Detection of Hα Emission in a Methane (T Type) Brown Dwarf
We report the detection of Hα emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log (L_(Hα)/L_(bol)) = -4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs. We speculate on several mechanisms that may be responsible for emission, including a strong magnetic field, continuous flaring, acoustic heat generation, and a close [α ~ (4–20)R_J] interacting binary, with the cooler component overflowing its Roche lobe. We suggest that the M9.5 Ve PC 0025+0447 could be a warm analog to 2MASS J1237+65 and may be powered by the latter mechanism.
Additional Information© 2000 American Astronomical Society. Received 2000 February 8; accepted 2000 March 17. A. J. B. acknowledges the assistance of Terry Stickel and Wayne Wack at the telescope, useful discussions with P. Goldreich and M. Marley, helpful comments from our referee, S. Hawley, and the foresight of S. Phinney for assigning the brown dwarf binary problem (eq. ) in class. A. J. B., J. D. K., I. N. R., J. E. G., and J. L. acknowledge funding through a NASA JPL grant to 2MASS Core Project science. A. J. B., J. D. K., and J. E. G. acknowledge the support of the Jet Propulsion Laboratory, California Institute of Technology, which is operated under contract with the National Aeronautics and Space Administration. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by generous financial support of the W. M. Keck Foundation.
Published - 1538-3881_120_1_473.pdf
Accepted Version - 0003291.pdf