The first brown dwarf/planetary-mass object in the 32 Orionis group
- Department of Physics, University of California, San Diego, CA 92093 (United States)
- Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States)
- Institut de Recherche sur les Exoplanètes (iREx), Université de Montréal, Dpartement de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada)
The 32 Orionis group is a co-moving group of roughly 20 young (24 Myr) M3-B5 stars 100 pc from the Sun. Here we report the discovery of its first substellar member, WISE J052857.69+090104.2. This source was previously reported to be an M giant star based on its unusual near-infrared spectrum and lack of measureable proper motion. We re-analyze previous data and new moderate-resolution spectroscopy from Magellan/Folded-port InfraRed Echellette to demonstrate that this source is a young near-infrared L1 brown dwarf with very low surface gravity features. Spectral model fits indicate T{sub eff} = 1880{sub −70}{sup +150} K and logg = 3.8{sub −0.2}{sup +0.2}, consistent with a 15–22 Myr object with a mass near the deuterium-burning limit. Its sky position, estimated distance, kinematics (both proper motion and radial velocity), and spectral characteristics are all consistent with membership in 32 Orionis, and its temperature and age imply a mass (M = 14{sub −3}{sup +4} M{sub J}) that straddles the brown dwarf/planetary-mass object boundary. The source has a somewhat red J−W2 color compared to other L1 dwarfs, but this is likely a low-gravity-related temperature offset; we find no evidence of significant excess reddening from a disk or cool companion in the 3–5 μm waveband.
- OSTI ID:
- 22890128
- Journal Information:
- Astrophysical Journal, Vol. 820, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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