The sub-Jupiter mass transiting exoplanet WASP-11b

We report the discovery of a sub-Jupiter mass exoplanet transiting a magnitude {V} = 11.6 host star 1SWASP J030928.54+304024.7. A simultaneous fit to the transit photometry and radial-velocity measurements yield a planet mass M_p = 0.53 ± 0.07 {M_J}, radius R_p = 0.91^+0.06_-0.03 {R_J} and an orbital period of 3.722465^+0.000006_-0.000008 days. The host star is an early to mid-K dwarf, with a spectral analysis yielding an effective temperature of 4800 ± 100 K and log g = 4.45 ± 0.2. It is amongst the smallest, least massive and lowest luminosity stars known to harbour a transiting exoplanet. WASP-11b is the third least strongly irradiated transiting exoplanet discovered to date, experiencing an incident flux F_p = 1.9×10⁸ erg s^-1 cm^-2 and having an equilibrium temperature T_eql = 960 ± 70 K.

Photometric measurements and Table 2 are 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/502/395