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Published January 2019 | Accepted Version + Published
Journal Article Open

Deep Exploration of ϵ Eridani with Keck Ms-band Vortex Coronagraphy and Radial Velocities: Mass and Orbital Parameters of the Giant Exoplanet


We present the most sensitive direct imaging and radial velocity (RV) exploration of epsilon Eridani to date. epsilon Eridani is an adolescent planetary system, reminiscent of the early solar system. It is surrounded by a prominent and complex debris disk that is likely stirred by one or several gas giant exoplanets. The discovery of the RV signature of a giant exoplanet was announced 15 yr ago, but has met with scrutiny due to possible confusion with stellar noise. We confirm the planet with a new compilation and analysis of precise RV data spanning 30 yr, and combine it with upper limits from our direct imaging search, the most sensitive ever performed. The deep images were taken in the Ms band (4.7 μm) with the vortex coronagraph recently installed in W.M. Keck Observatory's infrared camera NIRC2, which opens a sensitive window for planet searches around nearby adolescent systems. The RV data and direct imaging upper limit maps were combined in an innovative joint Bayesian analysis, providing new constraints on the mass and orbital parameters of the elusive planet. epsilon Eridani b has a mass of 0.78_(-0.12)^(+0.38} M_(Jup) and is orbiting epsilon Eridani at about 3.48 ± 0.02 au with a period of 7.37 ± 0.07 yr. The eccentricity of epsilon Eridani b's orbit is 0.07_(-0.05)^(+0.06), an order of magnitude smaller than early estimates and consistent with a circular orbit. We discuss our findings from the standpoint of planet–disk interactions and prospects for future detection and characterization with the James Webb Space Telescope.

Additional Information

© 2019. The American Astronomical Society. Received 2018 May 1; revised 2018 October 16; accepted 2018 October 29; published 2019 January 3. The authors would like to acknowledge the contributions and useful comments from Prof. Debra Fischer and Prof. James Graham. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work was partially performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. (C) 2017. All rights reserved. E.C. acknowledges support from NASA through Hubble Fellowship grant HF2-51355 awarded by STScI, which is operated by AURA, Inc. for NASA under contract NAS5-26555. We also acknowledge support from NASA/NExSS through grant no. NNX15AD95G. Software: RadVel (Fulton et al. 2018), emcee (Foreman-Mackey et al. 2013), VIP (Gomez Gonzalez et al. 2017), PyKLIP (Wang et al. 2015).

Attached Files

Published - Mawet_2019_AJ_157_33.pdf

Accepted Version - 1810.03794.pdf


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August 22, 2023
October 19, 2023