WASP-4b Arrived Early for the TESS Mission
Dai, F.; Winn, J. N.; Jenkins, J. M.; Ricker, G. R.; Seager, S.; Twicken, J. D.; Bouma, L. G.; Latham, D. W.; Vanderspek, R.; Kane, S. R.; Stassun, K. G.; Glidden, Ana; Désert, J. -M.; Baxter, C.; Bhatti, W.; Daylan, T.; Hill, M. L.; Villasenor, J.; Berta-Thompson, Z.; Colón, K.; Fausnaugh, M.; Guerrero, N.; Rodriguez, J. E.; Wohler, B.
United States, Netherlands
Abstract
The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6 ± 11.7 s earlier than had been predicted, based on data stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with a constant period, ruling out an 81.6 s offset at the 6.4σ level. The 1.3 day orbital period of WASP-4b appears to be decreasing at a rate of \dot{P}=-12.6+/- 1.2 ms per year. The apparent period change might be caused by tidal orbital decay or apsidal precession, although both interpretations have shortcomings. The gravitational influence of a third body is another possibility, though at present there is minimal evidence for such a body. Further observations are needed to confirm and understand the timing variation.