Stellar mass black holes accretion disks in the low-hard state

The geometry of the accretion flow in the low-hard state (LHS) remains uncertain. A cool accretion disk is usually invoked in all interpretations, however the extent of its inner radius differs significantly between them. Either the geometrically thin disk in the LHS extends close to the innermost stable circular orbit or is truncated far from the black hole. This issue is verifiable using high quality X-ray data. Here we summarise a comprehensive study of such systems in the low-hard state and argue that the accretion disk in these systems is truncated close to the central black hole. Furthermore, we show that in the cases where the physical parameters of the system (mass, distance and inclination) are constrained, the accretion disk is likely to be within 10 gravitational radii and consistent with extending to the innermost stable circular orbit in the canonical low-hard state.