HATS-2b: A transiting extrasolar planet orbiting a K-type star showing starspot activity
Abstract
We report the discovery of HATS-2b, the second transiting extrasolar planet detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a V=13.6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0.0230 0.0003 AU and with a period of 1.3541 days. The planetary parameters have been robustly determined using a simultaneous fit of the HATSouth, MPG/ESO~2.2\,m/GROND, Faulkes Telescope South/Spectral transit photometry and MPG/ESO~2.2\,m/FEROS, Euler~1.2\,m/CORALIE, AAT~3.9\,m/CYCLOPS radial-velocity measurements. HATS-2b has a mass of 1.37 0.16 MJ, a radius of 1.14 0.03 RJ and an equilibrium temperature of 1567 30 K. The host star has a mass of 0.88 0.04 MSun, radius of 0.89 0.02 RSun and shows starspot activity. We characterized the stellar activity by analysing two photometric follow-up transit light curves taken with the GROND instrument, both obtained simultaneously in four optical bands (covering the wavelength range of 3860-9520 ). The two light curves contain anomalies compatible with starspots on the photosphere of the parent star along the same transit chord.
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