GSP-spec line list for the parametrisation of Gaia -RVS stellar spectra

TL;DR

This paper develops a specialized line list for Gaia-RVS spectra analysis, improving the accuracy of stellar parameter estimation for late-type stars by refining atomic data based on observed and synthetic spectra comparisons.

Contribution

The authors created and validated a new line list optimized for Gaia-RVS spectra, enhancing the accuracy of stellar parameter determination for late-type stars.

Findings

The new line list yields high-quality synthetic spectra for reference stars.

It improves the accuracy of stellar atmospheric parameters in Gaia data.

The line list is adopted within the GSP-Spec pipeline.

Abstract

The Gaia mission is a magnitude-limited whole-sky survey that collects an impressive quantity of astrometric, spectro-photometric and spectroscopic data. Among all the on-board instruments, the Radial Velocity Spectrometer (RVS) produces millions of spectra up to a magnitude of G$_{RVS} \sim 16$. For the brightest RVS targets, stellar atmospheric parameters and individual chemical abundances are automatically estimated by the Generalized Stellar Parametriser - spectroscopy group (GSP-Spec). These data will be published with the third Gaia Data Release. Some major ingredients of the determination of these stellar parameters include the atomic and molecular line lists that are adopted to compute reference synthetic spectra, on which the parametrisation methods rely. We aim to build such a specific line list optimised for the analysis of RVS late-type star spectra. Starting from the Gaia-ESO line lists, we first compared the observed and synthetic spectra of six well-known reference late-type stars in the wavelength range covered by the RVS instrument. We then improved the quality of the atomic data for the transitions presenting the largest mismatches. The new line list is found to produce very high-quality synthetic spectra for the tested reference stars and has thus been adopted within GSP-Spec.