Sazuna/UAT_keywords huggingface dataset:
The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO). XI. Beam-corrected Gas Disk Sizes from Fitting <SUP>12</SUP>CO Moment Zero Maps. The inward drift of millimeter–centimeter sized pebbles in protoplanetary disks has become an important part of our current theories of planet formation and, more recently, planet composition as well. The gas-to-dust size ratio of protoplanetary disks can provide an important constraint on how pebbles have drifted inward, provided that observational effects, especially resolution, can be accounted for. Here we present a method for fitting beam-convolved models to integrated intensity maps of line emission using the astropy Python package and use it to fit 12CO moment zero maps of 10 Lupus and 10 Upper Scorpius protoplanetary disks from the ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO) Program, a sample of disks around M3-K6 stars that cover the ∼1–6 Myr of gas disk evolution. From the unconvolved best fit models, we measure the gas disk size ( RCO,90%model ), which we combine with the dust disk size ( Rdust,90%FRANK ) from continuum visibility fits from M. Vioque et al. to compute beam-corrected gas-to-dust size ratios. In our sample, we find gas-to-dust size ratios between ∼1 and ∼5.5, with a median value of  2.78‑0.32+0.37 . Contrary to models of dust evolution that predict an increasing size ratio with time, we find that the younger disks in Lupus have similar (or even larger) median ratios  (3.02‑0.33+0.33)  than the older disks in Upper Sco  (2.46‑0.38+0.53) . A possible explanation for this discrepancy is that pebble drift is halted in dust traps combined with truncation of the gas disk by external photoevaporation in Upper Sco, although survivorship bias could also play a role.

Keywords: Radio interferometry, Protoplanetary disks
The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO). XII. Extreme Millimeter Variability Detected in a Class II Disk. Variability of millimeter wavelength continuum emission from Class II protoplanetary disks is extremely rare, and when detected, it is usually interpreted as originating from nonthermal emission mechanisms that relate to the host star itself rather than its disk. During observations made as part of the AGE-PRO Large Program, significant variability in the brightness of the 2MASS J16202863-2442087 system was detected between individual executions. We report the observed properties of the variability detected at millimeter wavelengths and investigate potential driving mechanisms. To investigate the nature of the variability, we construct a light curve from the continuum observations and analyze images constructed from both flaring and quiescent emission. We characterize the dust disk around the star through analysis in the image and visibility plane, and carry out kinematic analysis of CO (2–1) emission from the gas disk. The continuum flux decays by a factor of 8 in less than an hour, and by a factor of 13 within 8 days. The peak brightness coincides with an expected brightness maximum extrapolated from the periodicity of previously observed optical variability. The flare is most likely the product of synchrotron emission in the close vicinity of the star. The nature of the millimeter flare closely resembles those detected in very close binary systems, and may be due to the interaction of magnetic fields in an as-yet undetected binary. Alternatively, if the central host is a single-star object, the flare may be due to the interaction of magnetic field loops at the stellar surface or a strong accretion burst.

Keywords: Low mass stars, Protoplanetary disks, Variable stars
Tidal Debris Candidates from the ω Centauri Accretion Event and Its Role Building Up the Milky Way Halo. We identify stellar tidal debris from the ω Centauri (ω Cen) system among field stars in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey via chemical tagging using a neural network trained on APOGEE observations of the ω Cen core. We find a total of 463 ω Cen debris candidates have a probability P &gt; 0.8 of sharing common patterns in their chemical abundances across a range of individual elements or element combinations, including [C+N], O, Mg, Al, Si, Ca, Ni, and Fe. Some debris candidates show prograde or retrograde disk-like kinematics, but most show kinematics consistent with the accreted halo, showing high radial actions, JR, values. We find that a sample of Gaia-Sausage-Enceladus (GES) members are chemically distinct from the ω Cen core, suggesting that ω Cen is associated with an independent merger event shaping the Milky Way halo. However, a connection between GSE and ω Cen cannot be ruled out. A detailed comparison with N-body simulations indicates that the ω Cen progenitor was a massive dwarf galaxy (≳108M⊙). The existence of a metal-poor high-α chemically homogeneous halo debris is also reported.

Keywords: Globular star clusters, Milky Way stellar halo
SRG/eROSITA No. 5: Discovery of Quasiperiodic Eruptions Every ∼3.7 days from a Galaxy at z &gt; 0.1. Quasiperiodic eruptions (QPEs) are repeating soft-X-ray bursts from the nuclei of galaxies, tantalizingly proposed to be extreme-mass-ratio inspirals. Here, we report the discovery of a new galaxy showing X-ray QPEs, the fifth found through a dedicated blind search of the Spectrum–Roentgen–Gamma/eROSITA all-sky survey data, hereafter named eRO-QPE5. Its QPE duration (tdur ∼ 0.6 days), recurrence time (trecur ∼ 3.7 days), integrated energy per eruption (∼3.4 × 1047 erg), and black hole mass ( MBH=2.9‑2.2+5.4×107M⊙ ) sit at the high end of the known population. Like other eROSITA or X-ray-discovered QPEs, no previous or concurrent optical–IR transient is found in archival photometric data sets, and the optical spectrum looks almost featureless. With a spectroscopic redshift of 0.1155, eRO-QPE5 is the most distant QPE source discovered to date. Given the number of recent discoveries, we test for possible correlations and confirm a connection between tdur and trecur, while we do not find any significant correlation involving either MBH or the QPE temperature. The slope of the tdur–trecur relation (1.14 ± 0.16) is roughly consistent with predictions from star–disk collision models, with a preference for those suggesting that QPEs are powered by stellar debris streams around the orbiter. Considering this and previous discoveries, eROSITA has proved extremely successful in finding many QPE candidates, given its grasp—namely, its its sensitivity and large field of view—and scanning capabilities over the full sky. We advocate the need for sensitive wide-area- and time-domain-oriented surveys from future-generation soft-X-ray missions.

Keywords: X-ray astronomy, Galaxy nuclei, X-ray transient sources, Time domain astronomy, Astrophysical black holes
Evaluation of Multiparameter Likelihoods through Iteration of Two-dimensional Slices. In this paper we introduce a method for resolving multiparameter likelihoods by fixing all parameter values but two. Evaluation of those two variables is followed by iteratively cycling through each of the parameters in turn until convergence. We test the technique on the temperature power spectrum of the lensed cosmic microwave background. That demonstration is particularly effective since one of the six parameters that define the power spectra, the power spectrum amplitude, As, nears linearity at small deviations, reducing computation to incrementation in one dimension, rather than over a two-dimensional (2D) grid. At each iterative step As is paired with a different parameter. The iterative process yields parameter values in agreement with those derived by Planck, and results are obtained within a few hundred calls for spectra. We further compute parameter values as a function of maximum multipole, ℓmax, spanning a range from ℓmax = 959 to 2500 and uncover bimodal behavior at the lower end of that range. In the general case, in which neither variable is linear, we identify moderating factors, such as changing both parameters per each iterative step, and thereby reducing the number of steps per iteration. Markov Chain Monte Carlo (MCMC) computation has been the dominant instrument for evaluating multiparameter functions. For applications with a quasi-linear variable such as, As, the 2D iterative method is orders of magnitude more efficient than MCMC.

Keywords: Cosmology, Computational methods, Cosmological parameters
Low-frequency, Wideband Study of an Active Repeater, FRB 20240114A, with the GMRT. We report the detection of 167 bursts from an active repeater, FRB 20240114A, using the upgraded Giant Metrewave Radio Telescope. The observations were carried out over a frequency range of 300–750 MHz, and on four different dates over a period of 6 months. Our analysis indicates that the fast radio bursts' emission properties are evolving, with both the median flux and emission rate of the bursts decreasing over time. The properties of the bursts also vary widely, with a wide range of intrinsic widths (0.246–39.364 ms), scattering timescales (0.004–28.289 ms), dispersion measures (524.07–533.56 pc cm‑3), and band occupancies (9–180 MHz). The distribution for the waiting time, twait, is bimodal, and follows a Weibull distribution, with a shape parameter k = 0.33; however, when the two distributions are fit separately, they follow a Weibull distribution with k = 0.63 for twait &lt; 1 s, and a log-normal distribution with a width of σ = 1.28 for twait &gt; 1 s. The isotropic energy distribution is seen to follow a log-normal distribution as well, with a width of σ = 0.83.

Keywords: Radio bursts, Radio astronomy, Transient sources, Radio transient sources
Dynamical Signatures of Trumpler 19: A Statistical and Photometric Perspective. We present a statistical approach to investigating the dynamical evolution of the old open cluster Trumpler 19. We identified 810 cluster members using an ensemble-based unsupervised machine learning method applied to Gaia Data Release 3 astrometric data. From the color–magnitude diagram, we identified 18 blue straggler stars (BSSs) in Trumpler 19. The mass function of the cluster shows a flatter slope, indicating strong mass segregation and advanced dynamical evolution. We fitted the radial surface density profile and found that the concentration parameter c &gt; 1, suggesting that the cluster has formed a clear core–halo structure as a result of dynamical evolution. We characterized the mass segregation among the cluster members as well as BSSs using the Minimum Spanning Trees method, indicating a significant central concentration. Additionally, the sedimentation level of the BSSs is measured as  Arh+=0.28±0.05 , further supporting radial segregation. To probe the BSS formation mechanisms, we estimated their fractional mass excess (Me), supporting binary mass transfer and mergers as the dominant channels. This is further supported by the presence of six variable BSSs. The dynamical evolution of the cluster is further assessed through its tidal interaction with the Galaxy. Trumpler 19 appears to be within the tidal regime, where strong Galactic tidal forces have a significant influence on the dynamical evolution. This indicates that the cluster may have undergone significant mass-loss processes, potentially leading to its eventual disruption, which is further supported by the orbit analysis of the cluster. We found that Trumpler 19 may have lost more than 95% of its initial mass due to dynamical evolution.

Keywords: Hertzsprung Russell diagram, Astronomy data analysis, Stellar dynamics, Stellar astronomy, Open star clusters, Blue straggler stars
Galaxy Cluster Constraints on Extensions of Modified Gravity. Modified Newtonian dynamics (MOND) has achieved notable success in explaining galaxy-scale phenomena and has made several unexpected, a priori predictions that align with observations. However, MOND struggles to account for the dynamics of galaxy groups and clusters without invoking additional unseen mass. To address these shortcomings, various extensions to MOND have been proposed. Among these, extended MOND (EMOND) and MOND combined with a form of dark matter (DM), denoted MOND + DM, offer distinct theoretical pathways. However, these models often introduce additional degrees of freedom or mathematical complexities that limit their falsifiability. In this work, we investigate the viability of EMOND and MOND + DM in the context of galaxy clusters using both observational and theoretical constraints. We use Chandra observations of cluster temperature profiles, alongside the assumption of hydrostatic equilibrium (HSE), to evaluate the predictive power of these extensions. Our analysis reveals that HSE imposes stringent constraints on MOND-based theories, highlighting points of failure in both the EMOND and MOND + DM paradigms. We derive new theoretical bounds that MOND + DM models must satisfy to remain consistent with observed mass and temperature distributions and show that these can be tested with X-ray observatories such as XRISM. For EMOND, we demonstrate significant inconsistencies between its predictions and observed cluster profiles, suggesting that EMOND is not a viable solution at the cluster scale. Our findings emphasize the need for further theoretical development within the MOND framework to reconcile its success at galaxy scales with its shortcomings in more massive systems.

Keywords: X-ray astronomy, Galaxy clusters, Modified Newtonian dynamics, Dark matter
Signatures of Electromagnetic and Sound Radiation Produced by Gravitational Waves in Core-collapse Supernovae. This paper presents the scenario that gravitational waves, generated in the core collapse of a pre-supernova star, can produce both electromagnetic radiation and sound radiation as gravitational waves propagate outward from the collapsing core. While the energy of this coproduced electromagnetic and sound radiation is orders of magnitude smaller than the initiating gravitational radiation, the power may be sufficient to reignite fusion outside the collapsing core. The nonequilibrium reignition of fusion, in roughly the same time frame as the strongest neutrino emissions, would change the configuration of the pre-supernova star and subsequently the ejecta and the evolution of the stellar expansion of the supernova remnant (SNR). Although the coproduced electromagnetic or sound radiation could not contribute directly to the supernova explosion, the associated nonequilibrium reignition of fusion would alter the state outside the core, leaving an observable signature in the ejecta of the SNR. The aim of this paper is to argue that including this hypothesized coproduced radiation in computational models of core-collapse supernovae would contribute to the evolution of the stellar expansion and consequently should be observable in the SNR, providing a confirmation of the conversion processes for gravitational radiation to electromagnetic and sound radiation.

Keywords: Supernova remnants, Magnetohydrodynamics, General relativity, Gravitational waves
Multiwavelength Analysis of GRB 250101A: From Gamma-Ray Prompt Emission to Optical Afterglow. The interaction between the relativistic jet and the circumburst medium produces a multiwavelength afterglow of a gamma-ray burst (GRBs). In this work, we present multiwavelength properties of GRB 250101A based on the observations of Swift, Fermi, and Mephisto. The spectral analysis of Swift/Swift Burst Alert Telescope (BAT) and Fermi/Gamma-ray Burst Monitor (GBM) reveals a soft prompt spectrum with a low-energy photon index of ‑1.18 and a peak energy of 33 keV, and the isotropic energy is 1.4 × 1052 erg. The prompt emission of GRB 250101A aligns with Type II GRBs in the Amati relation. Meanwhile, our analysis indicates that GRB 250101A is an X-ray-rich or X-ray-dominated GRB, with intrinsic properties suggesting that it is relatively softer than most classical GRBs. Optical observation with Mephisto, beginning 197 s post-trigger, shows a single power-law decay in uvgriz bands, with Fν,obs ∝ t‑0.76ν‑1.21. The observed spectral index significantly exceeds theoretical predictions under standard afterglow models, suggesting a color excess of ∼0.216 mag. However, combining X-ray and optical afterglow, we find that GRB 250101A is more likely a "normal burst" rather than an "optical-dark burst," and the dust extinction effect plays an important role in the optical blue bands. Furthermore, there is a structural change at T0 + 2924 s in the optical light curve, indicating a density drop of ∼50% in the interstellar medium at a distance of ∼0.13 pc. Our analysis shows that this GRB clearly shows some unique characteristics in its observed X-ray-rich prompt emission as well as the circumburst environment, implying a special progenitor.

Keywords: Optical astronomy, Light curves, Gamma-ray bursts
Role of Nonthermal Processes in the Quiescent and Active Millimeter Spectrum of a Young M Dwarf. Millimeter (mm) emission from F-M dwarfs (cool stars) primarily traces chromospheric activity, with thermal emission thought to dominate in quiescence. Despite the high chromospheric activity, the quiescent mm spectral fluence (mm-S(ν)) of young (&lt;1 Gyr) M dwarfs (dMs) remains largely unexplored. We present the quiescent mm-S(ν) of a young dM, AD Leo, observed around 94 GHz using the Northern Extended Millimetre Array. The observed quiescent mm-S(ν) exceeds the thermal flux density from a 1D chromospheric model, constrained by optical-UV spectroscopic data, by up to a factor of 7. This indicates a quasi-steady nonthermal emission powered by suprathermal electrons, unlike in old (&gt;1 Gyr) cool stars, whose quiescent mm-S(ν) generally agree with 1D thermal models. The mm-brightness temperature spectral index (αmm; TB(ν) ∼ν−αmm ) of AD Leo deviates by a factor of 3 from the αmm─Teff scaling law for old Sun-like stars (A. Mohan et al. 2022), while UV Ceti, an older M6V star, follows the trend. Also, we report a double-hump flare with second-scale variability in flux density and spectral index, and a frequency-rising nature with brightness increasing with frequency. The flare resembles certain solar events, but is unlike the second-scale events reported in dMs. The nonthermal flare humps suggest multiple injections of accelerated electrons. The mean flare luminosity (∼2─5 × 1015 erg s−1 Hz−1) and duration (18 ± 2 s) are comparable to flares reported in AU Mic and Proxima Cen, but 100─1000 times weaker than the minutes-long dM flares observed by the South Pole Telescope.

Keywords: Millimeter astronomy, Stellar chromospheres, Red dwarf flare stars, Stellar activity, Stellar coronae, Stellar atmospheres
The NGC 3109 Satellite System: The First Systematic Resolved Search for Dwarf Galaxies Around an SMC-mass Host. We report the results of the deepest search to date for dwarf galaxies around NGC 3109, a barred spiral galaxy with a mass similar to that of the Small Magellanic Cloud (SMC), using a semiautomated search method. Using the Dark Energy Camera, we survey a region covering a projected distance of ∼70 kpc of NGC 3109 (D = 1.3 Mpc, Rvir ∼ 90 kpc, M ∼ 108M*) as part of the MADCASH and DELVE-DEEP programs. We introduce a newly developed semiresolved search method, used alongside a resolved search, to identify crowded dwarf galaxies around NGC 3109. Using both approaches, we successfully recover the known satellites Antlia and Antlia B. We identified a promising candidate, which was later confirmed to be a background dwarf through deep follow-up observations. Our detection limits are well defined, with the sample ∼80% complete down to MV ∼ −8.0, and include detections of dwarf galaxies as faint as MV ∼ −6.0. This is the first comprehensive study of a satellite system through resolved stars around an SMC mass host. Our results show that NGC 3109 has more bright (MV ∼ −9.0) satellites than the mean predictions from cold dark matter models, but well within the host-to-host scatter. A larger sample of LMC/SMC-mass hosts is needed to test whether or not the observations are consistent with current model expectations.

Keywords: Dwarf galaxies
The Evolution of Substructure during Star Cluster Assembly. Star cluster formation and assembly occur inside filamentary and turbulent molecular clouds, which imprint both spatial and kinematic substructure on the young cluster. In this paper, we quantify the amount and evolution of this substructure in simulations of star cluster formation that include radiation magnetohydrodynamical evolution of the gas, coupled with detailed stellar dynamics, binary formation and evolution, and stellar feedback. We find that both spatial and kinematic substructure are present at early times. Both are erased as the cluster assembles through the formation of new stars as well as the merger of subclusters. Spatial substructure is erased over a timescale of approximately 2.5 times the initial freefall time of the cloud. Kinematic substructure persists for longer and is still present to the end of our simulations. We also explored our simulations for evidence of early dynamical mass segregation and concluded that the presence of a population of binary stars can accelerate and enhance the mass segregation process.

Keywords: Young massive clusters, Star forming regions, Young star clusters, Star formation, Star clusters
Spectral Evolution of GX 17+2 Using AstroSat and NICER Observations. We study the spectral evolution of the Z-track source GX 17+2 using AstroSat and NICER observations taken between 2016 and 2020. The AstroSat observations cover the period when the source is in the normal branch (NB) and the flaring branch (FB), while for the NICER ones the variability can be associated with the FB branch. The source spectra at different regions of the branches are well described by accretion disk emission, blackbody surface emission, and a thermal Comptonization component. In the NB, the total bolometric unabsorbed flux remains constant and the variation is due to changes in the Comptonization, disk fluxes. In particular, the inferred luminosity (LT) and accretion rate ( Ṁ ) remain constant, while there is significant variation in the inner disk radii and fraction of disk photons entering the corona, indicating changes in the geometry of the system. On the other hand, in the FB, there is significant variation in luminosity from ∼4.0 to ∼7.0 × 1038 erg s‑1. Despite this significant variation in luminosity and in the inner disk radii, the accretion efficiency, defined as  η=LT/Ṁc2 , remains nearly constant at ∼0.20 throughout the evolution of the source, as expected for a neutron star system.

Keywords: X-ray astronomy, Neutron stars, Stellar accretion disks, Stellar accretion, Low-mass x-ray binary stars