2026-06-27T11:08:56Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/508212024-09-06T16:42:57Zcom_20.500.14352_14col_20.500.14352_15

Antoranz Canales, Pedro Barrio Uña, Juan Abel Contreras González, José Luis Fonseca González, María Victoria Miranda Pantoja, José Miguel Nieto Castaño, Daniel 2023-06-20T10:37:39Z 2023-06-20T10:37:39Z 2008-09-20 2041-8205 10.1086/592348 https://hdl.handle.net/20.500.14352/50821 http://dx.doi.org/10.1086/592348 http://iopscience.iop.org 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 sigma. 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 +/- 0.11(stat) +/- 0.20(syst). 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. eng open access Very high energy gamma-ray observations of strong flaring activity in M87 in 2008 february journal article