Polarimetric Properties of Blazars Caught by the WEBT

Abstract

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called "blazars". The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the gamma-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

Review published in "Galaxies" as part of the Special Issue "Polarimetry as a Probe of Magnetic Fields in AGN Jets", Academic Editors: Margo Aller, Jose L. Gómez and Eric Perlman

References in corpus (9)

• Probing the Inner Jet of the Quasar PKS 1510-089 with Multi-waveband Monitoring during Strong Gamma-ray Activity
• Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007
• Multifrequency monitoring of the blazar 0716+714 during the GASP-WEBT-AGILE campaign of 2007
• RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
• Rapid Multiwaveband Polarization Variability in the Quasar PKS 0420-014: Optical Emission from the Compact Radio Jet
• The dual nature of blazar fast variability. Space and ground observations of S5 0716+714
• Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio
• The Outburst of the Blazar S40954+658 in March-April 2011
• Polarization swings in blazars

Cited by in corpus (9)

• The optical behaviour of BL Lacertae at its maximum brightness levels: a blend of geometry and energetics
• Variability and evolution of the optical polarization of a sample of gamma-ray blazars
• Blazar variability with the Vera C. Rubin Legacy Survey of Space and Time (LSST)
• Observational Implications of OJ 287's Predicted 2022 Disk Impact in the Black Hole Binary Model
• Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
• Polarization Studies in Different Blazar Types. Part I: Correlation between Optical Brightness and Polarization Degree
• Insights into the Long-term behavior of the optical polarization from the blazar 1ES 1959+650
• The observed polarization direction depending on geometrical and kinematic parameters of relativistic jets
• Peculiar Behavior of Optical Polarization in Blazar 1ES 1959+650: Role of Jet Magnetic Field and Geometry