Systematic Search for Water Fountain Candidates using the Databases of Circumstellar Maser Sources

TL;DR

This study systematically searches for water fountain candidates among circumstellar maser sources by analyzing velocity ranges, leading to the identification of new candidates and revealing potential for discovering other astrophysical objects.

Contribution

The paper introduces a novel velocity range criterion for identifying water fountain candidates from maser databases, expanding the scope to include other interesting objects.

Findings

Identified 11 new water fountain candidates.

Found two sources with IRAS colors typical of post-AGB stars.

Demonstrated the criterion can discover other astrophysical objects.

Abstract

Water fountains (WFs) are thought to be objects in the morphological evolution of the circumstellar envelopes of low- and intermediate-mass evolved stars, transitioning from spherically symmetric to asymmetric shapes. We used databases of circumstellar 1612 MHz OH and 22.235 GHz H$_2$O maser sources to search for new WF candidates using the criterion of a larger velocity range of the H$_2$O maser emission compared to that of the OH maser emission. Thus, it is in principle possible to identify WFs with an H$_2$O velocity ranges smaller than those for the previously known WFs. For the OH maser line, we analyzed database entries of 8,474 observations from 2,195 sources, and 6,085 observations from 3,642 sources for H$_2$O maser line. After a close examination of the velocity ranges and line profiles, we identified 11 sources that meet the criterion mentioned above. We examined the IRAS colors of the selected sources and found that two of them (IRAS 19069+0916 and IRAS 19319+2214) are in the color region for post-AGB stars. We find that the maser velocity criterion can discover other astrophysically interesting objects than just WFs. Such objects may include peculiar planetary nebulae with maser emissions and stellar merger remnants.