RT Journal Article
T1 Very high energy gamma-ray observations of strong flaring activity in M87 in 2008 february
A1 Antoranz Canales, Pedro
A1 Barrio Uña, Juan Abel
A1 Contreras González, José Luis
A1 Fonseca González, María Victoria
A1 Miranda Pantoja, José Miguel
A1 Nieto Castaño, Daniel
AB 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.
PB IOP Publishing
SN 2041-8205
YR 2008
FD 2008-09-20
LK https://hdl.handle.net/20.500.14352/50821
UL https://hdl.handle.net/20.500.14352/50821
LA eng
NO © The American Astronomical Society. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MCI is gratefully acknowledged. This work was also supported by ETH research grant TH 34/043, by the Polish MNiSzW grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. We thank Dan Harris for providing preliminary results on Chandra observations.
NO German BMBF
NO German MPG
NO Italian INFN
NO Spanish MCI
NO ETH
NO Polish MNiSzW
NO YIP of the Helmholtz Gemeinschaft
DS Docta Complutense
RD 7 jul 2025