Mon. Not. R. Astron. Soc., 388, 1001-1010 (2008/August-2)
A classification of the X-ray and radio states of Cyg X-3 and their long-term correlations.
SZOSTEK A., ZDZIARSKI A.A. and McCOLLOUGH M.L.
Abstract (from CDS):
We present a detailed classification of the X-ray states of Cyg X-3 based on the spectral shape and a new classification of the radio states based on the long-term correlated behaviour of the radio and soft X-ray light curves. We find a sequence of correlations, starting with a positive correlation between the radio and soft X-ray fluxes in the hard spectral state, changing to a negative one at the transition to soft spectral states. The temporal evolution can be in either direction on that sequence, unless the source goes into a very weak radio state, from which it can return only following a major radio flare. The flare decline is via relatively bright radio states, which results in a hysteresis loop on the flux-flux diagram. We also study the hard X-ray light curve, and find its overall anticorrelation with the soft X-rays. During major radio flares, the radio flux responds exponentially to the level of a hard X-ray high-energy tail. We also specify the detailed correspondence between the radio states and the X-ray spectral states. We compare our results to those of black hole and neutron star binaries. Except for the effect of strong absorption and the energy of the high-energy break in the hard state, the X-ray spectral states of Cyg X-3 closely correspond to the canonical X-ray states of black hole binaries. Also, the radio/X-ray correlation closely corresponds to that found in black hole binaries, but it significantly differs from that in neutron star binaries. Overall, our results strongly support the presence of a black hole in Cyg X-3.
© 2008 The Authors. Journal compilation © 2008 RAS
accretion, accretion discs - binaries: general - stars: individual: Cyg X-3 - radio continuum: stars - X-rays: binaries - X-rays: stars
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