  We report on XMM-Newton observations of GRO J1655-40 and GRS 1009-45, which
are two black hole X-ray transients currently in their quiescent phase. GRO
J1655-40 was detected with a 0.5 - 10 keV luminosity of 5.9 10^{31} erg/s. This
luminosity is comparable to a previous Chandra measurement, but ten times lower
than the 1996 ASCA value, most likely obtained when the source was not yet in a
true quiescent state. Unfortunately, XMM-Newton failed to detect GRS 1009-45. A
stringent upper limit of 8.9 10^{30} erg/s was derived by combining data from
the EPIC-MOS and PN cameras.
  The X-ray spectrum of GRO J1655-40 is very hard as it can be fitted with a
power law model of photon index ~ 1.3 +/- 0.4. Similarly hard spectra have been
observed from other systems; these rule out coronal emission from the secondary
or disk flares as the origin of the observed X-rays. On the other hand, our
observations are consistent with the predictions of the disc instability model
in the case that the accretion flow forms an advection dominated accretion flow
(ADAF) at distances less than a fraction ~ 0.1 - 0.3) of the circularization
radius. This distance corresponds to the greatest extent of the ADAF that is
thought to be possible.
