The magnetic field in the X-ray corona of Cygnus X-1

Understand

The different electron distributions in the hard and soft spectral states (HS and SS) of BH binaries could be caused by kinetic processes and changing because of varying physical conditions in the corona.

• In presence of a magnetic field in the corona, the electron distribution can appear thermal, even when acceleration mechanisms would produce non thermal distributions.
• This is due to fast and efficient thermalization through synchrotron self-absorption.
• We have analyzed data from 6 years of observations of Cygnus X-1 with the INTEGRAL observatory and produced 12 high-quality, stacked broad-band hard X-ray spectra representative of the whole range of spectral shapes observed.