Issue |
A&A
Volume 414, Number 3, February II 2004
|
|
---|---|---|
Page(s) | 1091 - 1104 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20031684 | |
Published online | 27 January 2004 |
Long term variability of Cyg X-1
II. The rms-flux relation
1
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, gleiss@astro.uni-tuebingen.de
Received:
19
August
2003
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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