Gamma-ray burst afterglow scaling relations for the full blast wave evolution

TL;DR

This paper introduces a scaling method for gamma-ray burst afterglow spectra and light curves, enabling efficient modeling across various parameters using minimal baseline calculations, thus improving fitting accuracy and late-time analysis.

Contribution

It presents a novel scaling approach that allows full afterglow light curve modeling from a single baseline simulation for each jet and observer angle.

Findings

Scaling relations enable quick generation of light curves for different parameters.

Jet break significantly influences synchrotron and cooling break frequencies.

Late-time Sedov-Taylor transition shape is now well-characterized for arbitrary explosion parameters.

Abstract

We demonstrate that gamma-ray burst afterglow spectra and light curves can be calculated for arbitrary explosion and radiation parameters by scaling the peak flux and the critical frequencies connecting different spectral regimes. Only one baseline calculation needs to be done for each jet opening angle and observer angle. These calculations are done numerically using high-resolution relativistic hydrodynamical afterglow blast wave simulations which include the two-dimensional dynamical features of expanding and decelerating afterglow blast waves. Any light curve can then be generated by applying scaling relations to the baseline calculations. As a result, it is now possible to fully fit for the shape of the jet break, e.g. at early time X-ray and optical frequencies. In addition, late-time radio calorimetry can be improved since the general shape of the transition into the Sedov-Taylor regime is now known for arbitrary explosion parameters so the exact moment when the Sedov-Taylor asymptote is reached in the light curve is no longer relevant. When calculating the baselines, we find that the synchrotron critical frequency and the cooling break frequency are strongly affected by the jet break. The synchrotron break temporal slope quickly drops to the steep late time Sedov-Taylor slope, while the cooling break first steepens then rises to meet the level of its shallow late time asymptote.