X-ray variability patterns and radio/X-ray correlations Cyg X-1

Abstract

We have studied the X-ray variability patterns and correlations of the radio and X-ray fluxes all spectral states of Cyg X-1 using X-ray data from the All-Sky Monitor onboard the Rossi X-ray Timing Explorer, Burst And Transient Source Experiment onboard the Compton Gamma Ray Observatory and the Burst Alert Telescope onboard Swift. the hard state, the dominant spectral variability is a changing of normalization with a fixed spectral shape, while the intermediate state, the slope changes, with a pivot point around 10keV. the soft state, the low-energy X-ray emission dominates the bolometric flux which is only loosely correlated with the high-energy emission. black hole binaries the hard state, the radio flux is generally found to depend on a power of the X-ray flux, FR∝FpX. We confirm this for Cyg X-1. Our new finding is that this correlation extends to the intermediate and soft states, provided the broad-band X-ray flux the Comptonization part of the spectrum (excluding the blackbody component) is considered instead of a narrow-band medium-energy X-ray flux. We find an index p≃ 1.7 ± 0.1 for 15-GHz radio emission, decreasing to p≃ 1.5 ± 0.1 at 2.25 GHz. We conclude that the higher value at 15 GHz is due to the effect of free-free absorption the wind from the companion. The intrinsic correlation index remains uncertain. However, based on a theoretical model of the wind Cyg X-1, it may to be close to ≃1.3, which, the framework of accretion/jet models, would imply that the accretion flow Cyg X-1 is radiatively efficient. The correlation with the flux due to Comptonization emission indicates that the radio jet is launched by the hot electrons the accretion flow all spectral states of Cyg X-1. On the other hand, we are able to rule out the X-ray jet model. Finally, we find that the index of the correlation, when measured using the X-ray flux a narrow energy band, strongly depends on the band chosen and is, general, different from that for either the bolometric flux or the flux the hot-electron emission. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.