The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution

¹ Institute of Theoretical Physics and Astrophysics, Masaryk University, 611 37 Brno, Czech Republic e-mail: krticka@physics.muni.cz
² Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovak Republic

Received: 24 October 2006
Accepted: 11 April 2007

Abstract

We simulate light curves of the helium strong chemically peculiar star HD 37776 assuming that the observed periodic light variations originate as a result of inhomogeneous horizontal distribution of chemical elements on the surface of a rotating star. We show that chemical peculiarity influences the monochromatic radiative flux, mainly due to bound-free processes. Using the model of the distribution of silicon and helium on HD 37776 surface, derived from spectroscopy, we calculate a photometric map of the surface and consequently the uvby light curves of this star. Basically, the predicted light curves agree in shape and amplitude with the observed ones. We conclude that the basic properties of variability of this helium strong chemically peculiar star can be understood in terms of the model of spots with peculiar chemical composition.