Optical brightening of BL Lacertae

ATel #15684; A. Marchini (University of Siena, Italy), F. Mortari, D. Gabellini (Hypatia Observatory, Rimini, Italy), T. Grishina, E. Kopatskaya, S. Savchenko (Saint Petersburg State University, Russia), M. Joner, D. Watts, M. Holland (Brigham Young University, Provo, USA), C. M. Raiteri, M. Villata (INAF-Osservatorio Astrofisico di Torino, Italy), G. Bonnoli (INAF-Osservatorio Astronomico di Brera, Italy)
on 15 Oct 2022; 19:45 UT
Credential Certification: Claudia M. Raiteri (claudia.raiteri@inaf.it)

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We report on a new optical flaring state of BL Lacertae. The blazar is regularly monitored in the framework of the GASP Project of the Whole Earth Blazar Telescope (WEBT; https://www.oato.inaf.it/blazars/webt/) Collaboration. Observations with the 90-cm telescope of the BYU West Mountain Observatory on October 11 (UT) showed:
JD=2459863.75728 R=12.177
JD=2459863.75794 R=12.173
JD=2459863.75861 R=12.169
JD=2459863.75927 R=12.176
while some hours later the LX-200 40-cm telescope of the Saint Petersburg University recorded:
JD=2459864.4091 R=12.02
JD=2459864.4174 R=12.04
On October 13 the same telescope registered:
JD=2459866.1778 R=11.92
JD=2459866.1843 R=11.94
JD=2459866.2520 R=11.94
JD=2459866.2591 R=11.91
The source was observed a bit later with the 25-cm telescope of the Hypatia Observatory:
JD=2459866.36454 R=11.986
JD=2459866.36933 R=11.974
JD=2459866.37653 R=11.991
JD=2459866.37892 R=12.009
JD=2459866.38373 R=12.030
After a sudden brightness increase of about 0.2 mag, a maximum brightness state:
JD=2459867.55454 R=11.827
was detected on October 15 by the 30-cm telescope of the University of Siena.
Then the source faded slightly; observations at the West Mountain Observatory show:
JD=2459867.77145 R=11.860
JD=2459867.77208 R=11.855
JD=2459867.77272 R=11.855
JD=2459867.77336 R=11.866
JD=2459867.77400 R=11.879
Errors are typically around 0.01 mag.
Multiwavelength observations are encouraged.