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The absence of rapid X-ray variability in active galaxies
Tennant, A. F.; Mushotzky, R. F.
AA(NASA, Goddard Space Flight Center, Laboratory for High Energy Astrophysics, Greenbelt; Maryland, University, College Park, MD), AB(NASA, Goddard Space Flight Center, Laboratory for High Energy Astrophysics, Greenbelt, MD)
Astrophysical Journal, Part 1, vol. 264, Jan. 1, 1983, p. 92-104. (ApJ Homepage)
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NASA/STI Keywords:
Active Galaxies, Galactic Nuclei, Seyfert Galaxies, Sidereal Time, Variations, X Ray Sources, Heao 1, Instrument Errors, Radiation Detectors, Xenon
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The authors have searched for variations on time scales ranging from minutes to several hours in the X-ray flux from 54 observations of 38 active galaxies. The sample is composed mostly of Seyfert I galaxies but also includes radio galaxies, narrow emission-line galaxies, BL Lac objects, and 3C 273. Only NGC 6814 varied on time scales as short as 100 s. No other source was observed to vary with a time scale of less than 12 hr. It is concluded that large-amplitude short-term variations are not a characteristic of the X-ray emission from active galaxies. Some hypotheses to reconcile the rapid variability seen for NGC 6814 with the general stability observed for the other objects are considered.

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