The exosat spectral survey of BL Lacertae objects

Abstract

The results of an analysis of the X-ray spectra of seventeen BL Lacertae objects measured in 66 observations are presented. The 0.1 - 10 keV spectra of these objects exhibit convex curvature in the log F_ν - log ν plane. This curvature is intrinsic to the continuum . No evidence for high energy tails is found, at least below energies of ≈8 − 10 keV, nor for very steep (energy spectral index α ≥2)soft X-ray spectra . A broken power law model gives an excellent fit to the spectra at each epoch but is unattractive from physical considerations and also when attempting to model the X-ray variability; other curved, convex continuum models should be considered.