Natalucci, Lorenzo3; Tomsick, John A.4; Bazzano, Angela3; Smith, David M.5; Bachetti, Matteo6; Barret, Didier6; Boggs, Steven E.4; Christensen, Finn Erland1; Craig, William W.7; Fiocchi, Mariateresa3; Fuerst, Felix14; Grefenstette, Brian W.14; Hailey, Charles J.15; Harrison, Fiona A.14; Krivonos, Roman4; Kuulkers, Erik16; Miller, Jon M.11; Pottschmidt, Katja12; Stern, Daniel14; Ubertini, Pietro3; Walton, Dominic J.14; Zhang, William W.17
1 National Space Institute, Technical University of Denmark2 Astrophysics, National Space Institute, Technical University of Denmark3 National Institute for Astrophysics4 University of California at Berkeley5 University of California, Santa Cruz6 Université de Toulouse7 University of California8 California Institute of Technology9 Columbia University10 European Space Astronomy Centre11 University of Michigan12 University of Maryland13 NASA Goddard Space Flight Center14 California Institute of Technology15 Columbia University16 European Space Astronomy Centre17 NASA Goddard Space Flight Center
The microquasar 1E1740.7-2942, also known as the "Great Annihilator", was observed by NuSTAR in the Summer of 2012. We have analyzed in detail two observations taken ~2 weeks apart, for which we measure hard and smooth spectra typical of the low/hard state. A few weeks later the source flux declined significantly. Nearly simultaneous coverage by INTEGRAL is available from its Galactic Center monitoring campaign lasting ~2.5 months. These data probe the hard state spectrum from 1E1740.7-2942 before the flux decline. We find good agreement between the spectra taken with IBIS/ISGRI and NuSTAR, with the measurements being compatible with a change in flux with no spectral variability. We present a detailed analysis of the NuSTAR spectral and timing data and upper limits for reflection of the high energy emission. We show that the high energy spectrum of this X-ray binary is well described by thermal Comptonization.
Astrophysical Journal, 2014, Vol 780, Issue 1
Accretion; Accretion disks; Black hole physics; X-ray: binaries; X-ray: individual