SIMBAD references

We present the results of a ¹²CO (J=1->0) and (J=2->1) survey on a sample of 46 objects classified as AGB and post-AGB stars. We have obtained fully sampled high resolution maps of their ¹²CO (J=1->0) emission by combining visibilities from the IRAM interferometer with short spacing observations from the IRAM 30 m telescope. Properties of their circumstellar envelopes like fluxes, radii, and positions are derived from model fits to the visibilities and compared to the results obtained from ¹²CO (J=2->1) maps observed at the IRAM 30 m telescope. From the ¹²CO (J=1->0) observations we have derived mass loss rates for 38 stars and established an empirical relation between the CO photodissociation radius of an envelope and the measured radius in the (J=1->0) emission.