Gamma-Ray and Multi-Wave Band Emission from Gamma-Ray-loud Blazars

Abstract

Using multiwave band data for 61 -rayloud blazars (17 BL Lacertae objects and 44 flat-spectrum radio quasars [FSRQs]), we have studied the possible correlation between flux densities (FR, FK, FO, FX, and F) in the radio, infrared, optical, X-ray, and -ray wave bands, in both the low and high states. For some blazars, it is hard to determine whether they are in a low or a high state because only one data point is available for each of them; initially, we exclude these blazars in our analysis. However, we include these blazars in later analysis by temporarily assuming them to be in a low state or a high state. Our main results are as follows. There are very strong correlations between FX and FO and between FO and FK in both low and high states. However, a strong correlation between FX and FK exists only in the low state. No definite correlation is found between -ray flux density and those of lower energy bands; however, there are hints of anticorrelation between F and FX as well as F and FO and a positive correlation between F and FR. From these results we suggest that (1) photons from infrared to X-rays are emitted by the same particles via synchrotron radiation and (2) if -rays are mainly produced by an inverse Compton scattering mechanism, it seems that the up-scattered soft photons are from external photons rather than synchrotron photons.