An Updated Model for ϵ Eridani b and Prospects for Imaging with the Roman Coronagraph

Abstract ϵ Eridani b, the nearest known Jupiter analog, has its orbit and mass constrained from radial velocity (RV) and absolute astrometry, and its atmosphere from JWST/NIRCam imaging upper limits in A. Sanghi et al. Here we follow up that work with a self-consistent model of ϵ Eridani b that treats all available data within a single Bayesian framework. We extend the RV data with new measurements, update the treatment of the astrometry data with a new model, and include the NIRCam observations with a grid of evolutionary and atmospheric models. We find a mass of 0.91 ± 0.04 M Jup and an orbit consistent with previous work. The imaging data helps constrain planet effective temperature, atmospheric metallicity, and surface gravity. The constraints are dependent on model assumptions: for an atmosphere in chemical equilibrium, an otherwise low statistically significant feature in one of the epochs is recovered as the planet at high confidence. When assuming chemical disequilibrium, the posteriors exhibit a bimodal distribution, with one mode consistent with zero flux and the other coinciding with the flux of the tentative feature. Consistent with previous work, the clear atmosphere models are found to be viable at very enhanced metallicity, whereas the cloudy models yield more moderate values. Applying these models to the Roman Coronagraph, we find that the predicted reflected-light fluxes place every cloudy atmosphere our fit allows within the instrument’s expected sensitivity. A nondetection would be very constraining: a final contrast sensitivity of 2 × 10 −9 would rule out all cloudy atmospheres under our model assumptions.

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Publication Details

Journal
The Astronomical Journal
Published
2026-10-30
DOI
https://doi.org/10.3847/1538-3881/aeb098
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
0.00

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article

An Updated Model for ϵ Eridani b and Prospects for Imaging with the Roman Coronagraph

Tiffany Meshkat, James J. Mang, William R. Thompson, Aniket Sanghi et al.
4 links
The Astronomical Journal
Stellar, planetary, and galactic studies
article

An Updated Model for ϵ Eridani b and Prospects for Imaging with the Roman Coronagraph

Tiffany Meshkat, James J. Mang, William R. Thompson, Aniket Sanghi, Charles Beichman, Jorge D. Llop-Sayson, Clarissa R. Do Ó, Andras Gáspár, G. Bryden, Isabela G. Huckabee, Schuyler Grace Wolff, Jean-Baptiste Ruffio, Dimitri P. Mawet, Caroline V. Morley, Jarron Leisenring, Marie Ygouf, Laurent A. Pueyo, Andre Fogal
article en

Abstract

Abstract ϵ Eridani b, the nearest known Jupiter analog, has its orbit and mass constrained from radial velocity (RV) and absolute astrometry, and its atmosphere from JWST/NIRCam imaging upper limits in A. Sanghi et al. Here we follow up that work with a self-consistent model of ϵ Eridani b that treats all available data within a single Bayesian framework. We extend the RV data with new measurements, update the treatment of the astrometry data with a new model, and include the NIRCam observations with a grid of evolutionary and atmospheric models. We find a mass of 0.91 ± 0.04 M Jup and an orbit consistent with previous work. The imaging data helps constrain planet effective temperature, atmospheric metallicity, and surface gravity. The constraints are dependent on model assumptions: for an atmosphere in chemical equilibrium, an otherwise low statistically significant feature in one of the epochs is recovered as the planet at high confidence. When assuming chemical disequilibrium, the posteriors exhibit a bimodal distribution, with one mode consistent with zero flux and the other coinciding with the flux of the tentative feature. Consistent with previous work, the clear atmosphere models are found to be viable at very enhanced metallicity, whereas the cloudy models yield more moderate values. Applying these models to the Roman Coronagraph, we find that the predicted reflected-light fluxes place every cloudy atmosphere our fit allows within the instrument’s expected sensitivity. A nondetection would be very constraining: a final contrast sensitivity of 2 × 10 −9 would rule out all cloudy atmospheres under our model assumptions.

The Astronomical JournalVol. 172(6)
California Institute of Technology (US), Herzberg Institute of Astrophysics (CA), Space Telescope Science Institute (US), University of Arizona (US), Cornell University (US), University of Victoria (CA), NASA Exoplanet Science Institute (US), University of California System (US), The University of Texas at Austin (US)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Jet Propulsion Laboratory
Openalex Percentile: Top 14%
Stellar, planetary, and galactic studies
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