Swift and Fermi observations of the early afterglow of the short Gamma-Ray Burst 090510

TL;DR

This paper reports multi-wavelength observations of the short gamma-ray burst GRB090510, revealing unique early afterglow features that challenge existing models and provide new insights into short burst physics.

Contribution

It presents the first detailed analysis of early optical and GeV emissions in a short GRB, highlighting behaviors previously observed only in long bursts.

Findings

Extended GeV emission detected by Fermi.

Optical emission initially rises, unlike typical short bursts.

X-ray flux shows a shallow initial decline followed by steepening.

Abstract

We present the observations of GRB090510 performed by the Fermi Gamma-Ray Space Telescope and the Swift observatory. This is a bright, short burst that shows an extended emission detected in the GeV range. Furthermore, its optical emission initially rises, a feature so far observed only in long bursts, while the X-ray flux shows an initial shallow decrease, followed by a steeper decay. This exceptional behavior enables us to investigate the physical properties of the GRB outflow, poorly known in short bursts. We discuss internal shock and external shock models for the broadband energy emission of this object.