2008/12/01 by Kelle L. Cruz, J. Davy Kirkpatrick, Adam J. Burgasser · 5 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Low Mass #Main sequence #Physics #Pleiades #Sky #Spectral line #Stars #Stellar classification #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1088/0004-6256/137/2/3345
Accepted to AJ
arxiv created 2008/12/01 · openalex publication_date 2009/01/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We present an analysis of 23 L dwarfs whose optical spectra display unusual features. Twenty-one were uncovered during our search for nearby, late-type objects using the Two Micron All Sky Survey, while two were identified in the literature. The unusual spectral features, notably weak FeH molecular absorption and weak Na i and K i doublets, are attributable to low gravity and indicate that these L dwarfs are young, low-mass brown dwarfs. We use these data to expand the spectral classification scheme for L0- to L5-type dwarfs to include three gravity classes. Most of the low-gravity L dwarfs have southerly declinations and distance estimates within 60 pc. Their implied youth, on-sky distribution, and distances suggest that they are members of nearby, intermediate-age (∼10–100 Myr), loose associations such as the β Pictoris moving group, the Tucana/Horologium Association, and the AB Doradus moving group. At an age of 30 Myr and with effective temperatures from 1500 to 2400 K, evolutionary models predict masses of 11–30 M Jupiter for these objects. One object, 2M 0355+11, with J − K s = 2.52 ± 0.03, is the reddest L dwarf found in the field and its late spectral type and spectral features indicative of a very low gravity suggest it might also be the lowest mass field L dwarf. However, before ages and masses can be confidently adopted for any of these low-gravity L dwarfs, additional kinematic observations are needed to confirm cluster membership.