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

Shporer, Avi and Zhou, George and Vanderburg, Andrew and Fulton, Benjamin J. and Isaacson, Howard and Bieryla, Allyson and Torres, Guillermo and Morton, Timothy D. and Bento, Joao and Berlind, Perry and Calkins, Michael L. and Esquerdo, Gilbert A. and Howard, Andrew W. and Latham, David W. (2017) Three Statistically Validated K2 Transiting Warm Jupiter Exoplanets Confirmed as Low-mass Stars. Astrophysical Journal Letters, 847 (2). Art. No. L18. ISSN 2041-8213. doi:10.3847/2041-8213/aa8bff.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Shporer, Avi0000-0002-1836-3120
Zhou, George0000-0002-4891-3517
Vanderburg, Andrew0000-0001-7246-5438
Fulton, Benjamin J.0000-0003-3504-5316
Isaacson, Howard0000-0002-0531-1073
Bieryla, Allyson0000-0001-6637-5401
Torres, Guillermo0000-0002-5286-0251
Morton, Timothy D.0000-0002-8537-5711
Calkins, Michael L.0000-0002-2830-5661
Esquerdo, Gilbert A.0000-0002-9789-5474
Howard, Andrew W.0000-0001-8638-0320
Latham, David W.0000-0001-9911-7388
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) - .
Group:Astronomy Department
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144152
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: eclipsing; stars: individual (K2-51, EPIC 202900527, K2-67, EPIC 206155547, K2-76, EPIC 206432863)
Issue or Number:2
Record Number:CaltechAUTHORS:20170927-095217774
Persistent URL:
Official Citation:Avi Shporer et al 2017 ApJL 847 L18
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81874
Deposited By: Tony Diaz
Deposited On:27 Sep 2017 17:16
Last Modified:15 Nov 2021 19:46

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