Mass Constraints of the WASP-47 Planetary System from Radial Velocities

February 2017 • 2017AJ....153...70S

Authors • Sinukoff, Evan • Howard, Andrew W. • Petigura, Erik A. • Fulton, Benjamin J. • Isaacson, Howard • Weiss, Lauren M. • Brewer, John M. • Hansen, Brad M. S. • Hirsch, Lea • Christiansen, Jessie L. • Crepp, Justin R. • Crossfield, Ian J. M. • Schlieder, Joshua E. • Ciardi, David R. • Beichman, Charles A. • Knutson, Heather A. • Benneke, Bjoern • Dressing, Courtney D. • Livingston, John H. • Deck, Katherine M. • Lépine, Sébastien • Rogers, Leslie A.

Abstract • 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 MJup) and constrain its eccentricity to < 0.021 at 3σ 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 that 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 MJup), 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 two to four times more precise than previous mass measurements.


IPAC Authors


Jessie Christiansen

Associate Scientist


David Ciardi

Senior Scientist


Benjamin Fulton

Assistant Scientist