We report the discovery of WASP-4b , a large transiting gas-giant planet with an orbital period of 1.34 days .
This is the first planet to be discovered by the SuperWASP-South observatory and CORALIE collaboration and the first planet orbiting a star brighter than 16 ^ { th } magnitude to be discovered in the Southern hemisphere .
A simultaneous fit to high-quality lightcurves and precision radial-velocity measurements leads to a planetary mass of 1.22 ^ { +0.09 } _ { -0.08 } M _ { Jup } and a planetary radius of 1.42 ^ { +0.07 } _ { -0.04 } R _ { Jup } .
The host star is USNO-B1.0 0479-0948995 , a G7V star of visual magnitude 12.5 .
As a result of the short orbital period , the predicted surface temperature of the planet is 1761 K , making it an ideal candidate for detections of the secondary eclipse at infrared wavelengths .