Using small automated telescopes in Arizona and Hawaii, the HATNet project has detected an object transiting one member of the double star system ADS 16402. This system is a pair of GO main-sequence stars with age about 3 Gyr at a distance of ∼ 139 pc and projected separation of ∼ 1550 AU. The transit signal has a period of 4.46529 days and depth of 0.015 mag. From follow-up photometry and spectroscopy, we find that the object is a "hot Jupiter" planet with mass about 0.53MJ and radius ∼1.36RJ traveling in an orbit with semimajor axis 0.055 AU and inclination about 85.9°, thus transiting the star at impact parameter 0.74 of the stellar radius. Based on a data set spanning 3 yr, ephemerides for the transit center are TC = 2453984.397 + Ntr × 4.46529. The planet, designated HAT-P-1b, appears to be at least as large in radius, and smaller in mean density, than any previously known planet.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Binaries: general
- Planetary systems
- Stars: individual (ADS 16402AB)