GSC 02620-00648

GSC 02620-00648 is a binary star system located approximately 1,660 light-years away in the constellation Hercules. The brighter of the pair is a magnitude 12 star about 1.45 times as massive as the Sun. It hosts one known exoplanet, TrES-4b.

Nomenclature

The designation GSC 02620-00648 comes from the Guide Star Catalog.
The star is sometimes called TrES-4, in reference to its planet discovered by the Trans-Atlantic Exoplanet Survey. The discovery paper and the SIMBAD database use this designation for the planet itself, but other sources call the star TrES-4 and the planet TrES-4b, following the standard exoplanet naming convention.

In 2008 a study was undertaken of 14 stars with exoplanets that were originally discovered using the transit method through relatively small telescopes. These systems were re-examined with the 2.2M reflector telescope at the Calar Alto Observatory in Spain. This star system, along with two others, was determined to be a previously unknown binary star system. The previously unknown secondary star is a dim magnitude 14 K or M-type star separated by about 755 AU from the primary, appearing offset from the primary by about one arc second in the images. This discovery resulted in a recalculation of parameters for both the planet and the primary star.

In 2006, the Trans-Atlantic Exoplanet Survey discovered the exoplanet TrES-4b using the transit method. This planet orbits the primary star. The planet is a low-density hot Jupiter, with a larger size than Jupiter but a smaller mass, and an orbital period of only four days.