Sazuna/UAT_keywords huggingface dataset:
Investigating the Bouncing Barrier with Collision Simulations of Compressed Dust Aggregates. The collision outcomes of dust aggregates in protoplanetary disks dictate how planetesimals form. Experimental and numerical studies have suggested that bouncing collisions occurring at low impact velocities may limit aggregate growth in the disks, but the conditions under which bouncing occurs have yet to be fully understood. In this study, we perform a suite of collision simulations of moderately compact dust aggregates with various impact velocities, aggregate radii, and filling factors ranging between 0.4 and 0.5. Unlike previous simulations, we generate compact aggregates by compressing more porous ones, mimicking the natural processes through which compact aggregates form. We find that the compressed aggregates bounce above a threshold mass, which decreases with impact velocity. The threshold mass scales with impact velocity as the –4/3 power, consistent with the findings of previous experiments. We also find that the threshold aggregate mass for bouncing depends strongly on filling factor, likely reflecting the strong filling-factor dependence of the compressive strength of compressed aggregates. Our energy analysis reveals that nearly 90% of the initial impact energy is dissipated during the initial compression phase, and over 70% of the remaining energy is dissipated during the subsequent stretching phase, regardless of whether the collision results in sticking or bouncing. Our results indicate that dust aggregates with a filling factor of 0.4 cease to grow beyond 100 μm as a result of the bouncing barrier.

Keywords: Dust physics, Collisional processes, Protoplanetary disks, Planetesimals, Planet formation
Binary Parameters for the Recurrent Nova T Coronae Borealis. T CrB is among the brightest novae. It is recurrent with outbursts happening approximately every 80 yr. The next outburst is imminent, expected in 2025. The T CrB binary consists of an M4 III red giant (RG) secondary and a white dwarf (WD) primary. A time series of spectra of the RG was obtained between 2022 and 2024. Radial velocities (RVs) from these data were combined with literature RVs and an updated orbit computed. The orbit is circular to a high precision and has a period of 227.5494 ± 0.0049 days for the circular solution. An eccentric solution yields an eccentricity of 0.0072 ± 0.0026. Rotational line broadening of the RG was also measured. Binary parameters are derived by maximum likelihood modeling of the available observational data. The WD, in accord with other estimates for recurrent novae, is massive. Assuming the Gaia distance, the WD mass is 1.37 ± 0.01M⊙ with the M giant secondary mass  . We discuss the evolution of this system and both paths to and limitations on further refining the values of the system parameters.

Keywords: Multiple star evolution, White dwarf stars, Ellipsoidal variable stars, Type Ia supernovae, Recurrent novae, Symbiotic binary stars
Jet Archaeology and Forecasting: Image Variability and Magnetic Field Configuration. We investigate how magnetic field variations around accreting black holes (BHs) on event horizon scales affect the morphology of magnetically driven jets on larger scales. By performing radiative transfer calculations on general relativistic magnetohydrodynamics simulations, we find that temporal variation in the magnetic flux on the event horizon and the jet power are imprinted on the variability of jet width up to several hundred gravitational radii. When the magnetic flux around the BH drops and then rises, the jet initially narrows or becomes truncated, then widens, creating a thin-thick pattern that propagates down the jet. This suggests that extended jet observations can provide a history record of horizon-scale magnetic field dynamics, and conversely, upcoming changes in the jet image can be predicted from direct observation of the magnetized accreting plasma near the BH. Furthermore, the pattern of jet width variations shows acceleration up to the relativistic regime as it moves away from the BH, aligning with plasma bulk motion. We also find in time-averaged images that both the bulk plasma motion and magnetic field configuration in the jet-launching region, which are sensitive to BH spin, shape diverse features through relativistic beaming and aberration. Higher BH spins result in more poloidal bulk motion and toroidal magnetic fields, leading to more symmetric jet images and linear polarization patterns. These results suggest a new method for testing the magnetically arrested disk model and the Blandford–Znajek process, and for determining the BH spin through observations bridging horizon and jet-launching scales.

Keywords: Black hole physics, Radio jets, Relativistic jets, Active galactic nuclei, Radiative transfer, Event horizons, Polarimetry
X-Ray Polarization of the High-synchrotron-peak BL Lacertae Object 1ES 1959+650 during Intermediate and High X-Ray Flux States. We report the Imaging X-ray Polarimetry Explorer (IXPE) polarimetric and simultaneous multiwavelength observations of the high-energy-peaked BL Lacertae object (HBL) 1ES 1959+650, performed in 2022 October and 2023 August. In 2022 October, IXPE measured an average polarization degree ΠX = 9.4% ± 1.6% and an electric-vector position angle ψX = 53° ± 5°. The polarized X-ray emission can be decomposed into a constant component, plus a rotating component, with the rotation velocity ωEVPA = (‑117 ± 12) deg day‑1. In 2023 August, during a period of pronounced activity of the source, IXPE measured an average ΠX = 12.4% ± 0.7% and ψX = 20° ± 2°, with evidence (∼0.4% chance probability) for a rapidly rotating component with ωEVPA = 1864 ± 34 deg day‑1. These findings suggest the presence of a helical magnetic field in the jet of 1ES 1959+650 or stochastic processes governing the field in turbulent plasma. Our multiwavelength campaigns from radio to X-ray reveal variability in both polarization and flux from optical to X-rays. We interpret the results in terms of a relatively slowly varying component dominating the radio and optical emission, while rapidly variable polarized components dominate the X-ray and provide minor contribution at optical wavelengths. The radio and optical data indicate that on parsec scales the magnetic field is primarily orthogonal to the jet direction. On the contrary, X-ray measurements show a magnetic field almost aligned with the parsec jet direction. Confronting with other IXPE observations, we guess that the magnetic field of HBLs on subparsec scale should be rather unstable, often changing its direction with respect to the Very Long Baseline Array jet.

Keywords: BL Lacertae objects, Spectropolarimetry, High energy astrophysics, Black holes, Blazars, Relativistic jets, Plasma astrophysics, Active galaxies, Polarimetry
A Spectroscopically Calibrated Prescription for Extracting Polycyclic Aromatic Hydrocarbon Flux from JWST MIRI Imaging. We introduce a prescription for estimating the flux of the 7.7 μm and 11.3 μm polycyclic aromatic hydrocarbon (PAH) features from broadband JWST/MIRI images. Probing PAH flux with MIRI imaging data has advantages in field of view, spatial resolution, and sensitivity compared with MIRI spectral maps, but comparisons with spectra are needed to calibrate these flux estimations over a wide variety of environments. For 267 MIRI/MRS spectra from independent regions in the four luminous infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey Early Release Science program, we derive synthetic filter photometry and directly compare estimated PAH fluxes to those measured from detailed spectral fits. We find that for probing PAH 7.7 μm, the best combination of filters is F560W, F770W, and either F1500W or F2100W, and the best for PAH 11.3 μm is F560W, F1000W, F1130W, and F1500W. The prescription with these combinations yields predicted flux densities that typically agree with values from spectral decomposition within ∼7% and ∼5% for PAH 7.7 and 11.3 μm, respectively.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, Luminous infrared galaxies
Simulating the Photospheric to Coronal Plasma Using Magnetohydrodyanamic Characteristics. II. Reflections on Non-reflecting Boundary Conditions. We present our implementation of non-reflecting boundary conditions in the magnetohydrodynamics (MHD) code LaRe3D. This implementation couples a characteristics-based boundary condition with a Lagrangian remap code, demonstrating the generality and flexibility of such non-reflecting boundary conditions for use with arbitrary grid-based MHD schemes. To test this implementation for perturbations on a background state, we present simulations of a hot sphere in an angled magnetic field. We then examine a series of simulations where we advect a spheromak through a non-reflecting boundary condition at four speeds related to the fast and slow magnetosonic speeds and the Alfvén speed. We compare the behavior of these simulations to ground truth simulations run from the same initial condition on an extended grid that keeps the spheromak in the simulation volume at all times. We find that the non-reflecting boundary condition can lead to severe, physical differences developing between a simulation using a non-reflecting boundary and a ground truth simulation using a larger simulation volume. We conclude by discussing the origins of these differences.

Keywords: Magnetohydrodynamical simulations
Discovery of Radio Recombination Lines from Proplyds in the Orion Nebula Cluster. We present new Atacama Large Millimeter/submillimeter Array observations that, for the first time, detect hydrogen and helium radio recombination lines from a protoplanetary disk. We imaged the Orion Nebula Cluster at 3.1 mm with a spectral setup that covered the n = 42 → 41 transitions of hydrogen (H41α) and helium (He41α). The unprecedented sensitivity of these observations enables us to search for radio recombination lines toward the positions of ∼200 protoplanetary disks. We detect H41α from 17 disks, all of which are HST-identified "proplyds." The detected H41α emission is spatially coincident with the locations of proplyd ionization fronts, indicating that proplyd H41α emission is produced by gas that has been photoevaporated off the disk and ionized by UV radiation from massive stars. We measure the fluxes and widths of the detected H41α lines and find line fluxes of ∼30─800 mJy km s−1 and line widths of ∼30─90 km s−1. The derived line widths indicate that the broadening of proplyd H41α emission is dominated by outflowing gas motions associated with external photoevaporation. The derived line fluxes, when compared with measurements of 3.1 mm free─free flux, imply that the ionization fronts of H41α-detected proplyds have electron temperatures of ∼6000─11,000 K and electron densities of ∼106─107 cm−3. Finally, we detect He41α toward one H41α-detected source and find evidence that this system is helium-rich. Our study demonstrates that radio recombination lines are readily detectable in ionized photoevaporating disks, providing a new way to measure disk properties in clustered star-forming regions.

Keywords: Proplyds, Photoionization, Young star clusters, Protoplanetary disks, Submillimeter astronomy, Radio interferometry, Radio astronomy, Planet formation
Analysis of CME Interactions in Solar Corona Combining Coronagraphic Observations with Wide-field Imagers from Solar Orbiter and Parker Solar Probe. Accurately determining the trajectory of coronal mass ejections (CMEs) is vital for space weather forecasting and assessing their potential impact on Earth. CMEs often deviate from a radial path, due to local pressure gradients or interactions with other CMEs. Combining coronagraphic and heliospheric observations offers deeper insights into these phenomena, enhancing future space weather prediction capabilities. On 2023 September 24, a sequence of four CMEs was observed by several spacecraft within 10 hr. This study provides a detailed analysis of these CMEs, with three-dimensional trajectories determined using a Graduated Cylindrical Shell forward-modeling technique. For the first time, this approach integrates quasi-simultaneous coronagraph data from STEREO-A and Solar and Heliospheric Observatory as well as heliospheric imaging from both Solar Orbiter and Parker Solar Probe. This multi-instrument, multi-viewpoint method allowed us to identify several indications of interaction between the second and third CMEs. This study aims to examine the consequences of interaction in low corona between two CMEs originating from closely spaced source regions on the propagation of both. In particular, the analysis revealed a southward deflection of approximately 15° in latitude for CME3 from its source region, as well as an acceleration of CME2. Following the acceleration, the two CMEs appear to propagate as a single entity at a uniform speed of approximately 750 km s‑1. Various interpretations are proposed to explain observations and indications of CME interactions.

Keywords: Active solar corona, Space weather, Solar coronal mass ejections, Solar corona
The Distant Milky Way Halo from the Southern Hemisphere: Characterization of the LMC-induced Dynamical Friction Wake. The infall of the Large Magellanic Cloud (LMC) into the Milky Way's halo impacts the distribution of stars and dark matter (DM) in our Galaxy. Mapping the observational consequences of this encounter can inform us about the properties of both galaxies, details of their interaction, and possibly distinguish between different DM models. N-body simulations predict a localized overdensity trailing the LMC's orbit both in baryonic and DM, known as the wake. We collected wide-field, deep near-infrared, and optical photometry using VIRCAM and DECam across four fields along the expected wake, covering the sky region expected to span most of its predicted density contrast. We identify over 400 stars comprising two different tracers, near main-sequence turnoff stars and red giants, which map the halo between 60 and 100 kpc, deriving stellar halo densities as a function of sky position and Galactocentric radius. We detect (1) a break in the halo radial density profile at 70 kpc not seen in northern halo studies and (2) a clear halo overdensity starting also at 70 kpc, with density contrast increasing steadily toward the expected current location of the wake. If this overdensity is the LMC wake, its peak density contrast is as pronounced as the most massive LMC model considered. Contamination from unidentified substructures may bias our wake detections, so wider-area surveys with similar depth are needed for confirmation.

Keywords: Milky Way dark matter halo, Small Magellanic Cloud, Large Magellanic Cloud, Milky Way stellar halo, Magellanic Clouds, Dark matter
Clustering Analysis of Ca I 4227 Line Polarization Using Magnetohydrodynamic Simulations of the Solar Atmosphere. The Ca I 4227 Å line is a strong resonance line formed in the solar chromosphere. At the limb, it produces the largest scattering polarization signal. So far, modeling the linear polarization in this line has been limited to the use of one-dimensional semiempirical models of the solar atmosphere. Using three-dimensional magnetohydrodynamical models of the solar atmosphere, in this paper, we perform 1.5D radiative transfer calculations to understand the formation of linear polarization profiles due to resonance scattering in this line at a near limb position. We focus on studying the sensitivity of the resonance scattering polarization to the temperature and the density structures in the atmosphere. We do not include the effects of magnetic and velocity fields in this study. We use clustering analysis to identify linear polarization profiles with similar shapes and group them accordingly for our study. We analyze the structure of the linear polarization profiles across 14 clusters, each representing different realizations of the solar atmosphere. Using source function ratio plots at various wing and core wavelength positions, we provide a qualitative explanation of linear polarization profiles in these clusters.

Keywords: Solar chromosphere, Clustering, Radiative transfer
AGILE Observations of a Sample of Repeating Fast Radio Burst Sources. Fast radio bursts (FRBs) are millisecond-duration bursts originating from distant sources. They are classified into two categories: non-repeating FRBs, which manifest as singular events, and repeater FRBs (R-FRBs), which emit multiple bursts over time. In this work, we report a search for X- and γ-ray counterparts to a selected sample of R-FRBs using data from the AGILE satellite. The sample focused on sources with an excess dispersion measure (DM) below 300 pc cm‑3. The analysis focused on the bursts covered by AGILE Mini-Calorimeter (MCAL) high-resolution data. No astrophysical signals were identified, and we derived upper limits (ULs) on the flux above 400 keV for the associated sources, adopting a spectral magnetar model, one of the leading models for FRB emission. Moreover, for a single burst of FRB 20200120E we estimated the flux ULs from the SuperAGILE detector data in the 18–60 keV energy range. We also performed a check of the GRID coverage for each burst in the 0.03–10 GeV energy band on short timescales, from 10 to 103 s, and on longer ones including the complete ∼17 yr AGILE/GRID archive. We then considered the famous event FRB 200428 from the Galactic magnetar SGR 1935+2154 as a reference to extrapolate a possible X-ray emission in MCAL and SuperAGILE bands from the radio energies of R-FRBs using the EX/Eradio of FRB 200428 as a fixed parameter. We compared these energies with historical magnetar X-ray bursts rescaled in the same bands. Our observations set useful constraints on the FRB magnetar model in particular, the MCAL ULs are currently the most stringent in the 0.4–30 MeV band.

Keywords: Gamma-ray astronomy, Radio transient sources
Discovery and Extensive Follow-up of SN 2024ggi, a Nearby Type IIP Supernova in NGC 3621. We present the discovery and early observations of the nearby Type II supernova (SN) 2024ggi in NGC 3621 at 6.64 ± 0.3 Mpc. The SN was caught   hr after its explosion by the ATLAS survey. Early-phase, high-cadence, and multiband photometric follow-up was performed by the Kilonova Finder (Kinder) project, collecting over 1000 photometric data points within 1 week. The combined o- and r-band light curves show a rapid rise of 3.3 mag in 13.7 hr, much faster than SN 2023ixf (another nearby and well-observed SN II). Between 13.8 and 18.8 hr after explosion, SN 2024ggi became bluer, with u ‑ g color dropping from 0.53 to 0.15 mag. The rapid blueward evolution indicates a wind shock breakout (SBO) scenario. No hour-long brightening expected for the SBO from a bare stellar surface was detected during our observations. The classification spectrum, taken 17 hr after the SN explosion, shows flash features of high-ionization species such as Balmer lines, He I, C III, and N III. Detailed light-curve modeling provides critical insights into the circumstellar material (CSM). Our favored model has an explosion energy of 2 × 1051 erg, a mass-loss rate of 10‑3 M⊙ yr‑1 (with an assumed 10 km s‑1 wind), and a confined CSM radius of 6 × 1014 cm. The corresponding CSM mass is 0.4 M⊙. Comparisons with SN 2023ixf highlight that SN 2024ggi has a less dense confined CSM, resulting in a faster rise and fainter UV flux. Citizen astronomer collaboration and extensive data are essential for SBO searches and detailed SN characterizations.

Keywords: Type II supernovae, Supernovae, Core-collapse supernovae
Revealing a Main-sequence Star that Consumed a Planet with JWST. The subluminous red nova (SLRN) Zwicky Transient Facility (ZTF) SLRN-2020 is the most compelling direct detection of a planet being consumed by its host star, a scenario known as a planetary engulfment event. We present JWST spectroscopy of ZTF SLRN-2020 taken +830 days after its optical emission peak using the NIRSpec fixed-slit 3─5 μm high-resolution grating and the MIRI 5─12 μm low-resolution spectrometer. NIRSpec reveals the 12CO fundamental band (ν = 1─0) in emission at ∼4.7 μm, Brackett-α emission, and the potential detection of PH3 in emission at ∼4.3 μm. The JWST spectra are consistent with the claim that ZTF SLRN-2020 arose from a planetary engulfment event. We utilize DUSTY to model the late-time ∼1─12 μm spectral energy distribution (SED) of ZTF SLRN-2020, where the best-fit parameters indicate the presence of warm,   K, circumstellar dust with a total dust mass of Log   M⊙. We also fit a DUSTY model to archival photometry taken +320 days after the peak that suggested the presence of a cooler,   K, and more massive, Log  , circumstellar dust component. Assuming the cool component originates from the ZTF SLRN-2020 ejecta, we interpret the warm component as fallback from the ejecta. From the late-time SED model, we measure a luminosity of   L⊙ for the remnant host star, which is consistent with a ∼0.7 M⊙ K-type star that should not yet have evolved off the main sequence. If ZTF SLRN-2020 was not triggered by stellar evolution, we suggest that the planetary engulfment was due to orbital decay from tidal interactions between the planet and the host star.

Keywords: Star-planet interactions, Planetary system evolution, Stellar mergers
Tight Bound on the Neutron Star Radius with Quasiperiodic Oscillations in Short Gamma-Ray Bursts. Quasiperiodic oscillations (QPOs) have been recently discovered in the short gamma-ray bursts (GRBs) 910711 and 931101B. Their frequencies are consistent with those of the quasiradial and quadrupolar oscillations of binary neutron star (BNS) merger remnants, as obtained in numerical relativity simulations. These simulations reveal quasi-universal relations between the remnant oscillation frequencies and the tidal coupling constant of the binaries. Under the assumption that the observed QPOs are due to these postmerger oscillations, we use the frequency─tide relations in a Bayesian framework to infer the source redshift, as well as the chirp mass and the binary tidal deformability of the BNS progenitors for GRBs 910711 and 931101B. We further use this inference to estimate bounds on the mass─radius relation for neutron stars. By combining the estimates from the two GRBs, we find a 68% credible range   km for the radius of a neutron star with mass M = 1.4 M⊙, which is one of the tightest bounds to date.

Keywords: Neutron stars, Stellar oscillations, Gamma-ray bursts, Gravitational waves
Gravitational Instability in Protoplanetary Disk with Cooling: 2D Global Analysis. Self-gravity is important in protoplanetary disks for planet formation through gravitational instability (GI). We study the cooling effect on GI in a thin two-dimensional protoplanetary disk. By solving the linear perturbation equations in global geometry, we obtain all the normal modes. Faster cooling leads to faster growth rate of GI with lower azimuthal wavenumber m. According to the spatial structure of normal modes at different mass-averaged Toomre number   and dimensionless cooling timescale β, we identify three modes: local, transitional, and global. The transitional modes are located in the outer disk, while the other two modes in the inner disk. At β ≈ 1 (the resonance of dynamical timescale and thermal timescale) the growth rate changes sharply and the transitional modes dominate. The disk α due to GI is much higher in the transitional modes than in the other two. Our results imply that the transitional modes at   and β ≈ 1 can plausibly interpret the substructures and planet/brown dwarf formation in the outer disk.

Keywords: Gravitational instability, Protoplanetary disks