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Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/47716
- N-body stellar evolution
- Hurley, Jarrod R.
- The advent of the Hubble Space Telescope (HST), with its ability to peer deep inside the globular clusters (GCs) of our Galaxy and resolve individual stars (Paresce et al. 1991), provided reason enough to include stellar evolution in cluster models.We only have to look at the beautiful images of stars in the core of, say, Omega Centauri1 (Carson, Cool & Grindlay 2000) to be motivated to produce colour-magnitude diagrams (CMDs) from simulations to match those emanating from HST. There are also a number of questions relating to stellar populations in star clusters that require a combination of stellar evolution and stellar dynamics for investigation. For example, population gradients are observed, which indicate a central concentration of blue stragglers (BSs) as well as a central depletion of red giants (Yanny et al. 1994). A possible explanation is that close encounters between stars in the dense core of a GC leads to enhanced production of BSs in collisions (or mergers) of main-sequence stars. Encounters are also then expected to enhance the stripping of the envelopes of giant stars to produce blue horizontal branch stars or white dwarfs (WDs). The situation is not straightforward though, as evidenced by the classic second-parameter pair of GCs, M3 and M13 (Ferraro et al. 1997). Here we have two clusters of the same mass, density, metallicity and (apparently) age, but with dramatic differences in their blue straggler and blue horizontal branch star populations. Also, HST is not alone in exposing the cores of star clusters – the Chandra X-ray Telescope has provided a wealth of complementary information on objects such as millisecond pulsars and cataclysmic variables (Grindlay et al. 2001a,b). Aside from a desire to produce models to match observations of stellar populations in star clusters, there is a more basic need for stellar evolution in N-body models. Here we are talking specifically about mass loss from stars as they evolve. This can have a dramatic effect on the lifetime and structure of a star cluster. Put simply, mass lost from stars in stellar winds is expected to escape from a cluster and therefore weakens its potential. The cluster then expands, which leads to a temporary increase in the loss of stars across the tidal boundary. This weakening of the potential leaves the cluster more exposed to the possibility of disruption if, for example, the cluster encounters a giant molecular cloud or orbits through the Galactic disc. In the long-term stellar evolution mass loss affects the timescale for two-body relaxation and core-collapse. Thus stellar and cluster evolution are intertwined and an accurate description of the former in concert with dynamics is required.
- Publication type
- Book chapter
- Research centre
- Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing
- Lecture notes in physics: the Cambridge N-Body lectures / Sverre J. Aarseth, Christopher A. Tout and Rosemary A. Mardling (eds.), Vol. 760, chapter 10, pp. 283-296
- Publication year
- Globular clusters; HST; Hubble Space Telescope; N-body models; Star clusters; Stellar evolution
- 0075-8450 (series ISSN)
- 9781402084300, 1402084307
- Publisher URL
- Copyright © Springer-Verlag Berlin Heidelberg 2008.
- Peer reviewed