Variability of BL Lac in the RATAN-600 radio telescope measurements
ATel #15709; S. A. Trushkin, N. N. Nizhelskij, P. G. Tsybulev (SAO RAS)
on 22 Oct 2022; 15:37 UT
Credential Certification: Sergei Trushkin (satr@sao.ru)
Subjects: Radio, AGN, Blazar
Referred to by ATel #: 15730
On October 17-20 2022 in frame of testing measurements after the antenna adjustment of RATAN-600 we have carried out observations at 4.7, 8.2 and 21.7 GHz of the blazar BL Lacertae,
which is very bright in the optical band (ATel #15684) and in the gamma-rays (ATel #15688). Our measured fluxes are 3.64+/-0.2Jy, 5.53+/-0.2 Jy and 5.4+/-0.2 Jy at 4.7 GHz, 11.2, and 21.7 GHz respectively, that is in well accordance with almost simultaneous measurements
with the Medicina 32m radio telescope by Marchili et al. (ATel #15705). Using similar archive data of the RATAN-600 observations from 2000 we followed for the variations of the radio spectra especially during last eight years. We propose that a fast increase of fluxes at 8.2 and 21.7 GHz (~2.5 times) happened from November 2020 to November 2021, when a normal optically thin spectrum (the spectral index of the power-law fitting SpI was equal to -0.35) became the optically thick with SpI=+0.3. This detailed data is presented in the figure below.
Radio spectra evolution of the Bl Lac
