A high-sensitivity OH 5-cm line survey in late-type stars^*

¹ Observatorio Astronómico Nacional (IGN), Apartado 1143, 28800 Alcalá de Henares, Spain
² Observatoire de l'Université de Bordeaux, URA 352 du CNRS, BP 89, 33270 Floirac, France
³ Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon Cedex, France
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Corresponding author: J.-F. Desmurs, desmurs@oan.es

Received: 7 May 2002
Accepted: 27 August 2002

Abstract

We have undertaken a comprehensive search for 5-cm excited OH maser emission from evolved stars representative of various stages of late stellar evolution. Observed sources were selected from known 18-cm OH sources. This survey was conducted with the 100-m Effelsberg telescope to achieve high signal to noise ratio observations and a sensitivity limit of about 0.05 to 0.1 Jy. A total of 65 stellar sources were searched for both main line and satellite line emission. We confirm the previous detection of 5 cm OH in Vy 2-2, do not confirm emission from NML-Cyg and do not report any other new detection within the above sensitivity limit.
Implications of these results on the pumping mechanism of the OH radical in circumstellar envelopes are briefly discussed.