OH/IR stars and their superwinds as observed by the Herschel Space Observatory
Artikel i vetenskaplig tidskrift, 2013

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 O-18/O-17 (similar to 0.1 compared to the solar abundance ratio of similar to 5) and C-12/C-13 (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-circle dot AGB stars.

quantitative-analysis

agb

submillimeter: stars

carbon

stars

oh-ir sources

mass-loss rates

mu-m

near-infrared photometry

circumstellar envelopes

isotopic-ratios

asymptotic giant branch

stars: AGB and post-AGB

evolved stars

stars: mass-loss

Författare

Kay Justtanont

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

D. Teyssier

European Space Astronomy Centre

M. J. Barlow

University College London (UCL)

M. Matsuura

University College London (UCL)

B. Swinyard

Rutherford Appleton Laboratory

University College London (UCL)

Lbfm Waters

Universiteit Van Amsterdam

Netherlands Institute for Space Research (SRON)

J. A. Yates

University College London (UCL)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 556 A101

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201321812