WASP-19b: THE SHORTEST PERIOD TRANSITING EXOPLANET YET DISCOVERED

Abstract

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M <sub>pl</sub> = 1.15 ± 0.08 M<sub>J</sub>, radius R <sub>pl</sub> = 1.31 ± 0.06 R<sub>J</sub>, and orbital period P = 0.7888399 ± 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity ([M/H] = 0.1 ± 0.1 dex) G-dwarf with T <sub>eff</sub> = 5500 ± 100 K. In addition, we detect periodic, sinusoidal flux variations in the light curve which are used to derive a rotation period for the star of P <sub>rot</sub> = 10.5 ± 0.2 days. The relatively short stellar rotation period suggests that either WASP-19 is somewhat young (~ 600 Myr old) or tidal interactions between the two bodies have caused the planet to spiral inward over its lifetime resulting in the spin-up of the star. Due to the detection of the rotation period, this system has the potential to place strong constraints on the stellar tidal quality factor, Q'<sub>s</sub>, if a more precise age is determined.