The microvariability and wavelength dependence of polarization degree/angle of BL Lacertae in the outburst 2020 to 2021
Abstract
We have obtained simultaneous and continuous photo-polarization observations of the blazar BL Lacertae in optical and near-infrared (NIR) bands during an historical outburst from 2020 to 2021. In total, 14 nights of observations were performed where 10 observations show microvariability on timescales of a few minutes to several hours. This suggests a compact emission region, and the timescales are difficult to explain by a one-zone shock-in-jet model. Moreover, we found significant differences in the polarization degree (PD) and angle between optical and NIR bands. Nine nights showed a PD in the optical band that is greater than or equal to that in the NIR band, which can be explained by either a shock-in-jet model or the Turbulent Extreme Multi-Zone (TEMZ) model. On the other hand, five nights showed higher PD in an NIR band than an optical band, which cannot be explained by simple shock-in-jet models nor the simple TEMZ model. The observed timescales and wavelength-dependency of the PD and polarization angle suggest the existence of complicated multiple emission regions such as an irregular TEMZ model.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- February 2023
- DOI:
- 10.1093/pasj/psac084
- arXiv:
- arXiv:2211.10300
- Bibcode:
- 2023PASJ...75....1I
- Keywords:
-
- galaxies: individual (BL Lacertae);
- galaxies: jets;
- methods: observational;
- techniques: polarimetric;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 19 pages, 8 figures