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For refcode 1990ApJ...362L..51B:
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1990ApJ...362L..51B HARD X-RAYS FROM COMA CLUSTER REGION A. BAZZANO, R. FUSCO-FEMIANO, AND P. UBERTINI Istituto di Astrofisica Spaziale, C.N.R., Frascati F. PEROTTI AND E. QUADRINI Istituto di Fisica Cosmica, C.N.R., Milano A. J. COURT, A. J. DEAN, N. A. DIPPER AND R. LEWIS Physics Department, Southampton University. Southampton, U.K. AND J. B. STEPHEN Istituto TESRE. C.N.R., Bologna Received 1990 May 31: accepted 1990 August 2 ABSTRACT The region containing the Coma cluster of galaxies was studied on 1987 July 15 in the energy range (15-310 keV) with a balloon-borne experiment, comprising scintillation and multiwire proportional counter detectors. During the observation, a high-energy nonthernal component was detected in the energy band 18-130 keV, and the emitted photon spectrum is well described by a single power law of photon index -1.77 with an intensity of 8.9 x 10^-5^ photons cm^-2^ s^-1^ keV^-1^ at 50 keV. This emission is not consistent with the thermal one detected by HEAO 1 A-2/A-4 (1978/1979) and supports the presence of a hard tail, as already suggested by early measurements from OSO 8 and the HXR/Frascati balloon experiment. The high-energy emission could be due to the inverse Compton mechanism (IC) of relativistic electrons permeating the cluster off the 2.7 K background radiation, or to the presence in the field of an active galactic nucleus, possibly X Comae, as suggested by the EXOSAT/CMA image. In the last case, the high-energy component varies more than a factor of 4 on a time scale of years, while assuming the hard X-rays as due to IC emission a lower limit of 0.37 x 10^-7^ G is derived for the intracluster magnetic field. Subject headings: galaxies: clustering - magnetic fields - radiation mechanisms - X-rays: sources ########################################################################## 1991ApJ...366L..95B ERRATUM In the Letter "Hard X-Rays from Coma Cluster Regions" by A. Bazzano, R. Fusco-Femiano, P. Ubertini, F. Perotti, E. Quadrini, A. J. Court, A. J. Dean, N. A. Dipper, R. Lewis, and J. B. Stephen (ApJ, 362, L51[1990]), a preliminary version of Figure 2 was printed in error. the final version of the figure and its legend appear below. The Journal regrets the error.
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