Sazuna/UAT_keywords huggingface dataset:
Cosmic-Ray-driven Thermal Modes in Partially Ionized Viscous Plasma with Hall Current. This research investigates the dynamics of cosmic-ray-driven thermal modes within a partially ionized plasma permeated by a magnetic field. A two-fluid model is adopted to capture the intricate physics arising from the presence of neutral dynamics. The ion–cosmic fluid is described using a nonideal magnetohydrodynamic framework, incorporating ion and neutral viscosities, the Hall current, and ion–neutral collisions. Neutral dynamics are characterized by neutral viscosity, pressure, and collisional interactions. The derived general dispersion relation reveals two dominant modes: a collisional neutral thermal viscous mode and a Hall-modified cosmic magnetothermal viscous mode. The domains of instability for the neutral thermal viscous mode are determined, while the stability of the ion–cosmic thermal viscous mode is assessed using the Routh–Hurwitz criterion, yielding critical lengths for isochoric, isobaric, and isentropic modes. In the collisional regime, a seventh-order dispersion relation is derived and analyzed numerically. Next, the second dominant mode of the general dispersion relation is further analyzed in both transverse and longitudinal directions relative to the magnetic field. In the transverse direction, a seventh-order collisional cosmic magnetothermal viscous mode is obtained, influenced by ion and neutral viscosities, the diffusion coefficient, collisions, and the cosmic and ion acoustic speeds. This mode is further investigated analytically and numerically. Numerical estimates demonstrate that the diffusion coefficient and cosmic pressure enhance the growth rate of thermal modes. The critical wavelength of the magnetothermal cosmic mode is calculated. In the longitudinal direction, the obtained modes exhibit no substantial cosmic influence, but instead represent Hall-modified collisional Alfvén waves.

Keywords: Cosmic rays, Magnetohydrodynamics, Plasma physics
UNCOVER: 404 Error—Models Not Found for the Triply Imaged Little Red Dot A2744-QSO1. JWST has revealed an abundance of compact, red objects at z ≈ 5–8 dubbed "little red dots" (LRDs), whose SEDs display a faint blue UV continuum followed by a steep rise in the optical. Despite extensive study of their characteristic V-shaped SEDs, the nature of LRDs remains unknown. We present a new analysis of the NIRSpec/PRISM spectrum of A2744-QSO1, a triply imaged LRD at z = 7.04 from the UNCOVER survey. The spectrum shows a strong Balmer break and broad Balmer emission lines, both of which are difficult to explain with models invoking exclusively AGN or stellar contributions. Our fiducial model decomposes the spectrum into a post-starburst galaxy dominating the UV-optical continuum and a reddened AGN being subdominant at all wavelengths and contributing at a level of ∼20%. However, this model infers a stellar mass of M⋆ ≈ 4 × 109 M⊙ within a radius of re &lt; 30 pc, driving its central density to the highest among observations to date. This high central density could be explained if A2744-QSO1 is the early-forming core of a modern-day massive elliptical galaxy that later puffed up via the inside-out growth channel. The models also necessitate an unusually steep dust extinction law to preserve the strong break strength, though this steepness may be explained by a deficit of large dust grains. It is also probable that these challenges reflect our ignorance of A2744-QSO1's true nature. Future variability and reverberation mapping studies could help disentangle the galaxy and AGN contribution to the continuum, and deeper redder observations could also unveil the dust properties in LRDs. *The error code 404 in the title represents that no satisfying model is found for A2744-QSO 1. In computer network communication, the code "404" refers to the error occurring when the server cannot find the requested information.

Keywords: High-redshift galaxies, Galaxy formation, Active galactic nuclei, Black holes
Limits on the Low-energy Electron Antineutrino Flux from the Brightest Gamma-Ray Burst of All Time. The electron antineutrino flux limits are presented for the brightest gamma-ray burst (GRB) of all time, GRB221009A, over a range of 1.8–200 MeV using the Kamioka Liquid Scintillator Antineutrino Detector. Using multiple time windows ranging from minutes to days surrounding the event to search for electron antineutrinos coincident with the GRB, we set an upper limit on the flux under the assumption of several power-law neutrino source spectra, with power-law indices ranging from 1.5 to 3 in steps of 0.5. No excess was observed in any time windows ranging from seconds to days around the event trigger time T0. For a power-law index of 2 and a time window of T0 ± 500 s, a flux upper limit of 2.34 × 109 cm‑2 was calculated. The limits are compared to the results presented by IceCube.

Keywords: Neutrino astronomy, Gamma-ray bursts
Gas-phase Oxygenation and Sulfurization Processes of Fullerene Cations. Atomic oxygen and sulfur are known to efficiently react with fullerenes and may thus form a long list of oxygenated and sulfurated fullerene species in the interstellar medium (ISM). In this work, the gas-phase collision reactions between fullerene (C60 and C54/56/58) cations and 18O or S atoms are investigated. Oxygenated and sulfurated fullerene cations ([C60 18O1‑6]+, [C54/56/58 18O1‑3]+ and [C60S1‑4]+, [C54/56/58S1‑4]+) are efficiently formed. Under laser irradiation, O-atom and CO-unit loss channels are identified in the photodeoxygenation processes; [C60O]+ only has an O-atom loss channel. Smaller fullerene cations can be produced through sequential steps, and species with repeatedly lost CO units, i.e., fullerenes containing odd carbon numbers (e.g., 55 or 57 C atoms), can be produced in the photodeoxygenation processes of oxygenated fullerene cations. A S-atom loss channel and no CS-unit loss channel are identified in the photodesulfurization processes. Through theoretical calculations, the structures of oxygenated and sulfurated fullerene cations (e.g., [C60 18O]+ and [C60S]+) and the bonding energies for the formation reaction pathways are investigated, together with their IR spectra. The exothermic energy for each reaction pathway is relatively high. Consequently, the oxygenation or sulfurization states and forms of fullerene compounds are intricate and complex. In addition, different types of oxygenation and sulfurization bonds are obtained with their evolution. Importantly, we infer that the photodeoxygenation of mono-oxygenated fullerene species or the photodesulfurization of sulfurated fullerene species is not involved in the top-down chemical evolution routes of buckminsterfullerene (C60) in the ISM.

Keywords: Interstellar molecules, Laboratory astrophysics, Astrochemistry, Interstellar medium, Diffuse molecular clouds
Measuring the Interstellar Medium Content of Nearby, Luminous, Type 1 and Type 2 QSOs through CO and [C II]. We present observations of CO(1─0) and CO(2─1) lines from the Institut de radioastronomie millimétrique 30 m telescope toward 20 nearby, optically luminous type 2 quasars (QSO2s) and observations of the [C II] 158 μm line from the Stratospheric Observatory for Infrared Astronomy for five QSO2s in the CO sample and five type 1 quasars (QSO1s). In the traditional evolutionary scenario explaining different types of QSOs, obscured QSO2s emerge from gas-rich mergers observed as luminous infrared galaxies (LIRGs) and then turn into unobscured QSO1s as the black holes clear out the obscuring material in a blowout phase. We test the validity of this theoretical prediction by comparing the gas fractions and star formation efficiencies among LIRGs and QSOs. We find that CO luminosity, CO-derived gas masses, and gas fractions in QSO1s are consistent with those estimated for QSO2s, while LIRGs exhibit a closer resemblance to QSO2s in terms of CO-derived gas masses and gas fractions. Comparisons between [C II] luminosity and star formation tracers such as the CO and infrared luminosity imply additional sources of [C II] emission in QSO1s likely tracing neutral atomic or ionized gas with the caveat of a small sample size. All three types of galaxies have statistically indistinguishable distributions of star formation efficiency. Our results are consistent with part of the evolutionary scenario where nearby QSO2s could emerge from LIRGs, but they may not be the precursors of nearby QSO1s.

Keywords: Galaxy evolution, Interstellar medium, Quasars
Hydrostatic Equilibrium Constraints in X-COP Galaxy Clusters: Testing Hyperconical Modified Gravity in Hot-gas-dominated Regions. Modified Newtonian dynamics (MOND) was originally proposed to model galaxy rotation curves without dark matter. However, MOND presents difficulties in explaining the radial acceleration relation observed in galaxy clusters, and moreover, it does not completely eliminate the need for dark matter, since it requires using nonluminous particles (e.g., cold molecular gas or dust, or neutrinos) to explain the observed hydrostatic equilibrium of the hot gas. Hyperconical modified gravity (HMG) offers a relativistic framework that recovers the success of MOND in galaxy rotation curves as a natural particular case, and it could potentially reconcile the previously described discrepancies without invoking any type of dark matter. This paper analyzes the performance of the HMG model for hydrostatic equilibrium in 12 XMM Cluster Outskirts Project galaxy clusters, with a special focus on 5 objects with available complete stellar mass information: A1795, A2029, A2142, A2319, and A644. Specifically, we used high-resolution X-ray data with which gas density and mass profiles were previously derived to constrain modified gravity models. Our results show that the hydrostatic equilibrium of analyzed cluster gas is more naturally adjusted to the HMG model beyond 1 Mpc, reducing the need to fit parameters, but further research is required to expand to more spatial scales.

Keywords: Galaxy dynamics, Apollo group, Modified Newtonian dynamics
Shear Particle Acceleration in Structured Gamma-Ray Burst Jets. II. Viewing Angle Effect on the Prompt Emission and Application to GRB 170817A. Multimessenger observations suggest that the gamma-ray burst on 2017 August 17 (GRB 170817A) resulted from off-axial observations of its structured jet, which consists of a narrow ultrarelativistic jet core surrounded by a wide mild-relativistic cocoon. In a serious paper, we explore the emission of shear-accelerated electrons in the mixed jet-cocoon region in a series of papers. This paper focuses on the viewing angle effect for a structured jet by considering the emission from the shear-accelerated electrons. It is found that the observed synchrotron (Syn) emission peaks at the infrared band and the Syn self-Compton emission peaks at the band of hundreds of keV. They are not sensitive to the viewing angle. In the off-axis observations scenario, the prompt emission spectrum is dominated by the emission of the shear-accelerated electrons. The prompt gamma-ray spectrum of GRB 170817A can be well explained with our model by setting the velocity of the inner edge of the cocoon region as 0.9c, the magnetic field strength as 21 G, the injected initial electron Lorentz factor as 103, and the viewing angle as 0.44 rad. We argue that the joint observations in the infrared/optical and X-ray bands are critical to verify our model.

Keywords: Gamma-ray bursts, Non-thermal radiation sources
On the Feasibility of Deriving Pseudo-redshifts of Gamma-Ray Bursts from Two Phenomenological Correlations. Accurate knowledge of gamma-ray burst (GRB) redshifts is essential for studying their intrinsic properties and exploring their potential applications in cosmology. Currently, only a small fraction of GRBs have independent redshift measurements, primarily due to the need for rapid follow-up optical/IR spectroscopic observations. For this reason, many have utilized phenomenological correlations to derive pseudo-redshifts of GRBs with no redshift measurement. In this work, we explore the feasibility of analytically deriving pseudo-redshifts directly from the Amati and Yonetoku relations. We simulate populations of GRBs that: (i) fall perfectly on the phenomenological correlation track; and (ii) include intrinsic-scatter matching observations. Our findings indicate that in the case of the Amati relation, the mathematical formulation is ill-behaved, in that it yields two solutions within a reasonable redshift range z ∈ [0.1, 10]. When realistic scatter is included, it may result in no solution, or the redshift error range is excessively large. In the case of the Yonetoku relation, while it can result in a unique solution in most cases, the large systematic errors of the redshift call for attention, especially when attempting to use pseudo-redshifts to study GRB population properties.

Keywords: Cosmology, Gamma-ray bursts, Redshift surveys
On the Light Curves of Disk and Bulge Novae. We examine the light curves of a sample of novae, classifying them into single-peaked and multiple-peaked morphologies. Using accurate distances from Gaia, we determine the spatial distribution of these novae by computing their heights, Z, above the Galactic plane. We show that novae exhibiting a single peak in their light curves tend to concentrate near the Galactic plane, while those displaying multiple peaks are more homogeneously distributed, reaching heights up to 1000 pc above the plane. A K-S test rejects the null hypothesis that the two distributions originate from the same population at a significance level corresponding to 4.2σ.

Keywords: Classical novae
The Impacts of Magnetogram Projection Effects on Solar Flare Forecasting. This work explores the impacts of magnetogram projection effects on machine-learning-based solar flare forecasting models. Utilizing a methodology proposed by D. A. Falconer et al., we correct for projection effects present in Georgia State University's Space Weather Analytics for Solar Flares benchmark data set. We then train and test a support vector machine classifier on the corrected and uncorrected data, comparing differences in performance. Additionally, we provide insight into several other methodologies that mitigate projection effects, such as stacking ensemble classifiers and active region location-informed models. Our analysis shows that data corrections slightly increase both the true-positive (correctly predicted flaring samples) and false-positive (nonflaring samples predicted as flaring) prediction rates, averaging a few percent. Similarly, changes in performance metrics are minimal for the stacking ensemble and location-based model. This suggests that a more complicated correction methodology may be needed to see improvements. It may also indicate inherent limitations when using magnetogram data for flare forecasting.

Keywords: Space weather, Support vector machine, Solar flares
Correlated Molybdenum, Ruthenium, and Barium Isotope Anomalies in Presolar Silicon Carbide Grains. We have analyzed molybdenum, ruthenium, and barium isotopes simultaneously in 55 individual presolar silicon carbide (SiC) grains from the Murchison CM2 meteorite using the Chicago Instrument for Laser Ionization (or CHILI). Most grains show clear s-process signatures, which are strongly correlated for molybdenum and ruthenium. For all three elements, we provide estimates for s-process contributions from low-mass AGB stars with unprecedented precision. Variations in s-process production observed for some nuclides reflect a strong dependence on physical properties, neutron density, temperature, and timing, affecting various s-process branch points. Significant contamination can be excluded for a majority of grains. Instead, distributions along mixing lines in three-isotope diagrams reflect mixing between initial parent star material and matter synthesized in the star. The results suggest that the ratios between p- and r-process isotopes of molybdenum, ruthenium, and barium in presolar SiC from many parent stars are the same as the ones inferred for the solar system. This indicates that the products of these processes were well mixed by the time the molecular cloud collapsed to form the stars that eventually grew the SiC grains, and that this mixture did not change between formation of the precursor stars and formation of the Sun.

Keywords: Isotopic abundances, Nucleosynthesis, R-process, P-process, Circumstellar matter, Carbonaceous grains, Circumstellar grains, Meteorites, Stellar nucleosynthesis, Circumstellar dust, S-process
BASS. XLVII. 22 GHz Radio Atlas of Swift-BAT Selected AGN. We present the third phase of the largest high-frequency, high-resolution imaging survey of 231 nearby, hard X-ray selected active galactic nuclei (AGNs), with a very high 98% ± 1% detection fraction. This survey presents VLA 22 GHz radio observations with 1″ spatial resolution covering over 6 orders of magnitude in radio luminosity in nearby AGNs that span ∼4 orders of magnitude in black hole mass and X-ray luminosity. We identify three different radio morphologies: 44% ± 3% (102/231) are compact or unresolved, 46% ± 3% (106/231) show an extended structure (star formation, possible one-sided jets, etc.), and 8% ± 2% (19/231) have a biconical or two-sided jet-like morphology. The remaining 2% ± 1% (4/231) sources are nondetections. The radio-to-X-ray luminosity ratios of the Swift-BAT AGNs in our sample (LR/L14‑195keV ∼ 10‑5.5 and LR/L2‑10keV ∼ 10‑5 with a scatter of ∼0.5 dex) are similar to that of coronally active stars (LR/LX ∼ 10‑5). For most targets, extended emission in radio-quiet objects is broadly consistent with the expectation for star formation from previous far-infrared observations once the contribution from the radio core has been subtracted. Our sample represents nearby analogs of distant AGNs at the peak of black hole growth, and thus the high detection fraction in our work has important implications for future high frequency AGN radio surveys with the next generation Very Large Array or Square Kilometre Array, both of which should detect large fractions of more distant AGNs.

Keywords: Supermassive black holes, Extragalactic radio sources, Seyfert galaxies, Active galactic nuclei, Radio active galactic nuclei
MAGICS. III. Seeds Sink Swiftly: Nuclear Star Clusters Dramatically Accelerate Seed Black Hole Mergers. Merger rate predictions of massive black hole (MBH) seeds from large-scale cosmological simulations differ widely, with recent studies highlighting the challenge of low-mass MBH seeds failing to reach the galactic center, a phenomenon known as the seed sinking problem. In this work, we tackle this issue by integrating cosmological simulations and galaxy merger simulations from the MAGICS-I and MAGICS-II resimulation suites with high-resolution N-body simulations. Building on the findings of MAGICS-II, which showed that only MBH seeds embedded in stellar systems are able to sink to the center, we extend the investigation by incorporating nuclear star clusters (NSCs) into our models. Utilizing N-body resimulations with up to 107 particles, we demonstrate that interactions between NSCs and their surrounding galactic environment, particularly tidal forces triggered by cluster interactions, significantly accelerate the sinking of MBHs to the galactic center. This process leads to the formation of a hard binary in ≲500 Myr after the onset of a galaxy merger. Our results show that in eight out of 12 models, the high stellar density of the surrounding NSCs enhances MBH hardening, facilitating gravitational-wave mergers by redshift z = 4. We conclude that at z &gt; 4, dense NSCs serve as the dominant channel for MBH seed mergers, producing a merger rate of 0.3─0.6 yr−1 at z = 4, which is approximately 300─600 times higher than in non-NSC environments. In contrast, in environments without NSCs, surrounding dark matter plays a more significant role in loss-cone scattering.

Keywords: Galaxy dynamics, Gravitational waves, Black holes, Galaxy nuclei
Signatures of Black Hole Spin and Plasma Acceleration in Jet Polarimetry. We study the polarization of black hole jets on scales of 10‑103GM/c2 and show that large spatial swings in the polarization occur at three characteristic distances from the black hole: the radius where the counter-jet dims, the radius where the magnetic field becomes azimuthally dominated (the light cylinder), and the radius where the plasma reaches its terminal Lorentz factor. To demonstrate the existence of these swings, we derive a correspondence between axisymmetric magnetohydrodynamic outflows and their force-free limits, which allows us to analytically compute the plasma kinematics and magnetic field structure of collimated, general relativistic jets. We then use this method to ray trace polarized images of black hole jets with a wide range of physical parameters, focusing on roughly face-on jets like that of M87. We show that the location of the polarization swings is strongly tied to the location of the light cylinder and thus to the black hole's spin, illustrating a new method of measuring spin from polarized images of the jet. This signature of black hole spin should be observable by future interferometric arrays like the (Next Generation) Event Horizon Telescope, which will be able to resolve the polarized emission of the jet down to the near-horizon region at high dynamic range.

Keywords: Accretion, Black hole physics, Magnetohydrodynamics, Black holes, Very long baseline interferometry, Relativistic jets, Gravitational lensing, Active galactic nuclei
Discovery of a New Phase-transient Cyclotron Line in A0535+26: Constraints on the Accretion Geometry. In 2020 November, A0535+26 underwent one of its brightest outbursts, reaching nearly 12 Crab in X-ray flux. Observed by Insight-HXMT, NuSTAR, NICER, and AstroSat, this event provided valuable insights into Be/X-ray binaries. The pulse profiles evolved significantly with luminosity, transitioning from pencil-beam to fan-beam geometries. A0535+26, known for its fundamental cyclotron line at ∼44 keV, became only the second source to exhibit a negative correlation between cyclotron line energy and flux at high luminosities, with a plateau phase preceding the transition from positive to negative correlation. We report the discovery of a phase-transient low-energy cyclotron line, detected in a narrow phase range (∼16%) across all seven NuSTAR observations during the rising, peak, and declining phases of the outburst. The new line exhibited dramatic variations with pulse phase and luminosity. We explain this behavior using an accretion geometry where the accretion column sweeps across the line of sight.

Keywords: X-ray astronomy, Neutron stars, X-ray binary stars, High mass x-ray binary stars, Binary pulsars