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For refcode 1994ApJ...434..468S:
Retrieve 26 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
1994ApJ...434..468S THE X-RAY SPECTRA OF BLAZARS OBSERVED WITH EXOSAT RITA M. SAMBRUNA SISSA/ISAS, Strada Costiera 11,34014 Trieste, Italy; rita@tsmil9.sissa.it PAUL BARR ISO Observatory, European Space Agency, ESTEC, Postbus 229,2200 AG Noordwijk, The Netherlands PAOLO GIOMMI ESA/ESRIN, via Galileo Galilei, C.P. 64,0044 Frascati, Italy LAURA MARASCHI Dipartimento di Fisica, via Dodecaneso 33,16146 Genova, Italy GIANPIERO TAGLIAFERRI Osservatorio Astronomico di Brera, via Brera 28,1-20121 Milano, Italy AND ALDO TREVES SISSA/ISAS, Strada Costiera 11,34014 Trieste, Italy Received 1993 May 7; accepted 1994 April 26 ABSTRACT A systematic analysis of the X-ray spectra (0.1-10 keV) of all blazars observed with EXOSAT is presented. The objects include 16 X-ray-selected BL Lac objects (XBLs), five radio-selected BL Lac objects (RBLs), and five highly polarized quasars (HPQs). Comparing the results of single-power-law fits for the different classes, we find that XBLs have steeper X-ray spectra than HPQs (average photon indices <{GAMMA}> ~ 2.20_-0.15_^+0.17^ and 1.62_-0.24_^+0.11^, respectively). The X-ray luminosities of XBLs and RBLs are similar, while HPQs tend to be somewhat more luminous. For the three groups, a correlation between the average medium-energy luminosity and the average spectral index is found, in the sense that sources of higher luminosity have flatter spectra. For repeatedly observed objects (XBLs), the spectra harden systematically with increasing intensity. For seven (out of 16) XBLs, corresponding to the brightest objects in the sample, the X-ray spectrum is significantly better described by a convex, broken-power-law model than by a single power law. The results are discussed in the framework of current models for blazars. Subject headings: BL Lacertae objects: general - quasars: general - X- rays: galaxies
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