Enhancement of optical flux from the active blazar BL Lacertae

ATel #12722; Alessandro Marchini (Astronomical Observatory, Department of Physical Sciences, Earth and Environment (DSFTA), University of Siena - Italy), Giacomo Bonnoli, Lorenzo Bellizzi, Vincenzo Millucci, Riccardo Paoletti, Leonardo Stiaccini, Stefano Truzzi, Sofia Ventura (DSFTA, University of Siena - Italy), Paolo Da Vela (INFN-Pisa), Massimo Conti, Claudio Vallerani (Astronomical Observatory, University of Siena - Italy).
on 3 May 2019; 17:01 UT
Credential Certification: Giacomo Bonnoli (giacomo.bonnoli@unisi.it)

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We report that the blazar BL Lacertae (RA: 22 02 43.29 Dec: +42 16 39.98 J2000.0) reached on May 2.10 the optical magnitude R=12.80(0.01). The blazar is currently very active in gamma rays too, as reported by the Fermi Large Area Telescope Collaboration (see ATel #12718). We are monitoring it from the Astronomical Observatory of the University of Siena within our program devoted to known or potential TeV-emitting blazars. The following table reports our last BVRI measurements:

Civil Date(UT) Mag (dMag)
2019 May 2.11 B= 14.47 (0.02)
2019 May 2.10 V= 13.39 (0.01)
2019 May 2.10 R= 12.80 (0.01)
2019 May 2.10 I= 12.08 (0.01)


These measurements were obtained using the photometric sequence made available by the WEBT Collaboration (http://www.oato.inaf.it/blazars/webt/gasp/fc/2200fc.html ).
Regarding the reported R magnitude, we stress that similar or lower magnitudes have been reached only a few (4-5) times along the last 15 years according to the long term monitoring made publicly available by the Tuorla Observatory at http://users.utu.fi/kani/1m/BL_Lac.html .

Any enquiry on these observations can be addressed either to Alessandro Marchini (alessandro.marchini@unisi.it) or to Giacomo Bonnoli (giacomo.bonnoli@unisi.it). We will continue monitoring the source in the following nights. Multi-wavelength follow-up is encouraged.

We acknowledge excellent scientific cooperation with, and valuable support from, the WEBT Collaboration, the Tuorla Observatory and the MAGIC Collaboration.
A brief description of the instrumental setup is available at the official webpage of the Astronomical Observatory of the University of Siena (see link below).

Astronomical Observatory of the University of Siena - Official Webpage