2010ApJ...716.1431R

We present two Suzaku observations of the Galactic center microquasar 1E 1740.7-2942 separated by approximately 700 days. The source was observed on both occasions after a transition to the spectrally hard state. Significant emission from 1E 1740.7-2942 is detected out to an energy of 300 keV, with no spectral break or turnover evident in the data. We tentatively measure a lower limit to the cutoff energy of ∼380 keV. The spectra are found to be consistent with a Comptonized corona on both occasions, where the high energy emission is consistent with a hard power-law (Γ ∼ 1.8) with a significant contribution from an accretion disk with a temperature of ∼0.4 keV at soft X-ray energies. The measured value for the inner radius of the accretion disk is found to be inconsistent with the picture whereby the disk is truncated at large radii in the low-hard state and instead favors a radius close to the ISCO (R_in∼ 10-20 R_g).