EPIC 201702477b : a transiting brown dwarf from K2 in a 41 day orbit
D. Bayliss, S. Hojjatpanah, A. Santerne, D. Dragomir, G. Zhou, A. Shporer, J.-M. Almenara, D. J. Armstrong, D. Barrado, S. C. C. Barros, J. Bento, I. Boisse, F. Bouchy, D. J. A. Brown, T. M. Brown, A. C. Cameron, W. D. Cochran, O. Demangeon, M. Deleuil, B. J. Fulton, K. Horne, J. Lillo-Box, C. Lovis, , D. Mawet, H. Ngo, H. P. Osborn, E. Palle, E. Petigura, D. Pollacco, N. C. Santos, R. Sefako, R. J. Siverd, S. G. Sousa, M. Tsantaki, K. D. Colón, R. F. Dı́az, G. Hébrard
We report the discovery of EPIC 201702477b, a transiting brown dwarf in a long period (40.73691 ± 0.00037 day) and eccentric (e = 0.2281 ± 0.0026) orbit. This system was initially reported as a planetary candidate based on two transit events seen in K2 Campaign 1 photometry and later validated as an exoplanet candidate. We confirm the transit and refine the ephemeris with two subsequent ground-based detections of the transit using the Las Cumbres Observatory Global Telescope 1 m telescope network. We rule out any transit timing variations above the level of ∼30 s. Using high precision radial velocity measurements from HARPS and SOPHIE we identify the transiting companion as a brown dwarf with a mass, radius, and bulk density of 66.9 ± 1.7 MJ, 0.757 ± 0.065 RJ, and 191 ± 51 g cm-3 respectively. EPIC 201702477b is the smallest radius brown dwarf yet discovered, with a mass just below the H-burning limit. It has the highest density of any planet, substellar mass object, or main-sequence star discovered so far. We find evidence in the set of known transiting brown dwarfs for two populations of objects - high mass brown dwarfs and low mass brown dwarfs. The higher-mass population have radii in very close agreement to theoretical models, and show a lower-mass limit around 60 MJ. This may be the signature of mass-dependent ejection of systems during the formation process.
The Astronomical Journal
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