Author comment for 2006ApJ...642L.115H:
In this paper we presented a new method of deducing characteristic intrinsic brightness temperatures of AGN jet cores. We also compared the derived brightness temperatures to a canonical equipartition temperature of ~ 5 x 10^10 K. We have recently investigated in more detail the complex dependence of equipartition brightness temperature on the assumed source geometry. Given that the true source geometries should be represented by inhomogeneous cones at different lines of sight rather than simpler geometries (e.g., uniformly bright disks or homogeneous spheres), we estimate a reasonable range of equipartition brightness temperature is from 5 x 10^10 K up to 1.0 x 10^11 K. This does not seriously impact the results of our paper; however it does mean that for "median-low" states, the characteristic brightness temperature we deduced of 3 x 10^10 K should be considered to be at or below equipartition, rather than close to it. In the high states, our limit on the characteristic intrinsic temperature of > 2 x 10^11 K is still above equipartition, but not by as wide a margin as we originally suggested in the paper. We note that this uncertainty in the value of the equipartition brightness temperature does not affect the characteristic intrinsic brightness temperatures we deduced for the two states, and it is still true that between the median-low and high brightness temperature states the characteristic intrinsic brightness temperature increases by nearly an order of magnitude, indicating a large increase in the ratio of particle to field energy.
Author comment submitted on 24 October, 2006 by Daniel Homan (homand@denison.edu)