The variability of X-ray emission from active galaxies

Abstract

We use observations by the Ariel V Sky Survey Instrument extending over a 5-yr period to investigate the variability of the X-ray emission from 28 active galaxies. There is evidence for variability by a factor of up to 2 on time-scales of ≲ 1 yr in ∼ 50 per cent of the sources. X-ray flux variations on a time-scale of ∼0.5–5 day are reported for a number of sources including the QSOs 0241 + 622 and 3C 273. In some cases these variations take the form of short outbursts with an implied 2–10 keV energy content of ∼ 1047–1050 erg. No clear distinction is found in the X-ray variability of active galaxies with differing morphology or X-ray luminosity.