The 2009 Fermi Symposium

Photopolarimetric Monitoring Of 41 Blazars In Optical And Near-infrared Bands with the KANATA Telescope

Yuki Ikejiri

Abstract:

Some Active Galactic Nuclei (AGN) have relativistic jets. Blazars are a kind of AGN in which the jet is considered to be directed along the line of sight. Their spectral energy distribution consists of two components, a synchrotron component from radio to X-rays and an inverse-Compton scattering component from X-rays to gamma-rays. Blazars are characterized by strong and rapid variability of the flux and high polarization. While several objects show the trend that they become bluer when brighter, the number of well-observed objects is too small to establish this trend as a common feature in blazars. The number of polarimetric observations is further small. We performed a monitoring of 41 blazars in the optical and near-infrared regions from 2008 to 2009 using TRISPEC attached to the “KANATA” 1.5-m telescope. A photopolarimetric observation can be performed with TRISPEC in the optical and two near-infrared bands, simultaneously. As a result, we found that 24 blazars tend to be bluer when they are brighter and 3 blazars tend to be redder when they are brighter. Lower luminosity objects have smaller gradient ΔV/ Δ(V-J) in the color-magnitude relationship. The variation amplitudes of the V-J color are smaller in lower luminosity objects. We found that the polarization degree in V band significantly correlates with their flux in 10 objects and an.-correlates in 4 objects.