The bright optical/NIR afterglow of the faint GRB 080710 - Evidence for a jet viewed off axis

TL;DR

This paper analyzes the optical and near-infrared afterglow of GRB 080710, providing evidence that its rising light curve is due to an off-axis jet view, which has implications for understanding GRB geometries.

Contribution

It presents a model explaining the early rising afterglow as a result of an off-axis jet view, offering a new perspective on GRB afterglow light curves.

Findings

The afterglow's light curve is dominated by an initial rise followed by a shallow decay.

An off-axis jet model can explain the rising optical/NIR afterglow.

Late and shallow rises in GRB afterglows may be due to geometric effects.

Abstract

We investigate the optical/near-infrared light curve of the afterglow of GRB 080710 in the context of rising afterglows. Optical and near-infrared photometry was performed using the seven channel imager GROND and the Tautenburg Schmidt telescope. X-ray data were provided by the X-ray Telescope onboard the Swift satellite. The optical/NIR light curve of the afterglow of GRB 080710 is dominated by an initial increase in brightness, which smoothly turns over into a shallow power law decay. The initially rising achromatic light curve of the afterglow of GRB 080710 can be accounted for with a model of a burst viewed off-axis or a single jet in its pre deceleration phase and in an on-axis geometry. An unified picture of the afterglow light curve and prompt emission properties can be obtained with an off-axis geometry, suggesting that late and shallow rising optical light curves of GRB afterglows might be produced by geometric effects.