Long term variability of Cygnus X-1

T. Gleissner, J. Wilms, G. G. Pooley, M. A. Nowak, K. Pottschmidt, S. Markoff, S. Heinz, M. Klein-Wolt, R. P. Fender, R. Staubert
2004 Astronomy and Astrophysics  
Long time scale radio-X-ray correlations in black holes during the hard state have been found in many sources and there seems to emerge a universal underlying relationship which quantitatively describes this behavior. Although it would appear only natural to detect short term emission patterns in the X-ray and - with a certain time lag - in the radio, there has been little evidence for this up to now. The most prominent source for radio-X-ray correlations on short time scales (minutes) so far
more » ... (minutes) so far remains GRS 1915+105 where a single mass ejection could be detected successively in the X-ray, IR, and radio wavebands. We analyze a database of more than 4 years of simultaneous radio-X-ray data for Cygnus X-1 from the Ryle Telescope and RXTE PCA/HEXTE. We confirm the existence of a radio-X-ray correlation on long time scales, especially at hard energies. We show that apparent correlations on short time scales in the lightcurves of Cygnus X-1 are most likely the coincidental outcome of white noise statistics. Interpreting this result as a breakdown of radio-X-ray correlations on shorter time scales, this sets a limit to the speed of the jet.
doi:10.1051/0004-6361:20040280 fatcat:gkpgmx2sgrf7hf5pfb3l4sa42q