Spectral Line Distortions in the Presence of a Close-in Planet

Abstract

We discuss the interpretation of the distortions to the stellar spectral lines, with particular attention to line bisectors in the presence of an orbiting planetary companion. We present a simple model whereby light reflected by the companion can cause temporal variations to the observed line profiles. These distortions have a characteristic signature that depends on the inclination angle of the system. For the known close-in extrasolar giant planets, the expected amplitude of the effect might not be far from current detection capabilities. This method could be used to detect the presence of the companion directly, yielding the orbital inclination and hence the planetary mass. Furthermore, a detection would measure a combination of the planetary radius and albedo, from which a minimum radius may be deduced.