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 M_Jup) 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 M_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 two to four times more precise than previous mass measurements.

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IPAC Authors
(alphabetical)

Jessie Christiansen

Associate Scientist

David Ciardi

Senior Scientist

Benjamin Fulton

Assistant Scientist