adsabs/SciX_UAT_keywords huggingface dataset:
Dynamic Responses of Radiation Belt Electron Fluxes to Magnetic Storms and their Correlations with Magnetospheric Plasma Wave Activities

To investigate the responses of Earth's radiation belt electrons during magnetic storms and their correlations with magnetospheric chorus and plasmaspheric hiss waves, a statistical analysis is conducted using high-quality Van Allen Probes measurements during 68 isolated geomagnetic storms from 2012 September to 2017 December. The variations of radiation belt electron fluxes exhibit high dependence on electron kinetic energy, L-shell, and geomagnetic storm magnitude. It is found that the Increase-type events increase considerably with L-shell at L ∼ 3.0-5.0, the Decrease-type events tend to occur more frequently at L = 3.7-4.7 for <1 MeV electrons during weak storms and at L = 3.5-6 for >1 MeV electrons during moderate storms, and the No-change-type storm events are relatively dominant for extremely high-energy (>5.2 MeV) electrons. Superposed epoch analyses for the three types of storm events indicate that compared to relativistic (604 keV) electrons, ultrarelativistic (3.4 MeV) electron flux enhancements are more likely in association with elevated solar wind pressure during the storm initial phase, enhanced southward initial mass function Bz during the storm main phase, and prolonged high solar wind speed during the storm recovery phase. It is also shown that the dynamic variations of relativistic (604 keV) electron fluxes are closely connected to the activity level of chorus waves, but the three variation categories of ultrarelativistic (3.4 MeV) electrons have basically comparable intensities of chorus waves possibly due to the loss mechanisms becoming more dominate for their No-change-type or Decrease-type events. From a statistically observational perspective, chorus waves act as a critical candidate for relativistic electron acceleration and plasmaspheric hiss as a viable cause for relativistic electron loss.

Keywords: solar storm; van allen radiation belts; solar wind; plasmapause; interplanetary physics
A Special State Transition in the Blazar OT 081: Implication for the Unified State Transition Paradigm of Different-scale Black Hole Systems

Exploring the similar behavior of black hole systems with different scales will provide insight into the unified physical laws of black hole systems. Here, we report a special spectral state transition process in blazar OT 081, which is driven by a supermassive black hole. Based on the X-ray flux versus photon index distribution, stacked average X-ray spectra, L 2500Å - α ox parameters, and broadband spectral energy distributions, we conducted a pilot study on the spectral state transition for this blazar system. The analysis results suggest that the source transitions through a steady-state point from a strong corona, weak jet unsteady state to a weak corona, strong jet unsteady state. This state transition behavior is similar to that observed in the much smaller Galactic black hole binary systems, providing further observational evidence for the possible existence of a unified state transition paradigm for black hole systems with different scales.

Keywords: blazars
Mass Ratio Estimates for Overcontact Binaries Using the Derivatives of Light Curves

The photometric mass ratios of eclipsing binaries are usually estimated by light-curve modeling with an iterative method. We propose a new method for estimating the photometric mass ratio of an overcontact binary using the derivatives of a light curve, which provides a reasonable uncertainty value. The method mainly requires only the time interval value between two local extrema found in the third derivative of a light curve with no need of an iterative procedure. We applied the method to a sample of real overcontact binary data and compared the estimated mass ratios with their spectroscopically determined values. The comparison showed that our estimated mass ratios for ~67% of the samples agreed with their spectroscopic mass ratios within the estimated uncertainties, and the errors for 95% of them are within ±0.1. Our method should be useful for estimating mass ratios for numerous overcontact eclipsing binaries found with existing and future surveys, as well as for the light-curve analysis of each system.

Keywords: mass ratio; contact binary stars; eclipsing binary stars; astronomical methods
Gaussian Processes and Effective Field Theory of f(T) Gravity under the H 0 Tension

We consider the effective field theory formulation of torsional gravity in a cosmological framework to alter the background evolution. Then we use the latest H 0 measurement from the SH0ES Team, as well as observational Hubble data from cosmic chronometer and radial baryon acoustic oscillations, and we reconstruct the f(T) form in a model-independent way by applying Gaussian processes. Since the special square-root term does not affect the evolution at the background level, we finally summarize a family of functions that can produce the background evolution required by the data. Lastly, performing a fitting using polynomial functions and implementing the Bayesian information criterion, we find an analytic expression that may describe the cosmological evolution in great agreement with observations.

Keywords: cosmological parameters; hubble constant; cosmology; non-standard theories of gravity; dark energy
Re-crowning The Queen: Membership, Age, and Rotation Periods for the Open Cluster Coma Berenices

Coma Berenices (Coma Ber), an open cluster about the same age as Praesepe and the Hyades (700-800 Myr) is, despite being only 85 pc away, less well studied than its famous cousins. This is due principally to its sparseness and low proper motion, which together made Coma Ber's membership challenging to establish pre-Gaia. We have curated a new list of its members based on Gaia DR2 astrometry, derived its metallicity and interstellar reddening using LAMOST data, and inferred the cluster's age by fitting PARSEC isochrones to its color-magnitude diagram. We then measured rotation periods for Coma Ber's low-mass members using TESS and ZTF photometry. Our isochrone fitting and the TESS- and ZTF-derived rotation periods confirm that Coma Ber is coeval with the Hyades and Praesepe. This work is the first step toward re-establishing Coma Ber as another valuable benchmark cluster for age-rotation-activity studies.

Keywords: open star clusters; low mass stars
Physical Correlations and Predictions Emerging from Modern Core-collapse Supernova Theory

In this paper, we derive correlations between core-collapse supernova observables and progenitor core structures that emerge from our suite of 20 state-of-the-art 3D core-collapse supernova simulations carried to late times. This is the largest such collection of 3D supernova models ever generated and allows one to witness and derive testable patterns that might otherwise be obscured when studying one or a few models in isolation. From this panoramic perspective, we have discovered correlations between explosion energy, neutron star gravitational birth masses, 56Ni and α-rich freezeout yields, and pulsar kicks and theoretically important correlations with the compactness parameter of progenitor structure. We find a correlation between explosion energy and progenitor mantle binding energy, suggesting that such explosions are self-regulating. We also find a testable correlation between explosion energy and measures of explosion asymmetry, such as the ejecta energy and mass dipoles. While the correlations between two observables are roughly independent of the progenitor zero-age main-sequence (ZAMS) mass, the many correlations we derive with compactness cannot unambiguously be tied to a particular progenitor ZAMS mass. This relationship depends on the compactness/ZAMS mass mapping associated with the massive star progenitor models employed. Therefore, our derived correlations between compactness and observables may be more robust than with ZAMS mass but can nevertheless be used in the future once massive star modeling has converged.

Keywords: supernova dynamics
Testing Earthlike Atmospheric Evolution on Exo-Earths through Oxygen Absorption: Required Sample Sizes and the Advantage of Age-based Target Selection

Life has had a dramatic impact on the composition of Earth's atmosphere over time, which suggests that statistical studies of other inhabited planets' atmospheres could reveal how they coevolve with life. While many evolutionary pathways are possible for inhabited worlds, a possible starting hypothesis is that most of them evolve similarly to Earth, which we propose could lead to a positive "age-oxygen correlation" between the ages of inhabited planets and the fraction which have oxygen-rich atmospheres. We demonstrate that next-generation space observatories currently under consideration could test this hypothesis, but only if the stellar age distribution of the target sample is carefully considered. We explore three possible parameterizations of the age-oxygen correlation, finding that they yield similar results. Finally, we examine how abiotic oxygen sources could affect the results, and discuss how measuring the age dependence of oxygen could shed light on whether it is a reliable biosignature. Future efforts can expand upon this groundwork by incorporating detailed models of the redox balance of terrestrial planets and its dependence on stellar and planetary properties.

Keywords: astrobiology; habitable planets; biosignatures; exoplanet evolution
Of Harbingers and Higher Modes: Improved Gravitational-wave Early Warning of Compact Binary Mergers

A crucial component to maximizing the science gain from the multi-messenger follow-up of gravitational-wave (GW) signals from compact binary mergers is the prompt discovery of the electromagnetic counterpart. Ideally, the GW detection and localization must be reported early enough to allow for telescopes to slew to the location of the GW event before the onset of the counterpart. However, the time available for early warning is limited by the short duration spent by the dominant (ℓ = m = 2) mode within the detector's frequency band. Nevertheless, we show that including higher modes—which enter the detector's sensitivity band well before the dominant mode—in GW searches can enable us to significantly improve the early warning ability for compact binaries with asymmetric masses (such as neutron star-black hole (NSBH) binaries). We investigate the reduction in the localization sky-area when the ℓ = m = 3 and ℓ = m = 4 modes are included in addition to the dominant mode, considering typical slew-times of electromagnetic telescopes (30-60 s). We find that, in LIGO's projected "O5" ("Voyager") network with five GW detectors, some of the NSBH mergers, located at a distance of 40 Mpc, can be localized to a few hundred sq. deg. ∼45 s prior to the merger, corresponding to a reduction-factor of 3-4 (5-6) in sky-area. For a third-generation network, we get gains of up to 1.5 min in early warning times for a localization area of 100 sq. deg., even when the source is placed at 100 Mpc.

Keywords: gravitational wave astronomy; gravitational waves; compact binary stars
Radio Plateaus in Gamma-Ray Burst Afterglows and Their Application in Cosmology

The plateau phase in radio afterglows has been observed in very few gamma-ray bursts (GRBs), and in this paper, 27 radio light curves with plateau phases were acquired from the published literature. We obtain the related parameters of the radio plateau, such as temporal indexes during the plateau phase (α 1 and α 2), break time (T b,z), and the corresponding radio flux (F b). The two-parameter Dainotti relation between the break time of the plateau and the corresponding break luminosity (L b,z) in the radio band is ${L}_{{\rm{b}},{\rm{z}}}\propto {T}_{{\rm{b}},{\rm{z}}}^{-1.20\pm 0.24}$ . Including the isotropic energy E γ,iso and peak energy E p,i, the three-parameter correlations for the radio plateaus are written as ${L}_{{\rm{b}},{\rm{z}}}\propto {T}_{{\rm{b}},{\rm{z}}}^{-1.01\pm 0.24}{E}_{\gamma ,\mathrm{iso}}^{0.18\pm 0.09}$ and ${L}_{{\rm{b}},{\rm{z}}}\propto {T}_{{\rm{b}},{\rm{z}}}^{-1.18\pm 0.27}{E}_{{\rm{p}},{\rm{i}}}^{0.05\pm 0.28}$ , respectively. The correlations are less consistent with those of the X-ray and optical plateaus, implying that radio plateaus may have a different physical mechanism. The typical frequencies crossing the observational band may be a reasonable hypothesis that causes the breaks of the radio afterglows. We calibrate the GRB empirical luminosity correlations as a standard candle for constraining cosmological parameters and find that our samples can constrain the flat ΛCDM model well but are not sensitive to the nonflat ΛCDM model. By combining GRBs with other probes, such as supernovae and the CMB, the constraints on the cosmological parameters are Ωm = 0.297 ± 0.006 for the flat ΛCDM model and Ωm = 0.283 ± 0.008, ΩΛ = 0.711 ± 0.006 for the nonflat ΛCDM model.

Keywords: gamma-ray bursts; cosmological parameters
FAST Drift Scan Survey for HI Intensity Mapping: I. Preliminary Data Analysis

This work presents the initial results of the drift-scan observation for the neutral hydrogen (HI) intensity mapping survey with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The data analyzed in this work were collected in night observations from 2019 through 2021. The primary findings are based on 28 hr of drift-scan observation carried out over 7 nights in 2021, which covers 60 deg2 sky area. Our main findings are, first, our calibration strategy can successfully correct both the temporal and bandpass gain variation over the 4 hr drift-scan observation. Second, the continuum maps of the surveyed region are made with frequency resolution of 28 kHz and pixel area of $2.95\,{\mathrm{arcmin}}^{2}$ . The pixel noise levels of the continuum maps are slightly higher than the forecast assuming T sys = 20 K, which are 36.0 mK (for 10.0 s integration time) at the 1050-1150 MHz band, and 25.9 mK (for 16.7 s integration time) at the 1323-1450 MHz band, respectively. Third, the flux-weighted differential number count is consistent with the NRAO-VLA Sky Survey (NVSS) catalog down to the confusion limit ~7 mJy beam-1. Finally, the continuum flux measurements of the sources are consistent with those found in the literature. The difference in the flux measurement of 81 isolated NVSS sources is about 6.3%. Our research offers a systematic analysis for the FAST HI intensity mapping drift-scan survey and serves as a helpful resource for further cosmology and associated galaxies sciences with the FAST drift-scan survey.

Keywords: large-scale structure of the universe; astronomy data analysis; surveys
Detection of Lyman Continuum from 3.0 < z < 3.5 Galaxies in the HETDEX Survey

Questions as to what drove the bulk reionization of the universe, how that reionization proceeded, and how the hard ionizing radiation reached the intergalactic medium remain open and debated. Observations probing that epoch are severely hampered by the increasing amounts of neutral gas with increasing redshift, so a small, but growing, number of experiments are targeting star-forming galaxies (z ~ 3) as proxies. However, these studies, while providing fantastic detail, are time intensive, contain relatively few targets, and can suffer from selection biases. As a complementary alternative, we investigate whether stacking the already vast (and growing) numbers of low-resolution (Δλ/λ = 800) Lyα-emitting (LAE) galaxy spectra from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) can be used to measure ionizing photons (rest-frame 880-910 Å) escaping their galaxy hosts. As a blind survey, HETDEX avoids the biases from continuum-selected galaxies, and its planned 540 deg2 coverage promotes the statistical power of large numbers. In this paper, we confirm the feasibility of Lyman continuum detection by carefully selecting a sample of 214 high-redshift (z ~ 3) LAEs from a subset of HETDEX observations, stacking their spectra and measuring a ≳3σ detection of 0.10 μJy rest-frame Lyman continuum emission, uncorrected for attenuation in the intergalactic medium, over the full sample stack (3.0 < z < 3.5 and -22.0 ≲ MUV ≲ -19.0).

Keywords: reionization; lyman-alpha galaxies
Three-dimensional Structure and Dust Extinction in the Small Magellanic Cloud

We examine the three-dimensional structure and dust extinction properties in a ∼200 pc × 100 pc region in the southwest bar of the Small Magellanic Cloud (SMC). We model a deep Hubble Space Telescope optical color-magnitude diagram (CMD) of red clump and red giant branch stars in order to infer the dust extinction and galactic structure. We model the distance distribution of the stellar component with a Gaussian and find a centroid distance of 65.2 kpc (distance modulus μ = 19.07 mag) with an FWHM ≈ 11.3 kpc. This large extent along the line of sight reproduces results from previous studies using variable stars and red clump stars. Additionally, we find an offset between the stellar and dust distributions, with the dust on the near side relative to the stars by 3.22 ${}_{-1.44}^{+1.69}$ kpc, resulting in a 73% reddened fraction of stars. Modeling the dust layer with a log-normal AV distribution indicates a mean extinction ⟨AV⟩ = 0.41 ± 0.09 mag. We also calculate AV/NH = 3.2-4.2 × 10-23 mag cm2 H-1, which is significantly lower than the Milky Way value but is comparable to previous SMC dust-to-gas ratio measurements. Our results yield the first joint dust extinction and 3D geometry properties in a key region in the SMC. This study demonstrates that CMD modeling can be a powerful tool to simultaneously constrain dust extinction and geometry properties in nearby galaxies.

Keywords: interstellar dust; interstellar dust extinction; interstellar medium; magellanic clouds; small magellanic cloud; dwarf galaxies; galaxy structure; red giant clump; red giant branch; distance measure
Unresolved Multiple Stars and Galactic Clusters' Mass Estimates

If not properly accounted for, unresolved binary stars can induce a bias in the photometric determination of star cluster masses inferred from star counts and the luminosity function. A correction factor close to 1.15 (for a binary fraction of 0.35) was found in Borodina et al., which needs to be applied to blind photometric mass estimates. This value for the correction factor was found to be smaller than literature values. In an attempt to lift this discrepancy, in this work the focus is on higher order multiple stars with the goal of investigating the effect of triple and quadruple systems adopting the same methodology and data set as in the quoted work. The result is that when triple and quadruple, together with binary, systems are properly accounted for, the actual cluster mass (computed as all stars were single) should be incremented by a factor of 1.18-1.27, depending on the cluster and when the binary fraction α is 0.35. Fitting formulae are provided to derive the increment factor for different binary star percentages.

Keywords: binary stars; stellar mass functions; open star clusters
Study of the Dynamics of Convective Turbulence in the Solar Granulation by Spectral Line Broadening and Asymmetry

In quiet regions on the solar surface, turbulent convective motions of granulation play an important role in creating small-scale magnetic structures, as well as in energy injection into the upper atmosphere. The turbulent nature of granulation can be studied using spectral line profiles, especially line broadening, which contain information on the flow field smaller than the spatial resolution of an instrument. Moreover, the Doppler velocity gradient along a line of sight (LOS) causes line broadening as well. However, the quantitative relationship between velocity gradient and line broadening has not been understood well. In this study, we perform bisector analyses using the spectral profiles obtained using the spectropolarimeter of the Hinode/Solar Optical Telescope to investigate the relationship of line broadening and bisector velocities with the granulation flows. The results indicate that line broadening has a positive correlation with the Doppler velocity gradients along the LOS. We found excessive line broadening in fading granules, that cannot be explained only by the LOS velocity gradient, although the velocity gradient is enhanced in the process of fading. If this excessive line broadening is attributed to small-scale turbulent motions, the averaged turbulent velocity is obtained as 0.9 km s-1.

Keywords: solar photosphere; solar granules; solar granulation
The Orbital Structure and Selection Effects of the Galactic Center S-star Cluster

The orbital distribution of the S-star cluster surrounding the supermassive black hole in the center of the Milky Way is analyzed. A tight dependence of the pericenter distance r p on orbital eccentricity e ⋆ is found, $\mathrm{log}({r}_{{\rm{p}}})\sim (1-{e}_{\star })$ , which cannot be explained simply by a random distribution of semimajor axis and eccentricities. No stars are found in the region with high e ⋆ and large $\mathrm{log}({r}_{{\rm{p}}})$ or in the region with low e ⋆ and small $\mathrm{log}({r}_{{\rm{p}}})$ . Although the sample is still small, the G-clouds show a very similar distribution. The likelihood $P(\mathrm{log}({r}_{{\rm{p}}}),(1-{e}_{\star }))$ to determine the orbital parameters of S-stars is determined. P is very small for stars with large e ⋆ and large $\mathrm{log}({r}_{{\rm{p}}})$ . S-stars might exist in this region. To determine their orbital parameters, one however needs observations over a longer time period. On the other hand, if stars would exist in the region of low $\mathrm{log}({r}_{{\rm{p}}})$ and small e ⋆, their orbital parameters should by now have been determined. That this region is unpopulated therefore indicates that no S-stars exist with these orbital characteristics, providing constraints for their formation. We call this region, defined by $\mathrm{log}({r}_{{\rm{p}}}/\mathrm{AU})\lt 1.57+2.6(1-{e}_{\star })$ , the zone of avoidance. Finally, it is shown that the observed frequency of eccentricities and pericenter distances is consistent with a random sampling of $\mathrm{log}({r}_{{\rm{p}}})$ and e ⋆ if one takes into account the fact that no stars exist in the zone of avoidance and that orbital parameters cannot yet be determined for stars with large r p and large e ⋆.

Keywords: galactic center; massive stars; galaxy kinematics; galaxy dynamics
Hidden Companions to Intermediate-mass Stars. IX. Discovery of a 1.5 M ⊙, 1 au Companion to the Primary within the Multiple HIP 57606

HIP 57606 is an intermediate-mass a ~ 88 au visual binary (A+B) that also has 680 au (C) and a 120,000 au (D) companions. Here we report on a VLTI/GRAVITY interferometric observation that revealed that the primary star A is itself a close binary with a 83% K band flux ratio companion at a projected separation ρ = 14.8 mas ↔ 1.0 au. Through isochrone fitting we find masses M Aa = 1.58M ⊙, M Ab = 1.49M ⊙ and M B = 1.15M ⊙ and an age 1 Gyr for the inner triple. The latter will evolve to become a double or triple white dwarf system within about 6 Gyr and which will be under the dynamical influence of the outer companion C. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Keywords: f stars; optical interferometry; multiple stars