Line blanketed model atmospheres of Ap-stars. VI. HD 221568.

Abstract

Visual and UV spectroscopic observations of HD 221568 together with line blanketed model atmospheres show that the star has an effective temperature of 10300K if log g = 3.7 is assumed. The temperature may be lower by about 100K in the phase of reddest B-V. Models with variable chemical composition are not able to reproduce observed light variations, particularly a large decrease of flux between the Balmer jump and about 5000 Å observed in the "red" phase. It is suggested that this decrease may be due to numerous lines of rare earth elements not included in the computations. To explain observed light variations a small decrease of effective temperature in the "red" phase accompanied by an increase of the visible disk and increased line blanketing are suggested.