The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet β Pictoris b from Combined Direct Imaging and Astrometry

Authors

• Eric L. Nielsen, Stanford University
• Robert J. De Rosa, Stanford University
• Jason J. Wang, California Institute of Technology
• Johannes Sahlmann, Space Telescope Science Institute
• Paul Kalas, University of California, Berkeley
• Gaspard Duchêne, University of California, Berkeley
• Julien Rameau, Université Grenoble Alpes
• Mark S. Marley, NASA Ames Research Center
• Didier Saumon, Los Alamos National Laboratory
• Bruce MacIntosh, Stanford University
• Maxwell A. Millar-Blanchaer, Jet Propulsion Laboratory
• Meiji M. Nguyen, University of California, Berkeley
• S. Mark Ammons, Lawrence Livermore National Laboratory
• Vanessa P. Bailey, Jet Propulsion Laboratory
• Travis Barman, The University of Arizona
• Joanna Bulger, University Hawaii Institute for Astronomy
• Jeffrey Chilcote, University of Notre Dame
• Tara Cotten, University of Georgia
• Rene Doyon, Institut de Recherche sur les Exoplanètes
• Thomas M. Esposito, University of California, Berkeley
• Michael P. Fitzgerald, University of California, Los Angeles
• Katherine B. Follette, Amherst College
• Benjamin L. Gerard, University of Victoria
• Stephen J. Goodsell, Gemini Observatory
• James R. Graham, University of California, Berkeley
• Alexandra Z. Greenbaum, University of Michigan, Ann Arbor
• Pascale Hibon, Gemini ObservatorySouthern Operations Center
• Li Wei Hung, US National Park Service
• Patrick Ingraham, Large Synoptic Survey Telescope
• Quinn Konopacky, Center for Astrophysics & Space Sciences
• James E. Larkin, University of California, Los Angeles
• Jérôme Maire, Center for Astrophysics & Space Sciences
• Kimberly Ward-Duong, Amherst CollegeFollow
• et al, Various Institutions

Document Type

Article

Publication Date

2-1-2020

Publication Title

Astronomical Journal

Abstract

We present new observations of the planet β Pictoris b from 2018 with the Gemini Planet Imager (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 disfavors circular orbits. We consider orbit fits to several different imaging data sets, 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, β 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 (8.0 ± 2.6 M Jup) for the imaged planet β Pic b, 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.

Volume

159

Issue

2

DOI

https://doi.org/10.3847/1538-3881/ab5b92

ISSN

00046256

Rights

© 2020. The American Astronomical Society

Version

Version of Record

Recommended Citation

Nielsen, Eric L.; De Rosa, Robert J.; Wang, Jason J.; Sahlmann, Johannes; Kalas, Paul; Duchêne, Gaspard; Rameau, Julien; Marley, Mark S.; Saumon, Didier; MacIntosh, Bruce; Millar-Blanchaer, Maxwell A.; Nguyen, Meiji M.; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis; Bulger, Joanna; Chilcote, Jeffrey; Cotten, Tara; Doyon, Rene; Esposito, Thomas M.; Fitzgerald, Michael P.; Follette, Katherine B.; Gerard, Benjamin L.; Goodsell, Stephen J.; Graham, James R.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hung, Li Wei; Ingraham, Patrick; Konopacky, Quinn; Larkin, James E.; Maire, Jérôme; Ward-Duong, Kimberly; and al, et, "The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet β Pictoris b from Combined Direct Imaging and Astrometry" (2020). Astronomy: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/ast_facpubs/111