In the ongoing HATNet survey we have detected a giant planet , with radius 1.33 \pm 0.06 R _ { Jup } and mass 1.06 \pm 0.12 M _ { Jup } , transiting the bright ( V = 10.5 ) star GSC 03239-00992 .
The planet is in a circular orbit with period 3.852985 \pm 0.000005 days and mid-transit epoch 2 , 454 , 035.67575 \pm 0.00028 ( HJD ) .
The parent star is a late F star with mass 1.29 \pm 0.06 M _ { \sun } , radius 1.46 \pm 0.06 R _ { \sun } , T _ { eff } \sim 6570 \pm 80 \mathrm { K } , \mathrm { [ Fe / H ] } = -0.13 \pm 0.08 and age \sim 2.3 ^ { +0.5 } _ { -0.7 } \mathrm { Gy } .
With this radius and mass , HAT-P-6b has somewhat larger radius than theoretically expected .
We describe the observations and their analysis to determine physical properties of the HAT-P-6 system , and briefly discuss some implications of this finding .