TY - JOUR
T1 - Precise masses in the WASP-47 system
AU - Vanderburg, Andrew
AU - Becker, Juliette C.
AU - Buchhave, Lars A.
AU - Mortier, Annelies
AU - Lopez, Eric
AU - Malavolta, Luca
AU - Haywood, Raphaëlle D.
AU - Latham, David W.
AU - Charbonneau, David
AU - López-Morales, Mercedes
AU - Adams, Fred C.
AU - Bonomo, Aldo Stefano
AU - Bouchy, François
AU - Collier Cameron, Andrew
AU - Cosentino, Rosario
AU - Di Fabrizio, Luca
AU - Dumusque, Xavier
AU - Fiorenzano, Aldo
AU - Harutyunyan, Avet
AU - Johnson, John Asher
AU - Lorenzi, Vania
AU - Lovis, Christophe
AU - Mayor, Michel
AU - Micela, Giusi
AU - Molinari, Emilio
AU - Pedani, Marco
AU - Pepe, Francesco
AU - Piotto, Giampaolo
AU - Phillips, David
AU - Rice, Ken
AU - Sasselov, Dimitar
AU - Ségransan, Damien
AU - Sozzetti, Alessandro
AU - Udry, Stéphane
AU - Watson, Chris
N1 - Funding: European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n.313014 (ETAEARTH). Parts of this work have been supported by NASA under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. This publication was made possible through the support of a grant from the John Templeton Foundation.
PY - 2017/11/17
Y1 - 2017/11/17
N2 - We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈19 hr orbit, and a Neptune in a ≈ 9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transitphotometry, our mass measurements place strong constraints on the compositions of the two small planets. We find unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 M⊕) and radius (1.810 ± 0.027 R⊕) inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.
AB - We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈19 hr orbit, and a Neptune in a ≈ 9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transitphotometry, our mass measurements place strong constraints on the compositions of the two small planets. We find unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 M⊕) and radius (1.810 ± 0.027 R⊕) inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.
KW - Planets and satellites: composition
KW - Planets and satellites: detection
KW - Planets and satellites: dynamical evolution and stability
KW - Planets and satellites: fundamental parameters
KW - Planetes and satellites: gaseous planets
KW - Planets and satellites: interiors
U2 - 10.3847/1538-3881/aa918b
DO - 10.3847/1538-3881/aa918b
M3 - Article
SN - 0004-6256
VL - 154
JO - Astronomical Journal
JF - Astronomical Journal
IS - 6
M1 - 237
ER -