Variability in the Noise Properties of Cygnus X-1

T. Belloni, G. Hasinger

Astron. Astrophysics, 227, L33-L36 (1990)

Abstract

The aperiodic variability in the X-ray emission of Cyg X-1 is examined from 13 EXOSAT observations covering the period 1983 Jul -- 1985 Oct, by means of broad (10-3 - 102 Hz) power spectra. The total rms fractional variation in the range 0.016 -- 14 Hz is between 28 and 38%. The power distribution is flat below a characteristic break frequency vb, follows a power law with slope ~ (-1) up to ~ 1 Hz, and then steepends to a slope of roughly (-2). Some wiggles in the power spectra are also observed. The break frequency is observed to vary in the range 0.04-0.4, showing no correlation with the source flux. The results can be interpreted with a shot noise model with a distribution in shot times, in which the presence of long living shots determines the position of the break frequency vb.

1/f in astronomy section