Detecting exoplanets with the xallarap microlensing effect

Abstract

One of the successful techniques for the detection of exoplanets relies on the magnification of an observed star resulting from microlensing by a foreground star orbited by a planetary companion. We propose an alternative method for the detection of exoplanets by microlensing, in which the orbital motion of a planet around the source star induces a small motion of the star around the common barycentre, which leads to detectable deviations from the ordinary symmetric microlensing light curve. We show that favourable events for such deviations to occur involve lenses close to the source star and Einstein-radius crossing times substantially larger than the planet’s orbital period. From a Monte-Carlo simulation, we find that a monitoring programme of Galactic bulge stars, capable of providing a 2-hour sampling and 2 % photometric accuracy, can detect planets of Jupiter mass with a detection efficiency of around 1 %.