  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 semi-major axis of a =
0.0377 +/- 0.0005 AU. Ephemeris for the system is P = 2.2047299 +/- 0.0000040
days, mid-transit 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 Mp = 1.78+/-^{0.08}_{0.05} MJup and radius of Rp =
1.36+/-^{0.20}_{0.09} RJup. The parent star is a slightly evolved F6 star with
M = 1.47+/-^{0.08}_{-0.05} Msun,R = 1.84+/-^{0.23}_{0.11} Rsun, Teff = 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}) 10^9 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. (2007). If as predicted by Fortney et al. (2007) the planet
re-radiates 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.

Astrophysics