Is cygnus X-3 a low-mass X-ray binary?

Abstract

We present examples of the quasi-periodic variations in the X-ray flux of Cyg X-3 which we have recently found during observations of this source with EXOSAT. Amplitudes and periods of the variations range from 5% to 20% of the total flux and from 50 to 1500 s, respectively. Our tentative interpretation of these quasi-periodicities, the occurrence of quasi-periodic phenomena in an accretion disk which partially occults the X-ray source, points towards an analogy of Cyg X-3 with certain `dipping' low-mass X-ray binaries such as 4U 1822-37, as suggested /1/ previously. We point out, however, that there are also fundamental differences between Cyg X-3 and this type of low-mass X-ray binary.