We derive analytic formulas for the radiation power output when electrons are
accelerated by a relativistic comoving kinetic Poynting flux, and validate
these analytic results with Particle-In-Cell simulations. We also derive
analytically the critical frequency of the radiation spectrum. Potential
astrophysical applications of these results are discussed. A quantitative model
of gamma-ray bursts based on the breakout of kinetic Poynting flux is
presented.Comment: 30 pages 8 figures, resubmitted to ApJ, replaces earlier preprint
titled "Radiation from Kinetic Poynting Flux Acceleration" (arXiV:0704.1843);
most of the paper has been rewritte