Water maser detections in southern candidate post-AGB stars and planetary nebulae
UMR 6525 H.Fizeau, Université de Nice Sophia Antipolis, CNRS, OCA. Parc Valrose, 06108 Nice Cedex 2, France e-mail: firstname.lastname@example.org
2 Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain
3 Instituto de Ciencias de Espacio (CSIC)-IEEC, Facultat de Física, Planta 7a, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
4 Centro de Radioastronomía y Astrofísica, UNAM, Campus Morelia, Apdo. Postal 3-72, Morelia, Michoacán 58089, Mexico
5 Department of Earth Sciences, National Taiwan Normal University, 88 Sec. 4, Ting Chou Rd., Taipei 116, Taiwan
6 Academia Sinica Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 10617, Taiwan
7 Departament d'Astronomía i Meteorología, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
Accepted: 8 June 2009
Aims. We study the incidence and characteristics of water masers in the envelopes of stars in the post-AGB and PN evolutionary stages.
Methods. We used the 64-m antenna in Parkes (Australia) to search for water maser emission at 22 GHz, towards a sample of 74 sources with IRAS colours characteristic of post-AGB stars and PNe, at declination < -32°. In our sample, 39% of the sources are PNe or PNe candidates, and 50% are post-AGB stars or post-AGB candidates.
Results. We detected four new water masers, all of them in optically obscured sources: three are in PNe candidates (IRAS 12405-6219, IRAS 15103-5754, and IRAS 16333-4807) and one is in a post-AGB candidate (IRAS 13500-6106). The PN candidate IRAS 15103-5754 has water fountain characteristics and could be the first PN of this class found.
Conclusions. We confirm the trend suggested in Paper I that water maser emission during the post-AGB phase is more likely to be present in obscured sources with massive envelopes than in objects with optical counterpart. We propose an evolutionary scenario for water masers in the post-AGB and PNe stages, in which “water fountain” masers could develop during the post-AGB and early PN stages. Later PNe would exhibit lower velocity maser emission, both along jets and close to the central objects, with only the central masers remaining in more evolved PNe.
Key words: masers / surveys / stars: AGB and post-AGB / stars: mass-loss / planetary nebulae: general
© ESO, 2009