English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Water maser emission at 22 GHz is a useful probe to study the transitionbetween the nearly spherical mass-loss in the AGB to a collimated one in thepost-AGB phase. In their turn, collimated jets in the post-AGB phase coulddetermine the shape of planetary nebulae (PNe) once photoionization starts. Weintend to find new cases of post-AGB stars and PNe with water maser emission,including water fountains or water-maser-emitting PNe. We observed water maseremission in a sample of 133 objects, with a significant fraction being post-AGBand young PN candidate sources with strong obscuration. We detected thisemission in 15 of them, of which seven are reported here for the first time. Weidentified three water fountain candidates: IRAS 17291-2147, with a totalvelocity spread of ~96 km/s in its water maser components and two sources (IRAS17021-3109 and IRAS 17348-2906) that show water maser emission outside thevelocity range covered by OH masers. We have also identified IRAS 17393-2727 asa possible new water-maser-emitting PN. The detection rate is higher inobscured objects (14%) than in those with optical counterparts (7%), consistentwith previous results. Water maser emission seems to be common in objects thatare bipolar in the near-IR (43% detection rate). The water maser spectra ofwater fountain candidates like IRAS 17291-2147 show significantly less masercomponents than others (e.g., IRAS 18113-2503). We speculate that mostpost-AGBs may show water maser emission with wide enough velocity spread (> 100km/s) when observed with enough sensitivity and/or for long enough periods oftime. Therefore, it may be necessary to single out a special group of "waterfountains", probably defined by their high maser luminosities. We also suggestthat the presence of both water and OH masers in a PN is a better tracer of itsyouth, rather than the presence of just one of these species.

A search for water maser emission toward obscured post-AGB star and planetary nebula candidates