Modeling Synchrotron Self-Compton and Klein-Nishina Effects in Gamma-Ray Burst Afterglows

TL;DR

This paper introduces a self-consistent model for SSC and Klein-Nishina effects in gamma-ray burst afterglows, showing these effects significantly alter spectral shapes and can lead to misinterpretation of physical parameters if neglected.

Contribution

It provides an analytic approximation for SSC effects including Klein-Nishina suppression, integrated into afterglow modeling, improving accuracy over previous synchrotron-only models.

Findings

SSC effects significantly modify X-ray light curves.

Neglecting SSC leads to incorrect physical parameter estimates.

Inclusion of SSC effects improves broadband fit accuracy.

Abstract

We present a self-consistent way of modeling synchrotron self-Compton (SSC) effects in gamma-ray burst afterglows, with and without approximated Klein-Nishina suppressed scattering. We provide an analytic approximation of our results, so that it can be incorporated into the afterglow modeling code \texttt{boxfit}, which is currently based on pure synchrotron emission. We discuss the changes in spectral shape and evolution due to SSC effects, and comment on how these changes affect physical parameters derived from broadband modeling. We show that SSC effects can have a profound impact on the shape of the X-ray light curve using simulations including these effects. This leads to data that cannot be simultaneously fit well in both the X-ray and radio bands when considering synchrotron-only fits, and an inability to recover the correct physical parameters, with some fitted parameters deviating orders of magnitude from the simulated input parameters. This may have a significant impact on the physical parameter distributions based on previous broadband modeling efforts.