A TIME-RESOLVED STUDY OF THE BROAD-LINE REGION IN BLAZAR 3C 454.3.

We present multi-epoch optical observations of the blazar 3C 454.3 (z = 0.859) from 2008 August through 2011 December, using the Small and Medium Aperture Research Telescope System Consortium 1.5 m + RCSpectrograph and 1.3 m + ANDICAM in Cerro Tololo, Chile. The spectra reveal that the broad emission lines Mg II, Hβ, and Hγ are far less variable than the optical or γ-ray continuum. Although the γ-rays varied by a factor of 100 above the EGRET era flux, the lines generally vary by a factor of two or less. Smaller variations in the γ-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 γ-ray flares in 2009 December and 2010 November, when significant deviations from the mean line flux in Hγ and Mg II were observed. Hγ showed a maximum 3σ and 4σ deviation in each flare, respectively, corresponding to a factor of 1.7 and 2.5 increase in flux. Mg II showed a 2σ deviation in both flares; no variation was detected in Hβ during either flare. These significant deviations from the mean line flux also coincide with 7 mm core ejections reported previously (Jorstad et al.). The correlation of the increased emission line flux with millimeter core ejections and γ-ray, optical, and ultraviolet flares suggests that the broad-line region extends beyond the γ-emitting region during the 2009 and 2010 flares. [ABSTRACT FROM AUTHOR]