NONTHERMAL X-RAY-EMISSION FROM 3C-273 - THE CORE OF A KNOTTY PROBLEM

The quasar 3C 273 was observed in the hard X-ray region of the spectrum (15-300 keV) during a stratospheric balloon flight on 1987 July 15. The emitted photon spectrum is well described by a single power law of photon index -1.61 which corresponds to a hard (20-200 keV) X-ray luminosity of 0.8 × 1047 ergs s-1 (H0 = 50 km s-1 Mpc-1). This flux is consistent with the 1978/1979 HEAO 1 and AIT/MPI measurements and about a factor of 3 below the high state measured in 1981 (AIT/MPI). The implications of these results with respect to the location of the production site and mechanism are discussed.