Temporal variability studies on the blazar PKS 2155-304 with H.E.S.S

摘要

The High Energy Stereoscopic System (H.E.S.S) has measured the fluxes and characterized the spectral variabilityof several blazars on timescales ranging from months down to minutes. In most of those objects, the light curves show littlevariability, which only gives information about their quiescent state and their duty cycles. A few blazars provide us with anunprecedented rich dataset. In particular, the exceptional flaring periods of PKS 2155-304 in June 28-31 2006 allow us, for thefirst time in the very-high-energy domain, to investigate whether the observed light curve can be considered as the realizationof a random stationary Gaussian process. Due to large variations in the gamma-ray fluxes, the excess rms-flux correlationcould be investigated, showing that the logarithm of the flux is the relevant Gaussian variable and that the power densityspectrum is typical of a red noise.