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14741. Stellar parameters and assumed wind parameters
ID:
ivo://CDS.VizieR/J/A+A/603/A56
Title:
Stellar parameters and assumed wind parameters
Short Name:
J/A+A/603/A56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent observations have challenged our understanding of rotational mixing in massive stars by revealing a population of fast-rotating objects with apparently normal surface nitrogen abundances. However, several questions have arisen because of a number of issues (e.g., presence of numerous upper limits for the nitrogen abundance, unknown multiplicity status, mix of stars with different physical properties such as their mass and evolutionary state that are known to control the amount of rotational mixing), rendering a re-investigation necessary. We have carefully selected a large sample of bright, fast-rotating early-type stars of our Galaxy (40 objects with spectral types between B0.5 and O4). Their high-quality, high-resolution optical spectra were then analysed with the stellar atmosphere modelling codes DETAIL/SURFACE or CMFGEN, depending on the temperature of the target. Several internal and external checks were performed to validate our methods, notably comparing our results with literature data for some well-known objects, studying the effect of gravity darkening, or confronting the results provided by the two codes for stars amenable to both analyses. Furthermore, we have studied the radial velocities of the stars to assess their binarity. This first part of our study presents our methods and provides the derived stellar parameters, He, CNO abundances and the multiplicity status of every star of the sample. It is the first time that He and CNO abundances of such a large number of Galactic massive fast rotators are determined in a homogeneous way.
14742. Stellar parameters and extinction
ID:
ivo://CDS.VizieR/J/MNRAS/411/435
Title:
Stellar parameters and extinction
Short Name:
J/MNRAS/411/435
Date:
21 Oct 2021
Publisher:
CDS
Description:
Astrometric surveys provide the opportunity to measure the absolute magnitudes of large numbers of stars, but only if the individual line-of-sight extinctions are known. Unfortunately, extinction is highly degenerate with stellar effective temperature when estimated from broad band optical/infrared photometry. To address this problem, I introduce a Bayesian method for estimating the intrinsic parameters of a star and its line-of-sight extinction.
14743. Stellar parameters and Li abundances from GES iDR6
ID:
ivo://CDS.VizieR/J/A+A/653/A72
Title:
Stellar parameters and Li abundances from GES iDR6
Short Name:
J/A+A/653/A72
Date:
22 Feb 2022
Publisher:
CDS
Description:
After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various ^7^Li sources in enriching the interstellar medium (ISM) with this fragile element. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a sample of open clusters (OCs) and field stars for which high-precision ^7^Li abundances and stellar parameters are homogeneously derived by the Gaia-ESO Survey (GES). We derive possibly un-depleted ^7^Li abundances for 26 OCs and star forming regions with ages from young (~3Myr) to old (~4.5Gyr), spanning a large range of galactocentric distances, 5<RGC/kpc<15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain ^7^Li evolution in other Galactic components. The data are then compared to theoretical tracks from chemical evolution models that implement different ^7^Li forges. Thanks to the homogeneity of the GES analysis, we can combine the maximum average ^7^Li abundances derived for the clusters with ^7^Li measurements in field stars. We find that the upper envelope of the ^7^Li abundances measured in field stars of nearly solar metallicities (-0.3<[Fe/H]/dex<+0.3) traces very well the level of lithium enrichment attained by the ISM as inferred from observations of cluster stars in the same metallicity range. We confirm previous findings that the abundance of ^7^Li in the solar neighbourhood does not decrease at supersolar metallicity. The comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the ^7^Li abundance in meteorites comes from novae. Current data also seem to suggest that the nova rate flattens out at later times. This requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. Neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. This likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the ^7^Li abundance in the ISM of low-metallicity systems that would counterbalance the astration processes.
14744. Stellar parameters for 134 cool subdwarfs
ID:
ivo://CDS.VizieR/J/PASP/115/22
Title:
Stellar parameters for 134 cool subdwarfs
Short Name:
J/PASP/115/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a search for cool subdwarfs are presented. Kinematic (U, V, and W) and stellar parameters (Teff, logg, [Fe/H], and Vturb) are derived for 134 candidate subdwarfs based on high-resolution spectra. The observed stars span 4200K<Teff<6400K and -2.70<[Fe/H]<0.25 including only eight giants (logg<4.0). Of the sample, 100 stars have MgH bands present in their spectra. The targets were selected by their large reduced proper motion, by the offset from the solar-metallicity main sequence, or from the literature. We confirm the claims made by Ryan (1989, Cat. <J/AJ/98/1693>) that the NLTT catalog is a rich source of subdwarfs and verify the success of the reduced proper-motion constraint in identifying metal-poor stars.
14745. Stellar parameters for CoRoT exoplanet field stars
ID:
ivo://CDS.VizieR/J/A+A/581/A68
Title:
Stellar parameters for CoRoT exoplanet field stars
Short Name:
J/A+A/581/A68
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectroscopic observations represent a fundamental step in the physical characterization of stars and, in particular, in the precise location of stars in the HR diagram. Rotation is also a key parameter, impacting stellar properties and evolution, which modulates the interior and manifests itself on the surface of stars. To date, the lack of analysis based on large samples has prevented our understanding of the real impact of stellar parameters and rotation on the stellar evolution as well as on the behavior of surface abundances. The space missions, CoRoT and Kepler, are providing us with rotation periods for thousands of stars, thus enabling a robust assessment of the behavior of rotation for different populations and evolutionary stages. For these reasons, the follow-up programs are fundamental to increasing the returns of these space missions. An analysis that combines spectroscopic data and rotation/modulation periods obtained from these space missions provides the basis for establishing the evolutionary behavior of the angular momentum of solar-like stars at different evolutionary stages, and the relation of rotation with other relevant physical and chemical parameters. To support the computation and evolutionary interpretation of periods associated with the rotational modulation, oscillations, and variability of stars located in the CoRoT fields, we are conducting a spectroscopic survey for stars located in the fields already observed by the satellite. These observations allow us to compute physical and chemical parameters for our stellar sample. Using spectroscopic observations obtained with UVES/VLT and Hydra/Blanco, and based on standard analysis techniques, we computed physical and chemical parameters (T_eff_, log(g), [Fe/H], v_mic_, v_rad_, vsin(i), and A(Li)) for a large sample of CoRoT targets. We provide physical and chemical parameters for a sample comprised of 138 CoRoT targets. Our analysis shows the stars in our sample are located in different evolutionary stages, ranging from the main sequence to the red giant branch, and range in spectral type from F to K. The physical and chemical properties for the stellar sample are in agreement with typical values reported for FGK stars. However, we report three stars presenting abnormal lithium behavior in the CoRoT fields. These parameters allow us to properly characterize the intrinsic properties of the stars in these fields. Our results reveal important differences in the distributions of metallicity, T_eff_, and evolutionary status for stars belonging to different CoRoT fields, in agreement with results obtained independently from ground-based photometric surveys. Our spectroscopic catalog, by providing much-needed spectroscopic information for a large sample of CoRoT targets, will be of key importance for the successful accomplishment of several different programs related to the CoRoT mission, thus it will help further boost the scientific return associated with this space mission.
14746. Stellar parameters for 582 HARPS FGK stars
ID:
ivo://CDS.VizieR/J/A+A/533/A141
Title:
Stellar parameters for 582 HARPS FGK stars
Short Name:
J/A+A/533/A141
Date:
21 Oct 2021
Publisher:
CDS
Description:
To understand the formation and evolution of solar-type stars and planets in the solar neighborhood, we need to obtain their stellar parameters with high precision. We present a catalog of precise stellar parameters for low-activity FGK single stars in a volume-limited sample followed by the HARPS spectrograph in the quest to identify extra-solar planets. The spectroscopic analysis was completed assuming LTE with a grid of Kurucz atmosphere models and using the ARES code to perform an automatic measurement of the line equivalent widths. The results are compared with different independent methods and also with other values found in the literature for common stars. Both comparisons are consistent and illustrate the homogeneity of the parameters derived by our team. The derived metallicities of this sample reveal a somewhat different distribution for the present planet hosts, but still indicates the already known higher frequency of planets observed for the more metal-rich stars. We combine the results derived in this sample with the one from the CORALIE survey to present the largest homogeneous spectroscopic study of the metallicity-giant-planet relation using a total of 1830 stars.
14747. Stellar parameters for 131 Herbig Ae/Be stars
ID:
ivo://CDS.VizieR/J/AJ/157/159
Title:
Stellar parameters for 131 Herbig Ae/Be stars
Short Name:
J/AJ/157/159
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present study makes use of the unprecedented capability of the Gaia mission to obtain the stellar parameters such as distance, age, and mass of HAeBe stars. The accuracy of Gaia DR2 (Cat. I/345) astrometry is demonstrated from the comparison of the Gaia DR2 distances of 131 HAeBe stars with the previously estimated values from the literature. This is one of the initial studies to estimate the age and mass of a confirmed sample of HAeBe stars using both the photometry and distance from the Gaia mission. Mass accretion rates are calculated from H{alpha} line flux measurements of 106 HAeBe stars. Since we used distances and the stellar masses derived from the Gaia DR2 data in the calculation of the mass accretion rate, our estimates are more accurate than previous studies. The mass accretion rate is found to decay exponentially with age, from which we estimated a disk dissipation timescale of 1.9+/-0.1 Myr. The mass accretion rate and stellar mass exhibit a power-law relation of the form M_acc_{prop.to}M_*_^2.8+/-0.2^. From the distinct distribution in the values of the infrared spectral index, n_2-4.6_, we suggest the possibility of difference in the disk structure between Herbig Be and Herbig Ae stars.
14748. Stellar parameters for 13196 Kepler dwarfs
ID:
ivo://CDS.VizieR/J/AJ/160/90
Title:
Stellar parameters for 13196 Kepler dwarfs
Short Name:
J/AJ/160/90
Date:
21 Oct 2021
Publisher:
CDS
Description:
The rotational evolution of cool dwarfs is poorly constrained after ~1-2Gyr due to a lack of precise ages and rotation periods for old main-sequence stars. In this work, we use velocity dispersion as an age proxy to reveal the temperature-dependent rotational evolution of low-mass Kepler dwarfs and demonstrate that kinematic ages could be a useful tool for calibrating gyrochronology in the future. We find that a linear gyrochronology model, calibrated to fit the period-Teff relationship of the Praesepe cluster, does not apply to stars older than around 1Gyr. Although late K dwarfs spin more slowly than early-K dwarfs when they are young, at old ages, we find that late K dwarfs rotate at the same rate or faster than early-K dwarfs of the same age. This result agrees qualitatively with semiempirical models that vary the rate of surface-to-core angular momentum transport as a function of time and mass. It also aligns with recent observations of stars in the NGC6811 cluster, which indicate that the surface rotation rates of K dwarfs go through an epoch of inhibited evolution. We find that the oldest Kepler stars with measured rotation periods are late K and early M dwarfs, indicating that these stars maintain spotted surfaces and stay magnetically active longer than more massive stars. Finally, based on their kinematics, we confirm that many rapidly rotating GKM dwarfs are likely to be synchronized binaries.
14749. Stellar parameters from SDSS-III APOGEE DR10
ID:
ivo://CDS.VizieR/J/AJ/146/133
Title:
Stellar parameters from SDSS-III APOGEE DR10
Short Name:
J/AJ/146/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Sloan Digital Sky Survey III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a three-year survey that is collecting 10^5^ high-resolution spectra in the near-IR across multiple Galactic populations. To derive stellar parameters and chemical compositions from this massive data set, the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP) has been developed. Here, we describe empirical calibrations of stellar parameters presented in the first SDSS-III APOGEE data release (DR10). These calibrations were enabled by observations of 559 stars in 20 globular and open clusters. The cluster observations were supplemented by observations of stars in NASA's Kepler field that have well determined surface gravities from asteroseismic analysis. We discuss the accuracy and precision of the derived stellar parameters, considering especially effective temperature, surface gravity, and metallicity; we also briefly discuss the derived results for the abundances of the {alpha}-elements, carbon, and nitrogen. Overall, we find that ASPCAP achieves reasonably accurate results for temperature and metallicity, but suffers from systematic errors in surface gravity. We derive calibration relations that bring the raw ASPCAP results into better agreement with independently determined stellar parameters. The internal scatter of ASPCAP parameters within clusters suggests that metallicities are measured with a precision better than 0.1dex, effective temperatures better than 150K, and surface gravities better than 0.2dex. The understanding provided by the clusters and Kepler giants on the current accuracy and precision will be invaluable for future improvements of the pipeline.
14750. Stellar parameters from the 1st release of the MaSTar
ID:
ivo://CDS.VizieR/J/ApJ/899/62
Title:
Stellar parameters from the 1st release of the MaSTar
Short Name:
J/ApJ/899/62
Date:
14 Mar 2022 07:12:49
Publisher:
CDS
Description:
We report the stellar atmospheric parameters for 7503 spectra contained in the first release of the Mapping Nearby Galaxies at Apache Point Observatory survey (MaNGA) stellar library (MaStar) in Sloan Digital Sky Survey DR15. The first release of MaStar contains 8646 spectra measured from 3321 unique stars, each covering the wavelength range 3622-10354{AA} with a resolving power of R~1800. In this work, we first determined the basic stellar parameters: effective temperature (Teff), surface gravity (logg), and metallicity ([Fe/H]), which best fit the data using an empirical interpolator based on the Medium-resolution Isaac Newton Telescope library of empirical spectra (MILES), as implemented by the University of Lyon Spectroscopic analysis Software package. While we analyzed all 8646 spectra from the first release of MaStar, since MaStar has a wider parameter-space coverage than MILES, not all of these fits are robust. In addition, not all parameter regions covered by MILES yield robust results, likely due to the nonuniform coverage of the parameter space by MILES. We tested the robustness of the method using the MILES spectra itself and identified a proxy based on the local density of the training set. With this proxy, we identified 7503 MaStar spectra with robust fitting results. They cover the range from 3179 to 20517K in effective temperature (Teff), from 0.40 to 5.0 in surface gravity (logg), and from -2.49 to +0.73 in metallicity ([Fe/H]).

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