AAS 198th Meeting, June 2001
Session 49. Latest Results from 2MASS
Display, Tuesday, June 5, 2001, 10:00am-6:30pm, Exhibit Hall

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[49.03] Unusual T dwarfs Discovered by 2MASS

A. J. Burgasser (Caltech), 2MASS Rare Objects Team

To date, seventeen T dwarfs, brown dwarfs exhibiting CH4 absorption features in the near-infrared, have been identified in the 2MASS point source catalog. In this talk, I highlight two unusual discoveries, 2MASS 1237+6526 and 2MASS 0937+2931. The former object shows H alpha in emission (as first reported in Burgasser et al. 2000), contrary to activity trends seen in warmer L dwarfs and T dwarfs. We present observations showing that this emission is stable, and constraints on a possible interacting binary are made based on monitoring observations. The latter object is the bluest T dwarf so far identified, with J-Ks = -0.89, due to a highly suppressed K-band peak. We discuss how high gravity or low metallicity may be the source of this feature, and argue that the importance of H2 collision-induced absorption and the absence of dust in the cool photospheres of T dwarfs allow us to perceive these effects.

The author(s) of this abstract have provided an email address for comments about the abstract: diver@its.caltech.edu

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