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1221. Atmospheric parameters for 1273 stars
ID:
ivo://CDS.VizieR/J/A+A/525/A71
Title:
Atmospheric parameters for 1273 stars
Short Name:
J/A+A/525/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
Empirical libraries of stellar spectra play an important role in different fields. For example, they are used as reference for the automatic determination of atmospheric parameters, or for building synthetic stellar populations to study galaxies. The CFLIB (Coude-feed library, Indo-US) database is at present one of the most complete libraries, in terms of its coverage of the atmospheric parameters space (Teff, logg and [Fe/H]) and wavelength coverage 3460-9464{AA} at a resolution of ~1{AA} FWHM. Although the atmospheric parameters of most of the stars were determined from detailed analyses of high-resolution spectra, for nearly 300 of the 1273 stars of the library at least one of the three parameters is missing. For the others, the measurements, compiled from the literature, are inhomogeneous. In this paper, we re-determine the atmospheric parameters, directly using the CFLIB spectra, and compare them to the previous studies. Methods. We use the ULySS program to derive the atmospheric parameters, using the ELODIE library as a reference. Based on comparisons with several previous studies we conclude that our determinations are unbiased. For the 958 F,G, and K type stars the precision on Teff, logg, and [Fe/H] is respectively 43K, 0.13dex and 0.05dex. For the 53 M stars they are 82K, 0.22dex and 0.28dex. And for the 260 OBA type stars the relative precision on Teff is 5.1%, and on logg, and [Fe/H] the precision is respectively 0.19 dex and 0.16 dex. These parameters will be used to re-calibrate the CFLIB fluxes and to produce synthetic spectra of stellar populations.
1222. Atmospheric parameters from Fe lines
ID:
ivo://CDS.VizieR/J/MNRAS/429/126
Title:
Atmospheric parameters from Fe lines
Short Name:
J/MNRAS/429/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive analysis of different techniques available for the spectroscopic analysis of FGK stars and provide a recommended methodology which efficiently estimates accurate stellar atmospheric parameters for large samples of stars. Our analysis includes a simultaneous equivalent width analysis of FeI and FeII spectral lines, and for the first time, utilizes on-the-fly non-local thermodynamic equilibrium (NLTE) corrections of individual FeI lines. We further investigate several temperature scales, finding that estimates from Balmer line measurements provide the most accurate effective temperatures at all metallicities. We apply our analysis to a large sample of both dwarf and giant stars selected from the Radial Velocity Experiment (RAVE) survey. We then show that the difference between parameters determined by our method and that by the standard 1D LTE excitation-ionization balance of Fe reveals substantial systematic biases: up to 400K in effective temperature, 1.0dex in surface gravity and 0.4dex in metallicity for stars with [Fe/H]~-2.5. This has large implications for the study of the stellar populations in the Milky Way.
1223. Atmospheric parameters in luminous stars
ID:
ivo://CDS.VizieR/J/AJ/147/137
Title:
Atmospheric parameters in luminous stars
Short Name:
J/AJ/147/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
Parameters and abundances for 451 stars of spectral types F, G, and K of luminosity classes I and II have been derived. Absolute magnitudes and E(B-V) have been derived for the warmer stars in order to investigate the galactic abundance gradient. The value found here: d[Fe/H]/dR~-0.06dex/kpc, agrees well with previous determinations. Stellar evolution indicators have also been investigated with the derived C/O ratios indicating that standard CN processing has been operating. Perhaps the most surprising result found in these supposedly relatively young intermediate-mass stars is that both [O/Fe] and [C/Fe] show a correlation with [Fe/H] much the same as found in older populations. While the stars were selected based on luminosity class, there does exist a significant [Fe/H] range in the sample. The likely explanation of this is that there is a significant range in age in the sample; that is, some of the sample are low-mass red-giant stars with types that place them within the selection criteria.
1224. Atmospheric parameters in metal-poor stars. I
ID:
ivo://CDS.VizieR/J/A+A/314/191
Title:
Atmospheric parameters in metal-poor stars. I
Short Name:
J/A+A/314/191
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present atmospheric parameters for about 300 stars of different chemical composition, whose spectra will be used to study the galactic enrichment of Fe and light elements. These parameters were derived using an homogeneous iterative procedure, which considers new calibrations of colour-T_eff_ relations for F, G and K-type stars based on Infrared Flux Method (IRFM) and interferometric diameters for population I stars, and the Kurucz (1992) model atmospheres. We found that these calibrations yield a self-consistent set of atmospheric parameters for T_eff_>4400K, representing a clear improvement over results obtained with older model atmospheres. Using this T_eff_ -scale and Fe equilibrium of ionization, we obtained very low gravities (implying luminosities incompatible with that expected for RGB stars) for metal-poor stars cooler than 4400K; this might be due either to a moderate Fe overionization (expected from statistical equilibrium calculations) or to inadequacy of Kurucz models to describe the atmospheres of very cool giants. Our T_eff_ scale is compared with other scales recently used for metal-poor stars; it agrees well with those obtained using Kurucz (1992) models, but it gives much larger T_eff_'s than those obtained using OSMARCS models (Edvardsson et al. 1993). This difference is attributed to the different treatment of convection in the two sets of models. For the Sun, the Kurucz (1992) model appears to be preferable to the OSMARCS ones because it better predicts the solar limb darkening; furthermore, we find that our photometric T_eff_ 's for metal-poor stars agree well with both direct estimates based on the IRFM, and with T_eff_'s derived from H{alpha} wings when using Kurucz models.
1225. Atmospheric parameters in metal-poor stars. III.
ID:
ivo://CDS.VizieR/J/A+A/356/238
Title:
Atmospheric parameters in metal-poor stars. III.
Short Name:
J/A+A/356/238
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the analysis of an extensive set of new and literature high quality data concerning Fe, C, N, O, Na, and Mg. This analysis exploited the T_eff_ scale determined in Gratton et al. (1996, Cat. <J/A+A/314/191>), and the non-LTE abundance corrections computed in Gratton et al. (1999, Cat. <J/A+A/350/955>). Results obtained with various abundance indices are discussed and compared.
1226. Atmospheric parameters of DA white dwarfs
ID:
ivo://CDS.VizieR/J/ApJ/631/1100
Title:
Atmospheric parameters of DA white dwarfs
Short Name:
J/ApJ/631/1100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present atmospheric parameters for a large sample of DA white dwarfs that are known to be photometrically constant. For each star, we determine the effective temperature and surface gravity by comparing high signal-to-noise ratio optical spectra to the predictions of detailed model atmosphere calculations. We also report the successful prediction and detection of photometric variability in G232-38 based on similar Teff and logg determinations. The atmospheric parameters derived for this sample of constant stars, as well as those for the known sample of bright ZZ Ceti stars (now boosted to a total of 39), have been obtained in a highly homogeneous way.
1227. Atmospheric parameters of 1907 metal-rich stars
ID:
ivo://CDS.VizieR/J/ApJS/169/430
Title:
Atmospheric parameters of 1907 metal-rich stars
Short Name:
J/ApJS/169/430
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report high-precision atmospheric parameters for 1907 stars in the N2K low-resolution spectroscopic survey, designed to identify metal-rich FGK dwarfs likely to harbor detectable planets. Of these stars, 284 are in the ideal temperature range for planet searches, T_eff_<=6000K, and have a 10% or greater probability of hosting planets based on their metallicities. This catalog contains measurements of [Fe/H] (sigma_[Fe/H]_=0.07dex), T_eff_(sigma_Teff=82K), and logg (sigma_logg_=0.13dex). Atmospheric parameters are derived from Lick index measurements, as described in Robinson et al. (2006, Cat. <J/ApJ/637/1102>). Lick indices are measured from spectra obtained with the GCAM spectrograph on the 2.1m telescope at KPNO.
1228. Atmospheric parameters of M4 stars
ID:
ivo://CDS.VizieR/J/AJ/147/25
Title:
Atmospheric parameters of M4 stars
Short Name:
J/AJ/147/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report new metallicities for stars of Galactic globular cluster M4 using the largest number of stars ever observed at high spectral resolution in any cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the Very Large Telescope (VLT) FLAMES+GIRAFFE spectrograph at VLT. These medium-resolution spectra cover a small wavelength range, and often have very low signal-to-noise ratios. We approached this data set by reconsidering the whole method of abundance analysis of large stellar samples from beginning to end. We developed a new algorithm that automatically determines the atmospheric parameters of a star. Nearly all of the data preparation steps for spectroscopic analyses are processed on the syntheses, not the observed spectra. For 322 red giant branch (RGB) stars with V<=14.7, we obtain a nearly constant metallicity, <[Fe/H]>=-1.07 ({sigma}=0.02). No difference in the metallicity at the level of 0.01 dex is observed between the two RGB sequences identified by Monelli et al. (2013MNRAS.431.2126M). For 1869 subgiant and main-sequence stars with V>14.7, we obtain <[Fe/H]>=-1.16 ({sigma}=0.09) after fixing the microturbulent velocity. These values are consistent with previous studies that have performed detailed analyses of brighter RGB stars at higher spectroscopic resolution and wavelength coverage. It is not clear if the small mean metallicity difference between brighter and fainter M4 members is real or is the result of the low signal-to-noise characteristics of the fainter stars. The strength of our approach is shown by recovering a metallicity close to a single value for more than 2000 stars, using a data set that is non-optimal for atmospheric analyses. This technique is particularly suitable for noisy data taken in difficult observing conditions.
1229. Atmospheric parameters of nearby F-K stars
ID:
ivo://CDS.VizieR/J/PASJ/57/27
Title:
Atmospheric parameters of nearby F-K stars
Short Name:
J/PASJ/57/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on a collection of high-dispersion spectra obtained at Okayama Astrophysical Observatory, the atmospheric parameters (Teff, logg, vt, and [Fe/H]) of 160 mid-F through early-K stars were extensively determined by the spectroscopic method using the equivalent widths of Fe I and Fe II lines along with the numerical technique of Takeda et al. (2002PASJ...54..451T). The results are comprehensively discussed and compared with the parameter values derived by different approaches (e.g., photometric colors, theoretical evolutionary tracks, Hipparcos parallaxes, etc.) as well as with the published values found in various literature. It has been confirmed that our purely spectroscopic approach yields fairly reliable and consistent results.
1230. Atmospheric parameters of nearby giant stars
ID:
ivo://CDS.VizieR/J/A+A/536/A71
Title:
Atmospheric parameters of nearby giant stars
Short Name:
J/A+A/536/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
We are conducting a precision radial velocity study of a sample of 164 nearby giant stars in the southern hemisphere. In this work we present the spectroscopic atmospheric parameters (Teff, logg , vmic and [Fe/H]) for all of our targets. By comparing the position on the HR diagram with stellar evolutionary tracks, we derived the mass, radius and evolutionary status for every star in our sample. In addition, rotational velocities are also measured.

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