Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager

Mara Johnson-Groh , Christian Marois , Robert J. de Rosa , Eric L. Nielsen , Julien Rameau , Sarah Blunt , Jeffrey Vargas , S. Mark Ammons , Vanessa P. Bailey , Travis S. Barman , Joanna Bulger , Jeffrey K. Chilcote , Tara Cotten , René Doyon , Gaspard Duchêne (1) , Michael P. Fitzgerald , Kate B. Follette , Stephen Goodsell , James R. Graham , Alexandra Z. Greenbaum , Pascale Hibon , Li-Wei Hung , Patrick Ingraham , Paul Kalas , Quinn M. Konopacky , James E. Larkin , Bruce Macintosh , Jérôme Maire , Franck Marchis , Mark S. Marley , Stanimir Metchev , Maxwell A. Millar-Blanchaer , Rebecca Oppenheimer , David W. Palmer , Jenny Patience , Marshall Perrin , Lisa A. Poyneer , Laurent Pueyo , Abhijith Rajan , Fredrik T. Rantakyrö , Dmitry Savransky , Adam C. Schneider , Anand Sivaramakrishnan , Inseok Song , Remi Soummer , Sandrine Thomas , David Vega , J. Kent Wallace , Jason J. Wang , Kimberly Ward-Duong , Sloane J. Wiktorowicz , Schuyler G. Wolff

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

We present new observations of the low-mass companion to HD 984 taken with the Gemini Planet Imager (GPI) as a part of the GPI Exoplanet Survey campaign. Images of HD 984 B were obtained in the J (1.12-1.3 μm) and H (1.50-1.80 μm) bands. Combined with archival epochs from 2012 and 2014, we fit the first orbit to the companion to find an 18 au (70-year) orbit with a 68% confidence interval between 14 and 28 au, an eccentricity of 0.18 with a 68% confidence interval between 0.05 and 0.47, and an inclination of 119° with a 68% confidence interval between 114° and 125°. To address the considerable spectral covariance in both spectra, we present a method of splitting the spectra into low and high frequencies to analyze the spectral structure at different spatial frequencies with the proper spectral noise correlation. Using the split spectra, we compare them to known spectral types using field brown dwarf and low-mass star spectra and find a best-fit match of a field gravity M6.5 ± 1.5 spectral type with a corresponding temperature of {2730}_-180⁺¹²⁰ K. Photometry of the companion yields a luminosity of {log}({L}_{bol}/{L}_⊙ )=-2.88+/- 0.07 dex with DUSTY models. Mass estimates, again from DUSTY models, find an age-dependent mass of 34 ± 1 to 95 ± 4 M _Jup. These results are consistent with previous measurements of the object.

Mots clés: planetary systems; stars: individual: HD 984; Astrophysics - Earth and Planetary Astrophysics

Domaines: Planète et Univers [physics]

Mara Johnson-Groh, Christian Marois, Robert J. de Rosa, Eric L. Nielsen, Julien Rameau, et al.. Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager. The Astronomical Journal, 2017, 153, ⟨10.3847/1538-3881/aa6480⟩. ⟨insu-03692524⟩