New detections of H2O masers in planetary nebulae and post-AGB stars using the Robledo-70 m antenna*
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apartado 50727, 28080 Madrid, Spain e-mail: firstname.lastname@example.org
2 Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain
Aims.We investigated the possible relationship between the evolutionary stage of post-AGB stars and planetary nebulae (PNe) and the presence of water masers in their envelopes
Methods.We have used NASA's 70-m antenna in Robledo de Chavela (Spain) to search for the water maser transition at 22 235.08 MHz, towards a sample of 105 sources with IRAS colour characteristic of post-AGB stars and PNe at declination >-32°. 83% of the sources in the sample are post-AGB stars, 15% PNe or PN candidates, while only 2% seem to be HII regions.
Results.We have detected five water masers, of which four are reported for the first time: two in PNe (IRAS 17443-2949 and IRAS 18061-2505), a “water fountain” in a post-AGB star (IRAS 16552-3050), and one in a source previously catalogued as a PN, but whose classification is uncertain (IRAS 17580-3111).
Conclusions.The unexpected detections of water masers in two objects among the small subset of PNe led us to suggest that the PNe harbouring water masers are a special type of massive, rapidly evolving PNe.
Key words: surveys / masers / stars: AGB and post-AGB / ISM: planetary nebulae: general
© ESO, 2007