  We have detected an X-ray flare on the very low mass star VB 10 (GL 752 B; M8
V) using the ROSAT High Resolution Imager. VB 10 is the latest type (lowest
mass) main sequence star known to exhibit coronal activity. X-rays were
detected from the star during a single 1.1-ksec segment of an observation which
lasted 22 ksec in total. The energy released by this flare is on the order of
10^27 ergs/sec. This is at least two orders of magnitude greater than the
quiescent X-ray luminosity of VB 10, which has yet to be measured. This X-ray
flare is very similar in nature to the far ultraviolet flare which was observed
by Linsky et al. (1995) using the Goddard High Resolution Spectrograph onboard
Hubble Space Telescope. We discuss reasons for the extreme difference between
the flare and quiescent X-ray luminosities, including the possibility that VB
10 has no quiescent (10^6 K) coronal plasma at all.
