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

Rodriguez, Joseph E. and Becker, Juliette C. and Eastman, Jason D. and Hadden, Sam and Vanderburg, Andrew and Khain, Tali and Quinn, Samuel N. and Mayo, Andrew and Dressing, Courtney D. and Schlieder, Joshua E. and Ciardi, David R. and Latham, David W. and Rappaport, Saul and Adams, Fred C. and Berlind, Perry and Bieryla, Allyson and Calkins, Michael L. and Esquerdo, Gilbert A. and Kristiansen, Martti H. and Omohundro, Mark and Schwengeler, Hans Martin and Stassun, Keivan G. and Terentev, Ivan (2018) A Compact Multi-planet System with a Significantly Misaligned Ultra Short Period Planet. Astronomical Journal, 156 (5). Art. No. 245. ISSN 1538-3881. doi:10.3847/1538-3881/aae530.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rodriguez, Joseph E.0000-0001-8812-0565
Becker, Juliette C.0000-0002-7733-4522
Eastman, Jason D.0000-0003-3773-5142
Vanderburg, Andrew0000-0001-7246-5438
Khain, Tali0000-0001-7721-6457
Quinn, Samuel N.0000-0002-8964-8377
Mayo, Andrew0000-0002-7216-2135
Dressing, Courtney D.0000-0001-8189-0233
Schlieder, Joshua E.0000-0001-5347-7062
Ciardi, David R.0000-0002-5741-3047
Latham, David W.0000-0001-9911-7388
Rappaport, Saul0000-0003-3182-5569
Adams, Fred C.0000-0002-8167-1767
Bieryla, Allyson0000-0001-6637-5401
Calkins, Michael L.0000-0002-2830-5661
Esquerdo, Gilbert A.0000-0002-9789-5474
Stassun, Keivan G.0000-0002-3481-9052
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 (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, 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.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Harvard Future Faculty Leaders Postdoctoral FellowshipUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:planetary systems; planets and satellites: detection; stars: individual (K2-266, EPIC 248435395)
Issue or Number:5
Record Number:CaltechAUTHORS:20181115-105031930
Persistent URL:
Official Citation:Joseph E. Rodriguez et al 2018 AJ 156 245
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90917
Deposited By: George Porter
Deposited On:15 Nov 2018 20:52
Last Modified:16 Nov 2021 03:36

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