  We have re-analyzed two EXOSAT Medium Energy observations during part of the
1984 X-ray outburst of the black-hole candidate transient system 4U 1630-47.
One observation (May 10) shows fast timing properties (on timescales shorter
than ~250 s) typical of those of other black hole candidates in their high
states. The power-spectrum shows a power law with index 0.7 and fractional rms
amplitude (0.001-1 Hz) of 2%. Another observation, obtained one month earlier
(April 11), shows different fast timing behavior. The power spectrum of this
observation can be described by a power law with index 1.5 and fractional rms
amplitude (0.001-1 Hz) of 7%. This is inconsistent with the behavior during
low, high or very high states known to occur in most of the black hole
candidates. Instead, the timing properties resemble those recently reported
from ASCA observations of the superluminal black-hole candidates GRS 1915+105
and GRO J1655-40 (X-ray Nova Sco 1994). This timing behavior may represent a
new state of black hole candidates. In addition, the X-ray spectra of the three
sources show similar properties. Since GRS 1915+105 and GRO J1655-40 exhibit
superluminal jets, we propose that 4U 1630-47 is also a relativistic jet
source.
