2026-06-28T20:33:20Zhttps://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

Very high energy gamma-ray observations of strong flaring activity in M87 in 2008 february Antoranz Canales, Pedro Barrio Uña, Juan Abel Contreras González, José Luis Fonseca González, María Victoria Miranda Pantoja, José Miguel Nieto Castaño, Daniel 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. 2023-06-20T10:37:39Z 2023-06-20T10:37:39Z 2023-06-20T10:37:39Z 2008-09-20 journal article https://hdl.handle.net/20.500.14352/50821 2041-8205 10.1086/592348 eng TH 34/043 N203 390834 open access IOP Publishing