Infrared polarization and variability of blazarst

Correlation between the polarizations in the near-infrared and optical wavebands is studied with simultaneous observational data of blazars. It is found that the degree and angle of polarization in the near-infrared are correlated strongly with those in the optical. And so are the radiation fluxes at the two wavebands. It follows that the near-infrared radiation and polarization of blazars are mainly from synchrotron radiation of relativistic electrons, and come from the same region as the optical waveband. Correlations between the three near-infrared color indices J-H, H-K and J-K are also studied using the 2MASS data. It is found that both J-H and H-K are strongly correlated with J-K, while there is no correlation between J-H and H-K. Lastly, we studied the color index magnitude relationship and found that the near-infrared spectrum gets flatter as the source gets brighter.