Investigation of the Flaring Activity of BL Lac in July–November 2021статья
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Дата последнего поиска статьи во внешних источниках: 15 февраля 2024 г.
Аннотация:The source BL Lac exhibited an enhanced activity fromAugust 2020 to July 2022. This activitypeaked in July–August 2021. In this period the source reached historic brightness maxima in variousenergy ranges. Observations of this nonstandard maximumwere carried out by the SAI staff of the CrimeanStation of SAI and with the telescopes of the Caucasus Mountain Observatory (CMO SAI MSU). Opticaland near-infrared photometric data as well as optical polarimetric data were obtained. When investigatingthe correlation between the optical and gamma-ray fluxes and between the optical and infrared fluxes, itshigh degree with an almost zero lag was confirmed—thismeans that the emission regions spatially coincideor are very close together. The degree of linear polarization in the investigated period changed in a widerange, reaching 20%, with an anticorrelation between the degree of linear polarization and the brightnessof the object having been observed. A similar pattern of variation was also observed in the preceding flaresof this object. The changes in the electric vector position angle (EVPA) show a dependence on the rate ofchange of the object’s brightness. The EVPA changed greatly during flares and slowly at the times of aslow change in the intensity.