GRB 081029: Understanding Multiple Afterglow Components

TL;DR

This paper analyzes the complex optical and X-ray afterglow of GRB 081029, revealing that a multi-component jet model better explains the unusual light curve features than a single-component model.

Contribution

It introduces a multi-component jet model to explain the unusual afterglow features of GRB 081029, challenging previous single-component jet interpretations.

Findings

Optical afterglow shows an uncharacteristic rise at 5000 s.

X-ray afterglow exhibits a shallow decay followed by rapid decay.

Single-component jet models are inconsistent with observed data.

Abstract

We present an analysis of the unusual optical light curve of the gamma-ray burst GRB~081029, which occurred at a redshift of z = 3.8479$. We combine X-ray and optical observations from the Swift X-Ray Telescope and the Swift UltraViolet/Optical Telescope with optical and infrared data obtained using the REM and ROTSE telescopes to construct a detailed data set extending from 86 s to approximately 100,000 s after the BAT trigger. Our data also cover a wide energy range, from 10 keV to 0.77 eV (1.24 Angstrom to 16,000 Angstrom). The X-ray afterglow shows a shallow initial decay followed by a rapid decay starting at about 18,000s. The optical and infrared afterglow, however, shows an uncharacteristic rise at about 5000 s that does not correspond to any feature in the X-ray light curve. Our data are not consistent with synchrotron radiation from a single-component jet interacting with an external medium. We do, however, find that the observed light curve can be explained using multi-component model for the jet.