Volume 414, Number 3, February II 2004
|Page(s)||1091 - 1104|
|Section||Stellar structure and evolution|
|Published online||27 January 2004|
Long term variability of Cyg X-1
II. The rms-flux relation
Institut für Astronomie und Astrophysik – Abt. Astronomie, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
2 Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85748 Garching, Germany
3 INTEGRAL Science Data Centre, Chemin d'Écogia 16, 1290 Versoix, Switzerland
4 School of Physics and Astronomy, University of Southampton, Southampton S017 1BJ, UK
5 MIT-CXC, NE80-6077, 77 Massachusetts Ave., Cambridge, MA 02139, USA
Corresponding author: T. Gleissner, firstname.lastname@example.org
Accepted: 30 October 2003
We study the long term evolution of the relationship between the root mean square (rms) variability and flux (the “rms-flux relation”) for the black hole Cygnus X-1 as monitored from 1996 to 2003 with the Rossi X-ray Timing Explorer (RXTE). We confirm earlier results by [CITE] of a linear relationship between rms and flux in the hard state on time scales >5 s reflecting in its slope the fractional rms variability. We demonstrate the perpetuation of the linear rms-flux relation in the soft and the intermediate state. The existence of a non-zero intercept in the linear rms-flux relation argues for two lightcurve components, for example, one variable and one non-variable component, or a possible constant rms component. The relationship between these two hypothesized components can be described by a fundamental dependence of slope and intercept at time scales 10 ksec with long term averages of the flux.
Key words: black hole physics / stars: individual: Cyg X-1 / X-rays: binaries / X-rays: general
© ESO, 2004
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