Journal Article

Monte Carlo simulations of star clusters – VI. The globular cluster NGC 6397

Mirek Giersz and Douglas C. Heggie

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 2, pages 1173-1183
Published in print May 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Monte Carlo simulations of star clusters – VI. The globular cluster NGC 6397

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We describe Monte Carlo models for the dynamical evolution of the nearby globular cluster NGC 6397. The code includes treatments of two-body relaxation, most kinds of three- and four-body interactions involving primordial binaries and those formed dynamically, the Galactic tide and the internal evolution of both single and binary stars. We arrive at a set of initial parameters for the cluster which, after 12 Gyr of evolution, gives a model with a fairly satisfactory match to the surface brightness profile, the velocity dispersion profile and the luminosity function in two fields. We describe in particular those aspects of the evolution which distinguish this cluster from M4, which has a roughly similar mass and Galactocentric distance, but a qualitatively different surface brightness profile. Within the limitations of our modelling, we conclude that the most plausible explanation for the difference is fluctuations: both clusters are post-collapse objects, but sometimes have resolvable cores and sometimes not.

Keywords: stellar dynamics; methods: numerical; globular clusters: individual: NGC 6397; globular clusters: individual: M4

Journal Article.  9277 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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