Issue A&A Volume 450, Number 3, May II 2006 Page(s) 1051 - 1059 Section Interstellar and circumstellar matter DOI 10.1051/0004-6361:20054569

A&A 450, 1051-1059 (2006)
DOI: 10.1051/0004-6361:20054569

Near-infrared observations of water-ice in OH/IR stars

K. Justtanont¹, G. Olofsson¹, C. Dijkstra² and A. W. Meyer<sup>3

1</sup>  Stockholm Observatory, AlbaNova, Dept. of Astronomy, 106 91 Stockholm, Sweden
²  Dept. Physics & Astronomy, U. of Missouri Culombia, 300 Physics Building UMC, Columbia, MO 65211, USA
³  USRA/SOFIA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA

(Received 22 November 2005 / Accepted 24 January 2006)

Abstract
A search for the near-infrared water-ice absorption band was made in a number of very red OH/IR stars which are known to exhibit the 10 m silicate absorption. As a by-product, accurate positions of these highly reddened objects are obtained. We derived a dust mass loss rate for each object by modelling the spectral energy distribution and the gas mass loss rate by solving the equation of motion for the dust drag wind. The derived mass loss rates show a strong correlation with the silicate optical depth as well as that of the water-ice. The stars have a high mass loss rate ( > 10^-4  yr^-1) with an average gas-to-dust mass ratio of 110. In objects which show the 3.1 m water-ice absorption, the near-IR slope is much steeper than those with no water-ice. Comparison between our calculated mass loss rates and those derived from OH and CO observations indicates that these stars have recently increased their mass loss rates.

Key words: stars: AGB and post-AGB -- stars: circumstellar matter -- stars: evolution -- stars: late-type -- stars: mass-loss -- infrared: stars

SIMBAD Objects

© ESO 2006

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