A Time Resolved Study of the Broad Line Region in Blazar 3C 454.3

Abstract

We present multi-epoch optical observations of the blazar 3C 454.3 (z = 0.859) from 2008 August through 2011 December, using the SMARTS Consortium 1.5m+RCSpectrograph and 1.3m+ANDICAM in Cerro Tololo, Chile. The spectra reveal that the broad optical emission lines Mg II, H-beta and H-gamma are far less variable than the optical or gamma-ray continuum. Although, the gamma-rays varied by a factor of 100 above the EGRET era flux, the lines generally vary by a factor of 2 or less. Smaller variations in the gamma-ray flux did not produce significant variation in any of the observed emission lines. Therefore, to first order, the ionizing flux from the disk changes only slowly during large variations of the jet. However, two exceptions in the response of the broad emission lines are reported during the largest gamma-ray flares in 2009 December and 2010 November, when significant deviations from the mean line flux in H-gamma and Mg II were observed. H-gamma showed a maximum 3-sigma and 4-sigma deviation in each flare, respectively, corresponding to a factor of 1.7 and 2.5 increase in flux. Mg II showed a 2-sigma deviation in both flares; no variation was detected in H-beta during either flare. These significant deviations from the mean line flux also coincide with 7mm core ejections reported previously (Jorstad et al. 2012). The correlation of the increased emission line flux with mm core ejections, and gamma-ray, optical and UV flares suggests that the broad line region extends beyond the gamma-emitting region during the 2009 and 2010 flares.