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Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16 A

Winn, Joshua N. and Johnson, John Asher and Howard, Andrew W. (2011) Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16 A. Astrophysical Journal Letters, 741 (1). Art. No. L1. ISSN 2041-8205.

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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. 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%.

Item Type:Article
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URLURL TypeDescription
Winn, Joshua N.0000-0002-4265-047X
Johnson, John Asher0000-0001-9808-7172
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2011 The American Astronomical Society. Received 2011 August 3; accepted 2011 September 21; published 2011 October 5. We thank Brice-Olivier Demory, Nevin Weinberg, and Jamie Lloyd for helpful discussions. Work by J.N.W. and S.A. was supported by NASA Origins award NNX09AB33G. G.T. acknowledges partial support from the NSF through grant AST-1007992. Funding for the Kepler Discovery mission is provided by NASA’s Science Mission Directorate. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W. M. Keck Foundation. We extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Facilities: Keck:I(HIRES), Kepler
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: general; planets and satellites: formation; stars: individual (Kepler-16 A, KIC 12644769); stars: low-mass; stars: rotation
Issue or Number:1
Record Number:CaltechAUTHORS:20111207-111645632
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Official Citation:Spin-Orbit Alignment for the Circumbinary Planet Host Kepler-16 A Joshua N. Winn et al. 2011 ApJ 741 L1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28346
Deposited By: Ruth Sustaita
Deposited On:07 Dec 2011 21:26
Last Modified:09 Mar 2020 13:18

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