Transient quasi-periodic oscillations in in the X-ray flux of Cygnus X-3
Abstract
Cygnus X-3, a bright X-ray source at a distance1 of more than ~12 kpc beyond the edge of the galactic plane, has peculiar properties including very strong radio outbursts2, possibly showing jet-like features3, and emission in various γ-ray bands4-6 (but see ref. 7). The discovery of its 4.8-h X-ray period8 showed that the source is probably a compact (~1011 cm) binary system, but its nature and that of its companion, the mode of energy generation (accretion or Crab-like pulsar) and also the cause of the X-ray modulation are still uncertain. We describe here X-ray data on Cyg X-3, obtained with EXOSAT, showing transient quasi-periodic oscillations with amplitudes between 5 and 20% of the 1-10-keV flux and periods in the range 50-1,500 s. The oscillations persisted typically for 5-40 (quasi-oscillation) cycles, occurred exclusively in the phase interval 0.0-0.75 (rising branch and top of the X-ray light curve), were seen during the high state and probably also during the low state of the source, and, at least once, were observed with two different periods simultaneously. We suggest that the quasi-periodic flux variations are caused by quasi-periodic phenomena in an accretion disk which partially occults the X-ray source. This tentative interpretation is in accordance with the idea9 that the 4.8-h modulation of the X-ray flux in Cyg X-3 arises by partial occultations of the X-ray source by an accretion disk, like in low-mass X-ray binaries such as 4U1822-37.
- Publication:
-
Nature
- Pub Date:
- February 1985
- DOI:
- 10.1038/313768a0
- Bibcode:
- 1985Natur.313..768V
- Keywords:
-
- Binary Stars;
- Stellar Oscillations;
- X Ray Sources;
- Accretion Disks;
- Cygnus Constellation;
- Exosat Satellite;
- Light Curve;
- Pulsars;
- Radio Bursts;
- Stellar Occultation;
- Astrophysics