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

Abstract

We discuss the interpretation of distortions to 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 depending 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 directly detect the presence of the companion, yielding the orbital inclination and hence the planetary mass. Futhermore, a detection would measure a combination of the planetary radius and albedo, from which a minimum radius may be deduced.