| Description |
A subset of Asymptotic Giant Branch (AGB) stars loses mass at a very high rate. The dust effectively shields the radiation from the central star, allowing water-ice to condense onto existing silicate grains. Through the mass loss process, these stars provide a siginificant fraction to the gas and dust mass return to the interstellar medium. They are thought to be massive intermediate-stars (>5 Msun), close to the end of their AGB evolution. Using Herschel to obtain the full spectral coverage from 50 to 670 micron with PACS and SPIRE, we will obtain spectra of gas-phase H2O lines and derive the H2O abundance by modelling these lines, thought to be the main cooling agent in O-rich AGB star. This, combine with a few selected high resolution observations of CO lines with HIFI will allow us to explore both the temperature and density structures of the circumstellar envelope (CSE). These observations will enable us to study the H2O abundance as a function of distance from the star as well as explore the superwind region close to the central star and detect any departure from spherical symmetry in the structure of the CSE. We will also get a handle on the stellar mass from 12C-13C and the wealth of the molecular emission lines in this wavelength range will be used to study the ongoing chemistry in highly obscured circumstellar envelopes of AGB stars. |
| Publication |
The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder - II. Estimating radial velocity of SPIRE spectral observation sources . Scott Jeremy P. et al. . Monthly Notices of the Royal Astronomical Society . null . null . 2020MNRAS.496.4894S ,
The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder - III. Line identification and off-axis spectra . Benson Chris S. et al. . Monthly Notices of the Royal Astronomical Society . null . null . 2020MNRAS.496.4906B ,
Herschel observations of extreme OH-IR stars. The isotopic ratios of oxygen as a sign-post for the stellar mass . Justtanont K. et al. . Astronomy & Astrophysics, Volume 578, id.A115, 38 pp. . 578 . 10.1051/0004-6361/201526270 . 2015A&A...578A.115J ,
The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder I. The Spectral Feature Finder and Catalogue . Hopwood R. et al. . Monthly Notices of the Royal Astronomical Society . null . null . 2020MNRAS.496.4874H ,
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