Letter to the Editor
The frequency resolved spectroscopy of Cyg X-1: fast variability of the Fe line
M. Revnivtsev 1,2,
M. Gilfanov 2,1 and
E. Churazov 2,1
Received 11 May 1999 / Accepted 11 June 1999
We studied the frequency resolved energy spectra of Cyg X-1 during the standard low (hard) spectral state using the data of the Rossi X-Ray Timing Explorer. We found that the relative amplitude of the reflection features - the iron fluorescent line at keV and the smeared edge above keV - decreases with the increasing frequency. In particular we found that the equivalent width of the iron line decreases above Hz and drops twice in value at a frequency of Hz.
The assumption that such behavior is solely due to a finite light crossing time of the reflecting media, would imply the characteristic size of the reflector cm, corresponding to for a black hole. Alternatively the lack of high frequency oscillations of the reflected component may indicate that the short time scale, 50-100 msec, variations of the primary continuum appear in the geometrically different, likely inner, part of the accretion flow and give a rise to a significantly weaker, if any, reflected emission than the longer time scale events.
Key words: methods: data analysis stars: binaries: general stars: individual: (Cyg X-1) X-rays: general
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© European Southern Observatory (ESO) 1999
Online publication: June 30, 1999