SAtlas: Spherical Versions of the Atlas Stellar Atmosphere Program

TL;DR

This paper introduces SAtlas, a modified version of the Atlas stellar atmosphere program that incorporates spherical geometry to better model stars with extended atmospheres, especially in low gravity regimes.

Contribution

The paper presents the development of SAtlas, an open-source stellar atmosphere code with spherical geometry, enhancing modeling capabilities for stars with extended atmospheres.

Findings

SAtlas matches plane-parallel models at high gravity.

SAtlas aligns with Phoenix and MARCS models at low gravity.

SAtlas provides a versatile tool for stellar atmosphere modeling.

Abstract

Context: The current stellar atmosphere programs still cannot match some fundamental observations of the brightest stars, and with new techniques, such as optical interferometry, providing new data for these stars, additional development of stellar atmosphere codes is required. Aims: To modify the open-source model atmosphere program Atlas to treat spherical geometry, creating a test-bed stellar atmosphere code for stars with extended atmospheres. Methods: The plane-parallel Atlas has been changed by introducing the necessary spherical modifications in the pressure structure, in the radiative transfer and in the temperature correction. Results: Several test models show that the spherical program matches the plane-parallel models in the high surface gravity regime, and matches spherical models computed by Phoenix and by MARCS in the low gravity case.