Long term variability of Cygnus X-1

Abstract

Abstract. 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 remains GRS 1915+105 where a single mass ejection could be detected successively in 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.

X-ray timing analysis of the quasar PG 1211+143

“…This rms-flux relation is linear in the soft band, consistent with the rapid variability observed in accreting objects over a wide range in mass and luminosities such as XRBs, ULXs, AGN and CVs (e.g. Uttley & McHardy 2001;Gleissner et al 2004;Heil & Vaughan 2010;Scaringi et al 2012). A natural explanation for a linear rms-flux relation is in terms of the propagating fluctuations model, whereby the X-ray source responds to variations in the mass accretion rate, which multiplicatively couple to one another as they propagate inwards to the inner disc (e.g.…”

“…This is a relationship which shows that the absolute root-mean-square (rms) ampli- tude of variability scales linearly with the X-ray flux of the source, such that sources display more variability when they are brighter (e.g. Uttley & McHardy 2001;Gleissner et al 2004;Heil & Vaughan 2010). Here, we investigate the rms-flux behaviour for PG 1211+143.…”

The 2015 Decay of the Black Hole X-Ray Binary V404 Cygni: Robust Disk-Jet Coupling and a Sharp Transition Into Quiescence

“…If the X-ray variations are indeed propagating down the jet toward the radio photosphere, then in addition to the time delay, we expect the radio light curve to be a "smoothed" version of the X-ray light curve: the radio emitting region will have a larger physical size than the X-ray emitting one, thereby smearing the radio signal (according to the light travel time across the radio emitting region) and supressing the highest (temporal) frequency variations (see, e.g., Gleissner et al 2004, and references therein). If we smooth our X-ray light curve with a 10-minute sliding filter 21 , then the X-ray variations decrease from =  F 0.28 0.03 var (see Table 5) to =  F 0.23 0.03 var , which is similar to the observed radio light curve from which we measure =  F 0.22 0.02 var .…”

Long term variability of Cygnus X-1

“…This paper is a part of a series where we previously analyzed spectro-timing correlation in the hard state 1998 to 2001 (Pottschmidt et al 2003), the rms-flux relation (Gleissner et al 2004b), the radio-X-ray correlations (Gleissner et al 2004a), the spectral evolution 1999-2004 , and states and state transitions 1996-2012 with all sky monitors (Grinberg et al 2013). We start Sect.…”