We report high-energy results obtained with INTEGRAL and Rossi-XTE on two
microquasars: the persistent high-mass system Cygnus X-1 and the transient
low-mass binary SWIFT J1753.5-0127. INTEGRAL observed Cygnus X-1 from 2002 to
2004: the spectral (5-1000 keV) properties of the source, seen at least in
three distinct spectral states, show disc and corona changes. In 2003 June, a
high-energy tail at several hundred keV in excess of the thermal Comptonization
model was observed, suggesting the presence of an additional non-thermal
component. At that time, we detected an unusual correlation between radio data
and high-energy hardness. We also report and compare the results obtained with
simultaneous observations of the transient source SWIFT J1753.5-0127 performed
with Rossi-XTE, INTEGRAL, VLA, REM and NTT on 2005 August 10-12 near its hard
X-ray outburst. Broad-band spectra and fast time-variability properties are
derived on this source (probably located in the galactic halo) together with
radio, IR and optical data. We build a spectral energy distribution of the
source and derive interesting multiwavelength constraints. Significantly
detected up to 600 keV in a typical Low/Hard State, the transient does not seem
to follow the usual radio/X-ray correlation.Comment: 5 figures, 2 in colo
