Observations of a hard state of 1E 1740.7-2942 by NuSTAR and INTEGRAL
Abstract
NuSTAR observed the Galactic Center microquasar 1E 1740.7-2942, also known as "the Great Annihilator", in July-August 2012, during its Performance Verification campaign. Despite the shortness of the observations (the total net exposure is 8.5 ks) the very high sensitivity of NuSTAR has allowed us to characterize in detail the spectrum of this source up to ~70 keV. A few weeks later, the flux declined significantly and the source entered a supposed quiescence state. Nearly simultaneous exposures of INTEGRAL/IBIS, taken before the drop in intensity, were used to extend the spectral coverage up to the soft gamma-ray band. This allowed for the detection of an exponential cutoff, with an e-folding energy at ~160 keV. The spectrum of the source is smooth and consistent with thermal Comptonization, with no sign of reflection or reprocessing features. A detailed analysis of the spectral and timing data is presented, including upper limits for reflection and Fe line. Finally, our results are compared with previous observations of the hard state by INTEGRAL and Suzaku.
- Publication:
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American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22343818N