The 2Mass Wide-Field T Dwarf Search. I. Discovery of a Bright T Dwarf within 10 Parsecs of the Sun

We present the discovery of a bright (J = 13.94$\pm$0.03) T dwarf, 2MASS1503+2525, identified in a new, wide-field search for T dwarfs using therecently completed Two Micron All Sky Survey (2MASS). The 1--2.5 $\micron$spectrum of this object exhibits the strong H$_2$O and CH$_4$ bandscharacteristic of mid- and late-type T dwarfs, and we derive a spectral type ofT5.5 using both the Burgasser et al. and the Geballe et al. classificationschemes. Based on its spectral type and the absolute magnitudes of known Tdwarfs, we estimate the distance of this object as 8$\pm$3 pc if it is single,likely within 10 pc of the Sun. Our new 2MASS search, which covers 74% of thesky and greatly expands on earlier color constraints, should identify 15--25new T dwarfs with J $\leq$ 16. Combined with the 20 known members of this classthat already fall within our search criteria, our new sample will provideimproved statistics for such key quantities as the binary fraction and thefield substellar mass function. Furthermore, multiple detections fromoverlapping 2MASS scans provide multiple epoch astrometry and photometry, andwe present proper motions for five T dwarfs in our sample.Comment: accepted for publication to AJ February 2003; 10 pages including 4 figures, uses emulateapj5 packag