We report precise radial velocity ( RV ) measurements of WASP-47 , a G star that hosts three transiting planets in close proximity ( a hot Jupiter , a super-Earth and a Neptune-sized planet ) and a non-transiting planet at 1.4 AU .
Through a joint analysis of previously published RVs and our own Keck-HIRES RVs , we significantly improve the planet mass and bulk density measurements .
For the super-Earth WASP-47e ( P = 0.79 days ) , we measure a mass of 9.11 \pm 1.17 M _ { \oplus } , and a bulk density of 7.63 \pm 1.90 g cm ^ { -3 } , consistent with a rocky composition .
For the hot Jupiter WASP-47b ( P = 4.2 days ) , we measure a mass of 356 \pm 12 M _ { \oplus } ( 1.12 \pm 0.04 M _ { \mathrm { Jup } } ) and constrain its eccentricity to < 0.021 at 3- \sigma confidence .
For the Neptune-size planet WASP-47d ( P = 9.0 days ) , we measure a mass of 12.75 \pm 2.70 M _ { \oplus } , and a bulk density of 1.36 \pm 0.42 g cm ^ { -3 } , suggesting it has a thick H/He envelope .
For the outer non-transiting planet , we measure a minimum mass of 411 \pm 18 M _ { \oplus } ( 1.29 \pm 0.06 M _ { \mathrm { Jup } } ) , an orbital period of 595.7 \pm 5.0 days , and an orbital eccentricity of 0.27 \pm 0.04 .
Our new measurements are consistent with but 2–4 \times more precise than previous mass measurements .