Astron. J., 134, 1162-1182 (2007/September-0)
Discovery of 11 new T dwarfs in the Two Micron All Sky Survey, including a possible L/T transition binary.
LOOPER D.L., KIRKPATRICK J.D. and BURGASSER A.J.
Abstract (from CDS):
We present the discovery of 11 new T dwarfs, found during the course of a photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog and from a proper-motion-selected sample of ultracool dwarfs in the 2MASS Working Database. Using the NASA Infrared Telescope Facility SpeX spectrograph, we obtained low-resolution (R∼150) spectroscopy, allowing us to derive near-infrared spectral types of T2-T8. We also present improved signal-to-noise ratio SpeX low-resolution spectroscopy of the near-infrared T0 standard SDSS J120747.17+024424.8 and T1 standard SDSSp J083717.22-000018.3. One of these new T dwarfs, 2MASS J13243559+6358284, was also discovered independently by Metchev et al. This object is spectroscopically peculiar and possibly a binary and/or very young (<300 Myr). We specifically attempted to model the spectrum of this source as a composite binary to reproduce its peculiar spectral characteristics. The latest type object in our sample is a T8 dwarf, 2MASS J07290002-3954043, now one of the four latest type T dwarfs known. All 11 T dwarfs are nearby given their spectrophotometric distance estimates, with one T dwarf within 10 pc and eight additional T dwarfs within 25 pc, if single. These new additions increase the 25 pc census of T dwarfs by ∼14%. Their proximity offers an excellent opportunity to probe for companions at separations closer than are possible for more distant T dwarfs.
Stars: Low-Mass, Brown Dwarfs - Techniques: Spectroscopic
VizieR on-line data:
<Available at CDS (J/AJ/134/1162): table2.dat table4.dat table9.dat refs.dat>
Several 2MASS names in table 3 are erroneous.
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