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| Paper: |
Herschel/HIFI Results on Circumstellar Shells around Evolved Stars:
HIFISTARS and SUCCESS |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
577 |
| Authors: |
Bujarrabal, V.; and the HIFISTARS and SUCCESS teams |
| Abstract: |
The first observations performed with the high-resolution spectrometer
HIFI, on board Herschel, of circumstellar shells around evolved
stars (AGB, post-AGB, red supergiant and yellow hypergiant stars) are
summarized. Herschel/HIFI is able to obtain accurate data on
molecular lines in the sub-mm and FIR domains, which are very useful
to study the warm components of these objects. Such components are
particularly important to understand the structure, dynamics,
chemistry, and evolution of our nebulae. We focus on already
published data obtained as part of the key program
HIFISTARS and briefly present another key program, SUCCESS.
These data sets constitute
the vast majority of the data obtained so far by HIFI on this topic.
The interpretation of these Herschel/HIFI observations has already
yielded important results. Here we mainly consider our study of CO and
H2O emission, which has allowed the determination of physical
conditions and molecular abundances in a variety of regimes,
particularly in warm regions. We stress the detection of intense
H2O emission in O-rich, C-rich, and S-type AGB stars. We also
show our results on the NH3 rotational emission in O-rich evolved
stars, from which we deduce valuable information on the peculiar
chemistry of this molecule. Finally, we discuss the properties of CO
emission in the young planetary nebula CRL 618, which shows the
presence of relatively hot, recently shocked gas. |
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