NuSTAR AND INTEGRAL OBSERVATIONS OF A LOW/HARD STATE OF 1E1740.7-2942

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https://iopscience.iop.org/article/10.1088/0004-637X/780/1/63

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https://doi.org/10.1088/0004-637X/780/1/63
 http://hdl.handle.net/11603/29603

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UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
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UMBC Physics Department

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https://orcid.org/0000-0002-4656-6881

Date

2013-12-12

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journal articles
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Citation of Original Publication

Natalucci, Lorenzo, John A. Tomsick, Angela Bazzano, David M. Smith, Matteo Bachetti, Didier Barret, Steven E. Boggs, et al. “NuSTAR and INTEGRAL Observations of a Low/Hard State of 1E1740.7-2942.” The Astrophysical Journal 780, no. 1 (December 2013): 63. https://doi.org/10.1088/0004-637X/780/1/63.

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract

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.