MyGIsFOS: an automated code for parameter determination and detailed abundance analysis in cool stars

Abstract

Context. The current and planned high-resolution, high-multiplexity stellar spectroscopic surveys, as well as the swelling amount of underutilized data present in public archives, have led to an increasing number of efforts to automate the crucial but slow process of retrieving stellar parameters and chemical abundances from spectra. Aims. We present MyGIsFOS 1 , a code designed to derive atmospheric parameters and detailed stellar abundances from medium-to high-resolution spectra of cool (FGK) stars. We describe the general structure and workings of the code, present analyses of a number of well-studied stars representative of the parameter space MyGIsFOS is designed to cover, and give examples of the exploitation of MyGIsFOS very fast analysis to assess uncertainties through Monte Carlo tests. Methods. MyGIsFOS aims to reproduce a "traditional" manual analysis by fitting spectral features for different elements against a precomputed grid of synthetic spectra. The lines of Fe i and Fe ii can be employed to determine temperature, gravity, microturbulence, and metallicity by iteratively minimizing the dependence of Fe i abundance from line lower energy and equivalent width, and imposing Fe i-Fe ii ionization equilibrium. Once parameters are retrieved, detailed chemical abundances are measured from lines of other elements. Results. MyGIsFOS replicates closely the results obtained in similar analyses on a set of well-known stars. It is also quite fast, performing a full parameter determination and detailed abundance analysis in about two minutes per star on a mainstream desktop computer. Currently, its preferred field of application are high-resolution and/or large spectral coverage data (e.g., UVES, X-shooter, HARPS, Sophie).

GaiaFGK benchmark stars: Effective temperatures and surface gravities

“…The two solar-metallicity giants β And and δ Oph (T eff ≈ 3800 K) have been used as standard stars in the APOGEE survey (Smith et al 2013;Mészáros et al 2013) to test the pipeline for parameter determination and the line list for abundance measurements. Two metal-poor stars were among the reference stars used by Sbordone et al (2014) Basic information for the 102 stars explicitly mentioned in this section is given in Table B.1. Furthermore, we extracted parallax measurements from the SIMBAD database for all stars except one.…”

“…Arcturus, α Cen A, β Vir, γ Sge, ξ Hya, µ Cas, and µ Leo were used by Valentini et al (2013) to validate the GAUFRE tool for measuring atmospheric parameters from spectra by comparing the results of the tool with average spectroscopic parameters from the literature. In a similar way, Arcturus and HD 140283 were used by Sbordone et al (2014) to validate the MyGIsFOS code for spectroscopic derivation of atmospheric parameters, using various sources for the reference parameters.…”

Chemical abundances of giant stars in NGC 5053 and NGC 5634, two globular clusters associated with the Sagittarius dwarf spheroidal galaxy?

“…For this purpose, a grid of synthetic spectra covering the range between 480 nm and 690 nm was computed with the following characteristics (start value, end value, step, unit): T eff (4000, 5200, 200, K), log g (0. . This corresponds to a grid of 3024 atmosphere models, the majority of which belonged to the MPG grid described in Sbordone et al (2014), with the exception of the ones with T eff = 4000 K and log g = 0.5, which were computed for this work. The models were computed assuming mono-dimensional, plane-parallel, and local thermodynamical equilibrium (LTE) approximations, using ATLAS 12 (Kurucz 2005;Sbordone et al 2004;Sbordone 2005).…”

Lithium abundance in a turnoff halo star on an extreme orbit

“…With this temperature, we performed a classical LTE analysis of WISE J0725-2351 using the code MyGIsFOS (Sbordone et al 2014), as done by Caffau et al (2013) in the frame of the ESO Large Programme TOPoS. The microturbulence velocity was taken equal to 1.5 km s −1 , and the surface gravity log g = 4.2 was derived from the ionization equilibrium of iron.…”