July 24, 2012: The blazar BL Lac, the prototype of this class of variable objects, has brightened in the optical and radio wavelengths. ATel #4271 (Sh. A. Ehgamberdiev et al., http://www.astronomerstelegram.org/?read=4271) on July 23 announced this brightening. The ATel team reported that "the source brightness has recently increased from R = 13.66 +/- 0.01 on July 19.82 to R = 12.60 +/- 0.01 on July 22.97. This episode is similar to those that occurred in June 2012 (Atel #4155) and May 2011 (ATel #3371)."
Gary Poyner (Birmingham, England) reported BL Lac in outburst on 2012 July 23.057 UT at visual magnitude 13.2 (cvnet-outburst 4840).
As Mike Simonsen (Imlay City, MI) notes in his 2012 July 23 posting to the AAVSO Campaigns and Observation Reports forum (http://www.aavso.org/forums/variable-star-observing/campaigns-observation-reports, http://www.aavso.org/bl-lac-outburst), observations in the AAVSO International Database (AID) indicate that BL Lac has not been this bright since August 2004, when it reached visual magnitude 12.9 and was bright for about a month. Previous to the 2004 brightening, as shown in the AID, BL Lac had gone through a series of brightenings 1997-2004, reaching visual magnitude 13.0.
Recent observations reported to the AAVSO include: 2012 Jul 11.9201 UT, 14.6 (K. Wenzel, Grossostheim, Germany); 11.9208, <14.3 (J. Ripero Osorio, Madrid, Spain); 12.2813, 14.5 (M. Simonsen, Imlay City, MI); 15.9028, <14.3 (Ripero Osorio); 17.8993, 14.0 (Ripero Osorio); 18.9785, 14.4 (P. Dubovsky, Kolonica, Slovakia); 20.0158, 13.7 (Ripero Osorio); 21.0162, 13.6 (Ripero Osorio); 21.2129, 13.761 V +/-0.004 (B. Harris, New Smyrna Beach, FL); 21.9549, 13.1 (Wenzel); 22.3754, 13.665 V +/-0.004 (Harris); 23.0570, 13.2 (G. Poyner, Birmingham, England); 23.3932, 13.190 V +/-0.005 (Harris); 23.3968, 13.196 V +/-0.004 (Harris); 23.4005, 13.202 V +/-0.004 (Harris); 23.4071, 13.213 V +/-0.013 (Harris); 23.8924, 13.0 (Wenzel); 23.8931, 13.4 (W. Kriebel, Schierling/Walkenstetten, Germany); 23.9035, 13.5 (Dubovsky); 23.9460, 13.2 (Poyner);
Coordinates: 22 02 43.29 +42 16 39.9 (2000.0)
Charts for BL Lac may be created using the AAVSO Variable Star Plotter (VSP): http://www.aavso.org/vsp
Please report observations to the AAVSO International Database as BL LAC.
This AAVSO Special Notice was compiled by Elizabeth O. Waagen.
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