Astron. Astrophys. 347, L23-L26 (1999)

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 <sup>2,1

1</sup> Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117810 Moscow, Russia,
² Max-Planck-Institute für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching bei München, Germany

Received 11 May 1999 / Accepted 11 June 1999

Abstract

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

Send offprint requests to: revnivtsev@hea.iki.rssi.ru

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and data analysis
• 3. Frequency resolved spectral analysis
• 4. Results
• 5. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999
helpdesk.link@springer.de