Stellar atmospheric parameters for 754 spectra from the X-shooter Spectral Library

Abstract

Context. The X-shooter Spectral Library (XSL) is an empirical stellar library at medium spectral resolution covering the wavelength range from 3000 Å to 24 800 Å. This library aims to provide a benchmark for stellar population studies. Aims. In this work, we present a uniform set of stellar atmospheric parameters, effective temperatures, surface gravities, and iron abundances for 754 spectra of 616 XSL stars. Methods. We used the full-spectrum fitting package ULySS with the empirical MILES library as reference to fit the ultraviolet-blue (UVB) and visible (VIS) spectra. We tested the internal consistency and we compared our results with compilations from the literature. Results. The stars cover a range of effective temperature 2900 < T eff < 38 000 K, surface gravity 0 < log g < 5.7, and iron abundance −2.5 < [Fe/H] < +1.0, with a couple of stars extending down to [Fe/H] = −3.9. The precisions of the measurements for the G-and K-type stars are 0.9%, 0.14, and 0.06 in T eff , log g, and [Fe/H], respectively. For the cool giants with log g < 1, the precisions are 2.1%, 0.21, and 0.22, and for the other cool stars these values are 1%, 0.14, and 0.10. For the hotter stars (T eff > 6500 K), these values are 2.6%, 0.20, and 0.10 for the three parameters.

The X-shooter Spectral Library (XSL): Data release 2

“…At the time the target lists were prepared, large public catalogs of homogeneous stellar parameter estimates were still lacking, and we were unable to populate certain regions of parameters in a satisfactory way. In particular, some of the Bulge stars selected on the basis of high estimated metallicities turned out to be less metal-rich than expected (Arentsen et al 2019).…”

“…We obtained repeated observations for a fraction of the XSL stars (∼ 20% of our sample), mainly in the cases of luminous cool stars, known or suspected to vary in time. Figure 2 presents the stellar atmospheric parameters coverage of the XSL sample as determined by Arentsen et al (2019) and Gonneau et al (2017). We refer the reader to Figure 2 of Chen et al (2014) where the HR diagram is presented using literature values.…”

NGC 6397: The metallicity trend along the isochrone revisited

“…While observations of Galactic globular clusters are classical benchmark for population models, the empirical libraries are at best limited near the TO of these clusters, and the interpolated spectra used for the models are crudely approximate. The most recent library is the X-Shooter Spectral Library, XSL Arentsen et al (2019). It has a more uniform coverage of the metallicity range than earlier libraries, but also suffers from a relative shortage of TO and MS stars in the low metallicity regime.…”

“…The free parameters are T eff , [Fe/H], v rad , σ rel and the coefficients of P n (λ). See Arentsen et al (2019) for other details on the procedure.…”

“…For the 1 200 stars with two or more repeated observations, the spectra differ by the noise and by the propagation of systematics introduced by the spectrograph and data reduction. We assessed the precision by comparing the atmospheric parameters measured on each pair of observations as in Arentsen et al (2019). We computed for each pair of observations i:…”