The optical variability properties of flat spectrum radio quasar 3C 454.3

Abstract

The optical variability and property of color index of the flat spectrum radio quasar object 3C 454.3 have been studied. The source exhibits strong variability both in intraday and long-term timescale. The χ2 test suggests that 171 out of 285 nights in R band present intraday variability, and the typical intraday timescale is 0.02–0.1 day. The strong correlation between color index B–I and the brightness in I band imply that there is a general redder-when-brighter trend in faint state of I>14mag, in the sense that the spectrum steepens as the brightness increases. However, when the source is in the bright state, I<14mag, the spectrum remains unchanged. Using the minimum intraday timescale of 0.02±0.01 day and the typical Doppler factor δD=25, the radius of emission region of 3C 454.3 is estimated to be (7.0±3.5)×1014cm, and the upper limit of the central black hole is estimated to be M=(1.9±1.0)×1010M⊙.