Teyssier, D.Lunar Hernández, María Del RosarioBujarrabal, V.Yoshida, H.Phillips, T. G.2024-08-212024-08-212006Teyssier, D., et al. «CO line emission from circumstellar envelopes». Astronomy & Astrophysics, vol. 450, n.º 1, abril de 2006, pp. 167-79. DOI.org (Crossref), https://doi.org/10.1051/0004-6361:20053759.0004-636110.1051/0004-6361:20053759https://hdl.handle.net/20.500.14352/107595Aims.We present the results of a multi-transition CO observational program conducted on a sample of AGB and post-AGB stars envelopes. We have collected maps and single pointing observations of these envelopes in 5 rotational transitions ranging from J = 1–0 to J = 6–5, including in particular new observations of the CO line at 691 GHz at the CSO. The use of such a set of mm and submm CO line on stellar envelopes is rare and limited to the work of some authors on IRC+10216.Methods.Using a model for the CO emission of an AGB circumstellar envelope, in combination with a standard LVG approach, we have conducted a systematic modelling analysis using the whole set of CO data collected for a sample of 12 sources. We simultaneously fit all five transitions, taking into account the spatial information provided by the maps.Results.We find mass-loss rates in the range 1 10-7 to 4 10/yr, and envelope temperatures ranging from 20 K to 1000 K at a radius of 1016 cm. There seem to be a general anti-correlation between mass loss rates and temperature, the high mass loss rate AGBs having low temperatures, and vice versa. We show that most AGB data can be fitted using a constant mass loss rate, at least within the calibration uncertainties associated with the data collected at different frequencies. For some cases though (e.g. CIT 6, R Hya, χ Cyg), a change in the mass loss rate history needs to be invoked to reconcile data at low- and high-J, a scenario already mentioned by several authors to explain observations of WX Psc.engjournal article1432-0746https://doi.org/10.1051/0004-6361:20053759restricted access524.3stars: AGB and post-AGBstars: circumstellar matter, mass-lossinfrared: starsAstronomía (Física)AstrofísicaMineralogía (Geología)21 Astronomía y Astrofísica2506.11 Mineralogía