Sazuna/UAT_keywords huggingface dataset:
Effects of Magnetic Boundary Layer on Galactic Cosmic Rays during the Heliopause Crossing for Voyager 2. Voyager 2 crossed the heliopause in 2018 and observed a small-amplitude modulation of galactic cosmic rays beyond the heliopause, within a boundary layer approximately 0.57 au thick. Prior to this, it detected a similar boundary layer for both the cosmic rays and the magnetic field, with a scale of about 0.82 au inside the heliopause. In this study, we investigate the modulation of cosmic rays near the heliopause using numerical simulations that account for magnetic boundary layers on both sides of the heliopause. Our results indicate that the boundary layer beyond the heliopause leads to a significant reduction in the parallel diffusion coefficient for the cosmic rays, compared to values further into interstellar space, thereby causing modulation of cosmic rays beyond the heliopause. Inside the heliopause, the boundary layer reduces the perpendicular diffusion coefficient and potentially increases the parallel diffusion coefficient, relative to regions deep inside the heliosphere. This results in a steady increase in intensities of cosmic rays until a sudden jump at the heliopause. Our findings confirm that the presence of the boundary layer near the heliopause is crucial for explaining the observations of cosmic rays made by Voyager 2.

Keywords: Galactic cosmic rays, Heliosphere
Pulsar Coherent Radio Emission from Solitons: Average Emission Properties. Observations have established that coherent radio emission from pulsars arises at a few hundred kilometers above the stellar surface. Recent polarization studies have further demonstrated that plasma instabilities are necessary for charge bunching that gives rise to coherent emission. The formation of charged solitons in the electron–positron plasma is the only known bunching mechanism that can be realized at these heights. More than five decades of observations have revealed a number of emission features that should emerge from any valid radio emission mechanism. We have carried out numerical calculations to find the features of average emission from curvature radiation due to charged solitons. The characteristic curvature radiation spectrum has been updated from the well-known one-dimensional dependence to a general two-dimensional form, and the contribution from each soliton along the observer's line of sight (LOS) has been added to reproduce the pulsar emission. The outflowing plasma is formed by sparking discharges above the stellar surface that are located within concentric rings resembling the core–cone emission beam, and uniform distribution of solitons along any LOS has been assumed. The observed effects of radius-to-frequency mapping, where the lower-frequency emission originates from higher altitudes, are seen in this setup. The power-law spectrum and relative steepening of the core spectra with respect to the cones also emerge. The estimated polarization position angle reflects the geometrical configuration of pulsars as expected. These studies demonstrate the efficacy of coherent curvature radiation from charged solitons to reproduce the average observational features of pulsars.

Keywords: Radio pulsars
SZ–X-Ray Surface Brightness Fluctuations in the SPT-XMM Clusters. The hot plasma in galaxy clusters, the intracluster medium, is expected to be shaped by subsonic turbulent motions, which are key for heating, cooling, and transport mechanisms. The turbulent motions contribute to the nonthermal pressure, which, if not accounted for, consequently imparts a hydrostatic mass bias. Accessing information about turbulent motions is thus of major astrophysical and cosmological interest. Characteristics of turbulent motions can be indirectly accessed through surface brightness fluctuations. This study expands on our pilot investigations of surface brightness fluctuations in the Sunyaev–Zel'dovich and in X-ray data by examining, for the first time, a large sample of 60 clusters using both SPT-SZ and XMM-Newton data and spans the redshift range 0.2 &lt; z &lt; 1.5, thus constraining the respective pressure and density fluctuations within 0.6R500. We deem density fluctuations to be of sufficient quality for 32 clusters, finding mild correlations between the peak of the amplitude spectra of density fluctuations and various dynamical parameters. We infer turbulent velocities from density fluctuations with an average Mach number  M3D=0.52±0.14 , in agreement with numerical simulations. For clusters with inferred turbulent Mach numbers from fluctuations in both pressure,  MP , and density,  Mρ , we find broad agreement between  MP  and  Mρ . Our results suggest either a bimodal or a skewed unimodal Mach number distribution, with the majority of clusters being turbulence-dominated (subsonic) while the remainder are shock-dominated (supersonic).

Keywords: Galaxy clusters, Intracluster medium
Simultaneous Observation of Ion-scale Wave Packets with Opposite Polarizations and Their Implications on the Generation Region in the Inner Heliosphere. This paper reports a dispersion analysis of two wave packets simultaneously observed near the local proton gyrofrequency by the Parker Solar Probe. The observed wave event exhibits clear two-banded wave packets both propagating along the magnetic field, characterized by left-handed (L-mode) and right-handed (R-mode) polarizations simultaneously. By incorporating the Doppler shift effect into a linear dispersion analysis, we find two possible scenarios that explain these simultaneous opposite polarizations: (1) Two inherently L-mode waves in the plasma frame, propagate parallel and antiparallel to the solar wind velocity, with similar wave frequencies and wave numbers. The polarization of the antiparallel propagating wave reverses as it moves sunward in the plasma frame while still comoving with the solar wind in the stationary frame. This reversal manifests the polarization of the wave as an R-mode in the spacecraft frame. (2) Simultaneous L-mode and R-mode waves propagate parallel to the solar wind velocity, with different wave frequencies and wave numbers. Concurrent proton observations during the wave event reveal a dominant anisotropic ( T⊥/T∥&gt;1 ) core distribution with a drifting beam population. Estimation of the linear growth rate for both L-mode and R-mode waves suggests that both scenarios are plausible, indicating that the observation is near the wave-generation region. We explore the potential impact of these simultaneous waves on solar wind heating and scattering effects, hypothesizing that such waves might enhance efficiency compared to waves with a single wave packet, contingent upon the statistical significance of such waves.

Keywords: Space plasmas, The Sun, Solar wind
Main-sequence Turnoff Stars as Probes of the Ancient Galactic Relic: Chemo-dynamical Analysis of a Pilot Sample. The main-sequence turnoff (MSTO) stars well preserve the chemical properties where they were born, making them ideal tracers for studying the stellar population. We perform a detailed chemo-dynamical analysis on moderately metal-poor (‑2.0 &lt; [Fe/H] &lt; ‑1.0) MSTO stars to explore the early accretion history of the Milky Way. Our sample includes four stars observed with high-resolution spectroscopy using ESPaDOnS at the Canada–France–Hawaii Telescope and 163 nearby MSTO stars selected from the SAGA database with high-resolution results. Within the action-angle spaces, we identified Gaia–Sausage–Enceladus (GSE, 35 objects), stars born in the Milky Way (in situ, 31 objects), and other substructures (21 objects). We find that both GSE and in situ stars present a similar Li plateau around A(Li) ∼ 2.17. GSE shows a clear α-knee feature in Mg at [Fe/H] ∼ ‑1.60 ± 0.06, while the α-elements of in situ stars remain nearly constant within this metallicity range. The iron-peak elements show little difference between GSE and in situ stars except for Zn and Ni, which decrease in GSE at [Fe/H] &gt; ‑1.6, while they remain constant for in situ stars. Among heavy elements, GSE shows overall enhancement in Eu, with [Ba/Eu] increasing with the metallicity, while this ratio remains almost constant for in situ stars, suggesting the contribution of longer timescale sources to the s-process in GSE. Moreover, for the first time, we present the r-process abundance pattern for an extremely r-process enhanced (r-II) GSE star, which appears consistent with the solar r-process pattern except for Pr. Further investigation of larger GSE samples using high-resolution spectra is required to explore the reason for the significantly higher Pr in the GSE r-II star.

Keywords: Milky Way stellar halo, Milky Way dynamics, Chemical abundances
Galactic Isolated Stellar-mass Black Holes with the Magnetospheric Spark Gap as Possible GeV–TeV Gamma-Ray Unidentified Sources. Billions of isolated stellar-mass black holes (IBHs) are thought to wander through the interstellar medium (ISM) in the Galaxy, yet only one has been detected. IBHs embedded in ISM would accrete gas via Bondi–Hoyle–Littleton accretion, and with efficient magnetic flux accumulation, the magnetosphere would be formed in the vicinity of IBHs. We explore the detectability of such IBHs through high-energy gamma-rays from spark gaps in their magnetospheres based on our recent numerical simulation. Spark gap gamma-rays can be bright at the GeV–TeV energies when IBHs are in the dense ISM. About 103 and 10 IBHs might be contained in unidentified objects of the Fermi Large Area Telescope and the High Energy Stereoscopic System, respectively. A future Galactic plane survey by the Cherenkov Telescope Array Observatory would lead to ∼102 detections. We also evaluate the combined gamma-ray emission of IBHs in the Galaxy and find that the IBHs may contribute to the Galactic diffuse gamma-rays. IBHs will emit optical and X-ray photons from their accretion disk as counterparts, potentially useful for identifying candidates.

Keywords: Accretion, Gamma-ray sources, Plasma astrophysics, Black holes
Eccentric Features in the Gravitational-wave Phase of Dynamically Formed Black Hole Binaries. We study the gravitational-wave (GW) phase shift arising from center-of-mass accelerations of binary black hole (BBH) mergers formed dynamically in three-body systems, where both the inner orbit of the merging binary and the outer orbit are eccentric. We provide a semi-analytical model and several analytical approximations that allow for fast evaluation of both the temporal evolution and the maximum value of the phase shift. The highest phase shifts occur when the binary merges close to the pericenter of the outer orbit, and can in this case be orders of magnitude larger compared to the circular limit. At high outer-orbit eccentricities, the orbital curvature leaves distinct imprints on the phase shift if the binary passes the outer pericenter during its inspiral. By comparing with phase shifts measured in numerical chaotic three-body scatterings, we show that our model accurately describes the observed phase of dynamically assembled binary systems in realistic astrophysical scenarios, providing a way to directly determine their formation channel via single GW observations. Phase shifts produced in such environments may receive additional amplifications due to the tidal pull from the perturber on the BBH.

Keywords: Black holes, Gravitational wave sources
Exploring the Mysterious High-ionization Source Powering [Ne V] in High-z Analog SBS0335-052 E with JWST/MIRI. Nearby blue compact dwarf galaxies (BCDs) are considered analogs to objects from the Epoch of Reionization revealed by JWST, having similarly low stellar masses, low metallicities, and high specific star formation rates. Thus, they represent ideal local laboratories for detailed multiwavelength studies of their properties and mechanisms that shape them. We report the first JWST MIRI/MRS observations of the BCD SBS 0335-052 E, analyzing MIR emission lines tracing different levels of ionization (e.g., [Ne II], [S IV], [Ne III], [O IV], [Ne V]) of the ionized gas. SBS 0335-052 E MIR emission is characterized by a bright point source, located in one of the youngest and most embedded stellar clusters (t ∼ 3 Myr, AV ∼ 15), and underlying extended high-ionization emission (i.e., [O IV] and [Ne V]) from the surroundings of the older and less dusty stellar clusters (t &lt; 20 Myr, AV ∼ 8). From a comparison with state-of-the-art models, we can exclude shocks, X-ray binaries, and old stellar populations as the main sources of ionization. Interestingly, a 4%─8% contribution of a ∼105 M⊙intermediate massive black hole (IMBH) is needed to justify the strong [Ne V]/[Ne II] and would be consistent with optical/UV line ratios from previous studies. However, even IMBH models cannot explain the strongest [O IV]/[Ne III]. Also, star-forming models (regardless of including X-ray binaries) struggle to reproduce even the lower ionization line ratios (e.g., [S IV]/[Ne II]) typically observed in BCDs. Overall, while current models suggest the need to account for an accreting IMBH in this high-z analog, limitations still exist in predicting high-ionization emission lines (I.P. &gt; 54 eV) when modeling these low-metallicity environments, and thus other sources of ionization cannot be fully ruled out.

Keywords: Blue compact dwarf galaxies
Molecular Evolution of H<SUB>2</SUB>O:O<SUB>2</SUB> Ices at Different Temperatures in Simulated Space Environments. I. Chemical Kinetics and Equilibrium. We computationally investigated the chemical evolution of H2O:O2 ices (6:1 ratio) under irradiation by cosmic-ray analogs (0.8 MeV H+) at 9, 50, and 100 K to understand the implications the chemical evolution of O2-containing ices in space, such as the surface of the Moon, comets, outer solar system bodies such Europa and Enceladus, as well as Kuiper Belt objects, and cold regions of the interstellar medium (ISM). Using experimental data and the PROCODA code with 200 reactions coupled equations involving 12 species, we calculated physicochemical parameters such as effective rate coefficients (ERCs), chemical abundances, and desorption. Six species were observed experimentally (H2O, O2, HO2, H2O2, O3, and HO3), while six were predicted but not observed in the experiments (H, H2, H3, O, OH, and H3O). Our findings highlight the influence of temperature on chemical equilibria and desorption yields, with certain reaction rates diminishing at 50 K. Among the results were the lists with the ERCs, and the reaction branching ratio obtained by best-fit models can be employed in astrochemical models. Curiously, we observe that the average ERCs for bimolecular collisions decrease by half as the ice temperature increases, varying from 5.8e-25 to 2.9e-25 cm3 molecules‑1 s‑1 for the ices studied. These results enhance our understanding of the physical chemistry of astrophysical ices under ionizing radiation, providing valuable data for astrochemical models that assess the effects of cosmic radiation on the composition and stability of icy bodies in the solar system and denser and colder regions of the ISM.

Keywords: Laboratory astrophysics, Natural satellites (Solar system), Astrochemistry, Molecular reactions, Cosmic rays
Three-dimensional Orbit and Dynamical Masses of GJ 105 AC. The precision of stellar models is higher than the precision at which we are able to measure the masses of most stars, with the notable exception of binaries where we can determine dynamical masses of the component stars. In addition to well-measured stellar properties, the ideal benchmark star is far enough from its companion that its properties are indistinguishable from an otherwise identical single star. Currently, there are a handful of stars with precise (±3%), model-independent mass measurements that are "effectively single" and for which we can obtain clean spectra (i.e., spectra that are not blended with a close companion). In this paper, we introduce GJ 105 AC as the newest members of this exclusive population. We present an updated orbital analysis for the long-period K3+M7 binary GJ 105 AC. We jointly analyze radial velocity (RV) and relative astrometry data, including new RVs from the Miniature Exoplanet Radial Velocity Array that capture the full periapsis passage and the RV minimum of the 76.0 ± 1.3 yr orbit for the first time. We derive precise dynamical masses of M1 = 0.78 ± 0.02 M⊙ and M2 = 0.098 ± 0.002 M⊙. We find that of all stars with similarly precise masses (∼2%), GJ 105 AC stands out as having the widest on-sky separation after α Centauri AB, making it one of the most easily accessible to spectroscopy, as well as the the second-widest true separation, ensuring that its members are truly "effectively single" in terms of their evolution.

Keywords: Multiple star evolution, Stellar evolutionary models, Spectroscopic binary stars, Astrometric binary stars, Astrometry, Companion stars, Radial velocity, Stellar evolution
Height-dependent Slow Magnetoacoustic Wave Amplitude and Energy Flux in Sunspot Atmospheres. Slow magnetoacoustic waves (SMAWs) have been considered a possible candidate for chromospheric heating in the past. This study analyzed 20 active regions observed between 2012 and 2016 to examine the amplitude and energy flux variation of SMAWs in the umbral atmosphere. Six different wavelength channels from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, covering regions from the photosphere to the low corona, were utilized for this purpose. The wave amplitude estimations show a gradual increase in 3 minute oscillation amplitude, peaking between 700 and 900 km, followed by a steady decrease; further, at altitudes greater than 1800 km, it appears to increase and decrease again. The corresponding energy flux, on the other hand, displays a steady and monotonous decrease with a significant reduction in value from approximately 3.32 ± 0.50 kW m‑2 near the photosphere to about 6.47 ± 3.16 ×10‑4 W m‑2 at an altitude of 2585 km. This decay may be attributed to radiative damping and shock dissipation in the lower altitudes and thermal conduction and viscosity in the higher altitudes. The missing flux is a factor of 3–15 lower than that required to counterbalance the chromospheric radiative losses.

Keywords: Solar coronal heating, Solar active regions, Solar chromospheric heating, Magnetohydrodynamics
High-resolution Observational Features of Type I Solar Radio Bursts. In this paper, we statistically studied the characteristic features of solar radio Type I bursts observed by Chashan broadband solar radio spectrometer at meter wavelengths from 00:06 to 07:28 UT on 2023 December 13. Based on the image morphology, we develop a method to identify individual Type I bursts on the dynamic spectra from a connected region with a ratio of the duration to bandwidth less than or equal to 3.8 and the area sum (total pixels) greater than 4. In total, 102,073 and 78,773 bursts are detected on right-hand circular polarization and left-hand circular polarization components, respectively. We find Type I bursts with a mean lifetime of 0.7 s, a mean bandwidth of 5.6 MHz, and a relative bandwidth Δf/f0 of about 2%–3%. Consistent with the previous findings of hard X-ray pulses, microwave pulses, Type III bursts, and decimetric spikes, Type I bursts exhibit their duration, bandwidth, peak intensity, and area sum with a power-law distribution. From the linear fitting in log–log space, we obtain the slope index between 1 and 3.5 for various parameters. Meanwhile, Type I bursts display the mean polarization degree in the range from ‑22% to 33%, and different bursts have various degrees. We find that Type I bursts tend to appear as a chain, and the short periods of 0.92 and 1.22 s are detected in two burst chains. Our finding would be an observational constraint for the emission mechanism and physical model of solar Type I radio bursts.

Keywords: Solar storm, Solar radio emission
Modeling Fast X-Ray Variability around an Accreting Black Hole. X-ray interband time lags are observed during the outbursts of black hole X-ray binaries. Timing analysis of fast variability in low Fourier frequency bands shows that high-energy photons lag behind low-energy photons, a phenomenon referred to as hard lag. Conversely, in high Fourier frequency bands, low-energy photons lag behind high-energy photons, known as soft lag. This frequency-dependent lag spectrum suggests that the lags arise from different physical processes. Notably, a trend has been observed wherein the lags shift toward shorter timescales during the rising hard state, indicating an evolution in the inner accretion flow. In this study, we simulate these interband lags by conducting Monte Carlo simulations of the rapid variability within the geometry of a jet base corona. We consider both inward propagating accretion rate fluctuations and reverberation (light-crossing) delays in our simulations. We successfully reproduce both low-frequency hard lags and high-frequency soft lags in a self-consistent manner. We replicate the observed evolution of the frequency-dependent lag spectra by varying the geometrical scale of the corona and the viscous frequency of the disk. Finally, we discuss the potential of a spherical corona and emphasize that polarization observations from the Imaging X-ray Polarimetry Explorer and the enhanced X-ray Timing and Polarimetry mission will be crucial for distinguishing the corona's geometry in future studies.

Keywords: Accretion, Black holes, High energy astrophysics
Searching for Compact Obscured Nuclei in Compton-thick Active Galactic Nuclei. Compact obscured nuclei (CONs) are heavily obscured infrared cores that have been found in local (ultra-)luminous infrared galaxies. They show bright emission from vibrationally excited rotational transitions of HCN, known as HCN-vib, and are thought to harbor Compton-thick (CT, NH ≥ 1024 cm‑2) active galactic nuclei (AGNs) or extreme compact starbursts. We explore the potential evolutionary link between CONs and CT-AGNs by searching for CONs in hard-X-ray-confirmed CT-AGNs from the Great Observatories All-sky LIRG Survey (GOALS). Here, we present new Atacama Large Millimeter/submillimeter Array Band 6 observations that targeted HCN-vib emission in four hard-X-ray-confirmed CT-AGNs. We analyze these objects together with literature HCN-vib measurements of five additional hard-X-ray-confirmed CT-AGNs from the GOALS sample. We do not detect any CONs in this combined sample of nine CT-AGNs. We then explore a proposed evolutionary sequence in which CONs evolve into X-ray-detectable CT-AGNs once outflows and feedback reduce the column densities of the enshrouding gas. We find, however, no evidence of well-developed dense molecular outflows in the observed CT-AGNs. While this could suggest that CT-AGNs are not universally linked to CONs, it could also be explained by a short duty cycle for molecular outflows.

Keywords: Molecular gas, Jets, Active galaxies, Galaxy nuclei, Active galactic nuclei