Abstract Fourier analysis of an EXOSAT (ME) 30000 s observation of the Seyfert 1 galaxy NGC 4151 revealed a transient periodical phenomenon (period 131 ± 1 s and duration of a few thousand seconds) with a probability of a chance occurrence of the peak in the power spectrum of 2 10−3. Analysis of short data segments provides further evidence of this periodicity and indicates that the energy spectrum of this component becomes softer during the phenomenon. A careful analysis of possible instrumental effects does not appear to offer an explanation of the observed phenomenon.
Detection of transient periodicity in an EXOSAT observation of NGC4151
Advances in Space Research ; 8 , 2-3 ; 65-68
1988-01-01
4 pages
Article (Journal)
Electronic Resource
English
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