Sazuna/UAT_keywords huggingface dataset:
The Impact of Water Clouds on the Prospective Emission Spectrum of Teegarden's Star b as Observed by LIFE. Nontransiting terrestrial planets will be accessible by upcoming observatories of which LIFE is an example. Planet b orbiting Teegarden's Star is one of the optimal targets for such missions. We use a one-dimensional atmospheric model with real gas radiation, a multispecies pseudo-adiabatic convection-condensation scheme, and a water cloud scheme to estimate the impact of the cloud coverage on the emission spectrum of the target, as well as to assess how sensitive LIFE could be to changes in outgoing flux caused by these clouds. Though the emergent flux decreases with a higher cloud coverage, it does not decrease by more than 1 order of magnitude as the coverage increases from 0% to 90%. This allows LIFE to retain a high sensitivity to the cloud cover fraction for wavelengths longer than 7 μm. In this spectral range, with at least 1 bar of N2, LIFE is able to distinguish cloud cover fractions as small as 10% given an integration time of 24 hr, and yields much better precision with a week-long integration. An integration time of 1 week also allows the resolution of local variations in spectral flux, which can lead to easier molecule identification. This ability remains if the planet is a CO2-dominated Venus analog. Partial pressures of N2 lower than 1 bar may create a degeneracy with the cloud cover fraction. LIFE shows promising potential for detecting and characterizing atmospheres even with a high cloud coverage, and retaining a fine sensitivity to relatively small differences in cloud cover fractions.

Keywords: Extrasolar rocky planets, Astrobiology, Habitable planets, Exoplanet atmospheres
Origins of Very Low Helium Abundance Streams Detected in the Solar Wind Plasma. The abundance of helium (A He) in the solar wind exhibits variations typically in the range from 2% to 5% with respect to solar cycle activity and solar wind velocity. However, there are instances where the observed A He is exceptionally low (&lt;1%). These low-A He occurrences are detected both near the Sun and at 1 au. The low-A He events are generally observed near the heliospheric current sheet. We analyzed 28 low-A He events observed by the Wind spacecraft and 4 by Parker Solar Probe to understand their origin. In this work, we make use of the ADAPT-WSA model to derive the sources of our events at the base of the solar corona. The modeling suggests that the low-A He events originated from the boundaries of coronal holes, primarily from large quiescent helmet streamers. We argue that the cusp above the core of the streamer can produce such very low helium abundance events. The streamer core serves as an ideal location for gravitational settling to occur as demonstrated by previous models, leading to the release of this plasma through reconnection near the cusp, resulting in low-A He events. Furthermore, observations from Ulysses provide direct evidence that these events originated from coronal streamers.

Keywords: Heliosphere, Solar wind, Solar abundances, Solar magnetic fields, Solar corona
Investigation of Individual Pulse Emission Behaviors from Pulsar J1741–0840. We have carried out a detailed study of individual pulse emission from the pulsar J1741‑0840 (B1738‑08) observed using the Parkes and Effelsberg radio telescopes at the L band. The pulsar exhibits four emission components, which are not well resolved by employing multicomponent Gaussian fitting. The radio emission originates at a height of approximately 1000 km, with the viewing geometry characterized by inclination and impact angles roughly estimated at 81° and 3°, respectively. Fluctuation spectral analysis of single pulse behavior reveals two prominent periodicities, around 32 and five rotation periods. The longer periodic modulation feature is linked to nulling behavior across the entire emission window, with an updated nulling fraction of 23% ± 2% derived from pulse energy distribution via Gaussian mixture modeling. In addition to quasiperiodic nulling, the pulsar also exhibits the presence of subpulse drifting in the trailing component, with the shorter periodic feature in the fluctuation spectra related to the phenomenon of subpulse drifting, and the longitudinal separation estimated to be about 5°. Both periodic modulations show significant temporal evolution with time-dependent fluctuation power. The implications of understanding the radio emission mechanisms are discussed.

Keywords: Pulsars, Radio pulsars
Universal Nonthermal Power-law Distribution Functions from the Self-consistent Evolution of Collisionless Electrostatic Plasmas. Collisionless systems often exhibit nonthermal power-law tails in their distribution functions. Interestingly, collisionless plasmas in various physical scenarios (e.g., the ion population of the solar wind) feature a v ‑5 tail in their velocity (v) distribution, whose origin has been a long-standing puzzle. We show this power-law tail to be a natural outcome of the collisionless relaxation of driven electrostatic plasmas. Using a quasi-linear analysis of the perturbed Vlasov–Poisson equations, we show that the coarse-grained mean distribution function (DF), f 0, follows a quasi-linear diffusion equation with a diffusion coefficient D(v) that depends on v through the plasma dielectric constant. If the plasma is isotropically forced on scales larger than the Debye length with a white-noise-like electric field, D(v) ∼ v 4 for σ &lt; v &lt; ω P/k, with σ the thermal velocity, ω P the plasma frequency, and k the characteristic wavenumber of the perturbation; the corresponding quasi-steady-state f 0 develops a v ‑(d + 2) tail in d dimensions (v ‑5 tail in 3D), while the energy (E) distribution develops an E ‑2 tail independent of dimensionality. Any redness of the noise only alters the scaling in the high v end. Nonresonant particles moving slower than the phase velocity of the plasma waves (ω P/k) experience a Debye-screened electric field, and significantly less (power-law suppressed) acceleration than the near-resonant particles. Thus, a Maxwellian DF develops a power-law tail, while its core (v &lt; σ) eventually also heats up but over a much longer timescale. We definitively show that self-consistency (ignored in test-particle treatments) is crucial for the emergence of the universal v ‑5 tail.

Keywords: Space plasmas, Heliosphere, Plasma physics, Solar wind, Plasma astrophysics, Analytical mathematics, Interplanetary particle acceleration, Perturbation methods
OCS<SUB>2</SUB> Isomers in the Venusian Atmospheric Chemistry: Spectroscopic Characterization and Photochemistry. The atmosphere of Venus exhibits absorption in the 300–500 nm wavelength range, which is driven by unknown chemical processes. In our study, we explore electronic transitions in molecules that may exist in the Venusian atmosphere, specifically focusing on the photoabsorption cross sections and the lowest singlet and triplet electronic states of the OCS2, SSCO, and OSCS isomers using highly accurate ab initio methods. Our analysis suggests that the SSCO isomer is a strong candidate for explaining the unknown UV absorption. Furthermore, these isomers may serve as significant astrochemical reservoirs in the atmosphere of Venus, where photodissociation could produce atomic sulfur in both its ground and excited states along with OCS and CS2, offering a plausible mechanism for the sulfur cycle dynamics and the formation of S x  species. This study provides valuable insights into the complex sulfur chemistry within the atmosphere of Venus.

Keywords: Venus, Solar system terrestrial planets
Revisiting the Chemical Composition of WD 1145+017: Impact of Circumstellar Disk Contamination on Photospheric Abundances. We performed a chemical analysis of the asteroid-bearing white dwarf WD 1145+017 using optical and ultraviolet spectroscopic data from 25 epochs between 2015 and 2023. We present an updated gas disk model with improved opacity calculations and temperature profiles to properly account for all circumstellar absorption features. Incorporating these changes into our models, we identified at least 11 elements in the disk, including a detection of circumstellar Na. We detected 16 elements in the photosphere, including new detections of P, Co, and Cu. At 16 elements, WD 1145+017 ties GD 362 as one of the most polluted white dwarfs in terms of the number of elements detected. We find that both the disk and photosphere compositions align, to first order, with CI Chondrite. Our study underscores the importance of accounting for circumstellar absorption, as neglecting them leads to significant abundance errors. Additionally, the analysis of the disk's opacity highlighted an ultraviolet flux reduction due to a pseudo-continuum due to an optically thick component. This result may affect previous analyses of other polluted white dwarfs, suggesting a need for revisiting some studies.

Keywords: Extrasolar rocky planets, White dwarf stars, Ultraviolet spectroscopy, Planetesimals, Circumstellar gas
Distribution and Anisotropy of the Energy Transfer Rate in the Solar Wind Turbulence. The distribution of the energy transfer rate is critical for the interpretation of the intermittent energy cascade in the solar wind turbulence. However, the true observational distribution of the energy transfer rate in the solar wind and its anisotropy remain unknown. Here, we use a 7 day interval measured by Wind in the fast solar wind and investigate the distribution and anisotropy of the energy transfer rate based on the log-Poisson model. We find that the probability density distribution consists of two parts. The majority part locates at smaller values and is consistent with the log-normal distribution. The estimated mean value and standard deviation of the logarithmic energy transfer rate for the majority are both smaller in the direction parallel to the local mean magnetic field than in the perpendicular direction. The mean value displays a power-law shape with respect to the scale, with flatter index in the parallel direction and steeper index in the perpendicular direction. The minority part locates at larger values and expands as the scale decreases, indicating the growing intermittency toward smaller scales. The flatness for parallel logarithmic energy transfer rate is larger than that for perpendicular. And it rises as the scale decreases for all directions, demonstrating the relatively longer tail of the distribution with decreasing scale. Our results provide new insight to help interpret the intermittent energy cascade process in the solar wind turbulence.

Keywords: Interplanetary turbulence, Interplanetary magnetic fields, Heliosphere, Fast solar wind
Are There Black Hole Symbiotic X-Ray Binaries?. While there are over a dozen known neutron star (NS) symbiotic X-ray binaries (SyXBs) in the Galaxy, no SyXBs containing a black hole (BH) have been detected. We address this problem by incorporating binary population synthesis and the accretion properties of BHs fed by the wind from red giant companions. We investigate the impact of different supernova mechanisms, kick velocity distributions, and wind velocities on the formation of both NS and BH SyXBs. Our simulations show that the number of BH SyXBs is at most one-sixth of that of NS SyXBs in the Galaxy provided that the common envelope efficiency parameter α ∼ 0.3–5, and less than ∼10 BH SyXBs could be detectable in X-ray, considering their low radiation efficiencies. These findings indicate a scarcity of BH SyXBs in the Galaxy.

Keywords: Low-mass x-ray binary stars, Stellar mass black holes
Asymmetries in the Simulated Ozone Distribution on TRAPPIST-1e due to Orography. TRAPPIST-1e is a tidally locked rocky exoplanet orbiting the habitable zone of an M dwarf star. Upcoming observations are expected to reveal new rocky exoplanets and their atmospheres around M dwarf stars. To interpret these future observations we need to model the atmospheres of such exoplanets. We configured Community Earth System Model version 2–Whole Atmosphere Community Climate Model version 6, a chemistry climate model, for the orbit and stellar irradiance of TRAPPIST-1e assuming an initial Earth-like atmospheric composition. Our aim is to characterize the possible ozone (O3) distribution and explore how this is influenced by the atmospheric circulation shaped by orography, using the Helmholtz wind decomposition and meridional mass streamfunction. The model included Earth-like orography, and the substellar point was located over the Pacific Ocean. For such a scenario, our analysis reveals a north–south asymmetry in the simulated O3 distribution. The O3 concentration is highest at pressures &gt;10 hPa (below ∼30 km) near the south pole. This asymmetry arises from the higher landmass fraction in the northern hemisphere, which causes drag in near-surface flows and leads to an asymmetric meridional overturning circulation. Catalytic species were roughly symmetrically distributed and were not found to be primary driver for the O3 asymmetry. The total O3 column density was higher for TRAPPIST-1e compared to Earth, with 8000 Dobson units (DUs) near the south pole and 2000 DU near the north pole. The results emphasize the sensitivity of O3 to model parameters, illustrating how incorporating Earth-like orography can affect atmospheric dynamics and O3 distribution. This link between surface features and atmospheric dynamics underlines the importance of how changing model parameters used to study exoplanet atmospheres can influence the interpretation of observations.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric dynamics, Transmission spectroscopy, James Webb Space Telescope, Exoplanet atmospheres
Magnetic Diagnostics of Prominence Eruptions through the Hanle Effect of the He I 1083 nm Line. The magnetic field vector of the solar corona is not regularly and comprehensively being measured because of the complexity and degeneracy inherently present in the types of observations currently available. To address some of the current limitations of coronal polarimetry, we present computations that demonstrate the possibility of magnetometry using the unsaturated Hanle effect of the He I 1083 nm line. The main purpose of this investigation is to show how the linear polarization of this line can be used to routinely diagnose the orientation of the field in erupting prominences, thus providing an important constraint on the B  z  determination at 1 AU. For this work, we adopted a simplified magnetic model of a flux rope, consisting of a toroidal helical structure embedded in a hydrostatically stratified corona. Our results demonstrate the possibility to discern different orientations of the magnetic field vector in such structures under rather general and practicable viewing conditions. In particular, observations from the Sun–Earth Lagrange points are found to provide excellent locations for the deployment of synoptic instruments aiming at the estimation of the magnetic field of Earth-directed coronal mass ejections. We complete our demonstration by showing how a small (∼5 cm) space-borne coronagraph can achieve sufficient signal-to-noise ratios to make the coronal magnetometry goal outlined above feasible.

Keywords: Solar magnetic fields, Spectropolarimetry, Solar corona
NEOWISE-R Caught the Luminous SN 2023ixf in Messier 101. During routine survey imaging, the reactivated Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE-R) serendipitously caught the Type II supernova SN 2023ixf in Messier 101 on the rise, starting day 3.6 through day 10.9, and again on the decline at late times from days 211 through 213 and days 370 through 372. We have considered these mid-IR data together with observations from the ultraviolet (UV) through the near-IR, when possible. At day 3.6 we approximated the optical emission with a hot, ∼26,630 K blackbody, with a notable UV excess inferred to result from strong supernova (SN) shock interaction with circumstellar matter (CSM). In the IR, however, a clear excess is also obvious, and we fit it with a cooler, ∼1620 K blackbody with a radius of ∼2.6 × 1015 cm, consistent with dust in the progenitor's circumstellar shell likely heated by the UV emission from the CSM interaction. On day 10.8, the light detected was consistent with SN ejecta-dominated emission. At late times we also observed a clear NEOWISE-R excess, which could arise either from newly formed dust in the inner ejecta or in the contact discontinuity between the forward and reverse shocks, or from more distant pre-existing dust grains in the SN environment. Furthermore, the large 4.6 μm excess at late times can also be explained by the emergence of the carbon monoxide 1–0 vibrational band. SN 2023ixf is the best-observed SN II in the mid-IR during the first several days after the explosion and one of the most luminous such SNe ever seen.

Keywords: Core-collapse supernovae, Type II supernovae, Dust formation, Circumstellar dust, Supernovae
Magnetohydrodynamic Instabilities of Double Magnetic Bands in a Shallow-water Tachocline Model. II. Teleconnection Between High- and Low-latitude Bands and Across Equator. The "extended solar cycle" indicates that there are two deeply seated toroidal magnetic field bands in each hemisphere. Both bands migrate equatorward as a sunspot cycle progresses. Here, we examine the consequences of global MHD instability of this migrating double-band system in tachocline on the latitudinal structure of unstable modes, which are essentially MHD Rossby waves. We find that latitude-location, latitude-separation, and the amplitude of the bands strongly influence the latitudinal structure and growth rates of the unstable modes of both symmetries about the equator. These properties can lead to "teleconnections" between low- and high-latitudes in each hemisphere and across the equator. High-latitude bands can destabilize low-latitude bands that would otherwise be stable. Stronger high-latitude bands lead to strong interactions between low and high latitude in each hemisphere, but inhibit cross-equatorial band-interaction. Strong cross-equatorial interactions of modes can synchronize cycle minima in north and south. Symmetric and antisymmetric modes of similar amplitudes can lead to substantial asymmetries between north and south. As a solar cycle progresses, excited MHD Rossby waves go through a sequence of changes in latitude structure and growth rate, while maintaining strong links in latitude. These changes and links are theoretical evidence of teleconnections between widely separated latitudes and longitudes in the Sun, which may explain many of the evolving surface magnetic patterns observed as a solar cycle progresses. The wider the separation between high- and low-latitude bands, the earlier the cross-equatorial teleconnection starts in a cycle, and hence the earlier the cycle starts declining.

Keywords: Solar cycle, Magnetohydrodynamics, Solar photosphere, Solar interior, Solar activity
Electrostatic Solitary Waves in Electronegative Martian Plasma. The solar wind interacts with planetary magnetospheres, generating plasma waves in both the upstream region and the magnetospheric environment. Mars, lacking an inherent magnetic field, has an induced magnetosphere formed through solar wind interaction with its ionosphere. These waves are crucial for momentum and energy exchange within the planetary plasma environment. This study focuses on the existence and dynamics of electrostatic solitary waves (ESWs) in Martian ionospheric plasma, characterized by various flowing ions. We employ a multifluid plasma model incorporating positive (streaming) ions, negative ions, and two distinct kappa-distributed electron populations to study ESW propagation in the Martian ionosphere from first principles. Linear analysis reveals four distinct modes, including a subsonic mode due to the negative-ion beam. Electrostatic waves may become unstable due to a beam instability excited at long wavelengths. Seeking stationary profile solutions, an energy balance equation is obtained in the moving reference frame, and the shape of the solitary wave can thus be predicted numerically. A meticulous analysis reveals that either positive- or negative-polarity ESWs (or both) may occur (simultaneously) in the Martian environment. In addition to conventional bipolar E-field waveforms, our theoretical model predicts the existence of wiggly bipolar pulses (supersolitary waves) and offset bipolar pulses (flat-top solitary waves) in Martian plasma. Comparison of our model's predictions with real observational plasma parameters indicates that, like Martian magnetosheath plasma, ionospheric plasma may sustain ESWs measuring several tens of millivolts per meter.

Keywords: Space plasmas
NNHMC: An Efficient Stokes Inversion Method Using a Neural Network (NN) Model Combined with the Hamiltonian Monte Carlo (HMC) Algorithm. The Milne–Eddington (M-E) atmosphere model is commonly adopted in the inversion of the magnetic fields in the solar photosphere. By applying the Levenberg–Marquardt algorithm or training a neural network (NN) model, the magnetic field vector can be quickly inferred from the Stokes profile but lacks reliable and statistically well-defined confidence intervals for parameters. To address this, we present an efficient Bayesian inference method called NNHMC, combining the NN model with the Hamiltonian Monte Carlo (HMC) algorithm. The NN model is used to speedily synthesize batches of synthetic Stokes profiles, accelerating the inference process. The HMC algorithm significantly improves sampling efficiency in high-dimensional parameter spaces and can handle large-scale data sets in batches. The spectropolarimetric observation of an active region obtained by the Hinode/spectropolarimeter (SP) is used to demonstrate the capability of the NNHMC method. The strength, inclination, and azimuth of the magnetic field and the line-of-sight velocity inferred with the NNHMC method are very similar to those derived with the MERLIN code. Furthermore, this study provided posterior distributions and uncertainties for these parameters. A test on the same hardware and software platform shows a speed increase of up to 2.5 orders of magnitude with respect to the traditional Markov Chain Monte Carlo method (without the NN, using the M-E atmosphere model), establishing the NNHMC method as a highly effective tool for Stokes inversion based on Bayesian inference.

Keywords: Markov chain Monte Carlo, Computational methods, Bayesian statistics, Solar magnetic fields
Mid-infrared Variability in Nearby Galaxies from the MaNGA Sample. We use mid-infrared variability in galaxies to search for active galactic nuclei (AGN) in the local universe. We use a sample of 10,220 galaxies from the Mapping Nearby Galaxies at Apache Point Observatory survey, part of the Sloan Digital Sky Survey. For each galaxy, we examine its mid-infrared variability in the W2 [4.6 μm] band over 13 years using data from the Wide Infrared Survey Explorer (WISE) All-Sky and Near Earth Objects WISE missions. We demonstrate that we can detect variability signatures as small as about 7% in the rms variation of W2 flux for the majority of cases. Using other AGN signatures of the variable galaxies, such as optical narrow lines, optical broad lines, and WISE W1 ‑ W2 colors, we show that ∼75% of the variables show these additional AGN signatures, indicating that the bulk of these cases are likely to be AGN. We also identify seven galaxies that have light curves characteristic of tidal disruption events. We present here a publicly available catalog of the light-curve variability in W2 of these galaxies.

Keywords: Active galactic nuclei