학술논문
Characterizing 51 Eri b from 1 to 5 μm: A Partly Cloudy Exoplanet
Document Type
article
Author
Rajan, A; Rameau, J; Rosa, RJD; 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; Duchêne, 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; Lafrenière, 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; Rantakyrö, 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
Source
Astronomical Journal. 154(1)
Subject
Language
Abstract
We present spectrophotometry spanning 1-5 μm of 51 Eridani b, a 2-10 planet discovered by the Gemini Planet Imager Exoplanet Survey. In this study, we present new K1 (1.90-2.19 μm) and K2 (2.10-2.40 μm) spectra taken with the Gemini Planet Imager as well as an updated L P (3.76 μm) and new M S (4.67 μm) photometry from the NIRC2 Narrow camera. The new data were combined with J (1.13-1.35 μm) and H (1.50-1.80 μm) 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⊙), 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⊕.