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An extensive modelling of CO line emission from the circumstellar envelopesaround a number of carbon stars is performed. By combining radio observationsand infrared observations obtained by ISO the circumstellar envelopecharacteristics are probed over a large radial range. In the radiative transferanalysis the observational data are consistently reproduced assuming aspherically symmetric and smooth wind expanding at a constant velocity. Thecombined data set gives better determined envelope parameters, and putsconstraints on the mass loss history of these carbon stars. The importance ofdust in the excitation of CO is addressed using a radiative transfer analysisof the observed continuum emission, and it is found to have only minor effectson the derived line intensities. The analysis of the dust emission also putsfurther constraints on the mass loss rate history. The stars presented here arenot likely to have experienced any drastic long-term mass loss ratemodulations, at least less than a factor of about 5, over the past thousands ofyears. Only three, out of nine, carbon stars were observed long enough by ISOto allow a detection of CO far-infrared rotational lines.Comment: 11pages, 7 figures, accepted by A&

Probing the mass loss history of carbon stars using CO line and dust continuum emission