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

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/780/1/63· OSTI ID:22348317

Natalucci, Lorenzo; Bazzano, Angela; Fiocchi, Mariateresa; Ubertini, Pietro ^[1]; Tomsick, John A.; Boggs, Steven E.; Craig, William W.; Krivonos, Roman ^[2]; Smith, David M. ^[3]; Bachetti, Matteo; Barret, Didier ^[4]; Christensen, Finn E. ^[5]; Fürst, Felix; Grefenstette, Brian W.; Harrison, Fiona A. ^[6]; Hailey, Charles J. ^[7]; Kuulkers, Erik ^[8]; Miller, Jon M. ^[9]; Pottschmidt, Katja ^[10]; Stern, Daniel ^[11] ; others, and

---

1. Istituto di Astrofisica e Planetologia Spaziali, INAF, via del Fosso del Cavaliere, I-00133 Roma (Italy)
2. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States)
3. Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA 95064 (United States)
4. Université de Toulouse, UPS-OMP, IRAP, Toulouse (France)
5. DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
6. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
7. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
8. European Space Astronomy Centre (ESA/ESAC), Science Operations Department, E-28691 Villanueva de la Cañada (Madrid) (Spain)
9. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
10. CRESST and NASA Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771 (United States)
11. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

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.

• OSTI ID: 22348317
• Journal Information: Astrophysical Journal, Vol. 780, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BINARY STARS
BLACK HOLES
COSMIC X-RAY SOURCES
EMISSION
ENERGY SPECTRA
QUASARS
REFLECTION
X RADIATION