LTE model atmospheres with new opacities

I. Methods and general properties

Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland

Received: 3 August 2005
Accepted: 13 January 2006

Abstract

We describe an opacity sampled version of the LTE model atmosphere code sterne with revised continuous opacities. In particular, we examine the results of replacing the existing treatment of the continuous opacities which followed the method of Kurucz (1970, SAOSR, No. 309) and Peach (1970, MNRAS, 73, 1), with photoionization cross-sections from the Opacity Project and the IRON Project, and the effects of substituting an opacity distribution function method for treating the line opacities with an opacity sampling method. In studying the application of these new models to atmospheres with hydrogen-rich and extreme chemical compositions, we find the new opacity treatment increases the temperature in the line forming region by up to 3000 K for extremely hydrogen-poor stars and up to 1250 K for hydrogen-rich stars with T_eff = 30 000 K and log g = 3.00. This translates into systematically cooler effective temperature measurements for these types of stars.