HAT-P-30b: A Transiting Hot Jupiter on a Highly Oblique Orbit

We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V = 10.419 dwarf star GSC 0208-00722. The planet has a period P = 2.810595 ± 0.000005 days, transit epoch T_c = 2455456.46561 ± 0.00037 (BJD), and transit duration 0.0887 ± 0.0015 days. The host star has a mass of 1.24 ± 0.04 M _sun, radius of 1.21 ± 0.05 R _sun, effective temperature of 6304 ± 88 K, and metallicity [Fe/H] = +0.13 ± 0.08. The planetary companion has a mass of 0.711 ± 0.028 M _J and radius of 1.340 ± 0.065 R _J yielding a mean density of 0.37 ± 0.05 g cm^-3. We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect, we measure an angle of λ = 73fdg5 ± 9fdg0 between the sky projections of the planet's orbit normal and the star's spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with T _effsstarf >~ 6250 K.

Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NASA (N167Hr). Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.