Transit leastsquares survey. III. A 1.9 R_{⊕} transit candidate in the habitable zone of Kepler160 and a nontransiting planet characterized by transittiming variations
Abstract
The Sunlike star Kepler160 (KOI456) has been known to host two transiting planets, Kepler160 b and c, of which planet c shows substantial transittiming variations (TTVs). We studied the transit photometry and the TTVs of this system in our search for a suspected third planet. We used the archival Kepler photometry of Kepler160 to search for additional transiting planets using a combination of our Wōtan detrending algorithm and our transit leastsquares detection algorithm. We also used the Mercury Nbody gravity code to study the orbital dynamics of the system in trying to explain the observed TTVs of planet c. First, we recovered the known transit series of planets Kepler160 b and c. Then we found a new transiting candidate with a radius of 1.91_{0.14}^{+0.17} Earth radii (R_{⊕}), an orbital period of 378.417_{0.025}^{+0.028} d, and Earthlike insolation. The vespa software predicts that this signal has an astrophysical falsepositive probability of FPP_{3} = 1.8 × 10^{3} when the multiplicity of the system is taken into account. Kepler vetting diagnostics yield a multiple event statistic of MES = 10.7, which corresponds to an ~85% reliability against false alarms due to instrumental artifacts such as rolling bands. We are also able to explain the observed TTVs of planet c with the presence of a previously unknown planet. The period and mass of this new planet, however, do not match the period and mass of the new transit candidate. Our Markov chain Monte Carlo simulations of the TTVs of Kepler160 c can be conclusively explained by a new nontransiting planet with a mass between about 1 and 100 Earth masses and an orbital period between about 7 and 50 d. We conclude that Kepler160 has at least three planets, one of which is the nontransiting planet Kepler160 d. The expected stellar radial velocity amplitude caused by this new planet ranges between about 1 and 20 m s^{1}. We also find the superEarthsized transiting planet candidate KOI456.04 in the habitable zone of this system, which could be the fourth planet.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 June 2020
 DOI:
 10.1051/00046361/201936929
 arXiv:
 arXiv:2006.02123
 Bibcode:
 2020A&A...638A..10H
 Keywords:

 eclipses;
 methods: data analysis;
 planets and satellites: detection;
 planetary systems;
 techniques: photometric;
 planets and satellites: individual: Kepler160;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 published in A&