TrES-3b is an extrasolar planet located approximately 1300 light-years away orbiting the star GSC 03089-00929. It has an orbital period of only 31 hours and is experiencing orbital decay from tidal effects. It has almost twice the mass of Jupiter.
It is the third transiting exoplanet discovered by the Trans-Atlantic Exoplanet Survey. It was discovered in the constellation Hercules about 10 degrees west of Vega, the brightest star in the summer sky. Its mass was confirmed through radial velocity measurements of the host star, which showed the presence of a planetary mass companion with the same period as the transits. The planet’s home star is slightly smaller and cooler than the sun. The orbital period is less than a third of a day and is one of the shortest known periods.
https://arxiv.org/abs/1211.6828