Search for Gamma-Ray Time Variability of Cygnus X-3 and CG 195+4

The ESA COS-B satellite investigated the high energy gamma ray emission from the Cygnus region of the galaxy during Nov. and Dec. 1975. From the counts observed to originate within the vicinity of Cygnus X-3, a phase histogram was derived using the 4.8 hr period observed at X-ray and IR wavelengths. The phase analysis reveals no evidence for a modulation of the gamma ray emission at the time of the COS-B observation. The short-term variability of the source CG 195+4 was investigated in detail. This source was found to pulsate with a period of 59.19687 sec and a period derivative of 1.385x10 exp (-9) with a multiple peak phase histogram, consistent with the SAS-2 results. The pulsed fraction above 100 MeV is 75 plus or minus 25%. This preliminary study also indicates a pulsed energy spectrum harder than that of the Crab pulsar.