Planet influence on the shape of the hosting star - ellipsoidal variations of tau Bootis

Abstract

This paper presents estimations on the possibility of detection of ellipsoidal variations by means of measuring brightness of the star distorted by a close massive planet using Wilson-Devinney method. The problem was already discussed by Phafl et al. (2008) and earlier by Loeb and Gaudi (2003). The effect is well known in the case of binary stars where it can produce light curves with amplitutudes of ellipsoidal variations of about 0.1 mag for distorted stars. For planets the effect is very small and usually less than 0.0001 mag. The detection of an exoplanet, by searching for small amplitude ellipsoidal variations, will be very difficult and affected by other photometric effects; however, it maybe possible for some extreme cases. Observations of ellipsoidal variations can provide additional constraints on the model of the system. Light curves for few star/planet systems have been calculated using PHOEBE eclipsing binary software based on Wilson-Devinney method. As an example of ellipsoidal variations the synthetic light curve for tau Bootis is presented. The amplitude of ellipsoidal variation is 0.01 mmag. The companion is massive 7.3 Mjup and short-period hot Jupiter.