Three newly discovered sub-Jupiter-mass planets: WASP-69b and WASP-84b transit active K dwarfs and WASP-70Ab transits the evolved primary of a G4+K3 binary

We report the discovery of the transiting exoplanets WASP-69b, WASP-70Ab and WASP84b, each of which orbits a bright star (V similar to 10). WASP-69b is a bloated Saturn-mass planet (0.26 M-Jup, 1.06 R-Jup) in a 3.868-d period around an active, similar to 1-Gyr, mid-K dwarf. ROSAT detected X-rays 60 +/- 27 arcsec from WASP-69. If the star is the source then the planet could be undergoing mass-loss at a rate of similar to 10(12) g s(-1). This is one to two orders of magnitude higher than the evaporation rate estimated for HD 209458b and HD 189733b, both of which have exhibited anomalously large Lyman alpha absorption during transit. WASP-70Ab is a sub-Jupiter-mass planet (0.59 M-Jup, 1.16 R-Jup) in a 3.713-d orbit around the primary of a spatially resolved, 9-10-Gyr, G4+K3 binary, with a separation of 3.3 arcsec (>= 800 au). WASP-84b is a sub-Jupiter-mass planet (0.69 M-Jup, 0.94 R-Jup) in an 8.523-d orbit around an active, similar to 1-Gyr, early-K dwarf. Of the transiting planets discovered from the ground to date, WASP-84b has the third-longest period. For the active stars WASP-69 and WASP-84, we pre-whitened the radial velocities using a low-order harmonic series. We found that this reduced the residual scatter more than did the oft-used method of pre-whitening with a fit between residual radial velocity and bisector span. The system parameters were essentially unaffected by pre-whitening.