A Compact Multi-planet System with a Significantly Misaligned Ultra Short Period Planet

November 2018 • 2018AJ....156..245R

Authors • Rodriguez, Joseph E. • Becker, Juliette C. • Eastman, Jason D. • Hadden, Sam • Vanderburg, Andrew • Khain, Tali • Quinn, Samuel N. • Mayo, Andrew • Dressing, Courtney D. • Schlieder, Joshua E. • Ciardi, David R. • Latham, David W. • Rappaport, Saul • Adams, Fred C. • Berlind, Perry • Bieryla, Allyson • Calkins, Michael L. • Esquerdo, Gilbert A. • Kristiansen, Martti H. • Omohundro, Mark • Schwengeler, Hans Martin • Stassun, Keivan G. • Terentev, Ivan

Abstract • We report the discovery of a compact multi-planet system orbiting the relatively nearby (78 pc) and bright (K = 8.9) K-star, K2-266 (EPIC 248435473). We identify up to six possible planets orbiting K2-266 with estimated periods of P b = 0.66, P .02 = 6.1, P c = 7.8, P d = 14.7, P e = 19.5, and P .06 = 56.7 days, and radii of R P = 3.3 R , 0.646 R , 0.705 R , 2.93 R , 2.73 R , and 0.90 R , respectively. We are able to confirm the planetary nature of two of these planets (d and e) by analyzing their transit timing variations ({m}d={8.9}-3.8+5.7 {M}\oplus and {m}e={14.3}-5.0+6.4 {M}\oplus ), confidently validate the planetary nature of two other planets (b and c), and classify the last two as planetary candidates (K2-266.02 and .06). From a simultaneous fit of all six possible planets, we find that K2-266 b’s orbit has an inclination of 75.°32 while the other five planets have inclinations of 87°-90°. This observed mutual misalignment may indicate that K2-266 b formed differently from the other planets in the system. The brightness of the host star and the relatively large size of the sub-Neptune sized planets d and e make them well-suited for atmospheric characterization efforts with facilities like the Hubble Space Telescope and upcoming James Webb Space Telescope. We also identify an 8.5 day transiting planet candidate orbiting EPIC 248435395, a co-moving companion to K2-266.


IPAC Authors


David Ciardi

Senior Scientist