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Gamma-ray observations of Cygnus X-1 above 100 MeV in the hard and soft states by Sabatini, S.; Tavani, M.; Coppi, P.; Pooley, G.; Del Santo, M.; Campana, R.; Chen, A.; Evangelista, Y.; Piano, G.; Bulgarelli, A.; Cattaneo, P. W.; Colafrancesco, S.; Del Monte, E.; Giuliani, A.; Giusti, M.; Longo, F.; Morselli, A.; Pellizzoni, A.; Pilia, M.; Striani, E.; Trifoglio, M.; Vercellone, S. is a scholarly article available to read on EtoBox.

What is Gamma-ray observations of Cygnus X-1 above 100 MeV in the hard and soft states about?

We present the results of multi-year gamma-ray observations by the AGILE satellite of the black hole binary system Cygnus X-1. In a previous investigation we focused on gamma-ray observations of Cygnus X-1 in the hard state during the period mid-2007/2009. Here we present the results of the gamma-ray monitoring of Cygnus X-1 during the period 2010/mid-2012 carried out for which includes a remarkably prolonged `soft state' phase (June 2010 -- May 2011). Previous 1--10 MeV observations of Cyg X-1 in this state hinted at a possible existence of a non-thermal particle component with substantial modifications of the Comptonized emission from the inner accretion disk. Our AGILE data, averaged over the mid-2010/mid-2011 soft state of Cygnus X-1, provide a significant upper limit for gamma-ray emission above 100 MeV of F_soft < 20 x 10^{-8} ph/cm^2/s, excluding the existence of prominent non-thermal emission above 100 MeV during the soft state of Cygnus X-1. We discuss theoretical implications of our findings in the context of high-energy emission models of black hole accretion. We also discuss possible gamma-ray flares detected by AGILE. In addition to a previously reported episode observ

Author

Sabatini, S.; Tavani, M.; Coppi, P.; Pooley, G.; Del Santo, M.; Campana, R.; Chen, A.; Evangelista, Y.; Piano, G.; Bulgarelli, A.; Cattaneo, P. W.; Colafrancesco, S.; Del Monte, E.; Giuliani, A.; Giusti, M.; Longo, F.; Morselli, A.; Pellizzoni, A.; Pilia, M.; Striani, E.; Trifoglio, M.; Vercellone, S.

Published

2013

Language

EN