HAT-P-7b: An Extremely Hot Massive Planet Transiting a Bright Star in the Kepler Field^*

We report on the latest discovery of the HATNet project: a very hot giant planet orbiting a bright (V = 10.5) star with a small semimajor axis of a = 0.0377 ± 0.0005 AU. Ephemeris for the system is P = 2.2047299 ± 0.0000040 days, midtransit time E = 2,453,790.2593 ± 0.0010 (BJD). Based on the available spectroscopic data on the host star and photometry of the system, the planet has a mass of M_p = 1.78^{+ 0.08}_−0.05 M_J and radius of R_p = 1.36^{+ 0.20}_−0.09 R_J. The parent star is a slightly evolved F6 star with M_⋆ = 1.47^{+ 0.08}_−0.05 M_☉, R_⋆ = 1.84^{+ 0.23}_−0.11 R_☉, T_eff = 6350 ± 80 K, and metallicity [ Fe/H ] = + 0.26 ± 0.08. The relatively hot and large host star, combined with the close orbit of the planet, yield a very high planetary irradiance of 4.71^{+ 1.44}_−0.05 × 10⁹ erg cm⁻² s⁻¹, which places the planet near the top of the pM class of irradiated planets as defined by Fortney et al. If as predicted by Fortney et al. the planet reradiates its absorbed energy before distributing it to the night side, the day-side temperature should be about 2730^{+ 150}₋₁₀₀ K. Because the host star is quite bright, measurement of the secondary eclipse should be feasible for ground-based telescopes, providing a good opportunity to compare the predictions of current hot Jupiter atmospheric models with the observations. Moreover, the host star falls in the field of the upcoming Kepler mission; hence extensive space-borne follow-up, including not only primary transit and secondary eclipse observations but also asteroseismology, will be possible.