Decadal optical outbreak of BL Lac as observed at the Hans-Haffner-Sternwarte

ATel #13958; Remco Steineke, Lukas Waller, David Reinhart, Felix Hemrich, Kilian Schoch, Johannes Knoett, Nils Zottmann, Martin Feige, Christian Lorey (all Friedrich-Koenig-Gymnasium / Hans-Haffner-Sternwarte), Karl Mannheim (Universitaet Wuerzburg), Dominik Elsaesser (TU Dortmund)
on 21 Aug 2020; 08:57 UT
Credential Certification: Dominik Elsaesser (dominik.elsaesser@tu-dortmund.de)

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BL Lacertae (ICRS coords. (ep=J2000): RA 22 02 43.291 Dec +42 16 39.978) is the prototype of a subclass of AGN, the BL Lac objects.
Since July 22nd within the AGN monitoring program at the Naturwissenschaftliches Labor fuer Schueler am Friedrich-Koenig-Gymnasium (FKG) we have observed a strong increase in optical brightness, as has already been reported by other observers (ATEL#13930, ATEL#13956). Increased activity has also been detected in the gamma-ray regime (ATEL#13933).

In the last few nights, our data show that the increase in brightness observed over a period of 4 weeks (delta R mag circa 1.75) has continued although potentially slowing down. No firm trend can yet be deduced and we thus strongly encourage continued multi - wavelength and multi - messenger monitoring of this decadal optical maximum. The current outbreak is even brighter than the ones measured in May 2011 (R mag = 12.71; ATEL#3371), July 2012 (R mag = 12.60; ATEL#4271) and November 2013 (R mag = 12.34; ATEL#5597). Since that time, typical maximums of outbreaks had reached R - band brightness peaks in between 13 and 14 mag.

Here, we are reporting:


R - band magnitudes:

JD 2459053.4533: 13.731 +/- 0.004
JD 2459058.4053: 13.411 +/- 0.005
JD 2459060.4794: 13.317 +/- 0.003
JD 2459062.4598: 12.958 +/- 0.003
JD 2459067.4308: 13.055 +/- 0.004
JD 2459068.4662: 12.823 +/- 0.003
JD 2459069.3893: 12.703 +/- 0.003
JD 2459070.4651: 12.422 +/- 0.003
JD 2459079.3412: 12.108 +/- 0.003
JD 2459080.4978: 11.976 +/- 0.003
JD 2459081.4186: 12.082 +/- 0.002
JD 2459082.4149: 12.019 +/- 0.002
JD 2459082.5432: 11.918 +/- 0.002
JD 2459082.5758: 11.890 +/- 0.002


V - band magnitudes:

JD 2459053.4551: 14.460 +/- 0.005
JD 2459058.4073: 14.115 +/- 0.008
JD 2459060.4812: 14.029 +/- 0.004
JD 2459062.4616: 13.622 +/- 0.004
JD 2459067.4326: 13.757 +/- 0.005
JD 2459068.4681: 13.522 +/- 0.005
JD 2459069.3911: 13.412 +/- 0.004
JD 2459070.4669: 13.094 +/- 0.005
JD 2459079.3431: 12.762 +/- 0.004
JD 2459080.4941: 12.625 +/- 0.003
JD 2459081.4205: 12.740 +/- 0.003
JD 2459082.4169: 12.687 +/- 0.003
JD 2459082.5450: 12.574 +/- 0.003
JD 2459082.5776: 12.545 +/- 0.003


B - band magnitudes:

JD 2459053.4569: 15.477 +/- 0.009
JD 2459058.4092: 15.132 +/- 0.015
JD 2459060.4830: 15.011 +/- 0.007
JD 2459062.4634: 14.564 +/- 0.008
JD 2459067.4344: 14.768 +/- 0.011
JD 2459068.4700: 14.481 +/- 0.009
JD 2459069.3930: 14.370 +/- 0.008
JD 2459070.4688: 14.019 +/- 0.009
JD 2459079.3450: 13.689 +/- 0.007
JD 2459080.4959: 13.516 +/- 0.006
JD 2459081.4223: 13.641 +/- 0.005
JD 2459082.4189: 13.593 +/- 0.005
JD 2459082.5468: 13.472 +/- 0.005
JD 2459082.5794: 13.465 +/- 0.005



These measurements are carried out as part of the long-term AGN monitoring program of the Naturwissenschaftliches Labor fuer Schueler am Friedrich-Koenig-Gymnasium (FKG), the Universitaet Wuerzburg, and TU Dortmund with the 0.5m telescope at the school and university observatory Hans-Haffner-Sternwarte in Hettstadt (Germany). We encourage contact to our team in case coordinated observations are desired.

Naturwissenschaftliches Labor fuer Schueler am Friedrich-Koenig-Gymnasium (FKG)