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Very high energy gamma-ray observations of strong flaring activity in M87 in 2008 February
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M87 is the only known nonblazar 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 above 350 GeV on a timescale as short as 1 day at a significance level of 5.6 σ. The highest measured flux reached 15% of the Crab Nebula flux. We observed several substantial changes of the flux level during the 13 day observing period. The flux at lower energies (150-350 GeV), instead, is compatible with being constant. The energy spectrum can be described by a power law with a photon index of 2.30 ± 0.11stat ± 0.20syst. The observed day-scale flux variability at VHE prefers the M87 core as source of the emission and implies that either the emission region is very compact (just a few Schwarzschild radii) or the Doppler factor of the emitting blob is rather large in the case of a nonexpanding emission region.
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MAGIC Collaboration, BOSCH I RAMON, Valentí, RIBÓ GOMIS, Marc, PAREDES I POY, Josep maria. Very high energy gamma-ray observations of strong flaring activity in M87 in 2008 February. _Astrophysical Journal Letters_. 2008. Vol. 685, núm. 1, pàgs. 23-26. [consulta: 24 de gener de 2026]. ISSN: 2041-8205. [Disponible a: https://hdl.handle.net/2445/150143]