Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16A
Abstract
Kepler-16 is an eccentric low-mass eclipsing binary with a circumbinary transiting planet. Here we investigate the angular momentum of the primary star, based on Kepler photometry and Keck spectroscopy. The primary star's rotation period is 35.1 +/- 1.0 days, and its projected obliquity with respect to the stellar binary orbit is 1.6 +/- 2.4 degrees. Therefore the three largest sources of angular momentum---the stellar orbit, the planetary orbit, and the primary's rotation---are all closely aligned. This finding supports a formation scenario involving accretion from a single disk. Alternatively, tides may have realigned the stars despite their relatively wide separation (0.2 AU), a hypothesis that is supported by the agreement between the measured rotation period and the "pseudosynchronous" period of tidal evolution theory. The rotation period, chromospheric activity level, and fractional light variations suggest a main-sequence age of 2-4 Gyr. Evolutionary models of low-mass stars can match the observed masses and radii of the primary and secondary stars to within about 3%.
Cite
@article{arxiv.1109.3198,
title = {Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16A},
author = {Joshua N. Winn and Simon Albrecht and John Asher Johnson and Guillermo Torres and William D. Cochran and Geoffrey W. Marcy and Andrew Howard and Howard Isaacson and Debra Fischer and Laurance Doyle and William Welsh and Joshua A. Carter and Daniel C. Fabrycky and Darin Ragozzine and Samuel N. Quinn and Avi Shporer and Steve B. Howell and David W. Latham and Jerome Orosz and Andrej Prsa and Robert W. Slawson and William J. Borucki and David Koch and Thomas Barclay and Alan P. Boss and Jorgen Christensen-Dalsgaard and Forrest R. Girouard and Jon Jenkins and Todd C. Klaus and Soren Meibom and Robert L. Morris and Dimitar Sasselov and Martin Still and Jeffrey Van Cleve},
journal= {arXiv preprint arXiv:1109.3198},
year = {2015}
}
Comments
ApJ Letters, in press [7 pages]