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Optical polarization plane rotation for the blazar PG 1553+113

ATel #9458; D. Blinov (Univ. of Crete, Greece, St. Petersburg Univ., Russia), C. Casadio (MPIfR, Germany) on behalf of the RoboPol collaboration
on 5 Sep 2016; 21:19 UT
Credential Certification: Dmitriy Blinov (blinov@physics.uoc.gr)

Subjects: Optical, Gamma Ray, AGN, Black Hole

We report about RoboPol observations of the ongoing rotation of the optical polarization angle for the blazar PG 1553+113 (RA=15h55m43s; Dec=+11d11m24s). The rotation began around August, 19. So far the total amplitude of the rotation is ~130 degrees with an average rate of ~8 deg/day. During the rotation the polarization degree has been varying between 6.8% and 0.8%. At the same time the R-band light curve is showing a moderate flare reaching 9 mJy. Preliminary analysis of the publicly available Fermi LAT data for the source 3FGL J1555.7+1111 gives the average photon flux (E>100MeV) (7.9+/-1.2)x10^-8 ph cm^-2 s^-1 during the rotation period, while the average photon flux reported in 3FGL catalog is (5.7+/-0.5)x10^-8 ph cm^-2 s^-1. Multifrequency observations of the blazar 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).