ROSAT X-ray detection of a young brown dwarf in the chamaeleon I dark cloud
Photometry and spectroscopy of the object Cha Halpha 1, located in the Chamaeleon I star-forming cloud, show that it is a approximately 10(6)-year-old brown dwarf with spectral type M7.5 to M8 and 0.04 +/- 0.01 solar masses. Quiescent x-ray emission was detected in a 36-kilosecond observation with 31.4 +/- 7.7 x-ray photons, obtained with the Rontgen Satellite (ROSAT), with 9final sigma detection significance. This corresponds to an x-ray luminosity of 2.57 x 10(28) ergs per second and an x-ray to bolometric luminosity ratio of 10(-3.44). These are typical values for late M-type stars. Because the interior of brown dwarfs may be similar to that of convective late-type stars, which are well-known x-ray sources, x-ray emission from brown dwarfs may indicate magnetic activity.
R. Neuhauser, Max-Planck-Institut fur Extraterrestrische Physik, D-85740 Garching, Germany. E-mail: rne@mpe.mpg.de F. Comeron, European Southern Observatory, D-85748 Garching, Germany. E-mail: fcomeron@eso.org.
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Neuhauser
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Comeron