ESA Science & Technology - Observation of gamma rays with a 4.8 hour periodicity from Cygnus X-3

Publication date: 01 March 1977

Authors: Lamb, R.C., et al.

Journal: Astrophysical Journal Letters
Volume: 212
Page: 63-66
Year: 1977

Copyright: American Astronomical Society

Energetic (exceeding 35 MeV) gamma-rays have been observed from the direction of Cygnus X-3 with the SAS-2 gamma-ray telescope. The statistical significance of the excess above the galactic and diffuse radiation is approximately 4.5 sigma. In addition, the gamma-ray flux is modulated at the 4.8-hr period observed in the X-ray and infrared regions, and within the statistical error is in phase with this emission. The flux above 100 MeV has an average value of about 4.4 x 10^-6 photons cm^-2 s^-1. If the distance to Cygnus X-3 is 10 kpc, this flux implies a luminosity of more than 10³⁷ erg/s if the radiation is isotropic and about 10³⁶ erg/s if the radiation is restricted to a cone of 1 steradian, as it might be in a pulsar. Upper limits are presented for the gamma-ray flux from other known or suspected periodic X-ray sources.