Characterization of the gaseous companion κ Andromedae b New Keck and LBTI high-contrast observations
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Context. We previously reported the direct detection of a low-mass companion at a projected separation of 55 ± 2 AU around the B9-type star κ Andromedae. The properties of the system (mass ratio, separation) make it a benchmark for understanding the formation and evolution of gas giant planets and brown dwarfs on wide orbits. Aims. We present new angular differential imaging (ADI) images of the system at 2.146 (Ks), 3.776 (L'), 4.052 (NB_4.05), and 4.78 μm (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We aim to determine the near-infrared spectral energy distribution of the companion and use it to characterize the object. Methods. We used analysis methods adapted to ADI to extract the companion flux. We compared the photometry of the object to reference young, and old objects and to a set of seven PHOENIX-based atmospheric models of cool objects accounting for the formation of dust. We used evolutionary models to derive mass estimates considering a wide range of plausible initial conditions. Finally, we used dedicated formation models to discuss the possible origin of the companion. Results. We derive a more accurate J = 15.86 ± 0.21, H = 14.95 ± 0.13, Ks = 14.32 ± 0.09 mag for κ And b. We detect the companion in all our high-contrast observations. We confirm previous contrasts obtained at Ks and L' band. We derive NB_4.05 = 13.0 ± 0.2, and M′ = 13.3 ± 0.3 mag and estimate log 10(L/L⊙) = −3.76 ± 0.06. Atmospheric models yield Teff = 1900+100-200 K. They do not set any constraint on the surface gravity. "Hot-start" evolutionary models predict masses of 14+25-2 MJup based on the luminosity and temperature estimates, and when considering a conservative age range for the system (30+120-10 Myr), "warm-start" evolutionary tracks constrain the mass to M ≥ 10MJup. Conclusions. The mass of κ Andromedae b mostly falls in the brown-dwarf regime, owing to remaining uncertainties in age and in mass-luminosity models. According to the formation models, disk instability in a primordial disk may account for the position and a wide range of plausible masses of κ And b.
Bonnefoy , M , Currie , T , Marleau , G -D , Schlieder , J E , Wisniewski , J , Carson , J , Covey , K R , Henning , T , Biller , B , Hinz , P , Klahr , H , Boyer , A N M , Zimmerman , N , Janson , M , McElwain , M , Mordasini , C , Skemer , A , Bailey , V , Defrere , D , Thalmann , C , Skrutskie , M , Allard , F , Homeier , D , Tamura , M , Feldt , M , Cumming , A , Grady , C , Brandner , W , Helling , C , Witte , S , Hauschildt , P , Kandori , R , Kuzuhara , M , Fukagawa , M , Kwon , J , Kudo , T , Hashimoto , J , Kusakabe , N , Abe , L , Brandt , T , Egner , S , Guyon , O , Hayano , Y , Hayashi , M , Hayashi , S , Hodapp , K , Ishii , M , Iye , M , Knapp , G , Matsuo , T , Mede , K , Miyama , M , Morino , J -I , Moro-Martin , A , Nishimura , T , Pyo , T , Serabyn , E , Suenaga , T , Suto , H , Suzuki , R , Takahashi , T , Takami , M , Takato , N , Terada , H , Tomono , D , Turner , E , Watanabe , M , Yamada , T , Takami , H & Usuda , T 2014 , ' Characterization of the gaseous companion κ Andromedae b New Keck and LBTI high-contrast observations ' Astronomy & Astrophysics , vol 562 , A111 . DOI: 10.1051/0004-6361/201322119
Astronomy & Astrophysics
© ESO, 2014
J. Carson, J. Wisniewski, and C. Grady were supported by NSF awards 1009314, 1009203, and 1008440. Andrew Skemer was supported by the NASA Origins of Solar Systems Program, grant NNX13AJ17G. J. Kwon is supported by the JSPS Research Fellowships for Young Scientists (PD: 24 110). The research leading to these results has received funding from the French “Agence Nationale de la Recherche” through project grant ANR10-BLANC0504-01, the “Programme National de Physique Stellaire” (PNPS) of CNRS (INSU), and the European Research Council under the European Community’s Seventh Framework Programs (FP7/2007-2013 Grant Agreement no. 247060). It was also conducted within the Lyon Institute of Origins under grant ANR-10-LABX-66.
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