adsabs/SciX_UAT_keywords huggingface dataset:
The Initial-Final Mass Relation for Hydrogen-deficient White Dwarfs

The initial-final mass relation represents the total mass lost by a star during the entirety of its evolution from the zero age main sequence to the white-dwarf cooling track. The semiempirical initial-final mass relation (IFMR) is largely based on observations of DA white dwarfs, the most common spectral type of white dwarf and the simplest atmosphere to model. We present a first derivation of the semiempirical IFMR for hydrogen-deficient (non-DA) white dwarfs in open star clusters. We identify a possible discrepancy between the DA and non-DA IFMRs, with non-DA white dwarfs ≈0.07 M⊙ less massive at a given initial mass. Such a discrepancy is unexpected based on theoretical models of non-DA formation and observations of field white dwarf mass distributions. If real, the discrepancy is likely due to enhanced mass loss during the final thermal pulse and renewed post-AGB evolution of the star. However, we are dubious that the mass discrepancy is physical and instead is due to the small sample size, to systematic issues in model atmospheres of non-DAs, and to the uncertain evolutionary history of Procyon B (spectral type DQZ). A significantly larger sample size is needed to test these assertions. In addition, we also present Monte Carlo models of the correlated errors for DA and non-DA white dwarfs in the initial-final mass plane. We find the uncertainties in initial-final mass determinations for individual white dwarfs can be significantly asymmetric, but the recovered functional form of the IFMR is grossly unaffected by the correlated errors. * Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: white dwarf stars; db stars; da stars; post-asymptotic giant branch stars; open star clusters; stellar mass loss; stellar evolution; stellar remnants
Determination of 1929 Asteroid Rotation Periods from WISE Data

We used 22 μm (W4) Wide-field Infrared Survey Explorer (WISE) observations of 4420 asteroids to analyze lightcurves, and determined spin period estimates for 1929 asteroids. We fit second-order Fourier models at a large number of trial frequencies to the W4 data and analyzed the resulting periodograms. We initially excluded rotational frequencies exceeding 7.57 rotations per day (P < 3.17 hr), which are not sampled adequately by WISE, and periods that exceed twice the WISE observation interval, which is typically 36 hr. We found that three solutions accurately capture the vast majority of the rotational frequencies in our sample: the best-fit frequency and its mirrors around 3.78 and 7.57 rotations per day. By comparing our solutions with a high-quality control group of 752 asteroid spin periods, we found that one of our solutions is accurate (within 5%) in 88% of the cases. The best-fit, secondary, and tertiary solutions are accurate in 55%, 27%, and 6% of the cases, respectively. We also observed that suppression of aliased solutions was more effective with nonuniform sampling than with quasi-uniform sampling.

Keywords: asteroids; asteroid rotation; time series analysis; light curves; infrared photometry
Multiwavelength Variability Power Spectrum Analysis of the Blazars 3C 279 and PKS 1510-089 on Multiple Timescales

We present the results of variability power spectral density (PSD) analysis using multiwavelength radio to GeV γ-ray light curves covering timescales of decades/years to days/minutes for the blazars 3C 279 and PKS 1510-089. The PSDs are modeled as single power laws, and the best-fit spectral shape is derived using the "power spectral response" method. With more than 10 yr of data obtained with weekly/daily sampling intervals, most of the PSDs cover ~2-4 decades in temporal frequency; moreover, in the optical band, the PSDs cover ~6 decades for 3C 279 due to the availability of intranight light curves. Our main results are the following: (1) on timescales ranging from decades to days, the synchrotron and the inverse-Compton spectral components, in general, exhibit red-noise (slope ~2) and flicker-noise (slope ~1) type variability, respectively; (2) the slopes of γ-ray variability PSDs obtained using a 3 hr integration bin and 3 weeks total duration exhibit a range between ~1.4 and ~2.0 (mean slope = 1.60 ± 0.70), consistent within errors with the slope on longer timescales; (3) comparisons of fractional variability indicate more power on timescales ≤100 days at γ-ray frequencies compared to longer wavelengths, in general (except between the γ-ray and optical wavelengths for PKS 1510-089); (4) the normalization of intranight optical PSDs for 3C 279 appears to be a simple extrapolation from longer timescales, indicating a continuous (single) process driving the variability at optical wavelengths; and (5) the emission at optical/infrared wavelengths may involve a combination of disk and jet processes for PKS 1510-089.

Keywords: blazars; active galactic nuclei; galaxy jets
Solar Wind Electron Pressure Gradients, Suprathermal Spectral Hardness, and Strahl Localization Organized by Single-point Measurements of 0.1 nV m-1 Ambipolar E ∥

A new, fast technique to measure the solar wind's ambipolar E ∥ routinely with 10% precision and accuracy is demonstrated using 4 yr of 1 au electron data from the Wind 3DP experiment. The 3DP electron instrument duty cycle determines E ∥ ≃ 0.1 nV m-1 from a single spectrum over much shorter time intervals than those requiring radial transits for pressure profiles. The measured weak electric field is invariably strong (in the dimensionless sense of Dreicer), with a modal value of ${{\mathbb{E}}}_{\parallel }=0.8$ , and positively correlated with solar wind speed, while E ∥ decreases with increasing wind speed. These observations establish across all solar wind conditions the nearly equal accelerations provided by E ∥ and coulomb drags on thermal electrons, a central hypothesis of the Steady Electron Runaway Model (SERM) for the solar wind. Filtered E ∥ observations successfully recover previously reported 1 au bulk speed dependence of electron temperature gradients. The filter screens for unstructured spherically symmetric solar wind (USSSW) conditions of solar wind theory. Outside USSSW conditions much shorter scaled pressure gradients (of both signs) and stronger ∣E ∥∣ are observed predominantly in corotating regimes. Consistent with modeling by Dreicer and SERM, the observed spectral hardness of electrons at suprathermal energies is positively correlated with increasing local values of ${{\mathbb{E}}}_{\parallel }$ across the 4 yr data set. Virtually all strahl electrons, crucial to the electron heat flux, are shown to be confined within the local closed coulomb separatrix of each spectrum as determined using the locally measured value of ${{\mathbb{E}}}_{\parallel }$ .

Keywords: plasma astrophysics; solar wind; space plasmas; interplanetary particle acceleration; collision physics
Power Anisotropy, Dispersion Signature and Turbulence Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence

We explore the multifaceted important features of turbulence (e.g., anisotropy, dispersion, and diffusion) in the three-dimensional (3D) wavenumber domain (k ∥, k ⊥,1, k ⊥,2), by employing the k-filtering technique to high-quality measurements of fields and particles from the Magnetospheric Multiscale Mission (MMS) multi-spacecraft constellation. We compute the 3D power spectral densities (PSDs) of magnetic and electric field fluctuations (marked as PSD(δ B ( k )) and $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} }({\boldsymbol{k}}))$ , respectively), both of which show a prominent spectral anisotropy in the sub-ion range. We give the first 3D image of the bifurcation between the power spectra of the electric and magnetic fluctuations, by calculating the ratio between $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} }({\boldsymbol{k}}))$ and PSD(δ B ( k )), the distribution of which is related to the nonlinear dispersion relation. We also compute the ratio between electric spectra in different reference frames defined by the ion bulk velocity, $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\mathrm{local}\ {{\boldsymbol{v}}}_{{\rm{i}}}}^{{\prime} })/\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} })$ , to visualize the turbulent ion diffusion region (T-IDR) in wavenumber space. The T-IDR has an anisotropy and a preferential direction of wavevectors, which is generally consistent with the plasma wave theory prediction based on the dominance of kinetic Alfvén waves. This work demonstrates the worth of the k-filtering technique in diagnosing turbulence comprehensively, especially when the electric field is involved.

Keywords: interplanetary turbulence; space plasmas; solar wind
Observations of a Flare-ignited Broad Quasiperiodic Fast-propagating Wave Train

Large-scale extreme-ultraviolet (EUV) waves are frequently observed as an accompanying phenomenon of flares and coronal mass ejections (CMEs). Previous studies mainly focused on EUV waves with single wave fronts that are generally thought to be driven by the lateral expansion of CMEs. Using high spatiotemporal resolution multi-angle imaging observations taken by the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory, we present the observation of a broad quasiperiodic fast-propagating (QFP) wave train composed of multiple wave fronts along the solar surface during the rising phase of a GOES M3.5 flare on 2011 February 24. The wave train transmitted through a lunate coronal hole (CH) with a speed of ~840 ± 67 km s-1, and the wave fronts showed an intriguing refraction effect when they passed through the boundaries of the CH. Due to the lunate shape of the CH, the transmitted wave fronts from the north and south arms of the CH started to approach each other and finally collided, leading to a significant intensity enhancement at the collision site. This enhancement might hint at the occurrence of interference between the two transmitted wave trains. The estimated magnetosonic Mach number of the wave train is about 1.13, which indicates that the observed wave train was a weak shock. Period analysis reveals that the period of the wave train was ~90 s, in good agreement with that of the accompanying flare. Based on our analysis results, we conclude that the broad QFP wave train was a large-amplitude fast-mode magnetosonic wave or a weak shock driven by some nonlinear energy release processes in the accompanying flare.

Keywords: solar coronal waves; alfven waves; solar corona
Energy Budget of Plasma Motions, Heating, and Electron Acceleration in a Three-loop Solar Flare

Nonpotential magnetic energy promptly released in solar flares is converted to other forms of energy. This may include nonthermal energy of flare-accelerated particles, thermal energy of heated flaring plasma, and kinetic energy of eruptions, jets, upflows/downflows, and stochastic (turbulent) plasma motions. The processes or parameters governing partitioning of the released energy between these components are an open question. How these components are distributed between distinct flaring loops and what controls these spatial distributions are also unclear. Here, based on multiwavelength data and 3D modeling, we quantify the energy partitioning and spatial distribution in the well-observed SOL2014-02-16T064620 solar flare of class C1.5. Nonthermal emission of this flare displayed a simple impulsive single-spike light curve lasting about 20 s. In contrast, the thermal emission demonstrated at least three distinct heating episodes, only one of which was associated with the nonthermal component. The flare was accompanied by upflows and downflows and substantial turbulent velocities. The results of our analysis suggest that (i) the flare occurs in a multiloop system that included at least three distinct flux tubes; (ii) the released magnetic energy is divided unevenly between the thermal and nonthermal components in these loops; (iii) only one of these three flaring loops contains an energetically important amount of nonthermal electrons, while two other loops remain thermal; (iv) the amounts of direct plasma heating and that due to nonthermal electron loss are comparable; and (v) the kinetic energy in the flare footpoints constitutes only a minor fraction compared with the thermal and nonthermal energies.

Keywords: solar flares; solar x-ray emission; solar radio emission; solar extreme ultraviolet emission; solar magnetic fields; solar coronal heating
Testing Relativistic Reflection Models with GRMHD Simulations of Accreting Black Holes

X-ray reflection spectroscopy is currently one of the leading techniques for studying the inner part of accretion disks around black holes, measuring black hole spins, and even testing fundamental physics in strong gravitational fields. However, the accuracy of these measurements depends on the reflection models employed for the spectral analysis, which are sometimes questioned. In this work, we use a general relativistic magnetohydrodynamic code to generate a thin accretion disk in Kerr spacetime and ray-tracing techniques to calculate its relativistically broadened reflection spectrum. We simulate NuSTAR observations and we test the capability of current reflection models to recover the correct input parameters. Our study shows that we can measure the correct input parameters in the case of high inclination angle sources, while we find some minor discrepancies when the inclination angle of the disk is low.

Keywords: accretion; astrophysical black holes; x-ray astronomy
The Fundamental Plane Is Not a Plane: Warped Nature of the Fundamental Plane of Early-type Galaxies and Its Implication for Galaxy Formation

Based on 16,283 early-type galaxies (ETGs) in 0.025 ≤ z spec < 0.055 from Sloan Digital Sky Survey data, we show that the fundamental plane (FP) of ETGs is not a plane in the strict sense but is a curved surface with a twisted shape whose orthogonal direction to the surface is shifted as the central velocity dispersion (σ 0) or mean surface brightness within the half-light radius (μ e ) changes. When ETGs are divided into subsamples according to σ 0, the coefficient of μ e of the FP increases, whereas the zero-point of the FP decreases at higher σ 0. Taking the z band as an example, the coefficient of μ e rises from 0.28 to 0.36 as σ 0 increases from ~100 to ~300 km s-1. At the same time, the zero-point of the FP falls from -7.5 to -9.0 in the same σ 0 range. The consistent picture on the curved nature of the FP is also reached by inspecting changes in the FP coefficients for ETG subsamples with different μ e . By examining scaling relations that are projections of the FP, we suggest that the warped nature of the FP may originate from dry merger effects that are imprinted more prominently in ETGs with higher masses.

Keywords: early-type galaxies; galaxy evolution; galaxy formation; galaxy mergers; galaxy properties; red sequence galaxies
Estimating the Atmospheric Parameters of Early-type Stars from the Chinese Space Station Telescope (CSST) Slitless Spectra Survey

The measurement of atmospheric parameters is fundamental for scientific research using stellar spectra. The Chinese Space Station Telescope (CSST), scheduled to be launched in 2024, will provide researchers with hundreds of millions of slitless spectra for stars during a 10 yr survey. And machine learning has unparalleled efficiency in processing large amounts of data compared to manual processing. Here we studied the stellar parameters of early-type stars (effective temperature T eff > 15,000 K) based on the design indicators of the CSST slitless spectrum and the machine learning algorithm, Stellar LAbel Machine. We used the Potsdam Wolf–Rayet (POWR) synthetic spectra library for cross validation. Then we tested the reliability of machine learning results by using the Next Generation Spectrum Library (NGSL) from Hubble Space Telescope observation data. In an ideal case for full-wavelength spectra without any noise, the average absolute value of the relative deviation is 2.7% (800 K) for T eff, and 3.5% (0.11 c.g.s) for surface gravity . We use the spectra with the impact of interstellar extinction (AV = 0, 0.5, 1, 1.5, 2 mag) and radial velocity (RV = ‑50, ‑30, 0, 30, 50 km s‑1) from the POWR library as the test set. When RV = 0 km s‑1 and AV = 0 mag, the average value and standard deviation for 3 wavelength ranges (2550–4050 Å (R = 287); 4050–6300 Å (R = 232); 6300–10000 Å (R = 207)) are –66 ± 3351 K, 550 ± 3536 K, and 356 ± 3616 K for T eff, and 0.004 ± 0.224 c.g.s, –0.024 ± 0.246 c.g.s, and 0.01 ± 0.212 c.g.s for . When using the observed data from NGSL as the testing samples, the deviation of T eff is less than 5% (1500 K), and the deviation of is less than 11% (0.33 c.g.s). In addition, we also test the influence of shifting of spectra on the parameters' accuracy. The deviation of T eff for the case with a shift of 5 Å and 10 Å are 3.6% (1100 K) and 4.3% (1300 K), respectively; the deviation of are 4.2% (0.13 c.g.s) and 5.1% (0.15 c.g.s). These results demonstrate that we can obtain relatively accurate stellar parameters of a population of early-type stars with the CSST slitless spectra and a machine-learning method.

Keywords: early-type stars; effective temperature; surface gravity
The NuSTAR, XMM-Newton, and Suzaku View of A3395 at the Intercluster Filament Interface

Galaxy clusters are the largest virialized objects in the universe. Their merger dynamics and their interactions with the cosmic filaments that connect them are important for our understanding of the formation of large-scale structure. In addition, cosmic filaments are thought to possess the missing baryons in the universe. Studying the interaction of galaxy clusters and filaments therefore has the potential to unveil the origin of the baryons and the physical processes that occur during merger stages of galaxy clusters. In this paper, we study the connection between A3395 and the intercluster filament with NuSTAR, XMM-Newton, and Suzaku data. Since the NuSTAR observation is moderately contaminated by scattered light, we present a novel technique developed for disentangling this background from the emission from the intracluster medium. We find that the interface of the cluster and the intercluster filament connecting A3395 and A3391 does not show any signs of heated plasma, as was previously thought. This interface has low temperature, high density, and low entropy, thus we suggest that the gas is cooling, being enhanced by the turbulent or tidal "weather" driven during the early stage of the merger. Furthermore, our temperature results from the NuSTAR data are in agreement with those from XMM-Newton and from joint NuSTAR and XMM-Newton analysis for a region with ~25% scattered light contamination within 1σ. We show that the temperature constraint of the intracluster medium is valid even when the data are contaminated up to ~25% for ~5 keV cluster emission.

Keywords: galaxy clusters; intracluster medium; high energy astrophysics; cosmic web; large-scale structure of the universe
Gaia Astrometry and MIKE+PFS Doppler Data Joint Analysis Reveals that HD 175167b is a Massive Cold Jupiter

HD 175167b is a cold (P b ~ 1200 days) Jupiter with a minimum mass of ${M}_{p}\,\sin \,i=7.8\pm 3.5\ {M}_{J}$ orbiting a Sun-like star, first discovered by the Magellan Planet Search Program based on MIKE observations. Through a joint analysis of the MIKE data and the Gaia two-body orbital solution, Winn found a companion mass of M p = 14.8 ± 1.8 M J and suggested that it might be better designated as a brown dwarf. Additional publicly available radial velocity data from Magellan/PFS better constrains the model, and reveals that the companion is a massive cold Jupiter with a mass of M p = 10.2 ± 0.4 M J and a period of P b = 1275.8 ± 0.4 days. The planet orbit is inclined by i = 38.°6 ± 1.°7 with an eccentricity of 0.529 ± 0.002.

Keywords: astrometry; radial velocity; extrasolar gaseous giant planets
The Prospects for Hurricane-like Vortices in Protoplanetary Disks

When ice on the surface of dust grains in protoplanetary disk sublimates, it adds its latent heat of water sublimation to the surrounding flow. Drawing on the analogy provided by tropical cyclones on Earth, we investigate whether this energy source is sufficient to sustain or magnify anticyclonic disk vortices that would otherwise fall victim to viscous dissipation. An analytical treatment, supported by exploratory two-dimensional simulations, suggests that even modestly undersaturated flows can extend the lifetime of vortices, potentially to a degree sufficient to aid particle trapping and planetesimal formation. We expect the best conditions for this mechanism to occur will be found near the disk's water ice line if turbulent motions displace gas parcels out of thermodynamic equilibrium with the dust midplane.

Keywords: hydrodynamics; protoplanetary disks; circumstellar disks; planet formation; astrophysical fluid dynamics
The Effect of Salinity on Ocean Circulation and Ice-Ocean Interaction on Enceladus

Observational data suggest that the ice shell on Enceladus is thicker at the equator than at the pole, indicating an equator-to-pole ice flow. If the ice shell is in an equilibrium state, the mass transport of the ice flow must be balanced by the freezing and melting of the ice shell, which in turn is modulated by the ocean heat transport. Here we use a numerical ocean model to study the ice-ocean interaction and ocean circulation on Enceladus with different salinities. We find that salinity fundamentally determines the ocean stratification. A stratified layer forms in the low-salinity ocean, affecting the ocean circulation and heat transport. However, in the absence of tidal heating in the ice shell, the ocean heat transport is found to always be toward lower latitudes, resulting in freezing at the poles, which cannot maintain the ice shell geometry against the equator-to-pole ice flow. The simulation results suggest that either the ice shell on Enceladus is not in an equilibrium state or tidal dissipation in the ice shell is important in maintaining the ice shell geometry. The simulations also suggest that a positive feedback between cross-equatorial ocean heat transport and ice melting results in spontaneous symmetry breaking between the two hemispheres. This feedback may play a role in the observed interhemispheric asymmetry in the ice shell.

Keywords: enceladus