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

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

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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 Pb = 0.66, P.02 = 6.1, Pc = 7.8, Pd = 14.7, Pe = 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 (md=8.9 +5.7/-3.8 M ⊕ and me = 14.3  +6.4/-5-0 M⊕) 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.
Original languageEnglish
Article number245
JournalAstrophysical Journal
Volume156
Issue number5
Number of pages20
ISSN1538-3881
DOIs
Publication statusPublished - 2018

Keywords

  • Planetary systems
  • Planets and satellites: detection
  • stars: individual (K2-266, EPIC 248435395)

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