The strong flaring activity of M87 in early 2008 as observed by the MAGIC telescope

TL;DR

This paper reports on the detection of a rapid, day-scale gamma-ray flare from M87 in 2008 by MAGIC, indicating the core as the likely emission source due to observed variability.

Contribution

It provides the first detailed observation of a rapid VHE gamma-ray flare from M87, supporting the core as the emission origin.

Findings

Flux varied on a 1-day timescale

Flux reached 15% of Crab Nebula above 350 GeV

Lower energy flux remained constant

Abstract

M87 is the first known radio galaxy to emit very high energy (VHE) gamma-rays. During a monitoring program of M87, a rapid flare in VHE gamma-rays was detected by the MAGIC telescope in early 2008. The flux was found to be variable on a timescale as short as 1 day, reaching 15% of the Crab Nebula flux above 350 GeV. In contrast, the flux at lower energies (150 GeV to 350 GeV) is compatible with being constant. We present light curves and energy spectra, and argue that the observed day-scale flux variability favours the M87 core as source of the gamma-ray emission rather than the bright know HST-1 in the jet of M87.