Sazuna/UAT_keywords huggingface dataset:
On the Evolution of the Anisotropic Scaling of Magnetohydrodynamic Turbulence in the Inner Heliosphere. We analyze a merged Parker Solar Probe (PSP) and Solar Orbiter (SO) data set covering heliocentric distances 13 R ⊙ ≲ R ≲ 220 R ⊙ to investigate the radial evolution of power and spectral index anisotropy in the wavevector space of solar wind turbulence. Our results show that anisotropic signatures of turbulence display a distinct radial evolution when fast, V sw ≥ 400 km s-1, and slow, V sw ≤ 400 km s-1, wind streams are considered. The anisotropic properties of slow wind in Earth orbit are consistent with a "critically balanced" cascade, but both spectral index anisotropy and power anisotropy diminish with decreasing heliographic distance. Fast streams are observed to roughly retain their near-Sun anisotropic properties, with the observed spectral index and power anisotropies being more consistent with a "dynamically aligned" type of cascade, though the lack of extended fast wind intervals makes it difficult to accurately measure the anisotropic scaling. A high-resolution analysis during the first perihelion of PSP confirms the presence of two subranges within the inertial range, which may be associated with the transition from weak to strong turbulence. The transition occurs at κ d  i  ≈ 6 × 10-2 and signifies a shift from -5/3 to -2 and from -3/2 to -1.57 scaling in parallel and perpendicular spectra, respectively. Our results provide strong observational constraints for anisotropic theories of MHD turbulence in the solar wind.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Plasma astrophysics
Discovery of an Extended γ-Ray Emission around the Supernova Remnant Candidate Associated with PSR J0837-2454. Motivated by the recent discovery of a low-surface-brightness diffuse emission, a supernova remnant (SNR) candidate, surrounding the young pulsar PSR J0837-2454, we carry out a likelihood analysis of the γ-ray data obtained by the Fermi Gamma-ray Space Telescope from 2008 August to 2022 November. Using a 2D Gaussian spatial template, we detect a significant extended γ-ray emission with a 68% containment radius of ~1.°8, which is spatially coincident with the new SNR candidate at the ~12σ confidence level. The spectrum of the extended γ-ray emission, obtained in the energy range of 0.1-500.0 GeV, shows a significant spectral curvature at ~1 GeV, with a log-parabola spectral shape. Several scenarios, such as an SNR, pulsar wind nebula, and pulsar halo, are discussed as the potential origins of the extended γ-ray emission, and our model fitting results are preferred for the SNR scenario.

Keywords: Supernova remnants, Gamma-rays, Pulsars
A Quantum-mechanical Treatment of Electron Broadening in Strong Magnetic Fields. Spectral line-shape fitting is an extremely useful tool in determining the gravity of white dwarf stars. This method is so far limited to nonmagnetic white dwarfs largely because the theory of line broadening in high magnetic fields is not as complete as in the nonmagnetic case. Current Stark+Zeeman models treat plasma particles classically and ignore the motion of the nucleus. We develop the formalism for a quantum-mechanical treatment of the perturbing electrons and include the nuclear motion as part of the broadening and explore their relative importance. The conditions we explore are those found in white dwarf and neutron star atmospheres. We find that, contrary to previous studies, the quantized perturbing electrons create more broadening than perturbers on a straight-path trajectory. Additionally, the quantization of the plasma electrons gives rise to resonances away from the line center. The nuclear motion creates an additional electric field, which also leads to an increase in line broadening; however, this effect in neutron star atmospheres is not as large as previously estimated. This suggests that neutron star spectral lines are sensitive to density and that their mass and radius can be obtained from spectral line fitting, which would help constrain the neutron star equation of state.

Keywords: Neutron stars, Plasma physics, Fundamental parameters of stars, White dwarf stars, Atomic spectroscopy, Stellar atmospheres
Implications of the Conformal Constraint on Sound Speed on the Radius of PSR J0952-0607 within Rastall Gravity. It has been shown that the nonminimal coupling between geometry and matter can provide models for massive compact stars that are consistent with the conformal bound on the sound speed, $0\leqslant {c}_{s}^{2}\leqslant {c}^{2}/3$ , where the core density approaches a few times the nuclear saturation density. We impose the conformal upper bound on the sound speed on Rastall's field equations of gravity, with Krori-Barua potentials in the presence of an anisotropic fluid as a matter source, to estimate the radius of the most massive pulsar ever observed, PSR J0952-0607. For its measured mass M = 2.35 ± 0.17 M ⊙, we obtain a radius R = 14.087 ± 1.0186 km as inferred by the model. We investigate a possible connection between Rastall gravity and the MIT bag model with an equation of state, ${p}_{r}(\rho )\approx {c}_{s}^{2}\left(\rho -{\rho }_{{\rm{s}}}\right)$ , in the radial direction, with ${c}_{s}=c/\sqrt{3}$ and a surface density ρ s slightly above the nuclear saturation density ρ nuc = 2.7 × 1014 g cm-3. The corresponding mass-radius diagram is in agreement with our estimated value of the radius and with astrophysical observations of other pulsars at 68% confidence level.

Keywords: Stellar structures, Neutron star cores, Millisecond pulsars, Massive stars, Non-standard theories of gravity
High-density Reflection Spectroscopy of Black Hole X-Ray Binaries in the Hard State. We present a high-density relativistic reflection analysis of 21 spectra of six black hole X-ray binaries in the hard state with data from NuSTAR and Swift. We find that 76% of the observations in our sample require a disk density higher than the 1015 cm-3 assumed in the previous reflection analysis. Compared with the measurements from active galactic nuclei, stellar mass black holes have higher disk densities. Our fits indicate that the inner disk radius is close to the innermost stable circular orbit in the luminous hard state. The coronal temperatures are significantly lower than the prediction of a purely thermal plasma, which can be explained with a hybrid plasma model. If the disk density is fixed at 1015 cm-3, the disk ionization parameter is overestimated while the inner disk radius is unaffected.

Keywords: Accretion, X-ray binary stars, Stellar mass black holes, High energy astrophysics
A UFO Seen Edge-on? Resolving Ultrafast Outflow Emission on  200 pc Scales with Chandra in the Active Nucleus of Mrk 34. We present Chandra ACIS imaging spectroscopy of the nucleus of the Seyfert 2 Galaxy Mrk 34. We identify spatially and spectrally resolved features in the band that includes Fe Kα, Fe XXV, and Fe XXVI. These features suggest high-velocity (≳15,000 km s-1 line-of-sight) material spanning ~0.″5, within ~200 pc of the nucleus. This outflow could have deprojected velocities ~12-28× greater than the [O III]-emitting outflows, and could potentially dominate the kinetic power in the outflow. This emission may point to the origins of the optical and X-ray winds observed at larger radii, and could indicate a link between ultrafast outflows and AGN feedback on ≳kiloparsec scales.

Keywords: AGN host galaxies, Seyfert galaxies, X-ray active galactic nuclei
Fraction of Clumpy Star-forming Galaxies at 0.5 ≤ z ≤ 3 in UVCANDELS: Dependence on Stellar Mass and Environment. High-resolution imaging of galaxies in rest-frame UV has revealed the existence of giant star-forming clumps prevalent in high-redshift galaxies. Studying these substructures provides important information about their formation and evolution and informs theoretical galaxy evolution models. We present a new method to identify clumps in galaxies' high-resolution rest-frame UV images. Using imaging data from CANDELS and UVCANDELS, we identify star-forming clumps in an HST/F160W ≤ 25 AB mag sample of 6767 galaxies at 0.5 ≤ z ≤ 3 in four fields, GOODS-N, GOODS-S, EGS, and COSMOS. We use a low-passband filter in Fourier space to reconstruct the background image of a galaxy and detect small-scale features (clumps) on the background-subtracted image. Clumpy galaxies are defined as those having at least one off-center clump that contributes a minimum of 10% of the galaxy's total rest-frame UV flux. We measure the fraction of clumpy galaxies (f clumpy) as a function of stellar mass, redshift, and galaxy environment. Our results indicate that f clumpy increases with redshift, reaching ~65% at z ~ 1.5. We also find that f clumpy in low-mass galaxies ( $9.5\leqslant \mathrm{log}({M}_{* }/{M}_{\odot })\leqslant 10$ ) is 10% higher compared to that of their high-mass counterparts ( $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.5$ ). Moreover, we find no evidence of significant environmental dependence of f clumpy for galaxies at the redshift range of this study. Our results suggest that the fragmentation of gas clouds under violent disk instability remains the primary driving mechanism for clump formation, and incidents common in dense environments, such as mergers, are not the dominant processes.

Keywords: Galaxy environments, Galaxy formation, Galaxy evolution, Star forming regions
Search for Young and Intermediate-age Stellar Populations in the Galactic Center with Subaru/MOIRCS and CO Narrowband Filters. Extinction toward the Galactic Center (GC) is extreme and limits observations of its stars to the infrared. In addition, the extinction varies on scales of arcseconds. It is therefore highly challenging to distinguish between different stars photometrically and to identify young, massive, or intermediate-age stars that can trace recent star formation. Here we report the results of near-infrared imaging observations of a $6\buildrel{\,\prime}\over{.} 0\times 3\buildrel{\,\prime}\over{.} 3$ region at the GC that encompasses the northwest part of the nuclear star cluster and parts of the nuclear stellar disk. We carried out the observations with the wide-field camera MOIRCS of the Subaru Telescope, using three narrowband (NB) filters. Two of the filters trace the stellar continuum, while we use the third one to measure the strength of the CO absorption features that are prominent in the spectra of cool giants, shallower in the spectra of warmer stars, and absent in young massive stars. Thus, we aim to distinguish between old late-type giants and young and intermediate-age stars. We have found 131 candidates of young and intermediate-age stars. The magnitude limit is ≈11.25 in the extinction-corrected K-band magnitude. The contamination of the candidates by old giants is estimated to be 26%. We show that our method allows us to identify correctly four out of five spectroscopically confirmed massive stars, and 68 of 75 spectroscopically confirmed cool stars (91%). Our results suggest that imaging observations with a CO NB filter can be complementary to other methods to identify massive stars in the GC.

Keywords: Narrow band photometry, Galactic center, Infrared photometry
Flares, Warps, Truncations, and Satellite: The Ultra-thin Galaxy UGC 11859. The structure of the outskirts of galaxies provides valuable information about their past and evolution. Due to their projected orientation, edge-on isolated galaxies effectively serve as test labs in which to study the three-dimensional structures of galaxies, including warps and flares, and to explore the possible sources of such distortions. We analyzed the structure of the apparently isolated edge-on ultra-thin galaxy UGC 11859 to look for the presence of distortions. The deep optical imaging observations ( ${\mu }_{\mathrm{lim}}=30.6$ and 30.0 $\mathrm{mag}\ {\mathrm{arcsec}}^{-2}$ in the g- and r-bands, respectively) we acquired with the 10.4 m Gran Telescopio Canarias are used to derive the radial and vertical surface brightness profiles and g - r color radial profile. We find that UGC 11859's disk displays a significant gravitational distortion. A warp is clearly detected on one side of the disk, and the galactic plane on both sides of the center shows increasing scale height with an increasing galactocentric radius, indicating the presence of a flare in the stellar distribution. The surface brightness profile of the disk shows a sharp break at 24 kpc galactocentric radius, and a steep decline to larger radii, an "edge-on truncation," which we associate with the presence of the flare. The present study is the first observational support for a connection between truncations and flares. Just beyond the warped side of the disk, a faint galaxy is observed within a small angular distance, identified as a potential interacting companion. Based on ultradeep g and r photometry we estimate that if the potential companion is at the same distance as UGC 11859, the stellar mass of the satellite galaxy is log10(M ⊙) = ${6.33}_{-0.02}^{+0.02}$ .

Keywords: Spiral galaxies, Disk galaxies, Galaxy structure, Dwarf galaxies, Galaxy evolution, Galaxies, Low surface brightness galaxies
Formation of Complex Organic Molecules on Interstellar CO Ices? Insights from Computational Chemistry Simulations. The carbon (3P) atom is a reactive species that, according to laboratory experiments and theoretical calculations, condensates with interstellar ice components. This fact is of uttermost importance for the chemistry in the interstellar medium (ISM) because the condensation reaction is barrierless, and the subsequent species formed are still reactive given their open-shell character. Carbon condensation on CO-rich ices forms the C=C=O (3Σ-) species, which can be easily hydrogenated twice to form ketene (H2CCO). Ketene is very reactive in terrestrial conditions, usually found as an intermediate that is difficult to isolate in chemical synthesis laboratories. These characteristics suggest that ketene can be a good candidate to form interstellar complex organic molecules via a two-step process, i.e., its activation followed by a radical-radical coupling. In this work, reactions between ketene and atomic H and the OH and NH2 radicals on a CO-rich ice model have been explored by means of quantum chemical calculations complemented by kinetic calculations to evaluate if they are favorable in the ISM. Results indicate that the addition of H to ketene (helped by tunneling) to form the acetyl radical (CH3CO) is the most preferred path as the reactions with OH and NH2 possess activation energies (≥9 kJ mol-1) hard to surmount in the ISM conditions unless external processes provide energy to the system. Thus, acetaldehyde (CH3CHO) and, probably, ethanol (CH3CH2OH) formation via further hydrogenations, are the possible unique operating synthetic routes. Moreover, from the computed, relatively large binding energies of OH and NH2 on CO ice, slow diffusion is expected, hampering possible radical-radical couplings with CH3CO. The astrophysical implications of these findings are discussed considering the incoming James Webb Space Telescope observations.

Keywords: Interstellar molecules, Interstellar dust, Reaction rates, Astrochemistry, Computational methods, Surface ices, Interstellar medium, Complex organic molecules
Understanding Sun-as-a-Star Variability of Solar Balmer Lines. Precise, high-cadence, long-term records of stellar spectral variability at different temporal scales lead to better understanding of a wide variety of phenomena including stellar atmospheres and dynamos, convective motions, and rotational periods. Here, we investigate the variability of solar Balmer lines (Hα, β, γ, δ) observed by space-borne radiometers (OSIRIS, SCIAMACHY, OMI, and GOME-2), combining these precise, long-term observations with high-resolution data from the ground-based NSO/ISS spectrograph. We relate the detected variability to the appearance of magnetic features on the solar disk. We find that on solar-rotational timescales (about 1 month), the Balmer line activity indices (defined as line-core to line-wing ratios) closely follow variations in the total solar irradiance (which is predominantly photospheric), thus frequently (specifically, during passages of sunspot groups) deviating from behavior of activity indices that track chromospheric activity levels. On longer timescales, the correlation with chromospheric indices increases, with periods of low correlation or even anticorrelation found at intermediate timescales. Comparison of these observations with estimates from semiempirical irradiance reconstructions helps quantify the contributions of different magnetic and quiet features. We conclude that both the lower sensitivity to network and in part the higher sensitivity to filaments and prominences, may result in complex, time-dependent relationships between Balmer and other chromospheric indices observed for the Sun and solar-like stars. The fact that core and wings contribute in a similar manner to the variability, and current knowledge of Balmer-lines formation in stellar atmospheres, supports the notion that Balmer line core-to-wing ratio indices behave more like photospheric rather than chromospheric indices.

Keywords: Solar cycle, Solar spectral irradiance, Solar faculae, Solar filaments, Solar radiation, Solar electromagnetic emission, Solar activity, Spectral index, Sunspot cycle
X-Ray Activity Variations and Coronal Abundances of the Star-Planet Interaction Candidate HD 179949. We carry out detailed spectral and timing analyses of the Chandra X-ray data of HD 179949, a prototypical example of a star with a close-in giant planet with possible star-planet interaction (SPI) effects. We find a low coronal abundance A(Fe)/AH) ≈ 0.2 relative to the solar photospheric baseline of Anders &amp; Grevesse, and significantly lower than the stellar photosphere as well. We further find low abundances of high first ionization potential (FIP) elements A(O)/A(Fe) ≲ 1, A(Ne)/A(Fe) ≲ 0.1, but with indications of higher abundances of A(N)/A(Fe) ≫ 1, A(Al)/A(Fe) ≲ 10. We estimate a FIP bias for this star in the range ≈ - 0.3 to -0.1, larger than the ≲ -0.5 expected for stars of this type, but similar to stars hosting close-in hot Jupiters. We detect significant intensity variability over timescales ranging from 100 s to 10 ks, and also evidence for spectral variability over timescales of 1-10 ks. We combine the Chandra flux measurements with Swift and XMM-Newton measurements to detect periodicities, and determine that the dominant signal is tied to the stellar polar rotational period, consistent with expectations that the corona is rotational-pole dominated. We also find evidence for periodicity at both the planetary orbital frequency and at its beat frequency with the stellar polar rotational period, suggesting the presence of a magnetic connection between the planet and the stellar pole. If these periodicities represent an SPI signal, it is likely driven by a quasi-continuous form of heating (e.g., magnetic field stretching) rather than sporadic, hot, impulsive flare-like reconnections.

Keywords: Hot Jupiters, F stars, Exoplanets, Star-planet interactions
Life beyond 30: Probing the -20 &lt; M <SUB>UV</SUB> &lt; -17 Luminosity Function at 8 &lt; z &lt; 13 with the NIRCam Parallel Field of the MIRI Deep Survey. We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 &lt; z &lt; 13 derived from deep NIRCam observations taken in parallel with the MIRI Deep Survey of the Hubble Ultra Deep Field (HUDF), NIRCam covering the parallel field 2. Our deep (40 hr) NIRCam observations reach an F277W magnitude of 30.8 (5σ), more than 2 mag deeper than JWST public data sets already analyzed to find high-redshift galaxies. We select a sample of 44 z &gt; 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z &gt; 8, good fits based on χ 2 calculations, and predominant solutions compared to z &lt; 8 alternatives. We find mild evolution in the luminosity function from z ~ 13 to z ~ 8, i.e., only a small increase in the average number density of ~0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = - 2.2 ± 0.1, and M * = - 20.8 ± 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses ~108 M ⊙ during the first 350 Myr of the universe, z ~ 12, with models matching better the luminosity density observational estimations ~150 Myr later, by z ~ 9.

Keywords: Early universe, Galaxy formation, James Webb Space Telescope, Galaxy evolution, Broad band photometry, High-redshift galaxies
First Detection of a Linear Structure in the Midplane of the Young HH 211 Protostellar Disk: A Spiral Arm?. Spiral structures have been detected in evolved protostellar disks, driving the disk accretion toward the central protostars to facilitate star formation. However, it is still unclear if these structures can form earlier in young protostellar disks. With the Atacama Large Millimeter/submillimeter Array, we have detected and spatially resolved a very young and nearly edge-on dusty disk with a radius of only ~20 au in the HH 211 protostellar system at submillimeter wavelength. It is geometrically thick, indicating that the submillimeter-light-emitting dust grains have yet to settle to the midplane for planet formation. Intriguingly, it shows three bright linear structures parallel to the equatorial plane, resembling a three-layer pancake that has not been seen before. The top and bottom ones arise from the warm disk surfaces, unveiling the flared structure of the disk. More importantly, the middle one is in the dense midplane of the disk and can be modeled as a trailing spiral arm excited by disk gravity, as seen in evolved protostellar disks, supporting the presence of spiral structures in the very early phase for disk accretion.

Keywords: Stellar accretion disks, Jets, Star formation
Temporal Variation of the Rotation in the Solar Transition Region. The temporal variations of solar rotation in the photosphere, chromosphere, and corona have been widely investigated, whereas the rotation of the solar transition region is rarely studied. Here, we perform a primary study about the long-term variation of the rotation in the transition region using Lyα irradiance from 1947 February 14 to 2023 February 20. Correlation techniques are used, and the main results are as follows. (1) The sidereal rotation period of the solar transition region varies between 22.24 and 31.49 days, and the mean sidereal rotation period is 25.50 days for the studied time interval 1947-2022. (2) The rotation period of the transition region exhibits a clear downward trend during 1947-2022, which might be caused by the reduced heliospheric pressure and the weaker solar global magnetic fields. (3) Significant periodic signal of the quasi-Schwabe cycle is found in the rotation periods of the transition region. (4) The cross-correlation between the rotation periods of the solar transition region and sunspot activity corroborates a strong correlation with the Schwabe cycle. Possible mechanisms responsible for these results are discussed.

Keywords: Solar cycle, Solar rotation, Solar transition region