| Description |
Envelopes around evolved stars are factories of complex molecules (neutrals, anions and cations) and one of the main sites for dust formation. Most chemical studies have focused on C-rich envelopes, in particular on IRC+10216. Recent observations of metal bearing species and hydroxides in O-rich shells suggest that the chemistry in these objects can be as richer as in C-rich circumstellar envelopes. We propose to perform a complete line survey of the prominent O-rich star VY CMa with HIFI. This study will provide, in addition to all lines of CO, H2O, HCN, SiO, SO2, a complete inventory of the molecular gas in O-rich evolved stars. The comparison with the line survey of IRC+10216 (already carried out with HIFI-Herschel) will permit to distingush the different chemical processes in these objects and the subtle role of the C-O abundance ratio in the molecular composition of the gas at different distances from the central star. We will use our radiative transfer and chemistry models to reproduce the observed spectra and to derive molecular abundances. The data will also allow a better understanding of the physical structure of the envelope. |
| Publication |
Silicon isotopic abundance toward evolved stars and its application for presolar grains . Peng T.-C. et al. . Astronomy & Astrophysics, Volume 559, id.L8, 6 pp. . 559 . 10.1051/0004-6361/201322466 . 2013A&A...559L...8P ,
Circumstellar ammonia in oxygen-rich evolved stars . Wong K. T. et al. . Astronomy & Astrophysics, Volume 612, id.A48, 37 pp. . 612 . 10.1051/0004-6361/201731873 . 2018A&A...612A..48W ,
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