Fermi Gamma-ray Space Telescope

Optical and Radio Polarization of Fermi Blazars

Talvikki Hovatta
On behalf of the OVRO and RoboPol collaborations

Abstract:

We present results from two ongoing monitoring programs that observe blazars in linear polarization. RoboPol has been observing about 100 blazars in the Fermi sample since June 2013 in the optical R band. Observations of all sample sources are conducted with the 1.3m telescope at Skinakas Observatory in Crete on average twice per week. In the radio band, a new polarimetric receiver was installed on the Owens Valley Radio Observatory 40m telescope in May 2014. Observations of about 1800 sources, including all Fermi-detected blazars in the 2FGL sample, are obtained twice per week at 15 GHz. The results from the first season of RoboPol observations show that Fermi detected blazars are more polarized than the non-detected sources. Rotations in optical polarization angle also seem to be connected to gamma-ray events. The calibration of the 15 GHz linear polarization data is still ongoing and I will present some preliminary results from the monitoring, comparing the Fermi detected and non-detected objects.