文章基本信息

标题：Optimized transit detection algorithm to search for periodic transits of small planets
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作者：Michael Hippke ; René Heller
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：623
DOI：10.1051/0004-6361/201834672
语种：English
出版社：EDP Sciences
摘要：We present a new method to detect planetary transits from time-series photometry, the transit least squares (TLS) algorithm.TLSsearches for transit-like features while taking the stellar limb darkening and planetary ingress and egress into account. We have optimizedTLSfor both signal detection efficiency (SDE) of small planets and computational speed.TLSanalyses the entire, unbinned phase-folded light curve. We compensated for the higher computational load by (i.) using algorithms such as “Mergesort” (for the trial orbital phases) and by (ii.) restricting the trial transit durations to a smaller range that encompasses all known planets, and using stellar density priors where available. A typical K2 light curve, including 80 d of observations at a cadence of 30 min, can be searched withTLSin ∼10 s real time on a standard laptop computer, as fast as the widely used box least squares (BLS) algorithm. We perform a transit injection-retrieval experiment of Earth-sized planets around sun-like stars using synthetic light curves with 110 ppm white noise per 30 min cadence, corresponding to a photometrically quietKP = 12 star observed withKepler. We determine the SDE thresholds for bothBLSandTLSto reach a false positive rate of 1% to be SDE = 7 in both cases. The resulting true positive (or recovery) rates are ∼93% forTLSand ∼76% forBLS, implying more reliable detections withTLS. We also testTLSwith the K2 light curve of the TRAPPIST-1 system and find six of seven Earth-sized planets using an iterative search for increasingly lower signal detection efficiency, the phase-folded transit of the seventh planet being affected by a stellar flare.TLSis more reliable thanBLSin finding any kind of transiting planet but it is particularly suited for the detection of small planets in long time series fromKepler, TESS, and PLATO. We make ourpythonimplementation ofTLSpublicly available.
关键词：eneclipsesmethods: data analysisplanets and satellites: detectionplanets and satellites: individual: TRAPPIST-1methods: statistical