Sazuna/UAT_keywords huggingface dataset:
Dating and Tracing the Origin of Enstatite Chondrite Chondrules with Cr Isotopes. Chondrules are major components of chondrites and are believed to drive the accretion of planetary embryos. As such, constraining the timing and origin of chondrules is central for understanding the early evolution of the solar system and the formation of planets. Enstatite chondrites (ECs) have isotope compositions for multiple elements that match that of the Earth and, thus, are considered to be good analogs of the precursor material from which the Earth formed. Here, we report the first high-precision mass-independent Cr isotope data of nine chondrules in one of the least-altered EH chondrites, Sahara 97096. Seven primitive chondrules show typical 54Cr/52Cr ratios of bulk ECs, whereas two chondrules have ratios similar to carbonaceous chondrites. The presence of two chondrules with a carbonaceous chondrite signature suggests early inward transport of material to the EC accretion region. The Mn/Cr ratios of the EC-like chondrules (except one with high Fe content) correlate with their 53Cr/52Cr isotope ratios, which we interpret as a fossil isochron, with a slope corresponding to a 53Mn/55Mn initial ratio of (5.01 ± 0.59) × 10-6 (2σ). When anchored to the D'Orbigny angrite, this 53Mn/55Mn ratio returns an absolute age of 4565.7 ± 0.7 Ma for EC chondrule formation (precursor age), 1.6 ± 0.7 Ma after solar system formation. This protracted formation of EC chondrules may suggest that the mass transfer of outer solar system material started prior to the end of planetary embryo accretion, as chondrules could represent the main building blocks of terrestrial planets.

Keywords: Isotopic abundances, Cosmochemistry, Chondrites, Meteoroids, Nucleosynthesis, Solar system, Chondrules, Astrochemistry, Cosmochronology
Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX. We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (Teq ∼ 4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R ∼ 115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask cross-correlation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84 ± 14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10-3-10-5 bar level.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Exoplanet atmospheres
Modulation of Galactic Cosmic Rays by Plasma Disturbances Propagating Through the Local Interstellar Medium in the Outer Heliosheath. The modulation of cosmic rays by a propagating plasma disturbance, a global merged interaction region (GMIR), in the heliosheath is simulated using a Vlasov-Fokker-Planck equation for the transport of energetic particles with significant anisotropy. The prescribed plasma structure of the GMIR contains a shock front and plasma rarefaction region behind the shock, which propagate through a simplified paramagnetic shielding model of the heliosheath. When a GMIR goes through the heliospheric magnetic field in the inner heliosheath, its modulation effects on cosmic rays are consistent with typical Forbush decreases. When a GMIR goes through the interstellar magnetic field in the outer heliosheath, only cosmic rays with large pitch angles with respect to the magnetic field vector (cosine values close to zero) are modulated by it. The difference is due to the very weak scattering of particles by the interstellar turbulence. Particles trapped in the rarefied magnetic field inside a GMIR suffer a significant amount of adiabatic cooling, which results in a considerable intensity decrease and a bidirectional anisotropy. The simulation result can be used to explain what Voyager 1 observed in the very local interstellar medium. Depending on the strength of plasma compression inside a GMIR, some cosmic rays may be accelerated, but the GMIR effect on the cosmic-ray intensity is much weaker than that due to adiabatic cooling because particles have only a brief interaction with a GMIR without trapping.

Keywords: Forbush effect, Cosmic rays
Close Binary Companions to APOGEE DR16 Stars: 20,000 Binary-star Systems Across the Color-Magnitude Diagram. Many problems in contemporary astrophysics—from understanding the formation of black holes to untangling the chemical evolution of galaxies—rely on knowledge about binary stars. This, in turn, depends on the discovery and characterization of binary companions for large numbers of different kinds of stars in different chemical and dynamical environments. Current stellar spectroscopic surveys observe hundreds of thousands to millions of stars with (typically) few observational epochs, which allows for binary discovery but makes orbital characterization challenging. We use a custom Monte Carlo sampler (The Joker) to perform discovery and characterization of binary systems through radial velocities, in the regime of sparse, noisy, and poorly sampled multi-epoch data. We use it to generate posterior samplings in Keplerian parameters for 232,495 sources released in APOGEE Data Release 16. Our final catalog contains 19,635 high-confidence close-binary (P ≲ few years, a ≲ few $\mathrm{au}$ ) systems that show interesting relationships between binary occurrence rate and location in the color-magnitude diagram. We find notable faint companions at high masses (black hole candidates), at low masses (substellar candidates), and at very close separations (mass-transfer candidates). We also use the posterior samplings in a (toy) hierarchical inference to measure the long-period binary-star eccentricity distribution. We release the full set of posterior samplings for the entire parent sample of 232,495 stars. This set of samplings involves no heuristic "discovery" threshold and therefore can be used for myriad statistical purposes, including hierarchical inferences about binary-star populations and subthreshold searches.

Keywords: Binary stars, Bayesian statistics, Close binary stars, Surveys, Astronomy data analysis, Astrostatistics, Spectroscopy, Radial velocity
Predicting Solar Flares with Machine Learning: Investigating Solar Cycle Dependence. A deep learning network, long short-term memory (LSTM), is used to predict whether an active region (AR) will produce a flare of class Γ in the next 24 hr. We consider Γ to be ≥M (strong flare), ≥C (medium flare), and ≥A (any flare) class. The essence of using LSTM, which is a recurrent neural network, is its ability to capture temporal information on the data samples. The input features are time sequences of 20 magnetic parameters from the space weather Helioseismic and Magnetic Imager AR patches. We analyze ARs from 2010 June to 2018 December and their associated flares identified in the Geostationary Operational Environmental Satellite X-ray flare catalogs. Our results produce skill scores consistent with recently published results using LSTMs and are better than the previous results using a single time input. The skill scores from the model show statistically significant variation when different years of data are chosen for training and testing. In particular, 2015-2018 have better true skill statistic and Heidke skill scores for predicting ≥C medium flares than 2011-2014, when the difference in flare occurrence rates is properly taken into account.

Keywords: Solar activity, Solar flares
Streaming Instability in Turbulent Protoplanetary Disks. The streaming instability for solid particles in protoplanetary disks is reexamined assuming the familiar alpha (α) model for isotropic turbulence. Turbulence always reduces the growth rates of the streaming instability relative to values calculated for globally laminar disks. While for small values of the turbulence parameter, α &lt; 10-5, the wavelengths of the fastest growing disturbances are small fractions of the local gas vertical scale height H, we find that for moderate values of the turbulence parameter, I.e., α ∼ 10-5-10-3, the length scales of maximally growing disturbances shift toward larger scales, approaching H. At these moderate turbulent intensities and for local particle to gas mass density ratios ɛ &lt; 0.5, the vertical scales of the most unstable modes begin to exceed the corresponding radial scales so that the instability appears in the form of vertically oriented sheets extending well beyond the particle scale height. We find that for hydrodynamical turbulent disk models reported in the literature, with α = 4 × 10-5-5 × 10-4, together with state-of-the-art global evolution models of particle growth, the streaming instability is predicted to be viable within a narrow triangular patch of α-τs parameter space centered on Stokes numbers, τs ∼ 0.01 and α ∼ 4 × 10-5, and further, exhibits growth rates on the order of several hundreds to thousands of orbit times for disks with 1% (Z = 0.01) cosmic solids abundance or metallicity. Our results are consistent with, and place in context, published numerical studies of streaming instabilities.

Keywords: Protoplanetary disks, Hydrodynamics
HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars. Quantifying the evolution of stellar extreme ultraviolet (EUV, 100-1000 Å) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 ± 0.05 M⊙ stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t-1 after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star's UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet's potential for habitability.

Keywords: Stellar chromospheres, M stars, Ultraviolet astronomy, Stellar activity, Low mass stars, Stellar evolution
Spectral Signatures of Chromospheric Condensation in a Major Solar Flare. We study the evolution of chromospheric line and continuum emission during the impulsive phase of the X-class SOL2014-09-10T17:45 solar flare. We extend previous analyses of this flare to multiple chromospheric lines of Fe I, Fe II, Mg II, C I, and Si II observed with the Interface Region Imaging Spectrograph, combined with radiative-hydrodynamical (RHD) modeling. For multiple flaring kernels, the lines all show a rapidly evolving double-component structure: an enhanced emission component at rest, and a broad, highly redshifted component of comparable intensity. The redshifted components migrate from 25 to 50 km s-1 toward the rest wavelength within ∼30 s. Using Fermi hard X-ray observations, we derive the parameters of an accelerated electron beam impacting the dense chromosphere, using them to drive an RHD simulation with the RADYN code. As in Kowalski et al. (2017), our simulations show that the most energetic electrons penetrate into the deep chromosphere, heating it to T ∼ 10,000 K, while the bulk of the electrons dissipate their energy higher, driving an explosive evaporation, and its counterpart condensation—a very dense (ne ∼ 2 × 1014 cm-3), thin layer (30-40 km thickness), heated to 8-12,000 K, moving toward the stationary chromosphere at up to 50 km s-1. The synthetic Fe II 2814.45 Å profiles closely resemble the observational data, including a continuum enhancement, and both a stationary and a highly redshifted component, rapidly moving toward the rest wavelength. Importantly, the absolute continuum intensity, ratio of component intensities, relative time of appearance, and redshift amplitude are sensitive to the model input parameters, showing great potential as diagnostics.

Keywords: Solar flares, Solar ultraviolet emission, Solar activity, Radiative transfer simulations, Solar chromosphere
Are Persistent Emission Luminosity and Rotation Measure of Fast Radio Bursts Related?. The physical origin of fast radio bursts (FRBs) is still unknown. Multiwavelength and polarization observations of an FRB source would be helpful to diagnose its progenitor and environment. So far only the first repeating source FRB 121102 appears to be spatially coincident with a persistent radio emission. Its bursts also have very large values of the Faraday rotation measure (RM), I.e., $| \mathrm{RM}| \sim {10}^{5}\,\mathrm{rad}\,{{\rm{m}}}^{-2}$ . We show that theoretically there should be a simple relation between RM and the luminosity of the persistent source of an FRB source if the observed RM mostly arises from the persistent emission region. FRB 121102 follows this relation given that the magnetic field in the persistent emission region is highly ordered and that the number of relativistic electrons powering the persistent emission is comparable to that of nonrelativistic electrons that contribute to RM. The nondetections of persistent emission sources from all other localized FRB sources are consistent with their relatively small RMs ( $\left|\mathrm{RM}\right|\lesssim {\rm{a}}\,\mathrm{few}\times 100\,\mathrm{rad}\,{{\rm{m}}}^{-2}$ ) according to this relation. Based on this picture, the majority of FRBs without a large RM are not supposed to be associated with bright persistent sources.

Keywords: Radio continuum emission, Radio bursts, Radio transient sources
A Spectroscopic Method Based on the Shapes of Nuclear Deexcitation γ-Ray Lines in Solar Flares. The deexcitation γ-ray lines in solar flares result from energetic ions (e.g., protons, α-particles) interacting with the ambient nuclei in the solar atmosphere. The centroid and width of lines contain a wealth of information on the directionality, composition, and spectra of energetic ions as well as properties of the interaction sites. New calculations for the deexcitation γ-ray line shape analysis were done to study the properties of these ions. We calculate the shapes of the most intense deexcitation γ-ray lines in the solar flares, including the 12C 4.439 MeV, 16O 6.129 MeV, 24Mg 1.369 MeV, and 28Si 1.779 MeV lines, and explore the profiles of these line shapes as a function of the accelerated ion's energy spectra and composition, as well as the heliocentric angle of flare location. The merits of deexcitation γ-ray line shape analysis include (1) only a relatively small number of parameters being required in the fitting process and (2) the characteristics of accelerated ions with joint multi-line shape analysis being well constrained. We conclude that the measurement of the width and centroid of lines is an effective method for determining the properties of flare-accelerated ions.

Keywords: Solar energetic particles, Solar gamma-ray emission, The Sun, Solar flares
Quantifying the Effect of Field Variance on the Hα Luminosity Function with the New Numerical Galaxy Catalog (ν<SUP>2</SUP>GC). We construct a model of Hα emitters (HAEs) based on a semianalytic galaxy formation model, the New Numerical Galaxy Catalog (ν2GC). In this paper, we report our estimate for the field variance of the HAE distribution. By calculating the Hα luminosity from the star formation rate of galaxies, our model well reproduces the observed Hα luminosity function (LF) at z = 0.4. The large volume of the ν2GC makes it possible to examine the spatial distribution of HAEs over a region of (411.8 Mpc)3 in the comoving scale. The surface number density of z = 0.4 HAEs with ${L}_{{\rm{H}}\alpha }\geqslant {10}^{40}$ erg s-1 is 308.9 deg-2. We have confirmed that the HAE is a useful tracer for the large-scale structure of the universe because of their significant overdensity (&gt;5σ) at clusters and the filamentary structures. The Hα LFs within a survey area of ∼2 deg2 (typical for previous observational studies) show a significant field variance up to ∼1 dex. Based on our model, one can estimate the variance on the Hα LFs within given survey areas.

Keywords: Galaxy clusters, Luminosity function, Galaxy formation, Theoretical models, Galaxy evolution
Is Superorbital Modulation in SMC X-1 Caused by Absorption in a Warped Precessing Accretion Disk?. We present a broadband spectral-timing analysis of SMC X-1 at different intensity states of its superorbital variation using 10 Suzaku and 6 Nuclear Spectroscopic Telescope Array (NuSTAR) observations. The spectrum in all the states can be described by an absorbed power law with a high-energy cutoff and a blackbody component along with an iron emission line. Compared to other supergiant high-mass X-ray binaries, the Fe Kα line equivalent width is low in SMC X-1—from less than 10 eV in the high state to up to ∼270 eV in the low states. The spectral shape is dependent on flux, with the hard X-ray spectrum steepening with increasing flux. We also report a highly variable normalization of the power-law component across these 16 superorbital states. Pulsations in the hard X-rays for both the instruments were detected in all but two observations. The pulse profiles are near sinusoidal, with two peaks and the relative intensity of the second peak decreasing with decreasing luminosity. These findings suggest that the superorbital modulation in SMC X-1 is not caused by absorption in precessing warped accretion disk alone and there are intrinsic changes in X-rays emanating from the neutron star at different superorbital states. We also note a putative cyclotron line at ∼50 keV in the NuSTAR spectra of three bright states, indicating a possible magnetic field of ∼4.2 × 1012 G. Finally, with the new pulse period measurements reported here, the time base for the secular spin-up of SMC X-1 is increased by thirteen years and the complete pulse period history shows a sudden change in the spin-up trend around 1995.

Keywords: High mass x-ray binary stars, Compact objects
First Search for r-mode Gravitational Waves from PSR J0537-6910. We report results of the first search to date for continuous gravitational waves from unstable r-modes from the pulsar $\mathrm{PSR}\ {\rm{J}}0537\mbox{--}6910$ . We use data from the first two observing runs of the Advanced LIGO network. We find no significant signal candidate and set upper limits on the amplitude of gravitational-wave signals, which are within an order of magnitude of the spin-down values. We highlight the importance of having timing information at the time of the gravitational-wave observations, I.e., rotation frequency and frequency-derivative values, and glitch-occurrence times, such as those that a NICER campaign could provide.

Keywords: Neutron stars, Gravitational waves, Pulsars
Orbital Ingredients for Cooking X-structures in Edge-on Galaxies. X-structures are often observed in galaxies hosting the so-called B/PS (boxy/peanuts) bulges and are visible from the edge-on view. They are the most notable features of B/PS bulges and appear as four rays protruding from the disk of the host galaxy and distinguishable against the B/PS bulge background. In some works, their origin is thought to be connected with the so-called banana-shaped orbits with a vertical resonance 2:1. A star in such an orbit performs two oscillations in the vertical direction per one revolution in the bar frame. Several recent studies that analyzed ensembles of orbits arising in different N-body models do not confirm the dominance of the resonant 2:1 orbits in X-structures. In our work, we analyze two N-body models and show how the X-structure in our models is gradually assembled from the center to the periphery from orbits with less than 2:1 frequency ratio. The most number of such orbits is enclosed in a "farfalle"-shape (Italian pasta) form and turns out to be non-periodic. We conclude that the X-structure is akin to the envelope curve of regions of high density caused by the crossing or folding of different types of orbits at their highest points, and does not have a "backbone" similar to that of the in-plane bar. Comparing the orbital structure of two different numerical models, we show that the dominance of one or another family of orbits with a certain ratio of the vertical oscillations frequency to the in-plane frequency depends on the parameters of the underlying galaxy and ultimately determines the morphology of the X-structure and the opening angle of its rays.

Keywords: Disk galaxies, Galaxy structure, Galaxy dynamics, Galaxy bulges, Barred spiral galaxies, N-body simulations
Does Modified Gravity Predict Fast Stellar Bars in Spiral Galaxies?. The evolution of disk galaxies in modified gravity is studied by using high-resolution N-body simulations. More specifically, we use the weak field limit of two modified gravity theories, that is, nonlocal gravity and scalar-tensor-vector gravity, known as MOG, and ignore the existence of a dark matter (DM) halo. We construct the same models as in the standard DM model and compare their dynamics with the galactic models in modified gravity. It turns out that there are serious differences between galactic models in these different viewpoints. For example, we explicitly show that the galactic models in modified gravity host faster bars compared to the DM case, but the final stellar bars are weaker in modified gravity. These facts are not new and have already been reported in our previous simulations for exponential galactic models. Therefore, our main purpose is to show that the above-mentioned differences, with an emphasis on the speed of the bars, are independent of the initial density profile of the adopted disk and halo. To do so, we employ different profiles for the disk and halo and show that the results remain qualitatively independent of the initial galactic models. Moreover, a more accurate method has been used to quantify the kinematic properties of the stellar bars. Our results imply that, contrary to the DM models, bars in modified gravity are fast rotators that never leave the fast-bar region until the end of the simulation.

Keywords: Disk galaxies, Spiral galaxies, Scalar-tensor-vector gravity, Non-standard theories of gravity, Galaxy evolution