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Published October 1, 2017 | Submitted + Published
Journal Article Open

Three Statistically Validated K2 Transiting Warm Jupiter Exoplanets Confirmed as Low-mass Stars

Abstract

We have identified three K2 transiting star–planet systems, K2-51 (EPIC 202900527), K2-67 (EPIC 206155547), and K2-76 (EPIC 206432863), as stellar binaries with low-mass stellar secondaries. The three systems were statistically validated as transiting planets, and through measuring their orbits by radial velocity (RV) monitoring we have derived the companion masses to be 0.1459^(+0.0029)_(-0.0032) M⊙ (EPIC 202900527 B), 0.1612^(+0.0072)_(-0.0067) M⊙ (EPIC 206155547 B), and 0.0942 ± 0.0019 M⊙ (EPIC 206432863 B). Therefore, they are not planets but small stars, part of the small sample of low-mass stars with measured radius and mass. The three systems are at an orbital period range of 12–24 days, and the secondaries have a radius within 0.9–1.9 R_J, not inconsistent with the properties of warm Jupiter planets. These systems illustrate some of the existing challenges in the statistical validation approach. We point out a few possible origins for the initial misclassification of these objects, including poor characterization of the host star, the difficulty in detecting a secondary eclipse in systems on an eccentric orbit, and the difficulty in distinguishing between the smallest stars and gas giant planets as the two populations have indistinguishable radius distributions. Our work emphasizes the need for obtaining medium-precision RV measurements to distinguish between companions that are small stars, brown dwarfs, and gas giant planets.

Additional Information

© 2017 The American Astronomical Society. Received 2017 August 5; revised 2017 September 7; accepted 2017 September 11; published 2017 September 27. A.V. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1144152. G.T. acknowledges partial support for this work from NSF grant AST-1509375 and NASA grant NNX14AB83G (Kepler Participating Scientist Program). D.W.L. acknowledges partial support from the Kepler mission via Cooperative Agreement NNX13AB58A with the Smithsonian Astrophysical Observatory. This Letter includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. 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. Facilities: K2 - , Keck:I (HIRES) - , FLWO:1.5 m (TRES) - .

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Published - Shporer_2017_ApJL_847_L18.pdf

Submitted - 1708.08455.pdf

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Additional details

Created:
August 21, 2023
Modified:
October 17, 2023