Ultra Short Period Planets in K2 with companions: a double transiting system for EPIC 220674823

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 hours), while the other has a period of 13.3 days. Both planets are small, with the former having a radius of R_p1=1.5 R_E and the latter R_p2=2.5 R_E. Follow-up observations, including radial velocity (with uncertainties of 110 m/s) 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.

8 pages, 6 figures, 2 tables, accepted to AJ

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• TOI-1075 b: A Dense, Massive, Ultra-Short Period Hot Super-Earth Straddling the Radius Gap
• Probing Kepler's hottest small planets via homogeneous search and analysis of optical secondary eclipses and phase variations
• A Reanalysis of the Composition of K2-106b: an Ultra-short Period Super-Mercury Candidate
• A hot Mars-sized exoplanet transiting an M dwarf
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