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 \pm 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 \pm 0.16 M _ { J } , a radius of 1.14 \pm 0.03 R _ { J } and an equilibrium temperature of 1567 \pm 30 K. The host star has a mass of 0.88 \pm 0.04 M _ { \astrosun } , radius of 0.89 \pm 0.02 R _ { \astrosun } 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 Å ) .
The two light curves contain anomalies compatible with starspots on the photosphere of the host star along the same transit chord .