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LibraryI. McDonald, I. (Manchester), A.A. Zijlstra (Manchester), E. Lagadec (Obs. Cote d'Azur), G.C. Sloan (Cornell), M.L. Boyer (NASA/Goddard), M. Matsuura (Cardiff Univ.), R.J. Smith (Manchester), C.L. Smith (Manchester) J.A. Yates (Univ. Coll. London), J.Th. van Loon (Keele Univ.), O.C. Jones (Space Telescope), S. Ramstedt (Uppsala Univ.), A. Avison (Manchester), K. Justtanont (Chalmers Univ. of Tech.), H. Olofsson (Chalmers Univ. of Tech.), J.A.D.L. Blommaert (Vrije Univ. Brussel), S.R. Goldman (Keele Univ.), & M.A.T. Groenewegen (Roy. Obs. Belgium)
2015, MNRAS, 453, 4324
Full manuscript available or locally (PDF) from the arXiv (1508.05240).
ALMA observations show a surprising non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should lie in the vicinity of 1.2-3.5 x 10-7 Msun yr-1. Modeling the expected CO line fluxes leads to the conclusion that the strong ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc should be dissociating CO close to the stars. We estimate that the interstellar radiation field will truncate the CO envelopes at distances of a few hundred stellar radii and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars.
Last modified 28 October, 2021. © Gregory C. Sloan and others.