Improved determination of the atmospheric parameters of the pulsating sdB star Feige 48

¹ Département de Physique, Université de Montréal, Succ. Centre-Ville, CP. 6128, Montréal, QC H3C 3J7, Canada
² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA

^a e-mail: marilyn@astro.umontreal.ca

Abstract

Given the importance of Feige 48 as an sdB pulsator, we sought to obtain the best possible estimates of its spectroscopic parameters with a grid of NLTE metal-blanketed model atmospheres constructed especially for that star. This small grid of 150 models includes 8 metallic elements whose abundances have been determined previously and reported in the literature. Our fitting procedure found the following parameters for Feige 48: T_eff = 29 504 K, log g = 5.41 and log N(He)/N(H) = −2.90. These results are in very good agreement with previous spectroscopic estimates (which generally ignore either NLTE effects or metal blanketing), thus indicating that metal line-blanketing in NLTE – modeled for the first time here – is not a dominant factor in the atmosphere of Feige 48.