The 0.5MJ transiting exoplanet WASP-13b

We report the discovery of WASP-13b, a low-mass M_p = 0.46 ^{+ 0.06} _{- 0.05} M_J transiting exoplanet with an orbital period of 4.35298 ± 0.00004 days. The transit has a depth of 9 mmag, and although our follow-up photometry does not allow us to constrain the impact parameter well (0 < b < 0.46), with radius in the range R_p 1.06-1.21 R_J the location of WASP-13b in the mass-radius plane is nevertheless consistent with H/He-dominated, irradiated, low core mass and core-free theoretical models. The G1V host star is similar to the Sun in mass (M_* = 1.03^+0.11_ {- 0.09} M_⊙) and metallicity ([M/H] = 0.0±0.2), but is possibly older (8.5^{+ 5.5} _-4.9 Gyr).

The SuperWASP and JGT differential photometry, and SOPHIE radial velocities of WASP-13 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/391