  We report a transiting extrasolar giant planet around the star OGLE-TR-10
(orbital period = 3.1 days), which was uncovered as a candidate by the OGLE
team in their photometric survey towards the Galactic center (Udalski et al,
2002a). We observed OGLE-TR-10 spectroscopically over a period of two years
(2002-2004) using the HIRES instrument with an iodine cell on the Keck I
telescope, and measured small radial velocity variations that are consistent
with the presence of a planetary companion. This confirms the earlier
identification of OGLE-TR-10b by our team and also recently by Bouchy et al
(2004a) as a possible planet. Additionally, in this paper we are able to rule
out a blend scenario as an alternative explanation. From an analysis combining
all available radial velocity measurements with the OGLE light curve we find
that OGLE-TR-10b has a mass of 0.57+/-0.12 MJup and a radius of 1.24+/-0.09
RJup. These parameters bear close resemblance to those of the first known
transiting extrasolar planet, HD 209458b.
