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 \times 10 ^ { 31 } erg s ^ { -1 } .
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 \times 10 ^ { 30 } erg s ^ { -1 } 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 \sim 1.3 \pm 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 ( \sim 0.1 - 0.3 ) of the circularization radius .
This distance corresponds to the greatest extent of the ADAF that is thought to be possible .