ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

I. McDonald, Albert Zijlstra, E. Lagadec, G. C. Sloan, M. L. Boyer, M. Matsuura, Rowan Smith, C. L. Smith, J. A. Yates, van Loon, J. Th, O. C. Jones, S. Ramstedt, Adam Avison, K. Justtanont, H. Olofsson, J. A. D. L. Blommaert, S. R. Goldman, M. A. T. Groenewegen

    Research output: Contribution to journalArticlepeer-review


    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 ˜1.2-3.5 × 10-7 M⊙ yr-1. We would naïvely 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.
    Original languageEnglish
    Pages (from-to)4324-4336
    Number of pages12
    JournalRoyal Astronomical Society. Monthly Notices
    Issue number4
    Publication statusPublished - Nov 2015


    • stars: AGB and post-AGB
    • circumstellar matter
    • stars: mass-loss
    • stars: winds
    • outflows
    • globular clusters: individual: NGC 104
    • infrared: stars


    Dive into the research topics of 'ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae'. Together they form a unique fingerprint.

    Cite this