Sazuna/UAT_keywords huggingface dataset:
Martian Crustal Magnetic Field Effects on the Ionospheric Main Peak. Planetary magnetic fields can affect ionospheric plasma transport and coupling with the solar wind. In contrast to the terrestrial global magnetic field, there are only weaker and sporadic crustal magnetic fields on Mars. Many studies have indicated that Martian crustal fields can still modulate the topside ionosphere and its coupling with the solar wind. Nevertheless, it is unclear whether the crustal fields can affect the ionospheric main peak, which does not directly interact with the solar wind and is dominated by photochemical processes. In this study, the crustal field effect was identified from ionospheric measurements over unevenly distributed crustal fields. Both the intensity and configuration of the crustal fields were found to be capable of affecting the ionospheric main peak. The ionospheric peak electron density tends to decrease in the strong horizontal crustal field region. The results suggest that the crustal fields may affect the ionospheric main peak through modulating solar wind energetic particle precipitation; strong horizontal magnetic fields can partially prevent energetic particle precipitation and thus weaken impact ionization.

Keywords: Planetary ionospheres
The Energy Sources, the Physical Properties, and the Mass-loss History of SN 2017dio. We study the energy sources, the physical properties of the ejecta and the circumstellar medium (CSM), and the mass-loss history of the progenitor of SN 2017dio, which is a broad-lined Ic (Ic-BL) supernova (SN) having unusual light curves (LCs) and signatures of hydrogen-rich CSM in its early spectrum. We find that the temperature of SN 2017dio began to increase linearly about 20 days after the explosion. We use the 56Ni plus the ejecta–CSM interaction model to fit the LCs of SN 2017dio, finding that the masses of the ejecta, the 56Ni, and the CSM are ∼12.41 M ⊙, ∼0.17 M ⊙, and ∼5.82 M ⊙, respectively. The early-time photosphere velocity and the kinetic energy of the SN are, respectively, ∼1.89 × 104 km s‑1 and ∼2.66 × 1052 erg, which are comparable to those of SNe Ic-BL and hypernovae (HNe), respectively. We suggest that the CSM of SN 2017dio might be from a luminous blue variable–like outburst or pulsational pair instability ∼1.2‑11.4 yr prior to the SN explosion or binary mass transfer. Moreover, we find that its ejecta mass is larger than those of many SNe Ic-BL and that its 56Ni mass (M Ni) is approximately equal to the mean (or median) value of M Ni of SNe Ic-BL in the literature but lower than M Ni of prototype HNe (e.g., SN 1998bw and SN 2003dh).

Keywords: Type Ic supernovae, Circumstellar matter, Supernovae
Spatial Distribution of C<SUB>4</SUB>H and c-C<SUB>3</SUB>H<SUB>2</SUB> in Cold Molecular Cores. C4H and c-C3H2, as unsaturated hydrocarbon molecules, are important for forming large organic molecules in the interstellar medium. We present mapping observations of C4H (N = 9‑8) lines, c-C3H2 (J  Ka,Kb  = 21,2–10,1), and H13CO+ (J = 1‑0) toward 19 nearby cold molecular cores in the Milky Way with the IRAM 30 m telescope. C4H 9–8 was detected in 13 sources, while c-C3H2 was detected in 18 sources. The widely existing C4H and c-C3H2 molecules in cold cores provide material to form large organic molecules. Different spatial distributions between C4H 9–8 and c-C3H2 2–1 were found. The relative abundances of these three molecules were obtained under the assumption of local thermodynamic equilibrium conditions with a fixed excitation temperature. The abundance ratio of C4H to c-C3H2 ranged from 0.34 ± 0.09 in G032.93+02 to 4.65 ± 0.50 in G008.67+22. A weak correlation between C4H/H13CO+ and c-C3H2/H13CO+ abundance ratios was found, with a correlation coefficient of 0.46, which indicates that there is no tight astrochemical connection between C4H and c-C3H2 molecules.

Keywords: Interstellar molecules, Chemical abundances, Abundance ratios, Astrochemistry
Recurrent Nova V2487 Oph Had Superflares in 1941 and 1942 with Radiant Energies of 10<SUP>42.5+1.6</SUP> erg. V2487 Ophiuchi (V2487 Oph) is a recurrent nova with classical nova eruptions in 1900 and 1998, and it is also the most extreme known superflare star. These superflares are roughly hour-long flares with amplitudes and optical energies reaching up to 1.10 mag and 1039.21 erg, respectively, with the superflares recurring once a day. The V2487 Oph superflares are certainly operating with the same mechanism as all the other types of superflare stars, where magnetic loops are twisted and stretched until reconnection occurs, whereupon ambient electrons are accelerated to relativistic energies and then emit bremsstrahlung radiation from X-ray to radio. V2487 Oph is unique among known superflare stars in that one of the loop footprints is in an accretion disk. This exact mechanism was theoretically predicted by M. R. Hayashi and colleagues in 1996. Now, I have found two superflares recorded on Harvard archival photographs from 1941 and 1942. These two superflares have B-magnitude amplitudes of &gt;1.83 and &gt;2.00 mag and total radiated energies of 1042.4 and 1042.5 erg, respectively, with bolometric corrections. Each has emitted energies of ∼30 billion Carringtons, in units of the most energetic solar flare. Further, I find superflares in Zwicky Transient Factory light curves, so V2487 Oph has been superflaring from 1941 to 2023. For the observed number distribution of dN/dE = 4E ‑2 superflares per year, for E in units of 1041 erg, the emitted energy in superflare light is 1042.1 erg in each year, or 1044.1 erg from 1941 to 2023.

Keywords: Stellar flares, Recurrent novae, Classical novae
On Its Way to the Neutron Star─White Dwarf Binary Graveyard, IGR J16194−2810, A First Ascent M Giant X-Ray Binary. A single-lined spectroscopic orbit for the M giant in the X-ray binary IGR J16194−2810 is determined from a time series of optical spectra. The spectroscopic orbital period of 192.5 days is twice that of the photometric period, confirming that the M giant in the system is an ellipsoidal variable. The giant is identified as a first ascent giant approaching the red giant tip. The primary is a neutron star (NS) with its M giant companion filling its Roche lobe, verifying the system classification as a low-mass X-ray binary (LMXB). Stellar C, N, O, and Fe abundances are derived for the M giant with the C, N, and O values typical for a field giant with [Fe/H] = −0.14. The system does not have a large kick velocity. Models for the evolution of the system into a binary NS─white dwarf are presented. The X-ray properties are discussed in the context of this model. This binary is a rare example of a luminous, long orbital period LMXB early in the transient ellipsoidal phase.

Keywords: Neutron stars, Multiple star evolution, Stellar abundances, Ellipsoidal variable stars, Low-mass x-ray binary stars, Symbiotic binary stars
Very Long Baseline Array Observations of Parsec-scale Radio Emission in Dual Active Galactic Nuclei. It is believed that dual active galactic nuclei (AGN) form during galaxy mergers. Studying dual-AGN emission can provide valuable insights into galaxy merging and evolution. To investigate parsec-scale radio emission properties, we observed eight radio components of four selected dual-AGN systems using the Very Long Baseline Array (VLBA) at 5 GHz in multiple-phase-center mode. Among them, two compact radio components, labeled J0051+0020B and J2300-0005A, were detected clearly on parsec scales for the first time. However, the radio emission of the other six components was resolved out in the high-resolution images. We provide the values or upper limits of the brightness temperature and radio emission power, and analyze the emission origins in detail for each target. Based on their physical properties reported in this work and in the literature, we suggest that the radio emission in J0051+0020B and J2300-0005A originates primarily from compact jets, while the other six sources show more complex emission mechanisms. In addition, our VLBA observations suggest that the systematic X-ray deficit in our dual-AGN sample is likely attributed to the tidally induced effect and possibly a viewing angle effect.

Keywords: Jets, Very long baseline interferometry, Galaxy pairs, Active galactic nuclei, Galaxy mergers, Star formation
Accretion-modified Stars in Accretion Disks of Active Galactic Nuclei: Observational Characteristics in Different Regions of the Disks. Stars and compact objects embedded in accretion disks of active galactic nuclei (AGNs), dubbed accretion-modified stars (AMSs), often experience hyper-Eddington accretion in the dense gas environment, resulting in powerful outflows as the Bondi explosion and formation of cavities. The varying gas properties across different regions of the AGN disk can give rise to diverse and intriguing phenomena. In this paper, we conduct a study on the characteristics of AMSs situated in the outer, middle, and inner regions of the AGN disk, where the growth of the AMSs during the shift inward is considered. We calculate their multiwavelength spectral energy distributions (SEDs) and thermal light curves. Our results reveal that the thermal luminosity of the Bondi explosion occurring in the middle region leads to UV flares with a luminosity of ∼1044 erg s‑1. The synchrotron radiation of Bondi explosion in the middle and inner regions peaks at the X-ray band with luminosities of ∼1043 and ∼1042 erg s‑1, respectively. The γ-ray luminosity of inverse Compton radiation spans from 1042–1043 erg s‑1 peaked at the ∼10 MeV (outer region) and ∼GeV (middle and inner regions) bands. The observable flares of AMS in the middle region exhibit a slow rise and rapid Gaussian decay with a duration of months, while in the inner region, it exhibits a fast rise and slow Gaussian decay with a duration of several hours. These various SED and light-curve features provide valuable insights into the various astronomical transient timescales associated with AGNs.

Keywords: Supermassive black holes, High energy astrophysics, Light curves, Bondi accretion, Stellar mass black holes, Transient sources, Active galactic nuclei, Spectral energy distribution, Gamma-rays
Fermi GBM Observations of the Galactic Magnetar SGR 1935+2154 during Its 2022 January Activity. The X-ray and radio burst-emitting soft gamma-ray repeater SGR 1935+2154 has been the most active magnetar during the past decade, with at least one active episode each year since 2019. We report on the 2022 January activity as observed by the Fermi Gamma-Ray Burst Monitor and present the temporal and time-integrated spectral properties of the observed 112 X-ray bursts. No radio bursts were reported during the activity. The mean burst duration is comparable to most of the previous activities but is shorter than that of 2020, during which the magnetar emitted radio bursts. The mean burst spectrum is softer than the earlier activities and a long-term softening trend since 2016 is evident and is accompanied by a rise in the mean burst fluence and blackbody emission radii. The power-law indices of the  RBB2−kTBB  correlation also show an evolution during 2019─2022, where the soft component started becoming steeper, whereas the hard component shows a less steep trend. The burst properties show no significant evolution within the activity, which lasted for ∼ 45 days, and none of the observed bursts showed properties reminiscent of those of the hard, long X-ray counterpart to the 2020 fast radio burst FRB 200428 from the source. We discuss the results comparatively with the 8 yr history of the source since its discovery in 2014.

Keywords: Neutron stars, Magnetars, Soft gamma-ray repeaters, X-ray bursts
H I Lyα Emission from a Metal-poor Cool Stream Fueling an Early Dusty Starburst. The GAMA J0913−0107 system is a rare conjunction of a submillimeter galaxy (SMG) at z ≈ 2.7 and two background QSOs with projected separations &lt;200 kpc. Previous high-resolution QSO absorption-line spectroscopy has revealed high H I column density, extremely metal-poor (∼1% solar) gas streams in the circumgalactic medium of the SMG. Here we present deep optical integral-field spectroscopy of the system with the Keck Cosmic Web Imager (KCWI). Reaching a 2σ surface brightness limit ≈10−19 erg s−1 cm−2 arcsec−2 with ∼2 hr of integration time, we detect a filamentary Lyα nebula stretching ∼180 kpc from the SMG intercepting both QSO sightlines. This Lyα filament may correspond to the same cool gas stream penetrating through the hot halo seen in the absorption. In contrast to Lyα nebulae around QSOs, there is no obvious local source for photoionization due to the massive dust content. While uncertain, we consider the possibility that the nebula is ionized by shocks induced by the infall, obscured star formation, and/or a boosted UV background. The SMG─QSOs conjunction multiplied the efficiency of the KCWI observations, allowing a direct comparison of Lyα nebulae in two distinct environments. We find that the nebulae around the QSOs are much brighter and show steeper surface brightness profiles than the SMG nebula. This is consistent with the additional photoionization and Lyα scattering provided by the QSOs. While illustrating the challenges of detecting Lyα nebulae around SMGs, our work also demonstrates that important insights can be gained from comparative studies of high-z Lyα nebulae.

Keywords: Extragalactic astronomy, Starburst galaxies, Quasars, Circumgalactic medium
Systematically Revisiting All NuSTAR Spins of Black Holes in X-Ray Binaries. We extend our recent work on black hole spin in X-ray binary systems to include an analysis of 189 archival NuSTAR observations from 24 sources. Using self-consistent data reduction pipelines, spectral models, and statistical techniques, we report an unprecedented and uniform sample of 36 stellar-mass black hole spin measurements based on relativistic reflection. This treatment suggests that prior reports of low spins in a small number of sources were generally erroneous: our comprehensive treatment finds that those sources tend to harbor black holes with high spin values. Overall, within 1σ uncertainty, ∼86% of the sample are consistent with a ≥ 0.95, ∼94% of the sample are consistent with a ≥ 0.9, and 100% are consistent with a ≥ 0.7 (the theoretical maximum for neutron stars; a = cJ/GM 2). We also find that the high-mass X-ray binaries (those with A-, B-, or O-type companions) are consistent with a ≥ 0.9 within the 1σ errors; this is in agreement with the low-mass X-ray binary population and may be especially important for comparisons to black holes discovered in gravitational wave events. In some cases, different spectra from the same source yield similar spin measurements but conflicting values for the inclination of the inner disk; we suggest that this is due to variable disk winds obscuring the blue wing of the relativistic Fe K emission line. We discuss the implications of our measurements, the unique view of systematic uncertainties enabled by our treatment, and future efforts to characterize black hole spins with new missions.

Keywords: X-ray binary stars, Black holes, High energy astrophysics, Compact objects, Astrophysical black holes
Carbon Isotope Chemistry in Protoplanetary Disks: Effects of C/O Ratios. Carbon isotope fractionation of CO has been reported in the disk around TW Hya, where elemental carbon is more abundant than elemental oxygen ([C/O]elem &gt; 1). We investigated the effects of the [C/O]elem ratio on carbon fractionation using astrochemical models that incorporate isotope-selective photodissociation and isotope exchange reactions. The 12CO/13CO ratio could be lower than the elemental carbon isotope ratio due to isotope exchange reactions when the [C/O]elem ratio exceeds unity. The observed 12CO/13CO and H12CN/H13CN ratios around TW Hya could be reproduced when the [C/O]elem ratio is 2–5. In the vicinity of the lower boundary of the warm molecular layer, the formation of ices leads to the gas-phase [C/O]elem ratio approaching unity, irrespective of the total (gas + ice) [C/O]elem ratio. This phenomenon reduces the variation in the 12CO/13CO ratio across different [C/O]elem ratios.

Keywords: Protoplanetary disks, Astrochemistry
Low-frequency Absorption and Radio Recombination Line Features of the Galactic Center Lobe. The Galactic center lobe (GCL) is a ∼1° object located north of the Galactic center. In the mid-infrared, the GCL appears as two 8.0 μm filaments that roughly define an ellipse. There is strong 24 μm and radio continuum emission in the interior of the ellipse. Due to its morphology and location in the sky, previous authors have argued that the GCL is created by outflows from star formation in the central molecular zone or by activity of the central black hole Sgr A*. We present images of the GCL from the GaLactic and Extragalactic All-sky Murchison Widefield Array survey in radio continuum that show thermal absorption against the Galactic center, incompatible with an interpretation of synchrotron self-absorption. Estimates of the cosmic-ray emissivity in this direction allow us to place a distance constraint on the GCL. To be consistent with standard emissivity assumptions, the GCL would be located 2 kpc away. At a distance of 8 kpc, the synchrotron background emissivity is enhanced by ∼75% in the direction of the GCL. We also present radio recombination line data from the Green Bank Telescope that constrain the electron temperature and line widths in this region, which are also more explicable if the GCL lies relatively close.

Keywords: Interstellar line emission, Interstellar absorption, Interstellar medium, Radio continuum emission, H II regions
The Galactic Center Lobe as an H II Region. The Galactic center lobe (GCL) is an object ∼1° across that is located north of the Galactic center. In the mid-infrared (MIR) the GCL appears as two 8.0 μm filaments between which there is strong 24 μm and radio continuum emission. Due to its morphology and location in the sky, previous authors have argued that the GCL is located in the Galactic center region, created by outflows from star formation or by activity of the central black hole Sagittarius A*. In an associated paper, low-frequency radio emission indicates that the GCL must instead lie foreground to the Galactic center. If the GCL is foreground to the Galactic center, it is likely to be a type of object common throughout the Galactic disk; we here investigate whether its properties are similar to those of Galactic H II regions. We find that the GCL's MIR morphology, MIR flux densities, dust temperatures, and radio recombination line properties as traced by the Green Bank Telescope Diffuse Ionized Gas Survey are consistent with those of known Galactic H II regions, although the derived electron temperature is low. We search for the ionizing source(s) of the possible H II region and identify a stellar cluster candidate (Camargo #1092/Ryu &amp; Lee #532) and a cluster of young stellar objects (the SPICY cluster G359.3+0.3) whose members have Gaia parallaxes distances of 1.7 ± 0.4 kpc. Taken together, the results of our companion paper and those shown here suggest that the GCL has properties consistent with those of an H II region located ∼2 kpc from the Sun.

Keywords: Interstellar line emission, Galactic center, Interstellar medium, H II regions, Infrared photometry
Statistical Study of the Sub-ion-scale Magnetic Holes in the Lunar Space Environment. Sub-ion-scale magnetic holes play a significant role in electron transportation and energy dissipation. In the upstream region of the terrestrial bow shock, they are expected to originate from the upstream solar wind as well as the foreshock. The Moon can move into the solar wind; whether it can affect the observation of the sub-ion-scale magnetic holes is unclear. Here, we statistically investigate 268 sub-ion-scale magnetic holes in the lunar space environment based on observations of the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission. The median duration of these magnetic holes is ∼0.31 s, and the median size of their cross sections is ∼0.5 ρ i or ∼38.9 ρ e. We regard an isolated or a train of magnetic holes as an event; thus, these magnetic holes belong to 207 events. The data at X SSE &lt; 0 and |Y SSE| &lt; 2 R M (lunar radii) account for ∼21.7% of all observed data, but ∼89.4% of the events are observed in this region, suggesting that they are more likely to occur in the lunar wake. Furthermore, their occurrence rates in the lunar wake are much larger in the region close to its boundary than in other wake regions. And the occurrence rates in the lunar wake near the boundary at X SSE &gt; ‑3 R M are larger in the dawnside than that in the duskside. These observations suggest that the region in the lunar wake close to its boundary is a possible source of sub-ion-scale magnetic holes.

Keywords: Solar wind
Spectral Lags of 90 Swift Gamma-Ray Bursts and the Constraint on the Lorentz Invariance Violation. The arrival times of photons with different energy could be different, even when they are emitted from the same source simultaneously. Such a spectral lag is a common property among high-energy astrophysics phenomena like gamma-ray bursts (GRBs). The potential violation of the Lorentz invariance caused by quantum fluctuations in background spacetime metrics could cause the spectral lag. In this paper, we try to make a constraint on Lorentz invariance violation (LIV) with multiple energy bands light curves of GRBs. With a sample of 90 Swift GRBs with redshifts, we calculate their spectral offsets from four fixed energy bands within their source frame. With help from the cross-correlation function and kernel smooth procedure, we extract improved spectral shifts. By using these more general spectral lags, we obtain an upper limit on LIV, equivalent to a lower limit on the quantum-gravitational energy scale of E QG ≥ 2.2 × 1014GeV.

Keywords: Gamma-ray bursts, Gravitation, Quantum gravity, Time domain astronomy, Astronomical methods, Time series analysis
Impact of Self-shielding Minihalos on the Lyα Forest at High Redshift. Dense gas in minihalos with masses of 106‑108 M ⊙ can shield themselves from reionization for ∼100 Myr after being exposed to the UV background. These self-shielded systems, often unresolved in cosmological simulations, can introduce strong absorption in quasar spectra. This paper is the first systematic study on the impact of these systems on the Lyα forest. We first derive the H I column density profile of photoevaporating minihalos by conducting 1D radiation–hydrodynamics simulations. We utilize these results to estimate the Lyα opacity from minihalos in a large-scale simulation that cannot resolve self-shielding. When the ionization rate of the background radiation is 0.03 × 10‑12 s‑1, as expected near the end of reionization at z ∼ 5.5, we find that the incidence rate of damped Lyα absorbers increases by a factor of ∼2‑4 compared to at z = 4.5. The Lyα flux is, on average, suppressed by ∼3% of its mean due to minihalos. The absorption features enhance the 1D power spectrum up to ∼5% at k ∼ 0.1 h Mpc‑1 (or 10‑3 km‑1 s), which is comparable to the enhancement caused by inhomogeneous reionization. The flux is particularly suppressed in the vicinity of large halos along the line-of-sight direction at separations of up to 10 h ‑1 Mpc at r ⊥ ≲ 2 h ‑1 Mpc. However, these effects become much smaller for higher ionizing rates (≳0.3 × 10‑12 s‑1) expected in the post-reionization Universe. Our findings highlight the need to consider minihalo absorption when interpreting the Lyα forest at z ≳ 5.5. Moreover, the sensitivity of these quantities to the ionizing background intensity can be exploited to constrain the intensity itself.

Keywords: Radiative transfer simulations, Reionization, Hydrodynamical simulations, Lyman alpha forest