ATOM observations of continuing record flares of BL Lac objects BL Lacertae and PKS 0447-439

ATel #13956; F. Jankowsky, S. Wagner (LSW Heidelberg)
on 20 Aug 2020; 12:57 UT
Credential Certification: Felix Jankowsky (f.jankowsky@lsw.uni-heidelberg.de)

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Preliminary analysis of observations with the Automatic Telescope for Optical Monitoring (ATOM) reveal continued brightening of the optical flux of BL Lacertae (z=0.069). Observations conducted during the nights from 18 to 20 August 2020 resulted in several detections at R < 12.0 while showing significant intra-night variability. This optical brightness marks the historic maximum of BL Lacertae. BL Lacertae has already been reported as flaring in optical (ATel #13930) and high-energy gamma-rays (ATel #13933).

We also report a continuous optical flare in PKS 0447-439 (z=1.107) following the historic high state reported in ATel #13906. Since then, PKS 0447-439's optical emission has shown considerable variability, reaching a new high point at R=13.0 during the night from 18 to 19 August (MJD 59080.13).

Further multi-wavelength observations of both sources are encouraged.

ATOM is a 75cm optical telescope located at the H.E.S.S. site in Namibia. It monitors optical flux of known gamma-ray emitters since 2005. PKS 0447-439 -- one of the brightest blazars as seen with Fermi-LAT -- and BL Lacertae both form part of ATOM's monitoring programme since 2009.