Robert J. De Rosa, Stanford University
Eric L. Nielsen, Stanford University
Jason J. Wang, California Institute of Technology
S. Mark Ammons, Lawrence Livermore National Laboratory
Gaspard Duchene, University of California, Berkeley
Bruce MacIntosh, Stanford University
Julien Rameau, Université Grenoble Alpes
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
Justin Hom, School of Earth and Space Exploration
Li Wei Hung, US National Park Service
Patrick Ingraham, Large Synoptic Survey Telescope
Paul Kalas, University of California, Berkeley
Quinn Konopacky, Center for Astrophysics & Space Sciences
James E. Larkin, University of California, Los Angeles
Jérôme Maire, Center for Astrophysics & Space Sciences
Franck Marchis, SETI Institute
Mark S. Marley, NASA Ames Research Center
Christian Marois, University of Victoria
Stanimir Metchev, Western University
Kimberly Ward-Duong, Amherst CollegeFollow
et al, Various Institutions

Document Type


Publication Date


Publication Title

Astronomical Journal


We present a revision to the visual orbit of the young, directly imaged exoplanet 51 Eridani b using four years of observations with the Gemini Planet Imager. The relative astrometry is consistent with an eccentric (e= 0.53-0.13+0.09) orbit at an intermediate inclination (i= 13611+10°), although circular orbits cannot be excluded due to the complex shape of the multidimensional posterior distribution. We find a semimajor axis of 11.1-1.3+4.2 au and a period of 28.1-4.9+17.2 yr, assuming a mass of 1.75 M· for the host star. We find consistent values with a recent analysis of VLT/SPHERE data covering a similar baseline. We investigate the potential of using the absolute astrometry of the host star to obtain a dynamical mass constraint for the planet. The astrometric acceleration of 51 Eri derived from a comparison of the Hipparcos and Gaia catalogs was found to be inconsistent at the 2ω-3ω level with the predicted reflex motion induced by the orbiting planet. Potential sources of this inconsistency include a combination of random and systematic errors between the two astrometric catalogs and the signature of an additional companion within the system interior to current detection limits. We also explored the potential of using Gaia astrometry alone for a dynamical mass measurement of the planet by simulating Gaia measurements of the motion of the photocenter of the system over the course of the extended 8 yr mission. We find that such a measurement is only possible (>98% probability) given the most optimistic predictions for the Gaia scan astrometric uncertainties for bright stars and a high mass for the planet (≳3.6 MJup).










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