Photometric detection of non-transiting short-period low-mass companions through the beaming, ellipsoidal and reflection effects in Kepler and CoRoT light curves

Abstract

We present a simple algorithm, BEER, to search for a combination of the\nBEaming, Ellipsoidal and the Reflection/heating periodic modulations, induced\nby short-period non-transiting low-mass companions. The beaming effect is due\nto the increase (decrease) of the brightness of any light source approaching\n(receding from) the observer. To first order, the beaming and the\nreflection/heating effects modulate the stellar brightness at the orbital\nperiod, with phases separated by a quarter of a period, whereas the ellipsoidal\neffect is modulated with the orbital first harmonic. The phase and harmonic\ndifferences between the three modulations allow the algorithm to search for a\ncombination of the three effects and identify stellar candidates for low-mass\ncompanions. The paper presents the algorithm, including an assignment of a\nlikelihood factor to any possible detection, based on the expected ratio of the\nbeaming and ellipsoidal effects, given an order-of-magnitude estimate of the\nthree effects. As predicted by Loeb & Gaudi (2003) and Zucker, Mazeh &\nAlexander (2007), the Kepler and the CoRoT lightcurves are precise enough to\nallow detection of massive planets and brown-dwarf/low-mass-stellar companions\nwith orbital period up to 10-30 days. To demonstrate the feasibility of the\nalgorithm, we bring two examples of candidates found in the first 33 days of\nthe Q1 Kepler lightcurves. Although we used relatively short timespan, the\nlightcurves were precise enough to enable the detection of periodic effects\nwith amplitudes as small as one part in 10,000 of the stellar flux.\n