The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet beta Pictoris b from Combined Direct Imaging and Astrometry
Creators: name: Nielsen, Eric L.
name: De Rosa, Robert J.
name: Wang, Jason J.
name: Sahlmann, Johannes
name: Kalas, Paul
name: Duchene, Gaspard
name: Rameau, Julien
name: Marley, Mark S.
name: Saumon, Didier
name: Macintosh, Bruce
name: Millar-Blanchaer, Maxwell A.
name: Nguyen, Meiji M.
name: Ammons, S. Mark
name: Bailey, Vanessa P.
name: Barman, Travis
name: Bulger, Joanna
name: Chilcote, Jeffrey
name: Cotten, Tara
name: Doyon, Rene
name: Esposito, Thomas M.
name: Fitzgerald, Michael P.
name: Follette, Katherine B.
name: Gerard, Benjamin L.
name: Goodsell, Stephen J.
name: Graham, James R.
name: Greenbaum, Alexandra Z.
name: Hibon, Pascale
name: Hung, Li-Wei
name: Ingraham, Patrick
name: Konopacky, Quinn
name: Larkin, James E.
name: Maire, Jerome
name: Marchis, Franck
name: Marois, Christian
name: Metchev, Stanimir
name: Oppenheimer, Rebecca
name: Palmer, David
name: Patience, Jennifer
name: Perrin, Marshall
name: Poyneer, Lisa
name: Pueyo, Laurent
name: Rajan, Abhijith
name: Rantakyro, Fredrik T.
name: Ruffio, Jean-Baptiste
name: Savransky, Dmitry
name: Schneider, Adam C.
name: Sivaramakrishnan, Anand
name: Song, Inseok
name: Soummer, Remi
name: Thomas, Sandrine
name: Wallace, J. Kent
name: Ward-Duong, Kimberly
name: Wiktorowicz, Sloane
name: Wolff, Schuyler
Publisher: name: arXiv
Year: 2019
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present new observations of the planet beta Pictoris b from 2018 with GPI, the first GPI observations following conjunction. Based on these new measurements, we perform a joint orbit fit to the available relative astrometry from ground-based imaging, the Hipparcos Intermediate Astrometric Data (IAD), and the Gaia DR2 position, and demonstrate how to incorporate the IAD into direct imaging orbit fits. We find a mass consistent with predictions of hot-start evolutionary models and previous works following similar methods, though with larger uncertainties: 12.8 [+5.3, -3.2] M_Jup. Our eccentricity determination of 0.12 [+0.04, -0.03] disfavors circular orbits. We consider orbit fits to several different imaging datasets, and find generally similar posteriors on the mass for each combination of imaging data. Our analysis underscores the importance of performing joint fits to the absolute and relative astrometry simultaneously, given the strong covariance between orbital elements. Time of conjunction is well constrained within 2.8 days of 2017 September 13, with the star behind the planet's Hill sphere between 2017 April 11 and 2018 February 16 (+/- 18 days). Following the recent radial velocity detection of a second planet in the system, beta Pic c, we perform additional two-planet fits combining relative astrometry, absolute astrometry, and stellar radial velocities. These joint fits find a significantly smaller mass for the imaged planet beta Pic b, of 8.0 +/- 2.6 M_Jup, in a somewhat more circular orbit. We expect future ground-based observations to further constrain the visual orbit and mass of the planet in advance of the release of Gaia DR4.
description: 29 Pages, 23 Figures. Accepted to AJ