Astron. Astrophys. Suppl. Ser. 135, 383-390

An improved method for the determination of the orbital parameters of a binary system that contains a pulsating component

G. Molenberghs¹ - C. Aerts² - P. De Cat²

¹ Biostatistics, Limburgs Universitair Centrum, Universitaire Campus, Building D, B-3590 Diepenbeek, Belgium
² Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, B-3001 Heverlee, Belgium

Received September 7; accepted November 3, 1998

Abstract:

In this paper we present a method to assign statistical weights to radial-velocity measurements of a binary system of which one of the components is a variable star. The basic idea of the method is to separate the radial-velocity changes due to the intrinsic variability from those due to the orbital motion. This can be achieved if part of the data set consists of good coverages of the intrinsic variability cycle. These full coverages are used to estimate the variability for the nights on which only one or a few spectra were obtained. Our technique is applicable when the intrinsic variability has a period that is considerably shorter than the orbital period.

Once weights have been assigned, existing methods to derive the orbital parameters can be used with better accuracy compared to the case where all data points are treated as if no intrinsic variability were present (equal weights). We illustrate our method and compare the orbital solution obtained with and without assigning weights for three pulsating stars in a binary system: $\beta\,$Cru, $\varepsilon\,$Per, and $\kappa\,$Sco.

Key words: methods: statistical -- stars: oscillations -- binaries: spectroscopic