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

TL;DR

This paper investigates the potential to detect tiny brightness variations caused by a close massive planet distorting its host star, using modeling techniques, and discusses the challenges and implications of such measurements.

Contribution

It presents a method to estimate ellipsoidal variations in star brightness due to orbiting planets, including a case study of tau Bootis, highlighting the detection difficulties.

Findings

Ellipsoidal variations for tau Bootis are about 0.01 mmag.

Detection of such variations is very challenging due to their small amplitude.

Modeling can provide constraints on star-planet system parameters.

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.