Sazuna/UAT_keywords huggingface dataset:
Simulating the Eclipsing Binary Yields of the Rubin Observatory in the Galactic Field and Star Clusters. We present a study of the detection and recovery efficiency of the Rubin Observatory for detached eclipsing binaries (EBs) in the galactic field, globular clusters (GCs), and open clusters (OCs), with a focus on comparing two proposed observing strategies: a standard cadence (baseline) and a cadence that samples the galactic plane more evenly (colossus). We generate realistic input binary populations in all observing fields of the Rubin Observatory, simulate the expected observations in each filter, and attempt to characterize the EBs using these simulated observations. In our models, we predict that the baseline cadence will enable the Rubin Observatory to observe about three million EBs; our technique could recover and characterize nearly one million of these in the field and thousands within star clusters. If the colossus cadence is used, the number of recovered EBs would increase by an overall factor of about 1.7 in the field and in globular clusters, and a factor of about 3 in open clusters. Including semidetached and contact systems could increase the number of recovered EBs by an additional factor of about 2.5 to 3. Regardless of the cadence, observations from the Rubin Observatory could reveal statistically significant physical distinctions between the distributions of EB orbital elements between the field, GCs, and OCs. Simulations such as these can be used to bias correct the sample of Rubin Observatory EBs to study the intrinsic properties of the full binary populations in the field and star clusters.

Keywords: Globular star clusters, Stellar photometry, Astronomy data modeling, Stellar populations, Stellar astronomy, Eclipsing binary stars, Open star clusters, Time series analysis
The <SUP>59</SUP>Fe (n,γ) <SUP>60</SUP>Fe Cross Section from the Surrogate Ratio Method and Its Effect on the <SUP>60</SUP>Fe Nucleosynthesis. The long-lived 60Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction 59Fe(n,γ)60Fe on 59Fe (half-life = 44.5 days) is the key reaction for the production of 60Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 γ-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the 59Fe(n,γ)60Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5 ± 3.5 mb at kT = 30 keV and 13.4 ± 1.7 mb at kT = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of 60Fe from the 59Fe(n,γ)60Fe rate are at most 25%. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of 60Fe.

Keywords: Stellar nucleosynthesis, Massive stars, Nuclear physics
On the Use of Field RR Lyrae as Galactic Probes. V. Optical and Radial Velocity Curve Templates. We collected the largest spectroscopic catalog of RR Lyrae (RRLs) including ≍20,000 high-, medium-, and low-resolution spectra for ≍10,000 RRLs. We provide the analytical forms of radial velocity curve (RVC) templates. These were built using 36 RRLs (31 fundamental-split into three period bins-and five first-overtone pulsators) with well-sampled RVCs based on three groups of metallic lines (Fe, Mg, Na) and four Balmer lines (Hα, Hβ, Hγ, Hδ). We tackled the long-standing problem of the reference epoch to anchor light-curve and RVC templates. For the V-band, we found that the residuals of the templates anchored to the phase of the mean magnitude along the rising branch are ~35% to ~45% smaller than those anchored to the phase of maximum light. For the RVC, we used two independent reference epochs for metallic and Balmer lines and we verified that the residuals of the RVC templates anchored to the phase of mean RV are from 30% (metallic lines) up to 45% (Balmer lines) smaller than those anchored to the phase of minimum RV. We validated our RVC templates by using both the single-point and the three phase point approaches. We found that barycentric velocities based on our RVC templates are two to three times more accurate than those available in the literature. We applied the current RVC templates to Balmer lines RVs of RRLs in the globular NGC 3201 collected with MUSE at VLT. We found the cluster barycentric RV of Vγ = 496.89 ± 8.37(error) ± 3.43 (standard deviation) km s-1, which agrees well with literature estimates.

Keywords: Globular star clusters, Atomic spectroscopy, RR Lyrae variable stars, Radial velocity
Flattening of Dark Matter Cusps during Mergers: Model of M31. We run high-resolution fully GPU N-body simulations to demonstrate that the dark matter (DM) distribution in M31 is well fitted by a core-like profile. Rich observational data especially on the giant stellar stream provides stringent constraints on the initial conditions of our simulations. We demonstrate that the accretion of a satellite on a highly eccentric orbit heats up the central parts of M31, causes an outward migration of DM particles, flattens the central cusp over more than a decade in scale, and generates a new model-independent DM profile that is well fitted by a core. Our results imply that core-like central profiles could be a common feature of massive galaxies that have been initially cuspy but have accreted satellites on nearly radial orbits.

Keywords: Dark matter density, Galaxy dynamics, Andromeda Galaxy, Galaxy mergers
Phase Separation in Ultramassive White Dwarfs. Ultramassive white dwarfs are extreme endpoints of stellar evolution. Recent findings, such as a missing multi-Gyr cooling delay for a number of ultramassive white dwarfs and a white dwarf with a quasi-Chandrasekhar mass, motivate a better understanding of their evolution. A key process still subject to important uncertainties is the crystallization of their dense cores, which are generally assumed to be constituted of 16O, 20Ne, and a mixture of several trace elements (most notably 23Na and 24Mg). In this work, we use our recently developed Clapeyron integration technique to compute accurate phase diagrams of three-component mixtures relevant to the modeling of O/Ne ultramassive white dwarfs. We show that, unlike the phase separation of 22Ne impurities in C/O cores, the phase separation of 23Na impurities in O/Ne white dwarfs cannot lead to the enrichment of their cores in 23Na via a distillation process. This severely limits the prospect of transporting large quantities of 23Na toward the center of the star, as needed in the white dwarf core-collapse mechanism recently proposed by Caiazzo et al. We also show that despite representing ≈10% of the ionic mixture, 23Na and 24Mg impurities only have a negligible impact on the O/Ne phase diagram, and the two-component O/Ne phase diagram can be safely used in white dwarf evolution codes. We provide analytic fits to our high-accuracy O/Ne phase diagram for implementation in white dwarf models.

Keywords: Stellar interiors, Degenerate matter, Plasma physics, White dwarf stars, Stellar evolution
Fast Radio Bursts and Their High-energy Counterparts from Magnetar Magnetospheres. The recent discovery of a Galactic fast radio burst (FRB) occurring simultaneously with an X-ray burst (XRB) from the Galactic magnetar SGR J1935+2154 implies that at least some FRBs arise from magnetar activities. We propose that FRBs are triggered by crust fracturing of magnetars, with the burst event rate depending on the magnetic field strength in the crust. Since the crust-fracturing rate is relatively higher in polar regions, FRBs are more likely to be triggered near the directions of multipolar magnetic poles. Crust fracturing produces Alfvén waves, forming a charge-starved region in the magnetosphere and leading to nonstationary pair plasma discharges. An FRB is produced by coherent plasma radiation due to nonuniform pair production across magnetic field lines. Meanwhile, the FRB-associated XRB is produced by the rapid relaxation of the external magnetic field lines. In this picture, the sharp-peak hard X-ray component in association with FRB 200428 is from a region between adjacent trapped fireballs, and its spectrum with a high cutoff energy is attributed to resonant Compton scattering. The persistent X-ray emission is from a hot spot heated by the magnetospheric activities, and its temperature evolution is dominated by magnetar surface cooling. Within this picture, magnetars with stronger fields tend to produce brighter and more frequent repeated bursts.

Keywords: Pulsars, Non-thermal radiation sources, Exoplanet formation, X-ray bursts, Radio transient sources
The Role of Complex Ionized Absorbers in the Soft X-Ray Spectra of Intermediate Polars. In magnetic cataclysmic variables (mCVs), X-ray radiation originates from a shock-heated, multi-temperature plasma in the post-shock region near the white dwarf's surface. These X-rays are modified by a complex distribution of absorbers in the pre-shock region. The presence of photoionized lines and warm absorber features in the soft X-ray spectra of these mCVs suggests that these absorbers are ionized. We developed the ionized complex absorber model zxipab, which is represented by a power-law distribution of ionized absorbers in the pre-shock flow. Using the ionized absorber model zxipab along with a cooling flow model with a reflection component, we model the broadband Chandra/High-Energy Transmission Grating (HETG) and Nuclear Spectroscopic Telescope Array (NuSTAR) spectra of two intermediate polars (IPs): NY Lup and V1223 Sgr. We find that this model describes well many of the H- and He-like emission lines from medium-Z elements, which arise from a collisionally excited plasma. However the model fails to account for some of the He-like triplets from the medium-Z elements, which points toward their photoionized origin. We do not find compelling evidence for a blackbody component to model the soft excess seen in the residuals of the Chandra/HETG spectra, which could be due to uncertainties in the estimation of the interstellar absorption of these sources using the Chandra/HETG data and/or excess fluxes seen in some photoionized emission lines which are not accounted for by the cooling flow model. We describe the implications of this model with respect to the geometry of the pre-shock region for these two IPs.

Keywords: White dwarf stars, Cataclysmic variable stars, Astronomy data analysis
Effect of Dust Rotational Disruption by Radiative Torques and Implications for the F-corona Decrease Revealed by the Parker Solar Probe. The first-year results from the Parker Solar Probe (PSP) reveal a gradual decrease of F-coronal dust from distances of D = 0.166-0.336 au (or the inner elongations of ~9.22-18.69 R⊙) to the Sun. Such an F-corona decrease cannot be explained by the dust sublimation scenario of the popular silicate composition that implies a dust-free boundary zone at heliocentric radius R ≲ 4-5 R⊙, but it may be explained by appealing to various dust compositions with different sublimation fronts. In this paper, we present an additional explanation for the F-corona decrease using our newly introduced mechanism of dust destruction, the so-called Radiative Torque Disruption (RATD) mechanism. We demonstrate that the RATD rapidly breaks large grains into nanoparticles so that they can be efficiently destroyed by nonthermal sputtering induced by the bombardment of energetic protons from slow solar winds, which extends the dust-free zone established by thermal sublimation to Rdfz ~ 8 R⊙. Beyond this extended dust-free zone, we find that the dust mass decreases gradually from R ~ 42 R⊙ toward the Sun due to partial removal of nanodust by nonthermal sputtering. The joint effect of the RATD and nonthermal sputtering can successfully reproduce the gradual decrease of the F-corona between 19 and 9 R⊙ observed by the PSP. Finally, the RATD mechanism can efficiently produce nanoparticles usually observed in the inner solar system.

Keywords: Interstellar dust, Interplanetary dust, Solar F corona, Circumstellar dust
Broadband Variability Study of Maxi J1631-479 in Its Hard-intermediate State Observed with Insight-HXMT. We report the energy-resolved broadband timing analysis of the black hole X-ray transient MAXI J1631-479 during its 2019 outburst from February 11 to April 9, using data from the Insight-Hard X-ray Modulation Telescope (Insight-HXMT), which caught the source from its hard-intermediate state to the soft state. Thanks to the large effective area of Insight-HXMT at high energies, we are able to present the energy dependence of fast variability up to ~100 keV. Type-C quasi-periodic oscillations (QPOs) with a frequency varying between 4.9 and 6.5 Hz are observed in the 1-100 keV energy band. While the QPO fractional rms increases with photon energy from 1 keV to ~10 keV and remains more or less constant from ~10 keV to ~100 keV, the rms of the flat-top noise first increases from 1 keV to ~8 keV and then drops to less than 0.1% above ~30 keV. We suggest that the disappearance of the broadband variability above 30 keV could be caused by the nonthermal acceleration in the Comptonizing plasma. At the same time, the QPOs could be produced by the precession of either a small-scale jet or a hot inner flow model.

Keywords: Stellar accretion disks, Black hole physics, Low-mass x-ray binary stars
Multimessenger Implications of Sub-PeV Diffuse Galactic Gamma-Ray Emission. The diffuse Galactic gamma-ray flux between 0.1 and 1 PeV has recently been measured by the Tibet ASγ Collaboration. The flux and spectrum are consistent with the decay of neutral pions from hadronuclear interactions between Galactic cosmic rays and the interstellar medium (ISM). We derive the flux of the Galactic diffuse neutrino emission from the same interaction process that produces the gamma rays. Our calculation accounts for the effect of gamma-ray attenuation inside the Milky Way and uncertainties due to the spectrum and distribution of cosmic rays, gas density, and infrared emission of the ISM. We find that the contribution from the Galactic plane (GP) to the all-sky neutrino flux is ≲5%-10% around 100 TeV. The Galactic and extragalactic neutrino intensities are comparable in the GP region. Our results are consistent with the upper limit reported by the IceCube and ANTARES Collaborations, and predict that next-generation neutrino experiments may observe the Galactic component. We also show that the Tibet ASγ data imply either an additional component in the cosmic-ray nucleon spectrum or contribution from discrete sources, including PeVatrons such as superbubbles and hypernova remnants, and PeV electron accelerators. Future multimessenger observations between 1 TeV and 1 PeV are crucial to decomposing the origin of sub-PeV gamma-rays.

Keywords: Galactic cosmic rays, Neutrino astronomy, High-energy cosmic radiation
Predictions of Astrometric Jitter for Sun-like Stars. II. Dependence on Inclination, Metallicity, and Active-region Nesting. Ultra-precise astrometry from the Gaia mission is expected to lead to astrometric detections of more than 20,000 exoplanets in our Galaxy. One of the factors that could hamper such detections is the astrometric jitter caused by the magnetic activity of the planet host stars. In our previous study, we modeled astrometric jitter for the Sun observed equator-on. In this work, we generalize our model and calculate the photocenter jitter as it would be measured by the Gaia and Small-JASMINE missions for stars with solar rotation rate and effective temperature, but with various values of the inclination angle of the stellar rotation axis. In addition, we consider the effect of metallicity and of nesting of active regions (i.e., the tendency of active regions to emerge in the vicinity of each other). We find that, while the jitter of stars observed equator-on does not have any long-term trends and can be easily filtered out, the photocenters of stars observed out of their equatorial planes experience systematic shifts over the course of the activity cycle. Such trends allow the jitter to be detected with continuous measurements, in which case it can interfere with planet detectability. An increase in the metallicity is found to increase the jitter caused by stellar activity. Active-region nesting can further enhance the peak-to-peak amplitude of the photocenter jitter to a level that could be detected by Gaia.

Keywords: Solar activity, Exoplanet detection methods, Astrometry, Stellar activity
HARM3D+NUC: A New Method for Simulating the Post-merger Phase of Binary Neutron Star Mergers with GRMHD, Tabulated EOS, and Neutrino Leakage. The first binary neutron star merger has already been detected in gravitational waves. The signal was accompanied by an electromagnetic counterpart including a kilonova component powered by the decay of radioactive nuclei, as well as a short γ-ray burst. In order to understand the radioactively powered signal, it is necessary to simulate the outflows and their nucleosynthesis from the post-merger disk. Simulating the disk and predicting the composition of the outflows requires general relativistic magnetohydrodynamical (GRMHD) simulations that include a realistic, finite-temperature equation of state (EOS) and self-consistently calculating the impact of neutrinos. In this work, we detail the implementation of a finite-temperature EOS and the treatment of neutrinos in the GRMHD code HARM3D+NUC, based on HARM3D. We include formal tests of both the finite-temperature EOS and the neutrino-leakage scheme. We further test the code by showing that, given conditions similar to those of published remnant disks following neutron star mergers, it reproduces both recombination of free nucleons to a neutron-rich composition and excitation of a thermal wind.

Keywords: Nuclear astrophysics, General relativity, Relativistic disks, Magnetohydrodynamical simulations
Characteristic Scales of Magnetic Switchback Patches Near the Sun and Their Possible Association With Solar Supergranulation and Granulation. Parker Solar Probe (PSP) data recorded within a heliocentric radial distance of 0.3 au have revealed a magnetic field dominated by Alfvénic structures that undergo large local variations or even reversals of the radial magnetic field. They are called magnetic switchbacks, they are consistent with folds in magnetic field lines within a same magnetic sector and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either in the low solar atmosphere through magnetic reconnection processes or result from the evolution of turbulence or velocity shears in the expanding solar wind. In this work, we investigate the temporal and spatial characteristic scales of magnetic switchback patches. We define switchbacks as a deviation from the nominal Parker spiral direction and detect them automatically for PSP encounters 1, 2, 4, and 5. We focus in particular on a 5.1 day interval dominated by switchbacks during E5. We perform a wavelet transform of the solid angle between the magnetic field and the Parker spiral and find periodic spatial modulations with two distinct wavelengths, respectively consistent with solar granulation and supergranulation scales. In addition we find that switchback occurrence and spectral properties seem to depend on the source region of the solar wind rather than on the radial distance of PSP. These results suggest that switchbacks are formed in the low corona and modulated by the solar surface convection pattern.

Keywords: Supergranulation, Solar wind, Solar physics, Solar granulation, Solar magnetic fields, Wavelet analysis
Electron Acceleration at Rippled Low-mach-number Shocks in High-beta Collisionless Cosmic Plasmas. Using large-scale fully kinetic two-dimensional particle-in-cell simulations, we investigate the effects of shock rippling on electron acceleration at low-Mach-number shocks propagating in high-β plasmas, in application to merger shocks in galaxy clusters. We find that the electron-acceleration rate increases considerably when the rippling modes appear. The main acceleration mechanism is stochastic shock-drift acceleration, in which electrons are confined at the shock by pitch-angle scattering off turbulence and gain energy from the motional electric field. The presence of multiscale magnetic turbulence at the shock transition and the region immediately behind the main shock overshoot is essential for electron energization. Wide-energy non-thermal electron distributions are formed both upstream and downstream of the shock. The maximum energy of the electrons is sufficient for their injection into diffusive shock acceleration. We show for the first time that the downstream electron spectrum has a power-law form with index p ≈ 2.5, in agreement with observations.

Keywords: Galaxy clusters, Shocks, Computational methods, Plasma astrophysics
Connecting the Low to the High Corona: A Method to Isolate Transients in STEREO/COR1 Images. We present a method that isolates time-varying components from coronagraph and extreme ultraviolet images, allowing substreamer transients propagating within streamers to be tracked from the low to the high corona. The method uses a temporal bandpass filter with a transmission bandwidth of ~2.5-10 hr that suppresses both high- and low-frequency variations in observations made by the STEREO/SECCHI suite. We demonstrate that this method proves crucial in linking features in the low corona, where the magnetic field is highly nonradial, to their counterparts in the high corona, where the magnetic field follows a radial path, through the COR1 instrument. We also apply our method to observations by the COR2 and EUVI instruments on board SECCHI and produce height-time profiles that reveal small density enhancements, associated with helmet streamers propagating from ~1.2 R⊙ out to beyond 5 R⊙. Our processing method reveals that these features are common during the period of solar minimum in this study. The features recur on timescales of hours, originate very close to the Sun, and remain coherent out into interplanetary space. We measure the speed of the features and classify them as slow (a few to tens of kilometers per second) or fast (~100 km s-1). Both types of features serve as an observable tracer of a variable component of the slow solar wind to its source regions. Our methodology helps overcome the difficulties in tracking small-scale features through COR1. As a result, it proves successful in measuring the connectivity between the low and high corona and in measuring the velocities of small-scale features.

Keywords: Quiet sun, Solar wind, Astronomical techniques, Coronagraphic imaging, Solar corona
Mid-infrared Period-Luminosity Relations for Miras in the Large Magellanic Cloud. We present the mid-infrared (mid-IR) period-luminosity relations (PLRs) using over 1000 Mira variables in the Large Magellanic Cloud, for the four Wide-field Infrared Survey Explorer and the four Spitzer bands. These PLRs cover a mid-IR wavelength range from 3.4-22 μm and are presented separately for the oxygen-rich (O-rich) and carbon-rich (C-rich) Miras. These relations can be used to measure distances to individual O-rich and/or C-rich Mira stars with an accuracy of 5% and 12%, respectively. They are the most accurate Mira PLRs in the mid-IR to date.

Keywords: Pulsating variable stars, Carbon stars, Large Magellanic Cloud, Distance indicators, Asymptotic giant branch stars, Mira variable stars, Long period variable stars, Late-type giant stars, Stellar distance