The Soft Gamma‐Ray Spectral Variability of Cygnus X‐1

Citations Over TimeTop 10% of 2002 papers

Abstract

We have used observations of Cyg X-1 from the Compton Gamma Ray Observatory and BeppoSAX to study the variation in the MeV -ray emission between the hard and soft spectral states, using spectra that coverthe energy range from 20 keV up to 10 MeV. These data provide evidence for significant spectral variability at energies above 1 MeV. In particular, whereas the hard X-ray flux decreases during the soft state, theflux at energies above 1 MeV increases, resulting in a significantly harder -ray spectrum at energies above 1 MeV. This behavior is consistent with the general picture of galactic black hole candidates having two distinct spectral forms at soft -ray energies. These data extend this picture, for the first time, to energies above 1 MeV. We have used two different hybrid thermal/nonthermal Comptonization models to fit broadband spectral data obtained in both the hard and soft spectral states. These fits provide a quantitative estimate of the electron distribution and allow us to probe the physical changes that take place duringtransitions between the low and high X-ray states. We find that there is a significant increase (by a factor of 4) in the bolometric luminosity as the source moves from the hard state to the soft state. Furthermore, the presence of a nonthermal tail in the Comptonizing electron distribution provides significant constraints on the magnetic field in the source region.

Related Papers

• → Compton Effect: Historical Background(1964)10 cited
• → Azimuthal variation of Compton scattering of polarized gamma rays(1965)5 cited
• → Compton scattering of 279 keV gamma rays by L shell electrons of gold(1982)5 cited
• Design and Initial Operation of a Tunable Compton-Scattering Based Gamma-Ray Source(2007)
• COMPTON SCATTERING OF 662 kev GAMMA RAYS FROM IRON(1963)