We report the discovery of HAT-P-27b , an exoplanet transiting the moderately bright G8 dwarf star GSC 0333-00351 ( V = 12.214 ) .
The orbital period is 3.039586 \pm 0.000012 d , the reference epoch of transit is 2455186.01879 \pm 0.00054 ( BJD ) , and the transit duration is 0.0705 \pm 0.0019 d. The host star with its effective temperature 5300 \pm 90 K is somewhat cooler than the Sun , and is more metal-rich with a metallicity of +0.29 \pm 0.10 .
Its mass is 0.94 \pm 0.04 M _ { \sun } and radius is 0.90 _ { -0.04 } ^ { +0.05 } R _ { \sun } .
For the planetary companion we determine a mass of 0.660 \pm 0.033 M _ { J } and radius of 1.038 _ { -0.058 } ^ { +0.077 } R _ { J } .
For the 30 known transiting exoplanets between 0.3 M _ { J } and 0.8 M _ { J } , a negative correlation between host star metallicity and planetary radius , and an additional dependence of planetary radius on equilibrium temperature are confirmed at a high level of statistical significance .