Rapid variability of 10–140 keV X-rays from Cygnus X-1 |
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| Authors: | P L Nolan D E Gruber J L Matteson L E Peterson R E Rothschild |
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| Institution: | Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093, USA;Department of Physics and Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA |
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| Abstract: | On five occasions in 1977 and 1978, Cygnus X-1 was observed using the Low-Energy Detectors of the UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Experiment on the HEAO-1 satellite. Rapid (0.08 s ≤ t ≤ 1000 s) variability was found in the 10 – 140 keV band. The power spectrum was “white” for 10−3 Hz < f ≤ 5 × 10−2 Hz and was proportional to f−1 for 5 × 10−2 Hz ≤ f < 3 Hz, indicating correlations on all time scales < 20 s. If the emission is produced by Comptonization of a soft photon flux in a hot cloud, the heating of the cloud cannot be constant; it must vary on time scales up to 20 seconds. A variable accretion rate could cause the observed effects. |
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