Open AccessRadio flares and plasmon size in Cygnus X‐3
Author(s) -
Ogley R.N.,
Bell Burnell S.J.,
Spencer R.E.,
Newell S.J.,
Stirling A.M.,
Fender R.P.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04617.x
Subject(s) - physics , astrophysics , brightness , flare , flux (metallurgy) , brightness temperature , amplitude , astronomy , orbital period , light curve , stars , optics , materials science , metallurgy
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 ≥10 9 –10 10 K , with a number of small flares of 5‐min duration having brightness temperatures of T b ≥ few×10 11 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.