fBLS -- a fast-folding BLS algorithm

Abstract

We present fBLS -a novel fast-folding technique to search for transiting planets, based on the fast-folding algorithm (FFA), which is extensively used in pulsar astronomy. For a given lightcurve with 𝑁 data points, fBLS simultaneously produces all the binned phase-folded lightcurves for an array of 𝑁 𝑝 trial periods. For each folded lightcurve produced by fBLS, the algorithm generates the standard BLS periodogram and statistics. The number of performed arithmetic operations is O 𝑁 𝑝 • log 𝑁 𝑝 , while regular BLS requires O 𝑁 𝑝 • 𝑁 operations. fBLS can be used to detect small rocky transiting planets, with periods shorter than one day, a period range for which the computation is extensive. We demonstrate the capabilities of the new algorithm by performing a preliminary fBLS search for planets with ultra-short periods in the Kepler main-sequence lightcurves. In addition, we developed a simplistic signal validation scheme for vetting the planet candidates. This two-stage preliminary search identified all known ultra-short planet candidates and found three new ones.