Sazuna/UAT_keywords huggingface dataset:
Gravitational Wave Decoupling in Retrograde Circumbinary Disks. We present a study of the late-time interaction between supermassive black hole binaries and retrograde circumbinary disks during the period of gravitational wave-driven inspiral. While mergers in prograde disks have received extensive study, retrograde disks offer distinct dynamics that could promote mergers and produce unique observational signatures. Through 2D numerical hydrodynamical simulations, we explore the process of binary-disk decoupling, where the binary's orbital decay rate is faster than the disk's viscous response rate. We find the point of decoupling to be comparable in prograde and retrograde disks, suggesting that any associated electromagnetic (EM) signatures will be produced at comparable times preceding the merger. However, we find smaller central cavities for retrograde disks, likely leading to higher-frequency EM emissions and shorter postmerger rebrightening timescales compared to their prograde counterparts. Retrograde disks form intrabinary bridges, which are prone to instabilities when the viscosity is low. These instabilities manifest as quasiperiodic flares in the accretion rate, which may produce distinctive EM signatures for retrograde disks.

Keywords: Accretion, Supermassive black holes, Gravitational waves, Hydrodynamical simulations
The 6 yr Radio Light Curve of the Tidal Disruption Event AT2019azh. Analysis of radio emission from tidal disruption events (TDEs) allows for detailed constraints on the properties of ejected outflows and the host environment surrounding the black hole. However, the late-time radio behaviour of TDEs is not well studied due to a lack of observations. In this work we present long-term radio monitoring observations of the TDE AT2019azh spanning 1167─2159 days postdisruption. We fit a physically motivated synchrotron model to the radio spectra at each epoch and model the decay of the light curve under the assumption that the outflow transitions into the nonrelativistic Sedov─Taylor regime at late times. Through this modelling we obtain strong constraints on the density profile of the circumnuclear medium, finding an unusually flat density profile proportional to  r0.24−0.15+0.11 . Overall we find that unlike some TDEs, AT2019azh does not show late time rebrightening up to 6 yr postdisruption. The Sedov─Taylor light-curve decay model provides a good fit to the data, motivating the assumption that the outflow was produced by a single ejection of material close to the time of stellar disruption. From forward modelling the evolution of the radio light-curve decay we predict that the radio afterglow from AT2019azh should be detectable for decades at its current rate of evolution.

Keywords: Radio continuum emission, Black hole physics, Tidal disruption, Supermassive black holes
Investigating the Sightline of a Highly Scattered Fast Radio Burst through a Cosmic Sheet Structure in the Local Universe. Fast radio bursts (FRBs) are unique probes of extragalactic ionized baryonic structure as each signal, through its burst properties, holds information about the ionized matter it encounters along its sightline. FRB 20200723B is a burst with a scattering timescale of τ400 MHz &gt; 1 s at 400 MHz and a dispersion measure of DM ∼244 pc cm−3. Observed across the entire Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB frequency band, it is the single-component burst with the largest scattering timescale yet observed by CHIME/FRB. The combination of its high scattering timescale and relatively low dispersion measure present an uncommon opportunity to use FRB 20200723B to explore the properties of the cosmic web it traversed. With an ∼arcminute-scale localization region, we find the most likely host galaxy is NGC 4602 (with PATH probability P(O∣x) = 0.985), which resides ∼30 Mpc away within a cosmic sheet structure on the outskirts of the Virgo Cluster. We place an upper limit on the average free electron density of this cosmic structure of  &lt;ne&gt;&lt;4.6−2.0+9.6×10−5  cm−3, broadly consistent with expectations from cosmological simulations. We investigate whether the source of scattering lies within the same galaxy as the FRB, or at a farther distance from an intervening structure along the line of sight. Comparing with Milky Way pulsar observations, we suggest the scattering may originate from within the host galaxy of FRB 20200723B.

Keywords: Radio bursts, Intergalactic filaments, Radio astronomy, Radio transient sources
Asking Fast Radio Bursts for More than Reionization History. We propose different estimators to probe the intergalactic medium (IGM) during the epoch of reionization (EoR) using the dispersion measure (DM) of the fast radio bursts. We consider three different reionization histories, which we can distinguish with a total of ≲1000 DM measurements during EoR if their redshifts are known. We note that the redshift derivatives of DM are also directly sensitive to the reionization history. The major point of this work is to explore the variance in the DM measurements and the information encoded in them. We find that the all-sky average  DM̄(z)  gets biased from the line-of-sight fluctuations in the DM measurements introduced by the ionization of the IGM during EoR. We find that the ratio  σDM/DM̄  depends directly on the ionization bubble sizes as well as the reionization history. On the other hand, we also find that angular variance (coined as structure function) of DM encodes the information about the duration of reionization and the typical bubble sizes as well. We establish the usefulness of variances in DM using toy models of reionization and later verify it with the realistic reionization simulations.

Keywords: Large-scale structure of the universe, Radio bursts, Intergalactic medium, Reionization, Radio transient sources
JWST Photometry of Globular Cluster Populations in MACS0417.5−1154. Deep JWST imaging of the massive galaxy cluster MACS0417.5−1154, at redshift z = 0.443, reveals a huge population of globular clusters (GCs) and ultracompact dwarfs (UCDs) primarily distributed around its single central giant brightest cluster galaxy (BCG). We present Near-Infrared Camera (NIRCam)/short-wavelength channel photometry of the GC system in four bands (F090W, F115W, F150W, and F200W). The spatial distribution of the system matches well in radial and ellipticity profile with the high elongation (b/a ≃ 0.5) of the BCG halo light. The total GC population within MACS0417 is estimated to be near 1.5 × 105, similar to the systems in Abell 2744, Coma, and other galaxy clusters with comparable masses. With similar results for GC photometry in hand from other lensing clusters at a range of redshifts, it is now possible to trace, on purely observational grounds, the luminosity evolution of GC systems over many gigayears of lookback time, as seen through their color─magnitude diagrams. We show this sequence for five systems reaching lookback times of more than 7 Gyr. A systematic change in the GC/UCD sequence with lookback time is clearly visible, near what is expected for age-fading of a simple stellar population with time. Lastly, we evaluate the effectiveness of the various JWST NIRCam filters for broadband photometry of GC systems as a function of redshift as an aid to planning further studies.

Keywords: Globular star clusters, Brightest cluster galaxies, Rich galaxy clusters
Tensile Strength of Dust, Pebbles, and Planetesimals: A Simple Mathematical Formula from Aggregates to Monoliths Based on an Extension of an Elastic Theory for Particle Assemblies to Molecular Networks. The tensile strength of solid particles is the key parameter that controls not only the formation of planetesimals in protoplanetary disks but also outburst and splitting of comets and rotational bursting of asteroids in planetary systems. It is, therefore, highly desirable to find a mathematical model that properly provides the tensile strength of porous and nonporous solid particles as functions of their known material and structural properties. We demonstrate the applicability of a rigorous theory for the tensile strength of particle assemblies to both porous and nonporous solid particles, by treating the particles as solid media with cross-linked networks of molecules. The practicability of the analytical function for the tensile strength of solid particles provided in this paper is proven to a large extent by the reproduction of laboratory experiments and molecular dynamics simulations of water ice, silica, and carbon specimens, irrespective of their crystallinities. While there is still room for improvement, specifically, on the choice of material-dependent parameters, we may conclude that our formulation is a major step forward in the inference of small-bodies' material and structural properties from observational data on their tensile strengths.

Keywords: Dust physics, Dust destruction, Solid matter physics, Astrophysical dust processes, Planet formation
A Seven-day Multiwavelength Flare Campaign on AU Mic. III. Quiescent and Flaring Properties of the X-Ray Spectra and Chromospheric Lines. We present the X-ray quiescent and flaring properties from a unique, 7 days multiwavelength observing campaign on the M1 flare star AU Mic. Combining the XMM-Newton X-ray spectra with the chromospheric line and broadband near-UV (NUV) and optical continuum observations provides a data set that is one of the most comprehensive to date. We analyze the sample of 38 X-ray flares and study in detail the X-ray flare temperature (T) and emission measure (EM) evolutions of three largest flares with the X-ray flare energies of &gt;1033 erg. The T─EM evolution tracks and multiwavelength emission evolutions of the largest-amplitude Neupert-type flare reveal that the so-called "Flare H─R diagram" is consistent with thermal coronal flare emission evolution. The two other more gradual and longer duration X-ray flares are interpreted as having larger size scales. None of the 17 Hα and Hβ flares show clear blue/red wing asymmetries, including the ones associated with the potential X-ray dimming event previously reported. The above largest-amplitude Neupert flare shows clear symmetric Hα and Hβ broadenings with roughly ±400 and ±600 km s−1, respectively, which are synchronized with the optical/NUV continuum emission evolution. Radiative hydrodynamic modeling results suggest that electron beam heating parameters that have been used to reproduce M dwarf flare NUV/optical continuum emissions can reproduce these large broadenings of Hα and Hβ lines. These results suggest that these most energetic M dwarf flares are associated with stronger magnetic field flux densities and larger size scales than solar flares but can be interpreted in terms of the standard flare model.

Keywords: M dwarf stars, Stellar x-ray flares, Stellar chromospheres, Red dwarf flare stars, Flare stars, Stellar flares, Optical flares, Stellar coronal mass ejections, Stellar coronae
Mid-infrared Dust Evolution and Late-time Circumstellar Medium Interaction in SN 2017eaw. We present JWST/Mid-Infrared Instrument (MIRI) and complementary ground-based near-infrared observations of the Type II SN 2017eaw taken 6 yr postexplosion. SN 2017eaw is still detected out to 25 μm and there is minimal evolution in the mid-infrared spectral energy distribution (SED) between the newly acquired JWST/MIRI observations and those taken a year earlier. Modeling of the mid-infrared SED reveals a cool ∼160 K dust component of 5.5 × 10−4 M⊙ and a hot ∼1700 K component of 5.4 × 10−8 M⊙, both composed of silicate dust. Notably, there is no evidence of temperature or mass evolution in the cool dust component in the year between JWST observations. We also present new and archival HST and ground-based ultraviolet (UV) and optical observations which reveal reduced but continued circumstellar medium (CSM)─ejecta interaction at &gt;2000 days postexplosion. The UV and mid-infrared emission show similar decline rates, suggesting both probe the interface between the ejecta and CSM. Given the continued existence of boxy Hα emission in the nebular spectra, the low inferred optical depth of the dust, and the lack of temperature and mass evolution, we suggest that the cool dust component in SN 2017eaw may be primarily due to pre-existing dust rather than newly formed dust in the ejecta or cold dense shell.

Keywords: Core-collapse supernovae, Type II supernovae, Massive stars, Dust formation, Circumstellar matter, Supernovae
Dense Gas Properties and Star Formation in M82. High-density molecular gas plays a vital role in supporting star formation within galaxies. However, traditional tracers of dense gas, such as the low-J transitions of HCN and HCO+, are predominantly optically thick. This characteristic presents a significant challenge in accurately estimating the column density of dense gas and mapping its spatial distribution. Optically thin tracers, including HC3N (10─9) and isotopologues of HCN, HCO+, and HNC (1─0), among others, emerge as better tracers by enabling more precise measurements and analyses of the dense gas in galaxies. Here, we present the first high-resolution (∼3 .″ 8, corresponding to ∼65 pc) molecular line observations of the nearby starburst galaxy M82 with the IRAM Northern Extended Millimetre Array. Notably, HC3N (10─9) and H13CN (1─0) emission lines are brighter in the northeast part (NE lobe) than those in the southwest part (SW lobe) of M82, suggesting a higher accumulation of dense gas at the NE lobe. The spatial distributions of H41α and 3 mm continuum emission indicate that starburst activity varies across the central starburst disk, with more intense star formation occurring at the SW lobe compared to the NE lobe. The average optical depths of HCN and HCO+ (1─0) across the triple-peaked regions exhibit significant variation, with the highest values observed at the NE lobe. Our results suggest a potential evolutionary sequence in M82, where the distributions of star formation and dense gas appear to be partially decoupled—a phenomenon that classical dense gas tracers cannot adequately probe.

Keywords: Starburst galaxies, Active galaxies, Interstellar medium
Search for Gravitational Waves from Eccentric Binary Black Holes with an Effective-one-body Template. As gravitational wave (GW) astronomy has entered an era of routine detections, it becomes increasingly important to precisely measure the physical parameters of individual events and infer population properties. Eccentricity is a key observable, suggesting that binaries form in a dense stellar environment through dynamical encounters. This work performs the first matched-filtering search for GWs from eccentric binary black holes (BBHs) covering the mass range [5, 200] M⊙and eccentricity at 20 Hz up to 0.5 with a newly developed effective-one-body waveform model. Throughout the third observation run of LIGO, Virgo, and KAGRA, we identify 28 BBH events with a false alarm rate (FAR) below once per 100 yr, all of which were previously reported in the third Gravitational-wave Transient Catalog and fourth Open Gravitational-wave Catalog. Additional candidates with FARs between once per 1 and 100 yr are also reported. We perform an injection campaign to characterize the sensitive volume time of our search pipeline. Assuming that none of the eccentric BBH events were missed by previous searches, our results provide constraints on the event rate of eccentric BBHs in the mass range [5, 30] M⊙. For a 30─30 M⊙ BBH with eccentricity 0.5, the event rate is limited to less than 0.06 Gpc−3 yr−1; this marks a 1 order of magnitude improvement for sensitive volume compared with the previous search with a minimally modeled algorithm without using templates.

Keywords: Gravitational waves, Eccentricity, Astrophysical black holes
A Mechanism for Electrostatic Solitary Waves Observed in Ganymede's Magnetopause. On 2021 June 7, the Juno spacecraft carried out a close flyby of Ganymede, Jupiter's largest moon, traversing through the previously unexplored wake region as well as the magnetopause with a closest approach altitude of 1047 km. Electrostatic solitary waves (ESWs) were observed in the magnetopause and the wake region, raising fundamental questions about their origin. We explore the generation mechanism of ESWs at Ganymede's magnetopause boundary in terms of slow and fast ion-acoustic and electron-acoustic solitons. We model Ganymede's magnetopause using a fluid-magnetized plasma consisting of warm H+ and O+ ions, two counterstreaming electron beams, and κ-distributed suprathermal electrons. The model demonstrates that the presence of symmetric electron beams supports the coexistence of slow and fast ion-acoustic solitons, while in the presence of asymmetric electron beams, in addition to slow and fast ion-acoustic solitons, electron-acoustic solitons also exist. The predicted electric field amplitudes ∼(3─527) V m−1 and frequencies (17 Hz─1 kHz) can aptly explain the spacecraft measurements. This provides a explanation of the observed ESWs at the magnetopause. The model also predicts a plausible range of electric field amplitude and frequency, which can form the basis for the future observation by the Jupiter Icy Moons Explorer mission.

Keywords: Space plasmas
Excitation of Molecular Hydrogen in Seyferts: NGC 5506 and NGC 3081. We utilize James Webb Space Telescope (JWST) Mid Infrared Instrument (MIRI) integral field unit observations to investigate the behavior and excitation of H2 in the nearby Seyfert galaxies NGC 3081 and NGC 5506, both part of the Galactic Activity, Torus, and Outflow Survey (or GATOS). We compare population levels of the S(1) to S(8) rotational H2 emission lines visible to JWST/MIRI spectroscopy to models assuming local thermodynamic equilibrium (LTE), in order to estimate the column density and thermal scaling of the molecular gas. For the nuclear regions, we incorporate Very Large Telescope Spectrograph for INtegral Field Observations in the Near Infrared (or VLT/SINFONI) K-band observations to estimate population levels for available rovibrational H2 emission lines, and compare the resultant population curves to non-LTE radiative transfer models and shock modeling. We report a differing set of prominent active galactic nuclei (AGN)-driven excitation mechanisms between the two galaxies. For NGC 3081, we find that a non-LTE radiative transfer environment is adequate to explain observations of the nuclear region, indicating that the primary mode in which the AGN transfers excitation energy is likely irradiation. We estimate the extent of AGN photoionization along the ionization bicone to be ≍330 pc. In contrast, for NGC 5506, we find a shock scenario to be a more plausible excitation mechanism, a conclusion bolstered by an observed spatial correlation between higher-energy rotational H2 and [Fe II]5.34μm emission. In addition, we identify potential nuclear H2 outflows resulting from an interaction between the ionization bicone and the rotational disk. By isolating the outflowing component of the H2 emission, we estimate the warm molecular mass outflow rate to be 0.07 M⊙ yr−1.

Keywords: AGN host galaxies, Molecular gas, Active galactic nuclei, Galaxy evolution, Galaxy circumnuclear disk
Vanishing Refractories: Tracing Dust Evolution in the BP Tau Protoplanetary Disk. We present a multiwavelength analysis of the dust of BP Tau's protoplanetary disk. We use new optical spectra of BP Tau, taken with the Magellan/Magellan Inamori Kyocera Echelle spectrograph in tandem with archival UV and mid-infrared observations. We use the magnetospheric accretion model to analyze the Ca II K and Mg II λ2796.4 emission lines and derive the abundance of Ca and Mg in the accretion flows as a proxy for the refractory abundance in the innermost gas disk. Furthermore, we used irradiated accretion disk models to compare the spectral energy distribution (SED) to observations and model in detail the 10 and 20 μm silicate features to obtain the spatial distribution and stoichiometry of the dust in which the refractories are locked in the disk. We find a significant degree of depletion of refractory material in the innermost gas disk, with median abundances of  [Ca/H]=−2.0−0.0+0.1  and  [Mg/H]=−1.30−0.3+0.2 , and attribute this to both radial drift and dust trapping due to a pressure bump/gap. Our SED modeling recovers the inner cavity that extends up to 8 au, consistent with submillimeter observations. We found a significant decrease of the Mg-to-Fe ratio with decreasing radius, with Mg-rich silicates in the outer wall and fayalite in the inner wall, consistent with the Mg depletion inferred from the emission lines.

Keywords: T Tauri stars, Protoplanetary disks, Chemical abundances
Slab Turbulence in the Very Local Interstellar Medium and the IBEX Ribbon. In this study, we analyze an important property of the very local interstellar medium, i.e., turbulence that affects the intensity and shape of the Interstellar Boundary Explorer (IBEX) ribbon. Specifically, we simulate the propagation of the ribbon's parent ions before they become secondary energetic neutral atoms that can be observed at 1 au by IBEX. We then test how different slab/2D turbulence fractions affect the intensity and shape of the modeled ribbon and compare to the latest IBEX ribbon-separated data. We compare 1D cuts across the modeled and observed ribbon as a function of angle away from the ribbon center. We find that the intensities of the modeled ribbon are larger than most of the data, except near the ecliptic plane. However, the model intensities are sensitive to how we model the neutral solar wind, which forms the source ion population for the ribbon. We then compare the model and data by normalizing the fluxes to their respective peak intensities and find the peaks' angular distances from the ribbon center. We find that most of the model peaks lie within 3° of the data peaks, which we consider our 1σ uncertainty (half the size of an IBEX pixel). By averaging the instances where the model peaks match the data peaks (within 3°), we find that the mean is slab-50%, with a standard deviation of ±28% and standard error of ±5%.

Keywords: Heliosphere, Solar wind, Interstellar magnetic fields, Pickup ions, Ion-neutral reactions, Interstellar medium
Chandra/HETG and NuSTAR Observations of V750 Ara, a γ Cas-type Star. We present a 197 ks HETG and 95 ks NuSTAR spectra of the γ Cas-type object V750 Ara. The high-resolution X-ray spectra show that the target is similar to other objects of this class. Data are interpreted under the assumption that the X-rays come from an accreting white dwarf, and our analysis implies an accretion rate of about 3 × 10−11 M⊙ yr−1. Emission lines are weak and predominantly from hydrogen-like ions: Mg XII, Si XIV, and S XVI. H-like and He-like Fe are both present, but Fe K fluorescence is weak, being significantly detected only in the NuSTAR spectrum, but it was not obviously detected in the HETG dispersed or zeroth-order spectra. The flux was variable above a level expected by Poisson statistics. There were no significant changes in the spectral hardness, though we are limited by lack of soft signal below 1 keV. Emission lines of Mg and Si were strong enough to measure velocity offsets and widths that were found to be marginally inconsistent. The H-like Mg line is consistent with instrumental broadening only but shows a 300 km s−1 blueshift. He-like Mg and H-like Si lines have no significant shift in velocity but are broadened by about 1000 km s−1. This suggests either different physical origins or velocity structure differing with plasma temperature.

Keywords: Gamma Cassiopeiae stars, High resolution spectroscopy, X-ray astronomy