Radio flares and plasmon size in Cygnus X-3 |
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| Authors: | RN Ogley † SJ Bell Burnell RE Spencer SJ Newell AM Stirling RP Fender |
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| Institution: | 1Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, Buckinghamshire MK6 7AA;2University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL;3CFA, University of Central Lancashire, Preston PR1 2HE;4Astronomical Institute 'Anton Pannekoek' and Center for High-Energy Astrophysics, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands |
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| Abstract: | We have observed a number of minor radio flares in Cyg X-3 using the MERLIN array. Photometric observations show the system to be highly active with multiple flares on hourly time-scales over the one month observing programme. Analysis of the power spectrum of the source show no persistent periodicities in these data, and no evidence of the 4.8-h orbital period. An upper limit of 15 mJy can be placed on the amplitude of any sinusoidal variation of source flux at the orbital period. The brightness temperature of a flare is typically T b≥109–1010 K , with a number of small flares of 5-min duration having brightness temperatures of T b≥ few×1011 K . For such a change in flux to occur within a typical 10-min time-scale, the radiation must originate from plasmons with a size ≤1.22 au. This emission is unlikely to originate close to the centre of the system as both the jets and compact object are buried deep within an optically thick stellar wind. Assuming a spherically symmetric wind, plasmons would become visible at distances ～13 au from the core. |
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| Keywords: | binaries: close stars: individual: Cyg X-3 stars: variables: other stars: Wolf–Rayet radio continuum: stars X-rays: stars |
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