Long term variability of Cygnus X-1. I. X-ray spectral-temporal correlations in the hard state
By K. Pottschmidt, J. Wilms, Michael A. Nowak, G. Pooley, T. Gleißner, W. Heindl, D. Smith, Ronald A. Remillard, R. S. I. Tuebingen, Mit and 5 more. 2002
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We present the long term evolution of the timing properties of the black hole candidate Cygnus X-1 in the 0.002-128 Hz frequency range as monitored from 1998 to 2001 with the Rossi X-ray Timing Explorer (RXTE). For most of this period the source was in its hard state. The power spectral density (PSD) is well modeled as the sum of four Lorentzians, which describe distinct broad noise components. Before 1998 July, Cyg X-1 was in a "quiet" hard state characterized primarily by the first three of these broad Lorentzians being dominant. Around 1998 May, this behavior changed: the total fractional rms amplitude decreased, the peak frequencies of the Lorentzians increased, the average time lag slightly increased, and the X-ray spectrum softened. The change in the timing parameters is mainly due to a strong decrease in the amplitude of the third Lorentzian. Since this event, an unusually large number of X-ray flares have been observed, which we classify as "failed state transitions". During these failed state transitions, the X-ray power spectrum changes to that of the intermediate state. Modeling this PSD with the four Lorentzians, we find that the first Lorentzian component is suppressed relative to the second and third Lorentzian during the state transitions. We also confirm our previous conclusion that the frequency-dependent time lags in- crease significantly in the 3.2-10 Hz band during these transitions. We confirm the interpretation of the flares as failed state transitions with observations from the 2001 January and 2001 October soft states. Both the behavior of the PSD and the X-ray lag suggest that some or all of the Lorentzian components are associated with the accretion disk corona responsible for the hard state spectrum. We discuss the physical interpretation of our results.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/906417bf237e9a857b6b078ee365c5f77854c9a5
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Citations in the corpus
- WATCHDOG: A COMPREHENSIVE ALL-SKY DATABASE OF GALACTIC BLACK HOLE X-RAY BINARIES (2015, background): “…long continuous periods of time in the HCS (Churazov et al. 1993; Main et al. 1999; del Santo et al. 2004; Pottschmidt et al. 2006; Soleri et al. 2012; Shaw et al. 2013; Froning et al. 2014) or periodically undergoing “incomplete” state transitions (Pottschmidt et al. 2003; Soleri et al. 2012).”
- Investigating a fluctuating-accretion model for the spectral-timing properties of accreting black hole systems (2005, methodology): “We used broad input PSDs, with Q = 0.5, a value similar to the four-Lorentzian decomposition of the PSD of Cyg X-1 in the low/hard state (Pottschmidt et al. 2003) and also much narrower PSDs with Q = 10, to study the influence of this parameters on the final PSDs and Cross 1 The Lorentzian peak…”
- Non‐linear X‐ray variability in X‐ray binaries and active galaxies (2005, background): “In particular, the PSD shape changes dramatically between different spectral states in BHXRBs (e.g. McClintock & Remillard 2003; Pottschmidt et al. 2003).”
- Going with the Flow: Can the Base of Jets Subsume the Role of Compact Accretion Disk Coronae? (2005, methodology): “For instance, in the Galactic XRBsGX 339 4 and CygX-1, accretion without observable jets proceeds to accretion with discernible jets and back again every few years (Fender 2006; Pottschmidt et al. 2003; Gleissner et al. 2004b; Homan et al. 2005).”