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 inO-rich shells suggest that the chemistry in these objects can beas richer as in C-rich circumstellar envelopes. We propose toperform 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 subtlerole of the C/O abundance ratio in the molecular composition of the gas at differentdistances from the central star.We will use our radiative transfer and chemistry models to reproducethe observed spectra and to derive molecular abundances. The data willalso 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 | http://adsabs.harvard.edu/abs/2013A%26A...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 | http://adsabs.harvard.edu/abs/2018A%26A...612A..48W
Instrument
HIFI_HifiFS_freq
Temporal Coverage
2011-09-14T17:24:03Z/2012-04-26T15:07:48Z
Version
SPG v14.1.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, cernicharo et al., 2012, 'Molecular complexity in the circumstellar envelope of the O-rich evolved star VY CMa', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-7b72vyn
