Maser Surveys and Spectral Energy Distribution Studies of Oxygen-rich Evolved Stars with High Velocity Jets
Intermediate-mass stars such as our Sun will go through the asymptotic giant branch (AGB) phase and the post-AGB phase during their late-stage of stellar evolution, before reaching the planetary nebula (PN) phase. It is observed that high velocity jets are associated with some objects from the late/post-AGB phases. The mechanism behind these jets are still unclear, but it is suggested that such jets play an important role in shaping a spherical AGB star to a bipolar or even multi-polar PN. In this presentation, results of two maser surveys (for H2O and OH masers) are reported. One of the major goals here is to identify high velocity jets from oxygen-rich late/post-AGB stars. Such objects, called the "water fountains (WFs)", are still quite rare but they may provide us a better opportunity to understand the aforementioned shaping process. The preliminary results of an one-dimensional modelling of the spectral energy distributions of known WFs will also be discussed. It is found that WFs could be objects ranging from AGB to post-AGB stars, implying that the timing of the onset of jets could be more unpredictable than we expected.
Ostatnia aktualizacja: 17.05.2016 15:23