A STUDY OF THE SHORTEST-PERIOD PLANETS FOUND WITH KEPLER

By Roberto Sanchis-Ojeda, S. Rappaport, J. Winn, Michael C. Kotson, A. Levine, Ileyk El Mellah. 2014

130 citations recorded by the source corpus.

We present the results of a survey aimed at discovering and studying transiting planets with orbital periods shorter than one day (ultra-short-period, or USP, planets), using data from the Kepler spacecraft. We computed Fourier transforms of the photometric time series for all 200,000 target stars, and detected transit signals based on the presence of regularly spaced sharp peaks in the Fourier spectrum. We present a list of 106 USP candidates, of which 18 have not previously been described in the literature. This list of candidates increases the number of planet candidates with orbital periods shorter than about six hours from two to seven. In addition, among the objects we studied, there are 26 USP candidates that had been previously reported in the literature which do not pass our various tests. All 106 of our candidates have passed several standard tests to rule out false positives due to eclipsing stellar systems. A low false positive rate is also implied by the relatively high fraction of candidates for which more than one transiting planet signal was detected. By assuming these multi-transit candidates represent coplanar multi-planet systems, we are able to infer that the USP planets are typically accompanied by other planets with periods in the range 1–50 days, in contrast with hot Jupiters which very rarely have companions in that same period range. Another clear pattern is that almost all USP planets are smaller than 2 R⊕, possibly because gas giants in very tight orbits would lose their atmospheres by photoevaporation when subject to extremely strong stellar irradiation. Based on our survey statistics, USP planets exist around approximately (0.51 ± 0.07)% of G-dwarf stars, and (0.83 ± 0.18)% of K-dwarf stars.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

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Citations in the corpus

A SYSTEMATIC SEARCH FOR TRANSITING PLANETS IN THE K2 DATA (2015, methodology): “Therefore, we discard all signals with periods shorter than 4 days, acknowledging this will cause us to miss some planets (Sanchis-Ojeda et al. 2014).”
PLANETARY CANDIDATES OBSERVED BY KEPLER. VI. PLANET SAMPLE FROM Q1–Q16 (47 MONTHS) (2015, background): “Independent groups have constructed their own catalogs (Petigura et al. 2013; Schmitt et al. 2014; Sanchis-Ojeda et al. 2014), and derive their own occurrence rates (Foreman-Mackey et al. 2014).”
WASP-47: A HOT JUPITER SYSTEM WITH TWO ADDITIONAL PLANETS DISCOVERED BY K2 (2015, background): “…(Knutson et al. 2014; Endl et al. 2014) or a warm Jupiter (orbital period 6.3 - 15.8 days) and a close-in planet (for example, KOI 191: Steffen et al. 2010; Sanchis-Ojeda et al. 2014), searches for close-in, companions to hot Jupiters (as in Steffen et al. 2012) have not yet been successful.”
The Occurrence and Architecture of Exoplanetary Systems (2014, background): “These are the first sightings of spin-orbit misalignment for planets that seem quite distinct from hot Jupiters.”
The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets (2017, background): “A sharp decline in the occurrence rate of planets larger than approximately 1.6 R⊕ with orbital periods shorter than 10 days has been previously observed (Howard et al. 2012; Dong & Zhu 2013; Sanchis-Ojeda et al. 2014).”
Identifying Exoplanets with Deep Learning: A Five-planet Resonant Chain around Kepler-80 and an Eighth Planet around Kepler-90 (2017, background): “This system has two validated planets (Morton et al. 2016) and two candidates, including a warm Jupiter, an ultra-short-period planet (Sanchis-Ojeda et al. 2014), and a superEarth in between, giving it a distinct architecture reminiscent of the 55 Cnc (Nelson et al. 2014) and WASP-47 (Becker et al.…”
Optimized transit detection algorithm to search for periodic transits of small planets (2019, methodology): “Transit searches using the BLS algorithm usually operate with trial transit durations3 T14 that span 0.00125 – 0.07 (Petigura et al. 2013), 0.01 – 0.1 (Giacobbe et al. 2012), or 0.001 – 0.2 (Sanchis-Ojeda et al. 2014; Aigrain et al. 2016) times the orbital period.”
A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission (2014, background): “Ultra–short–period planets (e.g. Sanchis-Ojeda et al. 2014) could be difficult to discover if the planet’s orbital period is near the time scale of the Kepler thruster fires, which control the telescope pointing.”
The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, background): “Ultra-short period (USP) planets (Sanchis-Ojeda et al. 2014) have orbital periods shorter than one day.”