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 ± 1.17 M⊕, and a bulk density of 7.63 ± 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 ± 12 M⊕ (1.12 ± 0.04 M_\rm{Jup}) and constrain its eccentricity to <0.021 at 3-σ confidence. For the Neptune-size planet WASP-47d (P = 9.0 days), we measure a mass of 12.75 ± 2.70 M⊕, and a bulk density of 1.36 ± 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 ± 18 M⊕ (1.29 ± 0.06 M_\rm{Jup}), an orbital period of 595.7 ± 5.0 days, and an orbital eccentricity of 0.27 ± 0.04. Our new measurements are consistent with but 2−4× more precise than previous mass measurements.
@article{arxiv.1612.04851,
title = {Mass Constraints of the WASP-47 Planetary System from Radial Velocities},
author = {Evan Sinukoff and Andrew W. Howard and Erik A. Petigura and Benjamin J. Fulton and Howard Isaacson and Lauren M. Weiss and John M. Brewer and Brad M. S. Hansen and Lea Hirsch and Jessie L. Christiansen and Justin R. Crepp and Ian J. M. Crossfield and Joshua E. Schlieder and David R. Ciardi and Charles A. Beichman and Heather A. Knutson and Bjoern Benneke and Courtney D. Dressing and John H. Livingston and Katherine M. Deck and Sebastien Lepine and Leslie A. Rogers},
journal= {arXiv preprint arXiv:1612.04851},
year = {2017}
}