Discovery of Powerful Gamma-Ray Flares from the Crab Nebula

TL;DR

This paper reports the discovery of intense gamma-ray flares from the Crab Nebula, revealing rapid, powerful emissions that challenge existing models and suggest new acceleration mechanisms near the pulsar.

Contribution

It presents the first detection of strong gamma-ray flares from the Crab Nebula, indicating rapid particle acceleration and challenging standard nebular emission models.

Findings

Gamma-ray flux increased by a factor of 3 during flares.

Flares originate near the pulsar within approximately one day.

Standard models of nebular emission are challenged by these observations.

Abstract

The well known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally-powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here we report the detection of strong gamma-ray (100 MeV-10 GeV) flares observed by the AGILE satellite in September, 2010 and October, 2007. In both cases, the unpulsed flux increased by a factor of 3 compared to the non-flaring flux. The flare luminosity and short timescale favor an origin near the pulsar, and we discuss Chandra Observatory X-ray and HST optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within a ~1-day timescale.