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 a historical outburst from 2020 to 2021. In total, fourteen nights of observations were performed where ten 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 a 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.

19 pages, 8 figures

References in corpus (32)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• The Relation between Black Hole Mass, Bulge Mass, and Near-Infrared Luminosity
• The Spectral Energy Distribution of Fermi bright blazars
• The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
• Leptonic and Hadronic Modeling of Fermi-Detected Blazars
• Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Jet Kinematics from Bimonthly Monitoring with the Very Long Baseline Array
• Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars
• Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization
• The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei from Reverberation Mapping and Hubble Space Telescope Imaging
• Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
• RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars
• RoboPol: First season rotations of optical polarization plane in blazars
• Optical microvariability of EGRET blazars
• The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation
• Longterm Optical Monitoring of Bright BL Lacertae Objects with ATOM: Spectral Variability and Multiwavelength Correlations
• Kepler observations of rapid optical variability in the BL Lac object W2R1926+42
• Extremely violent optical microvariability in blazars: fact or fiction?
• Detection of Polarimetric Variations Associated with the Shortest Time-Scale Variability in S5 0716$+$714
• The dual nature of blazar fast variability. Space and ground observations of S5 0716+714
• Nature of Intra-night Optical Variability of BL Lacertae
• Frequency and Time Dependence of Linear Polarization in Turbulent Jets of Blazars
• Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare
• A Fast Very High Energy $\gamma$-ray Flare from BL Lacertae during a Period of Multiwavelength activity in June 2015
• Is BL Lacertae an "orphan" AGN? Multiband and spectroscopic constraints on the parent population
• Discovery of VHE gamma-ray emission from the BL Lac object B3 2247+381 with the MAGIC telescopes
• The jet collimation profile at high resolution in BL Lacertae
• Spectral States of OJ 287 blazar from Multi-wavelength Observations with $AstroSat$
• Understanding the General Feature of Microvariability in $Kepler$ Blazar W2R 1926$+$42
• Extreme HBL-like behavior of Markarian 421 and its two-zone photohadronic interpretation
• Measurement of Interstellar Polarization and Estimation of Galactic Extinction for the Direction of X-ray Black Hole Binary V404 Cygni
• Variations of the physical parameters of the blazar Mrk 421 based on the analysis of the spectral energy distributions

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