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Journal Articles Astronomy and Astrophysics - A&A Year : 2023

Revisiting the atmosphere of the exoplanet 51 Eridani b with VLT/SPHERE

S. Brown-Sevilla
  • Function : Author
P. Mollière
  • Function : Author
R. Gratton
  • Function : Author
V. d'Orazi
  • Function : Author
M. Langlois
  • Function : Author
D. Mesa
  • Function : Author
M. Meyer
  • Function : Author
A. Pavlov
  • Function : Author
C. Petit
  • Function : Author
D. Rouan
  • Function : Author
T. Schmidt
  • Function : Author
A. Vigan
  • Function : Author
L. Weber
  • Function : Author


Aims. We aim to better constrain the atmospheric properties of the directly imaged exoplanet 51 Eri b using a retrieval approach with data of higher signal-to-noise ratio (S/N) than previously reported. In this context, we also compare the results from an atmospheric retrieval to using a self-consistent model to fit atmospheric parameters. Methods. We applied the radiative transfer code petitRADTRANS to our near-infrared SPHERE observations of 51 Eri b in order to retrieve its atmospheric parameters. Additionally, we attempted to reproduce previous results with the retrieval approach and compared the results to self-consistent models using the best-fit parameters from the retrieval as priors. Results. We present a higher S/N YH spectrum of the planet and revised K1K 2 photometry ( M K 1 = 15.11 ± 0.04 mag, M K 2 = 17.11 ± 0.38 mag). The best-fit parameters obtained using an atmospheric retrieval differ from previous results using self-consistent models. In general, we find that our solutions tend towards cloud-free atmospheres (e.g. log τ clouds = −5.20 ± 1.44). For our 'nominal' model with new data, we find a lower metallicity ([Fe/H] = 0.26 ± 0.30 dex) and C/O ratio (0.38 ± 0.09), and a slightly higher effective temperature ( T eff = 807 ± 45 K) than previous studies. The surface gravity (log g = 4.05 ± 0.37) is in agreement with the reported values in the literature within uncertainties. We estimate the mass of the planet to be between 2 and 4 M Jup . When comparing with self-consistent models, we encounter a known correlation between the presence of clouds and the shape of the P – T profiles. Conclusions. Our findings support the idea that results from atmospheric retrievals should not be discussed in isolation, but rather along with self-consistent temperature structures obtained using the best-fit parameters of the retrieval. This, along with observations at longer wavelengths, might help to better characterise the atmospheres and determine their degree of cloudiness.
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Dates and versions

hal-04208505 , version 1 (18-09-2023)



S. Brown-Sevilla, A.-L. Maire, P. Mollière, M. Samland, M. Feldt, et al.. Revisiting the atmosphere of the exoplanet 51 Eridani b with VLT/SPHERE. Astronomy and Astrophysics - A&A, 2023, 673, pp.A98. ⟨10.1051/0004-6361/202244826⟩. ⟨hal-04208505⟩
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