X-ray/TeV-gamma-ray observations of several strong flares of Mkn 501 during 1997 and implications

Abstract

During more than 6 months in 1997, the BL Lac object Mkn 501 was in an exceptionally bright state, both in the X-ray band and in the Very High Energy (VHE) band. In this paper we present a multiwavelength study of Mkn 501 during this extraordinary outburst. We describe the analysis of a data base of X-ray observations acquired with the pointed X-ray telescopes on board the Rossi X-Ray Timing Explorer (RXTE) during April, May, and July, 1997. We combine this data set with detailed VHE spectral information obtained from simultaneous or nearly simultaneous observations with the stereoscopic Cherenkov telescope system of HEGRA. Several strong flares could clearly be resolved in both energy bands, making it possible to perform a detailed correlation analysis of the X-ray and VHE gamma-ray flux levels and spectra. We interpret the results in the framework of a Synchrotron Self Compton models and study the constraints on the model parameters. We show that the emission mechanism produces an Inverse Compton spectrum with a significant curvature in the TeV energy range and discuss the implications for estimates of the intergalactic extinction due to pair production processes of the VHE photons on the Diffuse Extragalactic Background Radiation.