Multiwavelength behaviour of Cygnus X-3 and related objects

Fender, Robert P. (1996). Multiwavelength behaviour of Cygnus X-3 and related objects. PhD thesis The Open University.



I present a detailed study of the behaviour of the exotic X-ray binary Cygnus X-3 at radio, (sub)mm, infrared, red-optical and X-ray wavelengths. Further unusual properties of the system are unearthed and previously expounded models are refined by new observations. In order to address the broader picture, a multiwavelength comparison of Cygnus X-3 with other ‘radio-jet’ X-ray binaries is also undertaken. Infrared observations of Cyg X-3 at high time resolution reveal many rapid flare events superimposed upon the 4.8 hr (presumed) orbital motion. Photometry simultaneously in the H & K-bands allows strong constraints to be placed upon T & Nε for the flaring component. Dereddening of RI- J-H-K-L-L’ photometry places limits on the likely extinction to Cyg X-3 of 4.5 ≤ AJ ≤ 7.5 mag. Further infrared study, simultaneous with radio monitoring and observations with OSSE/GRO and the INT shed greater light on the source, including possible orbital colour changes and a longterm correlation between radio and infrared flux levels. Deep imaging of the field reveals many previously undiscovered infrared sources within a few arcsec of Cyg X-3. Simultaneous millimetre and radio observations of Cyg X-3 reveal anomalously strong mm fluxes. Interpreting this in terms of significant absorption of the cm fluxes during the passage outwards of the radio-emitting plasmons, strengthens the case for a dense stellar wind in the Cyg X-3 system. Further radio and sub(mm) observations of Cyg X-3 during outburst confirm previously observed phenomena such as quenched radio emission prior to outburst, and establish the importance of radiation loss mechanisms in the decay of radio plasmons ejected from the source. A model describing the qualitative behaviour of the source during outburst is presented.

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