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

Creators: 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^(+5.7)_(−3.8) M_⊕ and m_e = 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 75fdg32 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.

Additional Information

© 2018. The American Astronomical Society. Received 2018 June 21; revised 2018 September 26; accepted 2018 September 28; published 2018 November 2. We thank Chelsea Huang, Laura Kreidberg, George Zhou, and Li Zeng for their valuable conversations. Work performed by J.E.R. was supported by the Harvard Future Faculty Leaders Postdoctoral fellowship. A.V.'s contribution to this work was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC,https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, particularly the institutions participating in the Gaia Multilateral Agreement. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. A portion of this work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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