Sazuna/UAT_keywords huggingface dataset:
The Role of Magnetospheric Rebound in Breaking Resonant Chains of Super-Earths and Mini-Neptunes. Stellar magnetic fields are thought to truncate the inner regions of protoplanetary disks around T Tauri stars, creating a magnetospheric cavity near the star. As the disk evolves and disperses, the truncation radius is expected to move outward as the balance between magnetic and viscous forces shifts. Planets migrating inward can become trapped near the inner edge, but as the edge itself moves outward, the evolving disk torques can drive planets to migrate outward as well. We employ N-body simulations to assess the influence of magnetospheric cavity expansion on the dynamical evolution and orbital architectures of compact resonant chains of super-Earths and mini-Neptunes. Our results show that rebound-driven expansion of the disk's inner edge plays a pivotal role in destabilizing resonant chains by spreading planetary systems outward, thereby triggering early dynamical instabilities and giant impacts. Despite this dynamical evolution, key observable properties of close-in planetary systems—such as the distribution of orbital period ratio, the intrasystem similarity in planet sizes ("radius uniformity"), and the bimodal distribution of planet radii known as the "radius valley"—remain largely consistent with those of systems formed without the rebound effect, in which the inner edge of the disk remains fixed. Thus, the primary consequence of the rebound appears to be the early disruption of resonant chains, rather than any significant alteration to the statistical properties of the resulting super-Earth and mini-Neptune populations.

Keywords: Exoplanet dynamics, Planetary-disk interactions, Super Earths, Orbital resonances, Mini Neptunes, Dynamical evolution
EELG1002: A Record-breaking [O III]+Hβ EW ∼ 3700 Å Galaxy at z ∼ 0.8—Analog of Early Galaxies?. Extreme emission line galaxies (EELGs) are powerful low-z analogs of high-z galaxies that can provide us valuable insights of early Universe conditions. We present a detailed analysis of EELG1002: a z = 0.8275 EELG identified within archival Gemini/GMOS spectroscopy as part of the ongoing COSMOS Spectroscopic Archive. We find EELG1002 is a low-mass (∼108 M⊙), compact (∼530 pc), bursty star-forming galaxy with a ∼15─35 Myr mass doubling timescale. EELG1002 has record-breaking rest-frame [O III]+Hβ EW ∼3100─3700 Å; ∼32─36× higher than typical z ∼ 0.8 [O III] emitters with similar stellar mass; and higher than typical z &gt; 5 galaxies. We find no clear evidence of an active galactic nucleus suggesting the emission lines are star formation driven. EELG1002 is chemically unevolved (direct Te;  12+log10(O/H)∼7.52  consistent with z &gt; 5 galaxies at fixed stellar mass) and may be undergoing a first intense, bursty star formation phase analogous to conditions expected of galaxies in the early Universe. We find evidence for a highly energetic interstellar medium ([O III]/[O II] ∼ 9) and hard ionizing radiation field (elevated [Ne III]/[O II] at fixed [O III]/[O II]). Coupled with its compact, metal-poor, and actively star-forming nature, EELG1002 is found to efficiently produce ionizing photons (ξion ∼ 1025.74 erg−1 Hz) and may have ∼10%─20% Lyman Continuum (LyC) escape suggesting such sources may be important analogs of galaxies responsible for reionization. We find a dynamical mass of ∼109 M⊙ suggesting copious amounts of gas to support intense star formation as also suggested by identified Illustris-TNG analogs. EELG1002 may be an ideal low-z laboratory of galaxies in the early Universe and demonstrates how archival data sets can support high-z science and next-generation surveys planned with Euclid and Roman.

Keywords: Starburst galaxies, Star formation, Galaxy evolution, Interstellar medium, High-redshift galaxies
Confirming Near- to Mid-infrared Photometrically Identified Obscured AGNs in the JWST Era. We evaluate the underlying assumptions for the identification of active galactic nuclei (AGNs) through near- and mid-infrared photometry and spectral energy distribution (SED) fitting out to z ∼ 3. For massive galaxies, log(M) ≥ 9.5, our high-resolution spectra of the rest optical range generally confirm the results of SED fitting, which relies primarily on excesses above the stellar emission between 1 and 6 μm to identify AGN. However, the method is undermined if the redshift used for the SED fitting is incorrect. Low-mass galaxies, log(M) &lt; 9.5, can contain relatively warm dust that emits in the 4─6 μm range. We show that the potential contamination of AGN samples by purely star-forming low-mass galaxies can be avoided by the use of the infrared properties of Haro 11 as a limiting star-forming SED template. However, relatively few star-forming galaxies emit as strongly in the 3─6 μm range as this template, so this could result in missing some obscured AGNs to avoid a minor contamination. Including the behavior of the galaxies at rest λ ∼ 13.5 μm can mitigate this problem and yield more complete samples of bona fide AGN. JWST/MIRI supports this approach out to z ≲ 0.6.

Keywords: James Webb Space Telescope, Active galactic nuclei
Probing the Dark Matter Halos of External Galaxies with Stellar Streams. Stellar streams have proven to be powerful tools for measuring the Milky Way's gravitational potential and hence its dark matter (DM) halo. In the coming years, the Vera Rubin Observatory, Euclid, ARRAKIHS, and the Nancy Grace Roman Space Telescope will uncover a plethora of streams around external galaxies. Although great in number, observations of these distant streams will often be limited to only the on-sky position of the stream. In this work, we explore how well we will be able to measure the DM halos of these galaxies by fitting simplified mock streams with a variety of intrinsic and orbital properties in a range of data availability scenarios. We find that results vary based on the interplay between the amount of information provided by a stream's intrinsic properties versus that of the observational uncertainties, as well as on the form of potential assumed. In general, we find streams with multiple wraps around their host galaxy can constrain the overall radial profile and scale radius of the potential without radial velocities. In many other cases, a single radial velocity measurement often provides a significant boost to constraining power for the radial profile, scale radius, and enclosed mass of the DM halo. Given the wealth of data expected soon, this suggests that we will be able to measure the DM halos of a statistically significant sample of galaxies with stellar streams in the coming years.

Keywords: Galaxy stellar halos, Galaxy dark matter halos, Stellar streams
XL-Calibur Polarimetry of Cyg X-1 Further Constrains the Origin of Its Hard-state X-Ray Emission. The balloon-borne hard X-ray polarimetry mission XL-Calibur observed the black hole X-ray binary (BHXRB) Cygnus X-1 (Cyg X-1) during its nearly 6 day long-duration balloon flight from Sweden to Canada in 2024 July. The XL-Calibur observations allowed us to derive the most precise constraints to date of the polarization degree (PD) and polarization angle (PA) of the hard X-ray emission from a BHXRB. XL-Calibur observed Cyg X-1 in the hard state and measured a ∼19─64 keV PD of ( 5.0−3.0+2.7 )% (equivalent to an upper limit, at the 99% level, of 11.1%) at a PA of −28° ± 17°, with an 8.7% chance probability of detecting larger PDs than the one observed, given an unpolarized signal. The XL-Calibur results are thus comparable to the 2─8 keV PD and PA found by Imaging X-ray Polarimetry Explorer (IXPE), with a similar agreement between the hard X-ray PA and the radio jet direction. We also discuss the implications of our polarization measurements in the context of models describing the origin of the broadband X-ray and γ-ray emission, to which XL-Calibur provides independent constraints on any proposed emission modeling.

Keywords: X-ray astronomy, Black hole physics, Black holes, High energy astrophysics, High mass x-ray binary stars, Stellar mass black holes, X-ray telescopes, High altitude balloons, X-ray sources
Estimating Cluster Masses: A Comparative Study between Machine Learning and Maximum Likelihood. We compare an autoencoder convolutional neural network (AE-CNN) with conventional maximum-likelihood estimation (MLE) for inferring cluster virial masses, Mv, directly from the galaxy distribution around clusters, without identifying members or interlopers. The AE-CNN is trained on mock galaxy catalogues, whereas the MLE assumes that clusters of similar mass share the same phase-space galaxy profile. Conceptually, the MLE returns an unbiased estimate of  logMv  at fixed true mass, whereas the AE-CNN approximates the posterior mean, so the true  logMv  is unbiased at fixed estimate. Using MultiDark Planck 2 mock clusters with redshift space number density as input, the AE-CNN attains an rms scatter of 0.10 dex between predicted and true  logMv , compared with 0.16 dex for the MLE. With inputs based on mean peculiar velocities, binned in redshift space or observed distance, the AE-CNN achieves scatters of 0.12 and 0.16 dex, respectively, despite strong inhomogeneous Malmquist bias.

Keywords: Galaxy clusters
After 54 Yr of Bar Instability Studies: A Fresh Surprise. The well-known bar instability of rotationally supported disk galaxy models has been studied extensively since its first discovery over half a century ago. We were therefore very surprised to find cases of disks embedded in rigid halos, which on the basis of widely cited criteria should be unstable, that appeared to be robustly stable. Here we show that the unstable bar mode in such simulations was being suppressed by changes to the disk caused by other instabilities having higher angular symmetry that were the first to saturate. Although this may seem like a promising solution to the long-standing puzzle presented by the apparent stability of real disk galaxies, we also show that instability is restored in the same models when the rigid halo is replaced by a live population of particles, where the usual stability conditions apply. Our study has been confined to a narrow range of models, and we cannot therefore exclude the possibility that mode interference may be able to prevent bar formation in other models having live halos.

Keywords: Spiral galaxies
Little Red Dots are Nurseries of Massive Black Holes. The James Webb Space Telescope has revealed a previously unknown population of compact, red galaxies at z ∼ 5, known as "little red dots" (LRDs). With effective radii of ∼100 pc and stellar masses of 109─1011 M⊙, a purely stellar interpretation implies extreme central densities, ρ⋆ ∼ 104─105 M⊙ pc−3 and in some cases up to ∼109 M⊙ pc−3, far exceeding those of globular clusters. At such densities, the dynamical friction time for 10 M⊙ stars in the central 0.1 pc is &lt;0.1 Myr, driving rapid mass segregation. We investigate the dynamical consequences of such an environment using (i) a Fokker─Planck analysis of long-term core evolution, (ii) an analytical model for the collisional growth of a very massive star (VMS), and (iii) direct N-body simulations. All approaches show that runaway collisions produce a VMS with mass 9 × 103 &lt; MVMS [M⊙] &lt; 5 × 104 within &lt;1 Myr. Once the supply of massive stars is depleted, the VMS contracts on a ∼8000 yr Kelvin─Helmholtz timescale and undergoes a general relativistic collapse, leaving a massive black hole of mass M∙ ∼ 104 M⊙. We conclude that LRDs are natural nurseries for the formation of heavy black hole seeds via stellar-dynamical processes. This pathway produces seed number densities that far exceed those expected from direct collapse models and, owing to the dense residual stellar core, can sustain high rates of tidal disruption events.

Keywords: Intermediate-mass black holes, Early universe, Galaxy dynamics, Galaxy evolution, N-body simulations, Galaxies
X-Ray Polarimetry in the Low-statistics Regime Using the Bayesian Approach Reveals Polarization Angle Variations. X-ray polarimetry of the accreting compact object has revealed fast time variations in the polarization angle (PA), suggesting that the geometry and/or optical depth of the Comptonization region is changing rapidly. This prompts investigations into how fast such variability can be. Conventionally, the data are often binned to examine the time variability such that the measurement in each bin is above the minimum detectable polarization (MDP). Here we demonstrate that this is unnecessary, and even below the MDP, one can infer the posterior distribution of PA reliably using the Bayesian approach and still be able to place useful constraints on the physics in many cases due to small relative uncertainties on the PA (e.g., ∆PA ≍ 10°−30° compared with a dynamical range of 180°). With this approach, we discovered that the PA variation in one of the Imaging X-ray Polarimetry Explorer (IXPE) observations of GX 13+1 is not following a linear rotation mode as suggested previously. Instead, the PA swings between two discrete angles, suggesting that there are two emitting components, e.g., the boundary layer and the spreading layer, competing with each other. In XTE J1701−462, we confirmed previous results for a variable PA in the normal branch and, furthermore, revealed that the variation timescale could be as short as 1.5 hr. During the IXPE observation of Sco X-1, a hint is found for the PA in the highest flux level to be different from the average but consistent with previous measurement results with PolarLight and OSO-8.

Keywords: Accretion, X-ray transient sources, Bayesian statistics, Polarimetry
Photometric Analysis of 30 Contact Binaries in M31. M31, as the largest galaxy in the Local Group, is of significant importance for the study of stellar formation and evolution. Based on the data of 5859 targets observed in M31 by Gu et al., we selected 30 contact binaries by visual inspection for further study. Using the PHysics Of Eclipsing BinariEs software and employing Bayesian optimization and Markov Chain Monte Carlo sampling, we determined the physical parameters of these 30 systems. The results show that 10 systems exhibit the O'Connell effect, which is well explained by introducing a dark spot on the primary star. A total of 11 systems have mass ratios below 0.15, classifying them as extremely low mass ratio contact binaries, making them promising candidates for binary mergers. Meanwhile, 6 systems have primary star temperatures exceeding 10,000 K, classifying them as early-type contact binaries. The absolute physical parameters reveal that 2 contact binary systems contain massive stellar components, which may eventually evolve into compact binary star systems. To compare the effects of different galactic environments on the evolution of contact binaries, we constructed evolutionary diagrams for these 30 targets and for contact binaries in the Milky Way. The results show that, at the same mass, our targets have larger radii, higher luminosities, and lower orbital angular momenta than contact binaries in the Milky Way, indicating that they are at more advanced evolutionary stages. This may be attributed to the higher metallicity in M31 compared to the Milky Way.

Keywords: Fundamental parameters of stars, Eclipsing binary stars, Andromeda Galaxy, Contact binary stars, Stellar evolution
Revising the Giant Planet Mass─Metallicity Relation: Deciphering the Formation Sequence of Giant Planets. The rate at which giant planets accumulate solids and gas is a critical component of planet formation models, yet it is extremely challenging to predict from first principles. Characterizing the heavy element (everything other than hydrogen and helium) content of giant planets provides important clues about their provenance. Using thermal evolution models with an updated H─He equation of state and atmospheric boundary conditions that vary with envelope metallicity, we quantify the bulk heavy element content of 147 warm (&lt;1000 K) giant planets with well-measured masses and radii, more than tripling the sample size studied in D. P. Thorngren et al. These measurements reveal that the population's heavy element mass follows the relation  MZ=Mcore+fZ(Mp−Mcore) , with  Mcore=14.7−1.6+1.8  M⊕, fZ = 0.09 ± 0.01, and an astrophysical scatter of 0.66 ± 0.08 × MZ. The classical core-accretion scenario (Zp = 1 at 10 M⊕ and Zp = 0.5 at 20 M⊕) is inconsistent with the population. At low planet masses (≪150 M⊕),  MZ∼Mcore  and as a result, Zp = MZ/Mp declines linearly with Mp. However, bulk metallicity does not continue to decline with planet mass and instead flattens out at fZ ∼ 0.09 (∼7 × solar metallicity). When normalized by stellar metallicity, Zp/Z⋆ flattens out at 3.3 ± 0.5 at high planet masses. This explicitly shows that giant planets continue to accrete material enriched in heavy elements during the gas accretion phase.

Keywords: Exoplanet evolution, Metallicity, Extrasolar gaseous giant planets, Planet formation
Investigating Non-LTE Abundances of Neodymium in Metal-poor FGK Stars. The dominant site(s) of the r-process are a subject of current debate. Ejecta from r-process-enrichment events like kilonovae are difficult to directly measure, so we must instead probe abundances in metal-poor stars to constrain r-process models. This requires state-of-the-art non-LTE (NLTE) modeling, as LTE is a poor approximation for the low-opacity atmospheres of metal-poor giants. Neodymium (Nd) is a prominent r-process element detected in both near-infrared kilonova spectra and the spectra of metal-poor stars, so precise Nd stellar abundances are particularly needed to model kilonovae and constrain r-process sites. We thus constructed an Nd I/Nd II model atom to compute NLTE abundances in FGK metal-poor stars. We obtain A(Nd)⊙ = 1.44 ± 0.05, in agreement with the meteoritic value, when calibrating the model atom with a Drawin hydrogen collision factor of SH = 0.1. For a sample of metal-poor r-process-enhanced stars with observed optical and near-infrared Nd II lines, we find NLTE Nd corrections in the range −0.3 to 0.3 dex. Optical and UV lines have positive NLTE corrections, whereas H-band lines have negative corrections. Additionally, we compute a large grid of NLTE corrections for 122 Nd II spectral lines ranging from the UV to the H band, for stellar parameters of typical metal-poor FGK dwarfs and giants with −3 ≤ [Fe/H] ≤ −1 and −2 ≤ A(Nd) ≤ 2. Within this grid, we find NLTE corrections ranging from −0.3 to +0.5 dex. Deviations from LTE are found to be strongest for blue lines with low excitation potentials in the most metal-poor giants.

Keywords: Stellar abundances, K stars, Galactic archaeology, Atomic data, Chemical abundances, G stars, F stars, Stellar atmospheres
Dynamically Controlled Transport of GeV Cosmic Rays in Diverse Galactic Environments. We study transport of GeV cosmic rays (CRs) in a set of high-resolution TIGRESS magnetohydrodynamic simulations of the star-forming interstellar medium (ISM). Our models of local disk patches sample a wide range of gas surface densities, gravitational potentials, and star formation rates (SFRs), and include a spiral arm simulation. Our approach incorporates CR advection by the background gas, streaming along the magnetic field limited by the local ion Alfvén speed, and diffusion relative to the Alfvén wave frame, with the diffusion coefficient set by the balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We find that dynamical transport mechanisms (streaming and advection) are almost solely responsible for GeV CR transport in the extraplanar regions of galaxies, while diffusion along the magnetic field dominates within the primarily neutral ISM of galactic disks. We develop a simple 1D predictive model for the CR pressure Pc, dependent only on injected CR flux and gas parameters. We demonstrate that the CR transport efficiency increases with increasing SFR, and provide a fit for the CR feedback yield ϒc ≡ Pc/ΣSFR as a function of ΣSFR, the SFR surface density. We analyze lateral CR transport within the galactic disk, showing that CRs propagate away from feedback regions in spiral arms into interarm regions by a combination of gas advection and field-aligned transport. Lastly, we develop an empirical subgrid model for the CR scattering rate that captures the impacts of the multiphase ISM on CR transport without the numerical burden of full simulations.

Keywords: Galactic cosmic rays, Interstellar medium, Magnetohydrodynamical simulations
Quasiperiodic Oscillations in a Highly Magnetized Ultracompact X-Ray Binary 4U 1626-67. We report the detection of mHz quasiperiodic oscillations (QPOs) in four Nuclear Spectroscopic Telescope Array observations of 4U 1626─67 during its recent spin-down episode. By using a novel method based on the Hilbert─Huang transform, we present the first QPO-phase-resolved timing and spectral analysis of accreting X-ray pulsars in low-mass X-ray binaries. Broadband QPO waveforms have been reconstructed and exhibit approximately sinusoidal shapes, with fractional amplitudes that vary with energy. In addition, we find that spin pulse profiles exhibit stable shapes between different QPO phases with different instantaneous fluxes, while the fractional rms is distinct for different observations. In this source, both QPO-phase-resolved and averaged spectra can be modeled with a negative and positive power-law exponential model, and their spectral evolutions show a similar trend, suggesting that the QPO modulation is caused by accretion rate variability instead of a geometric obscuration. These results provide new constraints on accretion physics in strongly magnetized neutron stars and the underlying mechanisms of QPOs.

Keywords: Accretion, X-ray astronomy, X-ray binary stars, Binary pulsars
Kink-driven Magnetic Reconnection as the Driver of a Laboratory Plasma Eruption. We report that kink-driven magnetic reconnection serves as an eruption mechanism for a laboratory jet. A flux rope is formed and becomes a filamentary jet. The jet becomes unstable due to kink instability when the Kruskal─Shafranov instability criterion is met, leading to an inflow of reconnecting fields. As a result of kink-driven magnetic reconnection, ions are substantially energized, resulting in enhanced acceleration of the jet. Based on the evidence observed from this laboratory experiment, we propose that kink-driven magnetic reconnection might act as a key driver for laboratory jet eruptions and might be relevant to solar jets associated with kink instability and magnetic reconnection.

Keywords: Solar magnetic reconnection
Dynamical Properties of Oscillating, Viscous, Transonic Accretion Disks around Black Holes. We investigate the time evolution of sub-Keplerian transonic accretion flow onto a nonrotating black hole using axisymmetric viscous hydrodynamic simulations. We simulate the accretion flow using boundary values from semianalytical analysis and set up three different models. Two of the models do not predict accretion shocks from the semianalytic analysis, while one of them does. We also consider radiative cooling along with viscosity in the simulation. Our two-dimensional simulation deviated from the one-dimensional semianalytical solution and admitted shocks in all three models. Viscous dissipation tends to push the shock front outward, and radiative cooling will push it in. Additionally, gravity is attractive. Depending on the competing strengths of all three processes, it may trigger shock oscillation. Different rates of angular-momentum transport in various layers may trigger eddies, which will enhance the shock oscillation. We show that any simple power law cannot approximate these solutions. We find that hot and higher angular-momentum flow requires higher viscosity to produce oscillatory shocks. From the temporal variation of the luminosity, shock oscillations generate quasiperiodic oscillations in the range of sub-Hertz to a few Hertz frequencies if a 10 M⊙ black hole is assumed.

Keywords: Accretion, Black hole physics, Shocks, Hydrodynamics