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

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: Teff = 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.