Three sub-Jupiter-mass planets: WASP-69b & 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 WASP-84b, each of which orbits a bright star ($V\sim10)$. WASP-69b is a bloated Saturn-mass planet (0.26 $M_{\rm Jup}$, 1.06 $R_{\rm Jup}$) in a 3.868-d period around an active, $\sim$1-Gyr, mid-K dwarf. ROSAT detected X-rays $60 \pm 27"$ from WASP-69. If the star is the source then the planet could be undergoing mass-loss at a rate of $\sim$10$^{12}$ g s$^{-1}$. This is 1 to 2 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 $M_{\rm Jup}$, 1.16 $R_{\rm Jup}$) in a 3.713-d orbit around the primary of a spatially-resolved, 9-to-10-Gyr, G4+K3 binary, with a separation of 3.3$'$ ($\geq$800 AU). WASP-84b is a sub-Jupiter-mass planet (0.69 $M_{\rm Jup}$, 0.94 $R_{\rm Jup)}$ in an 8.523-d orbit around an active, $\sim$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 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.