Supernova enrichment and dynamical histories of solar-type stars in clusters
Richard J. Parker
Melvyn B Davies
Michael R. Meyer
Summary, in English
We use N-body simulations of star cluster evolution to explore the hypothesis that short-lived radioactive isotopes found in meteorites, such as Al-26, were delivered to the Sun's protoplanetary disc from a supernova at the epoch of Solar system formation. We cover a range of star cluster formation parameter space and model both clusters with primordial substructure and those with smooth profiles. We also adopt different initial virial ratios - from cool, collapsing clusters to warm, expanding associations. In each cluster, we place the same stellar population; the clusters each have 2100 stars and contain one massive 25 M-circle dot star which is expected to explode as a supernova at about 6.6Myr. We determine the number of solar (G)-type stars that are within 0.1-0.3 pc of the 25 M-circle dot star at the time of the supernova, which is the distance required to enrich the protoplanetary disc with the 26Al abundances found in meteorites. We then determine how many of these G-dwarfs are unperturbed 'singletons'; stars which are never in close binaries, nor suffer sub-100 au encounters, and which also do not suffer strong dynamical perturbations. The evolution of a suite of 20 initially identical clusters is highly stochastic, with the supernova enriching over 10 G-dwarfs in some clusters, and none at all in others. Typically, only similar to 25 per cent of clusters contain enriched, unperturbed singletons, and usually only one to two per cluster (from a total of 96 G-dwarfs in each cluster). The initial conditions for star formation do not strongly affect the results, although a higher fraction of supervirial (expanding) clusters would contain enriched G-dwarfs if the supernova occurred earlier than 6.6Myr. If we sum together simulations with identical initial conditions, then similar to 1 per cent of all G-dwarfs in our simulations are enriched, unperturbed singletons.