Very high energy y-rays from Cygnus X-3

Very high energy y-rays (above 1012 eV) from Cyg X-3 have been observed for 7 years at the Crimean Astrophysical Observatory by means of the Cherenkov technique. These observations enable us to find the derivative with time of the 4.8 hour periodicity. As is well known, the observations of X -rays have revealed time variations of the Cyg X-3 period (see, for instance, Eisner et al. 1979). The ‘light’ curve for very high energy y-rays has a sharp peak lasting 15 minutes and differs significantly from the ‘light’ curve for X-rays. For this reason the comparison of the results in these two regions is important.