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


Publication Date


Publication Title

Astronomical Journal


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.










© 2020. The American Astronomical Society


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