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

Dimitri Mawet, Lea Hirsch, Eve J. Lee, Jean Baptiste Ruffio, Michael Bottom, Benjamin J. Fulton, Olivier Absil, Charles Beichman, Brendan Bowler, Marta Bryan, Elodie Choquet, David Ciardi, Valentin Christiaens, Denis Defrère, Carlos Alberto Gomez Gonzalez, Andrew W. Howard, Elsa Huby, Howard Isaacson, Rebecca Jensen-Clem, Molly KosiarekGeoff Marcy, Tiffany Meshkat, Erik Petigura, Maddalena Reggiani, Garreth Ruane, Eugene Serabyn, Evan Sinukoff, J Wang, Lauren Weiss, Marie Ygouf

Research output: Contribution to journalArticleResearchpeer-review

14 Citations (Scopus)


We present the most sensitive direct imaging and radial velocity (RV) exploration of Eridani to date. 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. Eridani b has a mass of M Jup and is orbiting Eridani at about 3.48 ± 0.02 au with a period of 7.37 ± 0.07 yr. The eccentricity of Eridani b's orbit is 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.

Original languageEnglish
Article number33
Number of pages20
JournalThe Astronomical Journal
Issue number1
Publication statusPublished - Jan 2019
Externally publishedYes


  • planet-disk interactions
  • planets and satellites: dynamical evolution and stability
  • planets and satellites: gaseous planets
  • stars: planetary systems
  • techniques: high angular resolution
  • techniques: radial velocities

Cite this