Abstract
view Abstract Citations (22) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Small-Amplitude Coherent Signals in the X-Ray Emission of NGC 4151 Fiore, F. ; Massaro, E. ; Perola, G. C. ; Piro, L. Abstract We present the results of the temporal analysis performed on four EXOSAT medium-energy observations of the Seyfert galaxy NGC 4151, selected for their long duration and background stability. The light curves can be adequately described in terms of regular trends (representing variations on time scales >= 1 day) to which small-amplitude fluctuations are superposed. The harmonic analysis, applied separately to each one of the observations, provides evidence that a substantial fraction of the power in these fluctuations is contained in coherent signals occurring at either one or both of the frequencies 7.9 x 10^-5^6 and 1.7 x 10^-4^ Hz, which, within the frequency resolution achieved, are in a ratio compatible with 2 and can be therefore assumed to be harmonically related. The amplitude (peak-to-peak) of these signals varies from one observation to the other and reaches at most 7%. If the period corresponding to the lower frequency is interpreted as the signature of the orbital time of matter near the innermost stable orbit around a collapsed object, its mass can be estimated to be close to 2.5 x 10^7^ M_sun_ for the Schwarzschild metric. Publication: The Astrophysical Journal Pub Date: December 1989 DOI: 10.1086/168106 Bibcode: 1989ApJ...347..171F Keywords: Coherent Electromagnetic Radiation; Light Curve; Seyfert Galaxies; X Ray Astronomy; X Ray Sources; Background Radiation; Exosat Satellite; Harmonic Analysis; Power Spectra; Schwarzschild Metric; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4151; GALAXIES: NUCLEI; GALAXIES: SEYFERT; GALAXIES: X-RAYS full text sources ADS | data products SIMBAD (3) NED (3)
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