Justtanont, K;
Teyssier, D;
Barlow, MJ;
Matsuura, M;
Swinyard, B;
Waters, LBFM;
Yates, J;
(2013)
OH/IR stars and their superwinds as observed by the Herschel Space Observatory.
Astronomy & Astrophysics
, 556
, Article A101. 10.1051/0004-6361/201321812.
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Abstract
Aims. In order to study the history of mass loss in extreme OH/IR stars, we observed a number of these objects using CO as a tracer of the density and temperature structure of their circumstellar envelopes. / Methods. Combining CO observations from the Herschel Space Observatory with those from the ground, we trace mass loss rates as a function of radius in five extreme OH/IR stars. Using radiative transfer modelling, we modelled the dusty envelope as well as the CO emission. The high-rotational transitions of CO indicate that they originate in a dense superwind region close to the star while the lower transitions tend to come from a more tenuous outer wind which is a result of the mass loss since the early AGB phase. / Results. The models of the circumstellar envelopes around these stars suggest that they have entered a superwind phase in the past 200–500 years. The low 18O/17O (~0.1 compared to the solar abundance ratio of ~5) and 12C/13C (3–30 cf. the solar value of 89) ratios derived from our study support the idea that these objects have undergone hot-bottom burning and hence that they are massive M ≥ 5 M⊙ AGB stars.
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