adsabs/SciX_UAT_keywords huggingface dataset:
Gas Evolution in Inner Disk Cavities from a Synergic Analysis of IR-CO and UV-H2 Spectra

We are conducting a multi-wavelength analysis of high-resolution molecular spectra that probe the evolution of gas in the inner 10 au in protoplanetary disks. A sample of 15 disks has been combined to probe a range of inner disk structures including small and large dust cavities. Half of the sample has been observed in far-ultraviolet H2 emission with a new HST-COS program (GO-14703), that we have combined to near-infrared spectra of CO emission as observed with VLT-CRIRES and IRTF-iSHELL. This synergic dataset traces the evolution and depletion of CO and H2 in inner disk cavities and shows an evolving radial stratification of the molecular gas, where CO lines are narrower than H2 lines in disks with cavities. CO rotation diagrams also show significant evolution, suggesting a change in gas excitation as CO emission recedes to larger disk radii.

Keywords: protoplanetary disks; molecular spectroscopy; exoplanet formation; circumstellar disks; near infrared astronomy; ultraviolet astronomy; molecular gas; pre-main sequence stars
Global Nature of Solar Coronal Shock Waves Shown by Inconsistency between EUV Waves and Type II Radio Bursts

We re-examine the physical relationship between extreme ultraviolet (EUV) waves and type II radio bursts. It has been thought that they are two observational aspects of a single coronal shock wave. However, a lack of their speed correlation hampers the understanding of their respective (or common) natures in a single phenomenon. Knowing the uncertainties in identifying true wave components from observations and measuring their speeds, we re-examine the speeds of EUV waves reported in previous literature and compare these with type II radio bursts and coronal mass ejections (CMEs). This confirms the inconsistency between the speeds of EUV waves and their associated type II radio bursts. Second, CME speeds are found to have a better correlation with type II radio bursts than EUV waves. Finally, type II speeds and their range tend to be much greater than those of EUV waves. We demonstrate that the speed inconsistency is in fact an intrinsic tendency and elucidate the nature of a coronal shock wave consisting of both driven and non-driven parts. This suggests that the speed inconsistency would remain even if all other uncertainties were removed.

Keywords: solar coronal waves
The Role of Inner H I Mass in Regulating the Scatter of the Mass-Metallicity Relation

We use 789 disk-like, star-forming galaxies (with 596 H I detections) from H I follow-up observations for the SDSS-IV MaNGA survey to study the possible role of inner H I gas in causing secondary dependences in the mass-gas-phase metallicity relation. We use the gas-phase metallicity derived at the effective radii of the galaxies. We derive the inner H I mass within the optical radius, but also use the total H I mass and star formation rate (SFR) for a comparison. We confirm the anticorrelation between the total H I mass and gas-phase metallicity at fixed stellar mass, but the anticorrelation is significantly strengthened when the total H I mass is replaced by the inner H I mass. Introducing a secondary relation with the inner H I mass can produce a small but noticeable decrease (16%) in the scatter of the mass-gas-phase metallicity relation, in contrast to the negligible effect with the SFR. The correlation with the inner H I mass is robust when using different diagnostics of metallicity, but the correlation with SFR is not. The correlation with the inner H I mass becomes much weaker when the gas-phase metallicity is derived in the central region instead of at the effective radius. These results support the idea that the scatter in the mass-metallicity relation is regulated by gas accretion, and not directly by the SFR, and stress the importance of deriving the gas mass and the metallicity from roughly the same region. The new relation between inner H I mass and gas-phase metallicity will provide new constraints for chemical and galaxy evolution models.

Keywords: galaxy evolution; galaxy formation; galaxy abundances; metallicity
New Generation Stellar Spectral Libraries in the Optical and Near-infrared. I. The Recalibrated UVES-POP Library for Stellar Population Synthesis

We present reprocessed flux-calibrated spectra of 406 stars from the UVES-POP stellar library in the wavelength range 320-1025 nm, which can be used for stellar population synthesis. The spectra are provided in the two versions having spectral resolving power R = 20,000 and R = 80,000. Raw spectra from the ESO data archive were re-reduced using the latest version of the UVES data reduction pipeline with some additional algorithms that we developed. The most significant improvements in comparison with the original UVES-POP release are (i) an updated echelle order merging, which eliminates "ripples" present in the published spectra; (ii) a full telluric correction; (iii) merging of nonoverlapping UVES spectral setups taking into account the global continuum shape; (iv) a spectrophotometric correction and absolute flux calibration; and (v) estimates of the interstellar extinction. For 364 stars from our sample, we computed atmospheric parameters T eff, surface gravity log g, metallicity [Fe/H], and α-element enhancement [α/Fe] by using a full-spectrum fitting technique based on a grid of synthetic stellar atmospheres and a novel minimization algorithm. We also provide projected rotational velocity $v\sin i$ and radial velocity v rad estimates. The overall absolute flux uncertainty in the reprocessed data set is better than 2%, with subpercent accuracy for about half of the stars. A comparison of the recalibrated UVES-POP spectra with other spectral libraries shows a very good agreement in flux; at the same time, Gaia DR3 BP/RP spectra are often discrepant with our data, which we attribute to spectrophotometric calibration issues in Gaia DR3. * Recalibrated spectra are available at https://sl.voxastro.org/.

Keywords: stellar atmospheres; stellar abundances; stellar effective temperatures; stellar populations; astronomy databases; star atlases; astronomical reference materials
Early Spectral Evolution of Classical Novae: Consistent Evidence for Multiple Distinct Outflows

The physical mechanism driving mass ejection during a nova eruption is still poorly understood. Possibilities include ejection in a single ballistic event, a common-envelope interaction, a continuous wind, or some combination of these processes. Here, we present a study of 12 Galactic novae, for which we have premaximum high-resolution spectroscopy. All 12 novae show the same spectral evolution. Before optical peak, they show a slow P Cygni component. After peak, a fast component quickly arises, while the slow absorption remains superimposed on top of it, implying the presence of at least two physically distinct flows. For novae with high-cadence monitoring, a third, intermediate-velocity component is also observed. These observations are consistent with a scenario where the slow component is associated with the initial ejection of the accreted material and the fast component with a radiation-driven wind from the white dwarf. When these flows interact, the slow flow is swept up by the fast flow, producing the intermediate component. These colliding flows may produce the γ-ray emission observed in some novae. Our spectra also show that the transient heavy-element absorption lines seen in some novae have the same velocity structure and evolution as the other lines in the spectrum, implying an association with the nova ejecta rather than a preexisting circumbinary reservoir of gas or material ablated from the secondary. While this basic scenario appears to qualitatively reproduce multiwavelength observations of classical novae, substantial theoretical and observational work is still needed to untangle the rich diversity of nova properties.

Keywords: novae; cataclysmic variable stars; classical novae; white dwarf stars; compact objects; high resolution spectroscopy; spectroscopy
Electrostatic Plasma Wave Excitations at the Interplanetary Shocks

Over the last few decades, different types of plasma waves (e.g., the ion acoustic waves (IAWs), electrostatic solitary waves, upper/lower hybrid waves, and Langmuir waves) have been observed in the upstream, downstream, and ramp regions of the collisionless interplanetary (IP) shocks. These waves may appear as short-duration (only a few milliseconds at 1 au) electric field signatures in the in-situ measurements, with typical frequencies of ~1-10 kHz. A number of IAW features at the IP shocks seem to be unexplained by kinetic models and require a new modeling effort. Thus, this paper is dedicated to bridging this gap in understanding. In this paper, we model the linear IAWs inside the shock ramp by devising a novel linearization method for the two-fluid magnetohydrodynamic equations with spatially dependent shock parameters. It is found that, for parallel propagating waves, the linear dispersion relation leads to a finite growth rate, which is dependent on the shock density compression ratio, as Wind data suggest. Further analysis reveals that the wave frequency grows towards the downstream region within the shock ramp, and the wave growth rate is independent of the electron-to-ion temperature ratio, as Magnetospheric Multiscale (MMS) in-situ measurements suggest, and is uniform within the shock ramp. Thus, this study helps in understanding the characteristics of the IAWs at the collisionless IP shocks.

Keywords: interplanetary shocks
Mode Conversion of Kinetic Alfvén Waves in the Presence of Proton Beams and Its Role in Plasma Heating in the Solar Corona

The density inhomogeneity is a typical feature in various magnetoplasmas in the corona, where kinetic Alfvén waves (KAWs) are effectively generated and contribute greatly to the inhomogeneous heating of coronal plasmas. Proton beams exist widely in various space and solar plasma environments. In this paper, based on the kinetic Vlasov theory, we investigate the resonant mode conversion of Alfvén waves to KAWs in the presence of proton beams in an inhomogeneous plasma and the plasma heating of KAWs due to wave-particle interactions. It is found that the wave properties of excited KAWs are highly sensitive to the density of proton beams n bi /n 0, the drift velocity of proton beams v bi /v A, the proton-to-electron temperature ratio T i /T e , and the proton-beam-to-proton-temperature ratio T bi /T i . In addition, the maximum heating rate of KAWs Q m /Q 0 obviously increases with increasing n bi /n 0 and/or v bi /v A. As the electron beta β e increases, Q m /Q 0 decreases sharply in the region of 6 × 10-4 < β e < 10-2 and decreases slowly in the region of β e > 10-2. In addition, the applications of KAW dissipation to plasma heating are discussed in the corona and coronal loops. The KAWs associated with perturbed electric field E x ~ a few V · m-1 are enough to supply the energy loss in the corona and coronal loops. The present results are of significant importance for comprehending the KAW excitation and the particle energization in the corona.

Keywords: alfven waves; solar coronal heating; solar coronal loops; solar coronal waves
Early Planet Formation in Embedded Disks (eDisk). VII. Keplerian Disk, Disk Substructure, and Accretion Streamers in the Class 0 Protostar IRAS 16544-1604 in CB 68

We present observations of the Class 0 protostar IRAS 16544-1604 in CB 68 from the "Early Planet Formation in Embedded Disks (eDisk)" ALMA Large program. The ALMA observations target continuum and lines at 1.3 mm with an angular resolution of ~5 au. The continuum image reveals a dusty protostellar disk with a radius of ~30 au seen close to edge-on and asymmetric structures along both the major and minor axes. While the asymmetry along the minor axis can be interpreted as the effect of the dust flaring, the asymmetry along the major axis comes from a real nonaxisymmetric structure. The C18O image cubes clearly show the gas in the disk that follows a Keplerian rotation pattern around a ~0.14 M ⊙ central protostar. Furthermore, there are ~1500 au scale streamer-like features of gas connecting from northeast, north-northwest, and northwest to the disk, as well as the bending outflow as seen in the 12CO (2-1) emission. At the apparent landing point of the NE streamer, there is SO (65-54) and SiO (5-4) emission detected. The spatial and velocity structure of the NE streamer can be interpreted as a free-falling gas with a conserved specific angular momentum, and the detection of the SO and SiO emission at the tip of the streamer implies the presence of accretion shocks. Our eDisk observations have unveiled that the Class 0 protostar in CB 68 has a Keplerian-rotating disk with a flaring and nonaxisymmetric structure associated with accretion streamers and outflows.

Keywords: star formation; interstellar medium; planet formation
Manifestation of Gravitational Settling in Coronal Mass Ejections Measured in the Heliosphere

Elemental composition in the solar wind reflects the fractionation processes at the Sun. In coronal mass ejections (CMEs) measured in the heliosphere, the elemental composition can vary between plasma of high and low ionization states as indicated by the average Fe charge state, <QFe>. It is found that CMEs with higher ionized plasma, <QFe> greater than 12, are significantly more enriched in low first ionization potential (FIP) elements compared to their less ionized, <QFe> less than 12, counterparts. In addition, the CME elemental composition has been shown to vary along the solar cycle. However, the processes driving changes in elemental composition in the plasma are not well understood. To gain insight into this variation, this work investigates the effects of gravitational settling in the ejecta to examine how that process can modify signatures of the FIP effect found in CMEs. We examine the absolute abundances of C, N, O, Ne, Mg, Si, S, and Fe in CMEs between 1998 and 2011. Results show that the ejecta exhibits some gravitational settling effects in approximately 33% of all CME periods in plasma where the Fe abundance of the ejecta compared to the solar wind (Fe/HCME:Fe/HSW) is depleted compared to the C abundance (C/HCME:C/HSW). We also find gravitational settling is most prominent in CMEs during solar minimum; however, it occurs throughout the solar cycle. This study indicates that gravitational settling, along with the FIP effect, can become important in governing the compositional makeup of CME source regions.

Keywords: solar coronal mass ejections; chemical abundances; solar cycle; solar coronal transients
Investigation of the Origins of Comets as Revealed through Infrared High-resolution Spectroscopy I. Molecular Abundances

We report and analyze updated molecular abundances in 20 comets obtained by employing modern data reduction procedures and molecular models. Using box and scatter plots, we examine how the different molecular species are distributed among the comet population, while by means of pie charts, we investigate the relative proportions of these molecular species in each comet. We compare these results with the orbital parameters of the selected comets to identify trends related to their dynamical history. With these analyses, we tentatively identify at least three chemical classes based mainly on relative abundances of CO, CH3OH, CH4, C2H6, HCN, and NH3. The combination of relative abundances and orbital parameters is then compared with recent chemical models of planetary system formation. This approach may help in investigating the origins and evolution of the material in cometary nuclei. Among other aspects, we underline the need to increase our sample size, especially for hypervolatiles (i.e., CH4 and CO) in Jupiter family comets.

Keywords: comets; solar system formation; comet volatiles
Superresolution Reconstruction of Severely Undersampled Point-spread Functions Using Point-source Stacking and Deconvolution

Point-spread function (PSF) estimation in spatially undersampled images is challenging because large pixels average fine-scale spatial information. This is problematic when fine-resolution details are necessary, as in optimal photometry where knowledge of the illumination pattern beyond the native spatial resolution of the image may be required. Here, we introduce a method of PSF reconstruction where point sources are artificially sampled beyond the native resolution of an image and combined together via stacking to return a finely sampled estimate of the PSF. This estimate is then deconvolved from the pixel-gridding function to return a superresolution kernel that can be used for optimally weighted photometry. We benchmark against the <1% photometric error requirement of the upcoming SPHEREx mission to assess performance in a concrete example. We find that standard methods like Richardson-Lucy deconvolution are not sufficient to achieve this stringent requirement. We investigate a more advanced method with significant heritage in image analysis called iterative back-projection (IBP) and demonstrate it using idealized Gaussian cases and simulated SPHEREx images. In testing this method on real images recorded by the LORRI instrument on New Horizons, we are able to identify systematic pointing drift. Our IBP-derived PSF kernels allow photometric accuracy significantly better than the requirement in individual SPHEREx exposures. This PSF reconstruction method is broadly applicable to a variety of problems and combines computationally simple techniques in a way that is robust to complicating factors such as severe undersampling, spatially complex PSFs, noise, crowded fields, or limited source numbers.

Keywords: astrostatistics techniques; deconvolution; astronomy data analysis; computational methods
Rotation Distributions around the Kraft Break with TESS and Kepler: The Influences of Age, Metallicity, and Binarity

Stellar rotation is a complex function of mass, metallicity, and age and can be altered by binarity. To understand the importance of these parameters in main-sequence stars, we have assembled a sample of observations that spans a range of these parameters using a combination of observations from The Transiting Exoplanet Survey Satellite (TESS) and the Kepler Space Telescope. We find that while we can measure rotation periods and identify other classes of stellar variability (e.g., pulsations) from TESS light curves, instrument systematics prevent the detection of rotation signals longer than the TESS orbital period of 13.7 days. Due to this detection limit, we also use rotation periods constrained using rotational velocities measured by the APOGEE spectroscopic survey and radii estimated using the Gaia mission for both TESS and Kepler stars. From these rotation periods, we (1) find we can track rotational evolution along discrete mass tracks as a function of stellar age, (2) find we are unable to recover trends between rotation and metallicity that were observed by previous studies, and (3) note that our sample reveals that wide binary companions do not affect rotation, while close binary companions cause stars to exhibit more rapid rotation than single stars.

Keywords: low mass stars; stellar rotation; binary stars; spectroscopic binary stars; astrometric binary stars; wide binary stars; close binary stars; stellar evolution; stellar evolutionary models
Prospects for 21 cm Galaxy Cross-correlations with HERA and the Roman High-latitude Survey

The cross-correlation between the 21 cm field and the galaxy distribution is a potential probe of the Epoch of Reionization (EoR). The 21 cm signal traces neutral gas in the intergalactic medium and, on large spatial scales, this should be anticorrelated with the high-redshift galaxy distribution, which partly sources and tracks the ionized gas. In the near future, interferometers such as the Hydrogen Epoch of Reionization Array (HERA) are projected to provide extremely sensitive measurements of the 21 cm power spectrum. At the same time, the Nancy Grace Roman Space Telescope (Roman) will produce the most extensive catalog to date of bright galaxies from the EoR. Using seminumeric simulations of reionization, we explore the prospects for measuring the cross-power spectrum between the 21 cm and galaxy fields during the EoR. We forecast a 12σ detection between HERA and Roman, assuming an overlapping survey area of 500 deg2, redshift uncertainties of σ z = 0.01 (as expected for the high-latitude spectroscopic survey of Lyα-emitting galaxies), and an effective Lyα emitter duty cycle of f LAE = 0.1. Thus the HERA-Roman cross-power spectrum may be used to help verify 21 cm detections from HERA. We find that the shot-noise in the galaxy distribution is a limiting factor for detection, and so supplemental observations using Roman should prioritize deeper observations, rather than covering a wider field of view. We have made a public GitHub repository containing key parts of the calculation, which accompanies this paper: https://github.com/plaplant/21cm_gal_cross_correlation.

Keywords: cosmology; large-scale structure of the universe; reionization
Effect of Dark Matter Distribution on Scalaron Gravity near the Galactic Center Black Hole and Its Prospects

In this paper, we report the effect of exponential and power-law dark matter density profiles near the Galactic Center black hole on the relative scalaron field amplitude , ψ 0/ϕ (ϕ being Newtonian potential and ψ 0 being the scalaron field amplitude), of f(R) gravity theory. Constraints on the density profiles derived earlier on the basis of orbital motion of the S-2 star are used in conjunction with scalarons having a mass range 10-22-10-16 eV to investigate the dependency of screening or unscreening of modified gravity on the dark matter density through the condition that the rate of pericenter shift due to dark matter is equal to that due to scalaron gravity + general relativistic effects. The semimajor axes are chosen as a = 45 au, 100 au, and 1000 au. It is found that scalarons get screened for extremely low and extremely high mass. This is found to be independent of the black hole spin in the range (χ = 0.1-0.9). For wider orbits scalarons of almost all the masses tend to remain unscreened for the dark matter profiles. It has been found that low dark matter density has a natural tendency to unscreen the scalaron gravity with extremely small coupling strength. We remap screened gravity in the available observational constraints on the scale of modified gravity near the black hole. Astrophysical prospects are presented.

Keywords: gravitation; galactic center; black hole physics; dark matter