The Apparently Decaying Orbit of WASP-12b

We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: (P)over dot = -29 +/- 3 ms yr(-1) andP/(P)over dot = 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 x 10(5). 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 Delta x(2) = 5.5 despite having two fewer free parameters than the precession model. The decay model implies that WASP-12 was discovered within the final similar to 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 it does require some mechanism to maintain an eccentricity of approximate to 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.