2022MNRAS.513.2732S

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 light curve with N data points, fBLS simultaneously produces all the binned phase-folded light curves for an array of N_p trial periods. For each folded light curve produced by fBLS, the algorithm generates the standard BLS periodogram and statistics. The number of performed arithmetic operations is $\mathcal {O}(N_p\cdot \log N_p)$, while regular BLS requires $\mathcal {O}(N_p\cdot N)$ 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 light curves. 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.