Ultra-short-period Planets in K2 with Companions: A Double Transiting System for EPIC 220674823
Baranec, Christoph; Cochran, William D.; Duev, Dmitry A.; Endl, Michael; Jensen-Clem, Rebecca; Law, Nicholas M.; Riddle, Reed; Salama, Maïssa; Ziegler, Carl; MacQueen, Phillip J.; Jackson, Brian; Adams, Elisabeth R.; Kulkarni, Shrinivas
United States
Abstract
Two transiting planets have been identified orbiting K2 target EPIC 220674823. One object is an ultra-short-period planet (USP) with a period of just 0.57 days (13.7 hr), while the other has a period of 13.3 days. Both planets are small, with the former having a radius of {R}{{p}1}=1.5 {R}\oplus and the latter {R}{{p}2}=2.5 {R}\oplus . Follow-up observations, including radial velocity (with uncertainties of 110 m s-1) and high-resolution adaptive optics imagery, show no signs of stellar companions. EPIC 220674823 is the 12th confirmed or validated planetary system in which a USP (I.e., having an orbital period less than 1 day) is accompanied by at least one additional planet, suggesting that such systems may be common and must be accounted for in models for the formation and evolution of such extreme systems.