Ultra-short-period Planets in K2 with Companions: A Double Transiting System for EPIC 220674823

Creators: Adams, Elisabeth R.; Jackson, Brian; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Duev, Dmitry A.; Jensen-Clem, Rebecca; Salama, Maïssa; Ziegler, Carl; Baranec, Christoph; Kulkarni, Shrinivas R.; Law, Nicholas M.; Riddle, Reed

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 hr), 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⊕ and the latter R_(p2) = 2.5 R⊕. Follow-up observations, including radial velocity (with uncertainties of 110 m s−1) and high-resolution adaptive optics imagery, show no signs of stellar companions. EPIC 220674823 is the 12th confirmed or validated planetary system in which a USP (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.

Additional Information

© 2017 The American Astronomical Society. Received 2016 November 1; revised 2016 December 16; accepted 2016 December 19; published 2017 January 25. Some of the data analyzed in this paper were collected by the K2 mission, funding for which is provided by the NASA Science Mission Directorate. The data were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. 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. Robo-AO KP is a partnership between the California Institute of Technology, the University of Hawai'i, the University of North Carolina at Chapel Hill, the Inter-University Centre for Astronomy and Astrophysics, and the National Central University, Taiwan. Robo-AO KP is supported by a grant from Sudha Murty, Narayan Murthy, and Rohan Murty, and by a grant from the John Templeton Foundation. The Robo-AO instrument was developed with support from the National Science Foundation under grants AST-0906060, AST-0960343, and AST-1207891, from the Mt. Cuba Astronomical Foundation, and by a gift from Samuel Oschin. Based (in part) on observations at Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: 15B-3001), which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This study is based on work supported by NASA under Grant no. NNX15AB78G issued through the Astrophysical Data Analysis Program by the Science Mission Directorate. M.E., W.D.C., and P.J.M. were supported by NASA K2 Guest Observer grants NNX15AV58G, NNX16AE70G, and NNX16AE58G to the University of Texas at Austin. C.B. acknowledges support from the Alfred P. Sloan Foundation. Much thanks to Tim Morton for help with vespa. Facilities: Kepler (K2) - , Keck:II (NIRC2) - , KPNO:2.1m (Robo-AO). Software: Batman v2.1.0 (Kreidberg 2015), EEBLS (Kovács et al. 2002), Kea (Endl & Cochran 2016), PyMC v2.3.4 (Fonnesbeck et al. 2015), pymodelfit v0.1.2 (Tollerud 2011), Uncertainties v2.4.6.1 (Lebigot 2014), vespa v0.4.9 (Morton 2012, 2015).

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