ROSAT X-ray detection of a young brown dwarf in the Chamaeleon I dark cloud

Photometry and spectroscopy of the object Cha H[Alpha] 1, located in the Chamaeleon I star-forming cloud, show that it is a ~[10.sup.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 9 Σ detection significance. This corresponds to an x-ray luminosity of 2.57 x [10.sup.28] ergs per second and an x-ray to bolometric luminosity ratio of [10.sup.-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.
A brown dwarf (BD) is an object with a mass [is less than or equal to] 0.08 solar masses (M??), which is insufficient to sustain nuclear fusion of hydrogen (1). [...]