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Cygnus X-3 observed at photon energies above 500 GeV

Naturevolume 296pages543544 (1982) | Download Citation



We have used the twin 11-m diameter mirrors of the NASA Jet Propulsion Laboratory's solar energy facility to observe high-energy γ rays from Cyg X-3 using the atmospheric Cerenkov technique. Observations of photons with energies above 1012 eV modulated with the 4.8 h period of the X-ray source have been reported previously by the Crimean Astrophysical Observatory1–6 and the Fred Whipple Observatory7,8. We report here data from 105 air shower events obtained 29 August–6 September 1981 with an approximate threshold energy of 500 GeV. A positive signal with an amplitude of 10.9±2.5% of the background cosmic ray rate appears near phase 0.6 of the 4.8-h cycle, in which phase 0.0 corresponds to minimum X-ray emission. This observation, together with previous Cerenkov detections, indicates that the high energy emission from Cyg X-3 is evolving on a time scale of a few years which suggests a recent origin for the system in its present form.

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  1. Iowa State University, Ames, Iowa, 50011, USA

    • R. C. Lamb
    •  & C. P. Godfrey
  2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109, USA

    • W. A. Wheaton
  3. University of California, Riverside, California, 92521, USA

    • T. Tümer


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