8-12 juin, 2014

Résumé

Characterization of Low-mass, Wide-separation Substellar Companions to Stars in Upper Scorpius: Near-infrared Photometry and Spectroscopy

François-René Lachapelle (Université de Montréal)

David Lafrenière (Université de Montréal), Ray Jayawardhana (University of Toronto), Markus Janson (Queen’s University), Christiane Helling (University of St Andrews), Soeren Witte (Hamburger Sternwarte)

We analyze nIR spectroscopy (R-1000), and Y , J, H, Ks, L' photometry, obtained at Gemini North, of four low-mass brown dwarf companions on wide orbits around young stars of the Upper Scorpius OB association: 1RXS J160929.1-210524B, HIP 78530B, [PGZ2001] J161031.9-191305B and GSC 06214-00210B. We use these data to assess the companions’ spectral type, temperature, surface gravity and mass, as well as the ability of the BT-Settl and Drift-Phoenix atmosphere models to reproduce the spectral features of young substellar objects. We find that these companions together span effective temperatures of 1800-2700 K and masses of 0.008-0.03 Msun. Synthetic spectra based on the BT-Settl and Drift-Phoenix atmosphere models generally offer a good fit to our observed spectra, although our analysis has highlighted a few problems. For example, the best fits in the individual near-infrared bands occur at different model temperatures: the best model fit in the H band is systematically obtained for higher temperatures than in the J and K bands. Also, temperature estimates based on a comparison of the broadband magnitudes and colors of the companions to synthetic magnitudes from the models are systematically lower than the temperature estimates based on a comparison with synthetic spectra.

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