We discuss the discovery and characterization of the circumbinary planet Kepler-38b. The stellar binary is single-lined, with a period of 18.8 days, and consists of a moderately evolved main-sequence star (M_A = 0.949 +/- 0.059 solar masses and R_A = 1.757 +/- 0.034 solar radii) paired with a low-mass star (M_B = 0.249 +/- 0.010 solar masses and R_B = 0.2724 +/- 0.0053 solar radii) in a mildly eccentric (e=0.103) orbit. A total of eight transits due to a circumbinary planet crossing the primary star were identified in the Kepler light curve (using Kepler Quarters 1 through 11), from which a planetary period of 105.595 +/- 0.053 days can be established. A photometric dynamical model fit to the radial velocity curve and Kepler light curve yields a planetary radius of 4.35 +/- 0.11 Earth radii, or 1.12 +/- 0.03 Neptune radii. Since the planet is not sufficiently massive to observably alter the orbit of the binary from Keplerian motion, we can only place an upper limit on the mass of the planet of 122 Earth masses (7.11 Neptune masses or 0.384 Jupiter masses) at 95% confidence. This upper limit should decrease as more Kepler data become available.
@article{arxiv.1208.3712,
title = {The Neptune-Sized Circumbinary Planet Kepler-38b},
author = {Jerome A. Orosz and William F. Welsh and Joshua A. Carter and Erik Brugamyer and Lars A. Buchhave and William D. Cochran and Michael Endl and Eric B. Ford and Phillip MacQueen and Donald R. Short and Guillermo Torres and Gur Windmiller and Eric Agol and Thomas Barclay and Douglas A. Caldwell and Bruce D. Clarke and Laurance R. Doyle and Daniel C. Fabrycky and John C. Geary and Nader Haghighipour and Matthew J. Holman and Khadeejah A. Ibrahim and Jon M. Jenkins and Karen Kinemuchi and Jie Li and Jack J. Lissauer and Andrej Prsa and Darin Ragozzine and Avi Shporer and Martin Still and Richard A. Wade},
journal= {arXiv preprint arXiv:1208.3712},
year = {2015}
}
Comments
32 pages, 9 figures, accepted to ApJ. The figures have been compressed