Case, Gary L. and Cherry, Michael L. and Ling, James C. and Wheaton, William A. (2008) Low Energy Gamma-Ray Emission from Galactic Black Holes. In: OBSERVATIONAL EVIDENCE FOR BLACK HOLES IN THE UNIVERSE: Proceedings of the 2nd Kolkata Conference on Observational Evidence for Black Holes in the Universe, Kolkata India, 10–15 February 2008 and the Satellite Meeting on Black Holes, Neutron ... American Institute of Physics Conference Proceedings (1053). American Institute of Physics , Melville, NY, pp. 145-152. ISBN 978-0-7354-0582-0 http://resolver.caltech.edu/CaltechAUTHORS:CASaipcp08
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X-ray observations of Galactic black holes (GBHs) such as Cygnus X-1 have greatly advanced the understanding of these objects. However, the vast majority of the observations have been restricted to energies below ~200 keV. The Compton Gamma-Ray Observatory (CGRO) allowed for the first time simultaneous observations at energies from ~25 keV up to >1 GeV. In particular, the BATSE experiment aboard CGRO was able to monitor low-energy gamma-ray emission from Cygnus X-1, as well as other GBHs, nearly continuously over a nine year period. Using the Enhanced BATSE Occultation Package (EBOP), light curves and spectra in the energy range 25–2000 keV have been obtained for six GBHs. Based on the spectra when the GBHs were in a high gamma-ray flux state, it is suggested that at least two different classes of GBHs exist. The first is characterized by a Comptonization spectrum below ~200 keV followed by a soft power law excess as exhibited by Cygnus X-1, GRO J0422+32, GRO J1719−24, and GX 339-4. The second class is characterized by simple power law spectrum in the full 25–2000 keV range, with no evidence for a Comptonization component, as exhibited by GRO J1655−40 and GRS 1915+105.Gamma-ray observations can serve as an important diagnostic in studying the physical processes around GBHs. More sensitive observations in the future at energies >250 keV will help answer questions regarding issues such as the nonthermal electron distribution, state transitions, and the connection to jets.
|Item Type:||Book Section|
|Additional Information:||© 2008 American Institute of Physics. Issue Date: 8 October 2008. The authors wish to acknowledge the contribution of Robert Radocinski in the development of the EBOP software. LSU students C. Britt, C. Fannin, J. Hostetter, J. Rodi, and C. Welch, and Caltech students V. Aguilar and D. Wells, participated in analyzing the BATSE data. This work was supported in part by NASA award NAG5-10253 and NASA/Louisiana Board of Regents grant NNX07AT62A/LEQSF(2007-10) Phase3-02.|
|Subject Keywords:||emission, Galactic centre, black holes, Gamma-rays, Galactic Black Holes, Cygnus X-1, GRO J0422+32, GRO J1719–24, GX 339–4, GRO J1655–40, GRS 1915+105|
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|Deposited By:||Archive Administrator|
|Deposited On:||29 Oct 2008 22:25|
|Last Modified:||26 Dec 2012 10:28|
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