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

Shporer, Avi and Zhou, George ORCID: 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. The Astrophysical Journal Letters, 847 (2):L18. pp. 1-7. ISSN 2041-8205

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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 0.1459-0.0032+0.0029 M⊙ (EPIC 202900527 B), (EPIC 206155547 B), 0.1612-0.00670.0072 M⊙ 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 Rj, 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.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 27 Jan 2022 22:43
Last Modified: 02 Feb 2022 05:01
Uncontrolled Keywords: binaries: eclipsing; stars: individual: K2-51; EPIC 202900527; K2-67; EPIC 206155547; K2-76; EPIC 206432863; Astrophysics - Solar and Stellar; Astrophysics
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
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