The Orbit of WASP-12b Is Decaying

Creators: Yee, Samuel W.; Winn, Joshua N.; Knutson, Heather A.; Patra, Kishore C.; Vissapragada, Shreyas; Zhang, Michael M.; Holman, Matthew J.; Shporer, Avi; Wright, Jason T.

Abstract

WASP-12b is a transiting hot Jupiter on a 1.09 day orbit around a late-F star. Since the planet's discovery in 2008, the time interval between transits has been decreasing by 29 ± 2 ms yr⁻¹. This is a possible sign of orbital decay, although the previously available data left open the possibility that the planet's orbit is slightly eccentric and is undergoing apsidal precession. Here, we present new transit and occultation observations that provide more decisive evidence for orbital decay, which is favored over apsidal precession by a ΔBIC of 22.3 or Bayes factor of 70,000. We also present new radial-velocity data that rule out the Rømer effect as the cause of the period change. This makes WASP-12 the first planetary system for which we can be confident that the orbit is decaying. The decay timescale for the orbit is P/P˙=3.25±0.23. Interpreting the decay as the result of tidal dissipation, the modified stellar tidal quality factor is Q′⋆=1.8×10⁵.

Additional Information

© 2019 The American Astronomical Society. Received 2019 September 30; revised 2019 November 14; accepted 2019 November 19; published 2019 December 27. We thank Jeremy Goodman and Luke Bouma for helpful discussions while preparing this manuscript. The authors gratefully acknowledge Leo Liu for helping obtain the WIRC observations. Work by S.W.Y and J.N.W was partly supported by the Heising-Simons Foundation. J.T.W. acknowledges support from NASA Origins of Solar Systems grant NNX14AD22G. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Software: astropy (Astropy Collaboration et al. 2013, 2018); emcee (Foreman-Mackey et al. 2013; Goodman & Weare 2010); radvel (Fulton et al. 2018); numpy (Van Der Walt et al. 2011); scipy (Jones et al. 2001).

Attached Files

Published - Yee_2020_ApJL_888_L5.pdf

Accepted Version - 1911.09131.pdf

Files

1911.09131.pdf

Files (3.2 MB)

Name	Size	Download all
1911.09131.pdf md5:2ffd31865e254fb3a7058bd1ab18e825	861.4 kB	Preview Download
Yee_2020_ApJL_888_L5.pdf md5:945379077c4d52eb4bda7b95f86e7290	2.3 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes