Article: Rajan, A; Rameau, J; De Rosa, RJ; Marley, MS; Graham, JR; Macintosh, B; Marois, C; Morley, C; Patience, J; Pueyo, L; Saumon, D; Ward-Duong, K; Ammons, SM; Arriaga, P; Bailey, VP; Barman, T; Bulger, J; Burrows, AS; Chilcote, J; Cotten, T; Czekala, I; Doyon, R; Duchene, G; Esposito, TM; Fitzgerald, MP; Follette, KB; Fortney, JJ; Goodsell, SJ; Greenbaum, AZ; Hibon, P; Hung, LW; Ingraham, P; Johnson-Groh, M; Kalas, P; Konopacky, Q; Lafreniere, D; Larkin, JE; Maire, J; Marchis, F; Metchev, S; Millar-Blanchaer, MA; Morzinski, KM; Nielsen, EL; Oppenheimer, R; Palmer, D; Patel, RI; Perrin, M; Poyneer, L; Rantakyro, FT; Ruffio, JB; Savransky, D; Schneider, AC; Sivaramakrishnan, A; Song, I; Soummer, R; Thomas, S; Vasisht, G; Wallace, JK; Wang, JJ; Wiktorowicz, S; Wolff, S; “Characterizing 51 Eri b from 1 to 5 mu m: A Partly Cloudy Exoplanet”, Astronomical Journal, 154 (1)
Abstract: We present spectrophotometry spanning 1-5 mu m of 51 Eridani b, a 2-10 M-Jup planet discovered by the Gemini Planet Imager Exoplanet Survey. In this study, we present new K1 (1.90-2.19 mu m) and K2 (2.10-2.40 mu m) spectra taken with the Gemini Planet Imager as well as an updated L-P (3.76 mu m) and new M-S (4.67 mu m) photometry from the NIRC2 Narrow camera. The new data were combined with J (1.13-1.35 mu m) and H (1.50-1.80 mu m) spectra from the discovery epoch with the goal of better characterizing the planet properties. The 51 Eri b photometry is redder than field brown dwarfs as well as known young T-dwarfs with similar spectral type (between T4 and T8), and we propose that 51 Eri b might be in the process of undergoing the transition from L-type to T-type. We used two complementary atmosphere model grids including either deep iron/silicate clouds or sulfide/salt clouds in the photosphere, spanning a range of cloud properties, including fully cloudy, cloud-free, and patchy/intermediate-opacity clouds. The model fits suggest that 51 Eri. b has an effective temperature ranging between 605 and 737 K, a solar metallicity, and a surface gravity of log(g) = 3.5-4.0 dex, and the atmosphere requires a patchy cloud atmosphere to model the spectral energy distribution (SED). From the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93 (logL/L circle dot),leaving 51 Eri b in the unique position of being one of the only directly imaged planets consistent with having formed via a cold-start scenario. Comparisons of the planet SED against warm-start models indicate that the planet luminosity is best reproduced by a planet formed via core accretion with a core mass between 15 and 127 M-circle plus.
Funding Acknowledgement: NSF [AST1411868, AST-1518332, DGE-1311230]; NASA [NNX14AJ80G]; Fonds de Recherche du Quebec; NASA Exoplanets Research Program (XRP) [NNX16AD44G]; JPL’s ESI program for GPIrelated; NASA’s Science Mission Directorate; NExSS [NNX15AD95G]; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]
Funding Text: The authors thank Gabriel Marleau for the discussion on warm-start models. The Gemini Observatory is operated by the AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ciencia, Tecnologia e Inovacao (Brazil), and Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina). This work was supported by NSF grants AST1411868 (A.R., J.L. P., B.M.), AST-1518332 ( R.J.D.R.), and DGE-1311230 (K.W.D.). F.M. and E.N. are supported by NASA Grant NNX14AJ80G. This work was supported by Fonds de Recherche du Quebec (J.R., R.D., D.L.). K.M.M. and T.S.B. are supported by the NASA Exoplanets Research Program (XRP) by cooperative agreement NNX16AD44G. G.V. and J.K.W. acknowledge JPL’s ESI program for GPIrelated funding. The results reported herein benefited from collaborations or information exchange within NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate and the NExSS grant NNX15AD95G. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This research has benefited from the SpeX Prism Library (or SpeX Prism Library Analysis Toolkit) maintained by Adam Burgasser at http://www.browndwarfs.org/ spexprism, the IRTF Spectral Library maintained by Michael Cushing, and the Montreal Brown Dwarf and Exoplanet Spectral Library maintained by Jonathan Gagne.