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 hours), while the other has a period of 13.3 days. Both planets are small, with the former having a radius of Rp1 = 1.5 R⊕ and the latter Rp2 = 2.5 R⊕. Follow-up observations, including radial velocity (with uncertainties of 110 ms−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 an ultra-short-period planet (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.
This is an author-created, un-copyedited version of an article published in The Astronomical Journal. IOP Publishing Ltd. is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. Copyright restrictions may apply. The Version of Record is available online at doi: 10.3847/1538-3881/153/2/82.
Jackson, Brian. (2017). "Ultra Short Period Planets in K2 with Companions: A Double Transiting System for Epic 220674823". The Astronomical Journal, 153(2), 82-1 - 82-7.