Grids of ATLAS9 Model Atmospheres and MOOG Synthetic Spectra

TL;DR

This paper presents a comprehensive grid of ATLAS9 stellar atmosphere models and MOOG synthetic spectra covering a wide range of stellar parameters, useful for analyzing stellar populations and abundance studies.

Contribution

It introduces an expanded grid of model atmospheres with a broader [alpha/Fe] range and provides synthetic spectra from 6300 to 9100 Angstroms, accessible online.

Findings

Expanded [alpha/Fe] range improves modeling of alpha-enhanced stars.

Synthetic spectra cover 6300-9100 Angstroms at 0.02 Angstrom resolution.

The grid is suitable for abundance analysis and stellar population synthesis.

Abstract

A grid of ATLAS9 model atmospheres has been computed, spanning 3500 K <= T_eff <= 8000 K, 0.0 <= log g <= 5.0, -4.0 <= [M/H] <= 0.0, and -0.8 < [alpha/Fe] <= +1.2. These parameters are appropriate for stars in the red giant branch, subgiant branch, and the lower main sequence. The main difference from a previous, similar grid (Castelli & Kurucz 2003) is the range of [alpha/Fe] values. A grid of synthetic spectra, calculated from the model atmospheres, is also presented. The fluxes are computed every 0.02 Angstrom from 6300 Angstrom to 9100 Angstrom. The microturbulent velocity is given by a relation to the surface gravity. This relation is appropriate for red giants, but not for subgiants or dwarfs. Therefore, caution is urged for the synthetic spectra with log g > 3.5 or for any star that is not a red giant. Both the model atmosphere and synthetic spectrum grids are available online through VizieR. Applications of these grids include abundance analysis for large samples of stellar spectra and constructing composite spectra for stellar populations.