An OH satellite line maser survey of cool IRAS sources and circumstellar envelope evolution

We present the results of a search for 1612 MHz OH circumstellar masers in a colour limited sample of cool IRAS sources. 41 previously unknown detections are reported. This work is the fourth part of the Nancay surveys of IRAS evolved stars. A comprehensive comparison between the results herein and those obtained previously, is developed. Special attention is given to the relationship between the satellite and main line data and, to the evolution of the circumstellar environment along the sequence of reddening colours. The maser profiles indicate an evolving envelope in which the main and satellite line masers are produced in regions with a similar velocity field