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Session 36 - Active Galactic Nuclei.
Display session, Tuesday, June 09
Atlas Ballroom,

[36.01] Examining Correlations between the Gamma-Ray and Optical Emission of Blazars

S. Bloom (NASA/GSFC/NRC), P. Sreekumar (NASA/GSFC/USRA)

We have analyzed the relationship between gamma-ray and optical emission during flaring and non-flaring states of blazars. During the flaring states, we note that there is a moderate correlation between gamma-ray and optical fluxes for some sources, with a possible redshift dependence of the correlation slope. Upon considering all of the EGRET/optical data from non-flaring states as well, we find a striking dependence of the gamma-ray to optical flux ratio on redshift. Though, its is unclear whether this is truely a redshift dependence or a correlation with luminosity. In general, for large samples of blazars, high z objects will tend to have higher Doppler factors, as inferred from VLBI. Thus, if the detected gamma-ray emission were to have a separate dependence on the Doppler beaming factor than the synchrotron emission, as is the case for external Compton scattering models, we would expect a redshift dependence of the gamma-ray/optical ratio. An alternative explanation is that certain processes are most efficient (and will dominate the SED) at higher luminosity. We discuss these findings in light of recent modeling of the SED's of blazars and consideration of possible selection effects.

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Program listing for Tuesday