Multicolor-optical observation of the flaring blazar BL Lacertae
ATel #14334; R. Hosokawa, K. L. Murata, M. Niwano, S. Wang, R. Adachi, F. Ogawa, N. Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration
on 20 Jan 2021; 06:14 UT
Credential Certification: Katsuhiro Murata (murata@hp.phys.titech.ac.jp)
Subjects: Optical, Blazar
The flaring blazar BL Lacertae was in the bright state in optical, X-ray and gamma-ray around August 2020 (ATel #13930, #13933, #13956, #13958, #13963, #13964) and in another bright state around October 2020 (ATel #14065, #14069, #14072, #14081, #14096). After that, it was brightening from the end of December 2020, and the brightness reached at R=11.5 on UTC January 17.8, 2021 (ATel #14328, #14329).
We monitored the blazar BL Lac with optical three bands (g', Rc, and Ic) using the MITSuME 50 cm Telescopes at Akeno Observatory and Okayama Astrophysical Observatory in Japan. We found that the optical brightness increased from g'=14.3+/-0.1, Rc=13.4+/-0.1, Ic=12.7+/-0.1 on December 25, 2020 (MJD 59208.39) with g'~0.074 mag/day, Rc~0.065 mag/day and Ic~0.056 mag/day, and reached g'=12.6+/-0.1, Rc=11.9+/-0.1, Ic=11.4+/-0.1 on January 17, 2021 (MJD 59231.40). The color became bluer when brightness increased.
We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al., https://doi.org/10.1093/pasj/psaa091, https://arxiv.org/abs/2008.11486; https://github.com/MNiwano/Eclaire).
