Worlds Next Door. III. Indirect Evidence for Enhanced Atmospheric Metallicity and/or the Presence of Water Clouds in the Nearest Jupiter-analog $epsilon$ Eri b
Aniket Sanghi, James Mang, Jorge Llop-Sayson, Eric Mamajek, William Thompson, Ankan Sur, Charles Beichman, Geoffrey Bryden, Andras Gaspar, Jarron Leisenring, Dimitri Mawet, Caroline Morley, Jean-Baptiste Ruffio, Schuyler Wolff, Marie Ygouf
arXiv:2602.23423v1 Announce Type: new
Abstract: We present the most sensitive direct imaging search for the nearest ($d = 3.2$ pc) Jupiter-analog exoplanet, $epsilon$ Eri b, with JWST/NIRCam coronagraphy between 4-5 $mu$m (F444W). We achieve a 5$sigma$ contrast sensitivity $approx3.0times10^{-7}$ ($Delta approx 16.3$ mag) in the F444W filter at the expected planet separation of $approx$1″. This is the deepest 4-5 $mu$m contrast performance achieved for any JWST/NIRCam observation to date at these separations (and $>10times$ better than ground-based limits). Yet, the planet remains elusive to imaging. We update the star’s age to $1.1pm0.1$ Gyr, older than previous age estimates, using the latest gyrochronology relations. This significantly impacts $epsilon$ Eri b’s inferred effective temperature ($T_{rm eff}$), which is now expected to lie between 150-200 K based on evolutionary models for a 1 $M_{rm Jup}$ planet. Using cloud-free Sonora Flame Skimmer models and custom PICASO patchy cloud models in the above $T_{rm eff}$ range, we find that the F444W non-detection of $epsilon$ Eri b can be explained by a metal-enriched atmosphere and/or an atmosphere containing water ice clouds. Both possibilities suggest that $epsilon$ Eri b’s atmosphere is strikingly similar to that of Jupiter in our Solar System. Alternatively, if we do not enforce the dynamical mass ($0.98 pm 0.09;M_{rm Jup}$), a solar metallicity, cloud-free, $lesssim0.81;M_{rm Jup}$ planet would be consistent with the NIRCam upper limit based on the Sonora Flame Skimmer evolutionary models. Finally, we place limits on the size of a potential ring system using the NIRCam/F210M data and discuss the opportunity to directly image $epsilon$ Eri b with additional JWST observations, the Roman Coronagraph Instrument, the ExtraSolar Coronagraph on the Lazuli Observatory, and EELT/METIS.arXiv:2602.23423v1 Announce Type: new
Abstract: We present the most sensitive direct imaging search for the nearest ($d = 3.2$ pc) Jupiter-analog exoplanet, $epsilon$ Eri b, with JWST/NIRCam coronagraphy between 4-5 $mu$m (F444W). We achieve a 5$sigma$ contrast sensitivity $approx3.0times10^{-7}$ ($Delta approx 16.3$ mag) in the F444W filter at the expected planet separation of $approx$1″. This is the deepest 4-5 $mu$m contrast performance achieved for any JWST/NIRCam observation to date at these separations (and $>10times$ better than ground-based limits). Yet, the planet remains elusive to imaging. We update the star’s age to $1.1pm0.1$ Gyr, older than previous age estimates, using the latest gyrochronology relations. This significantly impacts $epsilon$ Eri b’s inferred effective temperature ($T_{rm eff}$), which is now expected to lie between 150-200 K based on evolutionary models for a 1 $M_{rm Jup}$ planet. Using cloud-free Sonora Flame Skimmer models and custom PICASO patchy cloud models in the above $T_{rm eff}$ range, we find that the F444W non-detection of $epsilon$ Eri b can be explained by a metal-enriched atmosphere and/or an atmosphere containing water ice clouds. Both possibilities suggest that $epsilon$ Eri b’s atmosphere is strikingly similar to that of Jupiter in our Solar System. Alternatively, if we do not enforce the dynamical mass ($0.98 pm 0.09;M_{rm Jup}$), a solar metallicity, cloud-free, $lesssim0.81;M_{rm Jup}$ planet would be consistent with the NIRCam upper limit based on the Sonora Flame Skimmer evolutionary models. Finally, we place limits on the size of a potential ring system using the NIRCam/F210M data and discuss the opportunity to directly image $epsilon$ Eri b with additional JWST observations, the Roman Coronagraph Instrument, the ExtraSolar Coronagraph on the Lazuli Observatory, and EELT/METIS.