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T. J. Balonek (Colgate Univ.), K. Whitman (Cornell Univ.), S. M. Davis (Colgate Univ.), E. Beckerman (Wesleyan Univ.)
We report optical R filter CCD photometric observations from Colgate University's Foggy Bottom Observatory of the quasar BL Lacertae during the intense outburst in summer 1997. Throughout 1996 BL Lac hovered around a magnitude of R = 14.7-15.3, with night-to-night variations of several tenths of a magnitude. The 1997 outburst appears to be part of a general increase in activity which began after a minimum of 15.3 in July 1996. On June 23, 1997, BL Lac was observed to be at its brightest in 20 years, after which we commenced our intensive monitoring. BL Lac continued to be active during the next two months, flaring numerous times during this period within the range R = 14.2-12.4. Microvariability was observed on several timescales. First, there are the rises and declines, maxima and minima that occur over the entire night (or longer) of amplitude a magnitude or greater. A variability of 0.3-0.4 magnitudes over a six to eight hour period is most common, but occasionally larger changes occur. The maxima are very sharp, lasting only a matter of minutes with slopes of up to 0.4 magnitudes per hour near the peak, while the minima tend to be much more gradual. Secondly, there is variability of 0.04-0.10 magnitude amplitude on timescales of minutes on top of this night-long variation. The most common of these short-term variations seem to be small flares that last 20 to 40 minutes.
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The author(s) of this abstract have provided an email address for comments about the abstract: tbalonek@colgate.edu