of MVAB follows the criteria for the three variance ratios.

Keywords: Interplanetary discontinuities, Solar wind
Using Lithium and Beryllium to Study Structure and Evolution of Rotating Stars. The chemical composition of the Sun is still a highly controversial issue. No solar model has yet been able to simultaneously reproduce the solar lithium and beryllium abundances, along with helioseismic results, including the rotation profile. Lithium and beryllium are fragile elements that are highly sensitive to the physical conditions, as well as to transport and mixing processes within and below the convective zone (CZ). Uncovering the transport mechanisms responsible for the depletion of Li and Be in the Sun is crucial for using them as tools to understand stellar interiors and the associated transport and mixing processes. We constructed rotating solar models based on Magg's abundance scale, incorporating the effects of convective overshoot and magnetic fields. The rotating model exhibits superior sound speed and density profile and successfully reproduces the observed ratios r02 and r13. It also matches the seismically inferred CZ depth, surface helium abundance, and rotation profile, as well as the detected Li and Be abundances and neutrino fluxes within 1σ. The depletion of Li is dominated by convective overshoot and rotational mixing, while Be depletion is primarily driven by gravitational settling and rotational mixing. The presence of the tachocline accelerates Li depletion but slows down Be depletion. These distinct depletion mechanisms result in the surface abundances of Li and Be evolving differently over time.

Keywords: Solar interior, Helioseismology, Solar neutrinos, Solar abundances, Stellar rotation, Stellar evolution
Propagation of Waves in Weakly Ionized Two-fluid Plasmas. I. Small-amplitude Alfvénic Waves. The large abundance of electrically neutral particles has a remarkable impact on the dynamics of many astrophysical plasmas. Here, we use a two-fluid model that includes charge-neutral elastic collisions and Hall's current to study the propagation of magnetohydrodynamic (MHD) waves in weakly ionized plasmas. We derive the dispersion relation for small-amplitude incompressible transverse waves propagating along the background magnetic field. Then, we focus on the polarization relations fulfilled by the eigenmodes and their corresponding ratios of magnetic to kinetic energies, and we study their dependence on the relations between the oscillation, collision, and cyclotron frequencies. For low wave frequencies, the two components of the plasma are strongly coupled, the damping due to the charge-neutral interaction is weak, and the effect of Hall's term is negligible. However, as the wave frequency increases, phase shifts between the velocity of charges, the velocity of neutrals, and the magnetic field appear, leading to enhanced damping. The effect of collisions on the propagation of waves strongly depends on their polarization state, with the left-handed circularly polarized ion-cyclotron modes being more efficiently damped than the linearly polarized Alfvén waves and the right-handed circularly polarized whistler modes. Moreover, the equipartition relation between the magnetic energy and the kinetic energy of Alfvén waves does not hold in general when the collisional interaction and Hall's current are taken into account, with the magnetic energy usually dominating over the kinetic energy. This theoretical result extends previous findings from observational and numerical works about turbulence in astrophysical scenarios.

Keywords: Magnetohydrodynamics, Plasma physics, Plasma astrophysics, Solar physics, Alfven waves
Baryon Acoustic Oscillations Analyses with Density-split Statistics. Accurate modeling for the evolution of the baryon acoustic oscillation (BAO) is essential for using it as a standard ruler to probe cosmology. We explore the nonlinearity of the BAO in different environments using the density-split statistics and compare them to the case of the conventional two-point correlation function (2PCF). We detect density-dependent shifts for the position of the BAO with respect to its linear version using halos from N-body simulations. Around low/high-densities, the scale of the BAO expands/contracts due to nonlinear peculiar velocities. As the simulation evolves from redshift 1 to 0, the difference in the magnitude of the shifts between high- and low-dense regions increases from the subpercent to the percent level. The width of the BAO around high density regions increases as the universe evolves, similar to the known broadening of the BAO in the 2PCF due to nonlinear evolution. In contrast, the width is smaller and stable for low density regions. We discuss possible implications for the reconstructions of the BAO in light of our results.

Keywords: Baryon acoustic oscillations, N-body simulations, Large-scale structure of the universe
The Evolution of Hypervelocity Supernova Survivors and the Outcomes of Interacting Double White Dwarf Binaries. The recent prediction and discovery of hypervelocity supernova survivors has provided strong evidence that the "dynamically driven double-degenerate double-detonation" (D6) Type Ia supernova scenario occurs in nature. In this model, the accretion stream from the secondary white dwarf (WD) in a double WD binary strikes the primary WD violently enough to trigger a helium shell detonation, which in turn triggers a carbon/oxygen core detonation. If the secondary WD survives the primary's explosion, it will be flung away as a hypervelocity star. While previous work has shown that the hotter observed D6 stars can be broadly understood as secondaries whose outer layers have been heated by their primaries' explosions, the properties of the cooler D6 stars have proven difficult to reproduce. In this paper, we show that the cool D6 stars can be explained by the Kelvin─Helmholtz contraction of helium or carbon/oxygen WDs that underwent significant mass loss and core heating prior to and during the explosion of their WD companions. We find that the current population of known D6 candidates is consistent with ∼2% of Type Ia supernovae leaving behind a hypervelocity surviving companion. We also calculate the evolution of hot, low-mass oxygen/neon stars and find reasonable agreement with the properties of the LP 40─365 class of hypervelocity survivors, suggesting that these stars are the kicked remnants of near-Chandrasekhar-mass oxygen/neon WDs that were partially disrupted by oxygen deflagrations. We use these results as motivation for schematic diagrams showing speculative outcomes of interacting double WD binaries, including long-lived merger remnants, Type Ia supernovae, and several kinds of peculiar transients.

Keywords: White dwarf stars, Hypervelocity stars, Supernovae
The Ultraviolet Slopes of Early Universe Galaxies: The Impact of Bursty Star Formation, Dust, and Nebular Continuum Emission. JWST has enabled the detection of the ultraviolet (UV) continuum of galaxies at z &gt; 10, revealing extremely blue, potentially dust-free galaxies. However, interpreting UV spectra is complicated by the well-known degeneracy between stellar ages, dust reddening, and nebular continuum. The main goal of this paper is to develop a theoretical model for the relationship between galaxy UV slopes (β), bursty star formation histories, dust evolution, and nebular contributions using cosmological zoom-in simulations. We build a layered model where we simulate increasingly complex physics, including the impact of (i) unattenuated intrinsic stellar populations, (ii) reddened populations using a new on-the-fly evolving dust model, and (iii) populations including dust and nebular continuum. Unattenuated stellar populations with no nebular emission exhibit a diverse range of intrinsic UV slopes (β0 ≍ −3 → −2.2), with an inverse correlation between UV slope and specific star formation rate. When including dust, our model galaxies demonstrate a rapid rise in dust obscuration between z ≍ 8 and 10. This increase in dust mass is due to high grain─grain shattering rates, and enhanced growth per unit dust mass in very small grains, resulting in UV-detected galaxies at z ∼ 12 descending into Atacama Large Millimeter/submillimeter Array─detectable galaxies by z ∼ 6. The rapid rise in dust content at z ≍ 8─10 leads to a systematic reddening of the UV slopes during this redshift range. Nebular continuum further reddens UV slopes by a median ∆βneb ≍ 0.2─0.4, though notably the highest-redshift galaxies (z ≍ 12) are insufficiently blue compared to observations; this may imply an evolving escape fraction from H II regions with redshift.

Keywords: Interstellar dust, Starburst galaxies, Galaxy formation, Astrophysical dust processes, James Webb Space Telescope, Interstellar dust processes, High-redshift galaxies, Galaxies