Back to Volume
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.
Back to Volume