Abstract
We apply for the first time the transit least-squares (TLS) algorithm to search for new transiting exoplanets. TLS has been developed as a successor to the box least-squares (BLS) algorithm, which has served as a standard tool for the detection of periodic transits. In this proof-of-concept paper, we demonstrate that TLS finds small planets that have previously been missed. We show the capabilities of TLS using the K2 EVEREST-detrended light curve of the star K2-32 (EPIC 205071984), which has been known to have three transiting planets. TLS detects these known Neptune-sized planets K2-32 b, d, and c in an iterative search and finds an additional transit signal with a high signal detection efficiency (SDETLS) of 26.1 at a period of 4.34882−0.00075+0.00069 d. We show that this additional signal remains detectable (SDETLS = 13.2) with TLS in the K2SFF light curve of K2-32, which includes a less optimal detrending of the systematic trends. The signal is below common detection thresholds if searched with BLS in the K2SFF light curve (SDEBLS = 8.9), however, as in previous searches. Markov chain Monte Carlo sampling with the emcee software shows that the radius of this candidate is 1.01−0.09+0.10 R⊕. We analyzed its phase-folded transit light curve using the vespa software and calculated a false-positive probability FPP = 3.1 × 10−3. Taking into account the multiplicity boost of the system, we estimate an FPP < 3.1 × 10−4, which formally validates K2-32 e as a planet. K2-32 now hosts at least four planets that are very close to a 1:2:5:7 mean motion resonance chain. The offset of the orbital periods of K2-32 e and b from a 1:2 mean motion resonance agrees very well with the sample of transiting multiplanet systems from Kepler, lending further credence to the planetary nature of K2-32 e. We expect that TLS can find many more transits of Earth-sized and even smaller planets in the Kepler and K2 data that have so far remained undetected with algorithms that search for box-like signals.
Highlights
The data from the Kepler primary mission (K1; Borucki et al 2010), which operated from 2009 to 2013, and from the repurposed K2 mission (Howell et al 2014), which worked from 2014 to 2018, have both been subject to extensive transit searches
We show the capabilities of transit least-squares (TLS) using the K2 EVEREST-detrended light curve of the star K2-32 (EPIC 205071984), which has been known to have three transiting planets
Characterization of the new planet K2-32 e from Markov chain Monte Carlo (MCMC) model fitting to the full set of transits in the EVEREST light curve of K2-32
Summary
The data from the Kepler primary mission (K1; Borucki et al 2010), which operated from 2009 to 2013, and from the repurposed K2 mission (Howell et al 2014), which worked from 2014 to 2018, have both been subject to extensive transit searches Most of their confirmed or validated planets (2338 from K1 and 359 from K2) and of the candidates that are yet to be confirmed (2423 from K1 and 536 from K2) have been found using the box least-squares (BLS) transit search algorithm (Kovács et al 2002) or similar algorithms searching for box-like flux decreases in stellar light curves (Batalha et al 2013; Vanderburg et al 2016; Crossfield et al 2016, 2018; Mayo et al 2018; Livingston et al 2018a,b; Yu et al 2018; van Sluijs & Van Eylen 2018). We use TLS to search for so far unknown planets in the K2 data of K2-32 (EPIC 205071984), and we present our first discovery from our new data analysis campaign, the TLS survey
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
