Description

Binary star systems, which are pairs of stars that orbit each other, are very common. Roughly 50% of sun-like stars belong to such a system. A total of 17 out of the 5200+ confirmed exoplanets orbit both stars of a binary. We refer to these as circumbinary planets. To date, all circumbinary planets have been found in binary stars with orbital periods greater than a few days. Whether this is because it is harder to find them around shorter-period stars, or because such planets don’t exist, is unknown. Using archival data from NASA’s Kepler mission (2009-2013), we carefully re-examine the known short period eclipsing binary systems to search for circumbinary planets. The search process involves detrending the data to eliminate any confounding variations due to instrumental artifacts or actual stellar variability so we can detect planetary transits; a transit is a dip in the observed brightness of the system caused by the planet eclipsing the stars. The transit signature of a short-period binary is very different from that of a single star and current detection methods will not work in finding such a transit. In a short-period binary, the stars are so close to each other that they are tidally distorted and are almost always eclipsing, so the background light continuously varies – and by a large amount. This makes planet detection very difficult. Using improved detrending and detection techniques, we will undergo a systematic search for planets in short-period eclipsing binaries, which has not been carried out and published before. We hope to discover circumbinary planets, but if we do not detect any, that implies that they do not exist. While in some way disappointing, this would help confirm theories of close-binary star formation where the shrinking of the binary star’s orbit disrupts and ejects any planets.