- ID:
- ivo://CDS.VizieR/J/A+A/564/A133
- Title:
- Gaia FGK benchmark stars: metallicity
- Short Name:
- J/A+A/564/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To calibrate automatic pipelines that determine atmospheric parameters of stars, one needs a sample of stars, or "benchmark stars", with well-defined parameters to be used as a reference. We provide detailed documentation of the iron abundance determination of the 34 FGK-type benchmark stars that are selected to be the pillars for calibration of the one billion Gaia stars. They cover a wide range of temperatures, surface gravities, and metallicities.
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- ID:
- ivo://CDS.VizieR/III/281
- Title:
- Gaia FGK benchmark stars v2.1
- Short Name:
- III/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this era of large spectroscopic surveys of stars of the Milky Way, pipelines need to be tested and validated against a set of well-known stars. The Gaia FGK benchmark stars (GBS) are among the preferred samples of reference stars. They consist of a small but carefully selected sample of stars whose parameters are derived consistently and homogeneously. A series of papers has been published that discuss the definition and evolution of the sample of GBS. Here we summarise this work and provide our current list of stars with associated parameters which are recommended for validation and calibration purposes for stellar surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A70
- Title:
- Gaia FGK stars: low-metallicities candidates
- Short Name:
- J/A+A/592/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have entered an era of large spectroscopic surveys in which we can measure, through automated pipelines, the atmospheric parameters and chemical abundances for large numbers of stars. Calibrating these survey pipelines using a set of "benchmark stars" in order to evaluate the accuracy and precision of the provided parameters and abundances is of utmost importance. The recent proposed set of Gaia FGK benchmark stars has up to five metal-poor stars but no recommended stars within -2.0<[Fe/H]<-1.0dex. However, this metallicity regime is critical to calibrate properly. In this paper, we aim to add candidate Gaia benchmark stars inside of this metal-poor gap. We began with a sample of 21 metal-poor stars which was reduced to 10 stars by requiring accurate photometry and parallaxes, and high-resolution archival spectra. The procedure used to determine the stellar parameters was similar to the previous works in this series for consistency. The difference was to homogeneously determine the angular diameter and effective temperature (Teff) of all of our stars using the Infrared Flux Method utilizing multi-band photometry. The surface gravity (logg) was determined through fitting stellar evolutionary tracks. The [Fe/H] was determined using four different spectroscopic methods fixing the Teff and logg from the values determined independent of spectroscopy.
- ID:
- ivo://CDS.VizieR/J/AJ/159/280
- Title:
- Gaia-Kepler stellar properties catalog.I. KIC stars
- Short Name:
- J/AJ/159/280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An accurate and precise Kepler Stellar Properties Catalog is essential for the interpretation of the Kepler exoplanet survey results. Previous Kepler Stellar Properties Catalogs have focused on reporting the best-available parameters for each star, but this has required combining data from a variety of heterogeneous sources. We present the Gaia-Kepler Stellar Properties Catalog, a set of stellar properties of 186301 Kepler stars, homogeneously derived from isochrones and broadband photometry, Gaia Data Release 2 parallaxes, and spectroscopic metallicities, where available. Our photometric effective temperatures, derived from g to Ks colors, are calibrated on stars with interferometric angular diameters. Median catalog uncertainties are 112K for Teff, 0.05dex for logg, 4% for R_*_, 7% for M_*_, 13% for {rho}_*_, 10% for L_*_, and 56% for stellar age. These precise constraints on stellar properties for this sample of stars will allow unprecedented investigations into trends in stellar and exoplanet properties as a function of stellar mass and age. In addition, our homogeneous parameter determinations will permit more accurate calculations of planet occurrence and trends with stellar properties.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A20
- Title:
- Gaia RVS benchmark stars. I.
- Short Name:
- J/A+A/651/A20
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The Radial Velocity Spectrometer (RVS) on board the Gaia satellite is not provided with a wavelength calibration lamp. It uses its observations of stars with known radial velocity to derive the dispersion relation. To derive an accurate radial velocity calibration, a precise knowledge of the line spread function (LSF) of the RVS is necessary. Good-quality ground-based observations in the wavelength range of the RVS are highly desired to determine the LSF. Several radial velocity standard stars are available to the Gaia community. The highest possible number of calibrators will surely allow us to improve the accuracy of the radial velocity. Because the LSF may vary across the focal plane of the RVS, a large number of high-quality spectra for the LSF calibration may allow us to better sample the properties of the focal plane. We selected a sample of stars to be observed with UVES at the Very Large Telescope, in a setting including the wavelength range of RVS, that are bright enough to allow obtaining high-quality spectra in a short time. We also selected stars that lack chemical investigation in order to increase the sample of bright, close by stars with a complete chemical inventory. We here present the chemical analysis of the first sample of 80 evolved stars. The quality of the spectra is very good, therefore we were able to derive abundances for 20 elements. The metallicity range spanned by the sample is about 1dex, from slightly metal-poor to solar metallicity. We derived the Rb abundance for all stars and investigated departures from local thermodynamical equilibrium (NLTE) in the formation of its lines. The sample of spectra is of good quality, which is useful for a Gaia radial velocity calibration. The Rb NLTE effects in this stellar parameters range are small but sometimes non-negligible, especially for spectra of this good quality.
- ID:
- ivo://CDS.VizieR/J/A+A/392/491
- Title:
- Galactic abundance gradient. III.
- Short Name:
- J/A+A/392/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a continuation of our previous work, which concerned the radial abundance distribution in the galactic disc over the distances 4-10kpc this paper presents the first results on the metallicity in the outer disc (R_G_>10kpc). Based on high-resolution spectra obtained for 19 distant Cepheids we sampled galactocentric distances from 10 to 12 kpc. Combined with the results of our previous work on the inner and middle parts of the galactic disc, the present data enable one to study the structure of the radial abundance distribution over a large baseline. In particular, we find indications of a discontinuity in the radial abundance distribution for iron as well as a number of the other elements. The discontinuity is seen at a galactocentric distance R_G_=10kpc. This finding supports the results reported earlier by Twarog et al. (1997AJ....114.2556T).
- ID:
- ivo://CDS.VizieR/J/A+A/289/740
- Title:
- Galactic abundance gradients
- Short Name:
- J/A+A/289/740
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/413/159
- Title:
- Galactic abundance gradient. V.
- Short Name:
- J/A+A/413/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the spectroscopic investigation of 12 Cepheids which are situated in the crucial region of galactocentric distances from 9kpc to 12kpc, where according to our previous results (Andrievsky et al., 2002, Cat. <J/A+A/392/491>; Luck et al., 2003A&A...401..939L) the radial metallicity distribution experiences an obvious change. In particular, the wriggle in the iron abundance distribution is found to fall approximately at galactocentric distances 10-11kpc (assuming galactocentric distance of the Sun kpc). Within the transition zone from 10 to 11kpc the relative-to-solar iron abundance decreases approximately to -0.2dex. The new sample of stars, analyzed in present paper, gives results supporting the previous conclusion about the multimodal character of the metallicity distribution in galactic disc. Using a quite simple consideration of galactic chemical evolution we show that the observed distribution can be explained in the framework of a model which includes the spiral arms. In particular, the wriggle feature associated with 11 kpc can be interpreted as a change of metallicity level in the vicinity of the galactic corotation resonance.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/748
- Title:
- Galactic anticenter PNe and oxygen abundance
- Short Name:
- J/ApJ/724/748
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained spectrophotometric observations of 41 anticenter planetary nebulae (PNe) located in the disk of the Milky Way. Electron temperatures and densities, as well as chemical abundances for He, N, O, Ne, S, Cl, and Ar were determined. Incorporating these results into our existing database of PN abundances (Henry et al., 2004AJ....127.2284H, Milingo et al., 2010, Cat. J/ApJ/711/619) yielded a sample of 124 well-observed objects with homogeneously determined abundances extending from 0.9 to 21kpc in galactocentric distance. We performed a detailed regression analysis which accounted for uncertainties in both oxygen abundances and radial distances in order to establish the metallicity gradient across the disk to be 12+log(O/H)=(9.09+/-0.05)-(0.058+/-0.006)xR_g_, with R_g_ in kpc. While we see some evidence that the gradient steepens at large galactocentric distances, more objects toward the anticenter need to be observed in order to confidently establish the true form of the metallicity gradient.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A149
- Title:
- 417 Galactic bulge red giant O & Zn abund.
- Short Name:
- J/A+A/614/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Oxygen and zinc in the Galactic bulge are key elements for the understanding of the bulge chemical evolution. Oxygen-to-iron abundance ratios provide a most robust indicator of the star formation rate and chemical evolution of the bulge. Zinc is enhanced in metal-poor stars, behaving as an {alpha}-element, and its production may require nucleosynthesis in hypernovae. Most of the neutral gas at high redshift is in damped Lyman-alpha systems (DLAs), where Zn is also observed to behave as an {alpha}-element. The aim of this work is the derivation of the {alpha}-element oxygen, together with nitrogen, and the iron-peak element zinc abundances in 417 bulge giants, from moderate resolution (R~22000) FLAMES-GIRAFFE spectra. For stars in common with a set of UVES spectra with higher resolution (R~45000), the data are intercompared. The results are compared with literature data and chemodynamical models. We studied the spectra obtained for a large sample of red giant stars, chosen to be one magnitude above the horizontal branch, using FLAMES-GIRAFFE on the Very Large Telescope. We computed the O abundances using the forbidden [OI] 6300.3{AA} and Zn abundances using the ZnI 6362.34{AA} lines. Stellar parameters for these stars were established in a previous work from our group. We present oxygen abundances for 358 stars, nitrogen abundances for 403 stars and zinc abundances were derived for 333 stars. Having oxygen abundances for this large sample adds information in particular at the moderate metallicities of -1.6<[Fe/H]<-0.8. Zn behaves as an {alpha}-element, very similarly to O, Si, and Ca. It shows the same trend as a function of metallicity as the {alpha}-elements, i.e., a turnover around [Fe/H]~-0.6, and then decreasing with increasing metallicity. The results are compared with chemodynamical evolution models of O and Zn enrichment for a classical bulge. DLAs also show an enhanced zinc-to-iron ratio, suggesting they may be enriched by hypernovae.