ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae
Journal article, 2015
Atacama Large Millimetre Array observations show a 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 be similar to 1.2-3.5x10(-7) M-circle dot yr(-1). We would naively expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude that CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars 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.
stars: mass-loss
stars: winds
circumstellar matter
globular clusters: individual: NGC 104
infrared: stars
outflows
stars: AGB and post-AGB
Author
I. McDonald
University of Manchester
A. Zijlstra
University of Manchester
E. Lagadec
Cornell University
Observatoire de la Cote d'Azur
G. C. Sloan
Cornell University
M. Boyer
NASA Goddard Space Flight Center
M. Matsuura
University College London (UCL)
Cardiff University
R. J. Smith
University of Manchester
C. L. Smith
University of Manchester
J. A. Yates
University College London (UCL)
J. T. van Loon
Keele University
O. C. Jones
Space Telescope Science Institute (STScI)
University of Manchester
S. Ramstedt
Uppsala University
A Avison
University of Manchester
Kay Justtanont
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Hans Olofsson
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Jadl Blommaert
Vrije Universiteit Brussel (VUB)
S. R. Goldman
Keele University
M. A. T. Groenewegen
Royal Observatory of Belgium
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 453 4 4324-4336Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1093/mnras/stv1968