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Rotation of the optical polarization plane for the blazar OC 457

ATel #8254; I. Liodakis (U. Crete), T. Hovatta (Aalto U.), G. Panopoulou (U. Crete)
on 7 Nov 2015; 19:06 UT
Credential Certification: Talvikki Hovatta (talvikki.hovatta@aalto.fi)

Subjects: Optical, Blazar

We report RoboPol optical polarimetric observations of the ongoing rotation of the electric vector position angle (EVPA) in blazar OC 457 (a.k.a S4 0133+47, RA:01 36 58.60 Dec:+47 51 29.0). The rotation began between the 20th of September and 5th of October. So far the total amplitude of the rotation is approximately 217 degrees with an average rate of 5 degrees/day. During the rotation the polarization degree has been varying between 3% and 12% while the average R-band magnitude is 16.6 with no clear flare. According to the Fermi LAT data, there is no significant increase in the gamma-ray flux either. Multi-wavelength observations are encouraged.

The RoboPol program aims at understanding the AGN physics through optical linear polarization monitoring of a large sample of gamma-ray loud blazars as well as a comparison sample of gamma-ray quiet ones. It utilizes a novel-design 4-channel optical polarimeter mounted at the 1.3-m Skinakas telescope in Crete. It is a collaboration between the University of Crete (Greece), Max-Planck-Institut fur Radioastronomie (Germany), California Institute of Technology (USA), Nicolaus Copernicus University (Poland) and the Inter-University Centre for Astronomy and Astrophysics, (India).