NuSTAR and INTEGRAL observations of a low/hard state of 1E1740.7-2942

(11) Dept. of Astronomy; (12) CRESST; 13); (13) Center for Space Science; (14) Jet Propulsion Laboratory; (15) NASA/GSFC); (2) Space Sciences Laboratory; (3) Physics Dept.; (4) Universit\`e de Toulouse; 5)

arxiv: 1310.7870 · v1 · pith:45AIGZMOnew · submitted 2013-10-29 · 🌌 astro-ph.HE

NuSTAR and INTEGRAL observations of a low/hard state of 1E1740.7-2942

Lorenzo Natalucci (1) , John A. Tomsick (2) , Angela Bazzano (1) , David M. Smith (3) , Matteo Bachetti (4 , 5) , Didier Barret (4 , Steven E. Boggs (2)

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Finn E. Christensen (6) William W. Craig (2 7) Mariateresa Fiocchi (1) Felix Fuerst (8) Brian W. Grefenstette (8) Charles J. Hailey (9) Fiona A. Harrison (8) Roman Krivonos (2) Erik Kuulkers (10) Jon M. Miller (11) Katja Pottschmidt (12 13) Daniel Stern (14) Pietro Ubertini (1) Dominic J. Walton (8) William W. Zhang (15) ((1) Istituto di Astrofisica e Planetologia Spaziali INAF (2) Space Sciences Laboratory University of California Berkeley (3) Physics Dept. Institute for Particle Physics Santa Cruz (4) Universit\`e de Toulouse (5) Institut de Recherche en Planetologie et Astrophysique CNRS (6) DTU Space Technical University of Denmark (7) Lawrence Livermore National Laboratory (8) Cahill Center for Astronomy Astrophysics Caltech (9) Columbia Astrophysics Laboratory Columbia University (10) European Space Astronomy Centre (ESA) (11) Dept. of Astronomy University of Michigan (12) CRESST NASA/GSFC (13) Center for Space Science Technology University of Maryland Baltimore County (14) Jet Propulsion Laboratory (15) NASA/GSFC)

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classification 🌌 astro-ph.HE

keywords hardnustare1740fluxstatedataenergyhigh

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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.

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NuSTAR and INTEGRAL observations of a low/hard state of 1E1740.7-2942

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