The RoboPol Program: Optical Polarimetric Monitoring of Blazars

Abstract

After three years of polarimetric monitoring of blazars, the RoboPol project has uncovered several key characteristics of polarimetric rotations in the optical for these most variable sources. The most important of these is that polarization properties of the synchrotron emission in the optical appear to be directly linked with gamma-ray activity. In this paper, we discuss the evidence for this connection, as well as the broader features of polarimetric behavior in blazars that are key in making progress with theoretical modeling of blazar emission.

Two Flares with One Shock: The Interesting Case of 3C 454.3

“…The values of EVPA in this work are measured from North to East following the IAU convention (IAU Commission 40 1974). The 180 o ambiguity of EVPA was solved by minimization of the following value |EV P A i − EV P A i−1 | − σ(EV P A i ) 2 − σ(EV P A i−1 ) 2 for consecutive measurements (see Blinov & Pavlidou 2019, for related caveats).…”

Blazars from the new window of X-ray polarimetry: IXPE observations of Mrk 421

“…Finally, if turbulence is prevalent in the jet, one can expect a rapid and erratic variability in both Π and Ψ that could lead to canceling the polarization in day-long observations. Rotations of the optical polarization angle (Ψ O ) are another remarkable observational feature of blazars that is now routinely observed [2]. These episodes consist of a smooth, monotonic full rotation of Ψ O that occurs over the course of a few to a few hundred days at a typical rotation rate of a few to a few tenths • /day.…”