2017/03/31 by Kishore C. Patra, Joshua N. Winn, Matthew J. Holman +3 · 1 citation
Physics and Astronomy · #astro-ph.EP
paper · pdf · doi:10.3847/1538-3881/aa6d75
10 pages [AAS journals, in press, note added in proof]
arxiv created 2017/05/24 · arxiv updated 2017/06/28
We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: P=-29 ± 3 ms yr-1 and P/P= 3.2 Myr. However, it is difficult to tell whether we have observed orbital decay, or a portion of a 14-year apsidal precession cycle. If interpreted as decay, the star's tidal quality parameter Q_⋆ is about 2× 105. If interpreted as precession, the planet's Love number is 0.44± 0.10. Orbital decay appears to be the more parsimonious model: it is favored by Δχ2=5.5 despite having two fewer free parameters than the precession model. The decay model implies that WASP-12 was discovered within the final ∼0.2% of its existence, which is an unlikely coincidence but harmonizes with independent evidence that the planet is nearing disruption. Precession does not invoke any temporal coincidence, but does require some mechanism to maintain an eccentricity of ≈0.002 in the face of rapid tidal circularization. To distinguish unequivocally between decay and precession will probably require a few more years of monitoring. Particularly helpful will be occultation timing in 2019 and thereafter.