The atmospheric parameters and spectral interpolator for the stars of MILES

TL;DR

This paper refines the atmospheric parameters of stars in the MILES spectral library, creating a spectral interpolator with improved accuracy and stability for stellar classification and population synthesis.

Contribution

It provides a new, more precise atmospheric parameter catalog for MILES stars and develops an improved spectral interpolator tested against multiple stellar libraries.

Findings

Achieved parameter precisions of 60 K, 0.13 dex, 0.05 dex for FGK stars.

Constructed an interpolator more reliable than ELODIE for hot evolved stars.

Validated the interpolator's accuracy using MILES and CFLIB stars.

Abstract

Context. Empirical libraries of stellar spectra are used for stellar classification and synthesis of stellar populations. MILES is a medium spectral-resolution library in the optical domain covering a wide range of temperatures, surface gravities and metallicities. Aims. We re-determine the atmospheric parameters of these stars in order to improve the homogeneity and accuracy. We build an interpolating function that returns a spectrum as a function of the three atmospheric parameters, and finally, we characterize the precision of the wavelength calibration and stability of the spectral resolution. Methods. We use the ULySS program with the ELODIE library as a reference and compare the results with literature compilations. Results. We obtain precisions of 60 K, 0.13 and 0.05 dex respectively for Teff, log g and [Fe/H] for the FGK stars. For the M stars, the mean errors are 38 K, 0.26 and 0.12 dex, and for the OBA 3.5%, 0.17 and 0.13 dex. We construct an interpolator that we test against the MILES stars themselves. We test it also by measuring the atmospheric parameters of the CFLIB stars with MILES as reference and find it to be more reliable than the ELODIE interpolator for the evolved hot stars, like in particular those of the blue horizontal branch.