The nature of the hard state of Cygnus X-3

Understand

The X-ray binary Cygnus X-3 is a highly variable X-ray source that displays a wide range of observed spectral states.

• One of the main states is significantly harder than the others, peaking at ~ 20 keV, with only a weak low-energy component.
• Due to the enigmatic nature of this object, hidden inside the strong stellar wind of its Wolf-Rayet companion, it has remained unclear whether this state represents an intrinsic hard state, with truncation of the inner disc, or whether it is just a result of increased local absorption.
• We study the X-ray light curves from RXTE/ASM and CGRO/BATSE in terms of distributions and correlations of flux and hardness and find several signs of a bimodal behaviour of the accretion flow that are not likely to be the result of increased absorption in a surrounding medium.