A. Ernst, A. Just, P. Berczik, C. Olczak
Context: Using the recent observational data of R\"oser et al. we present
$N$-body simulations of the Hyades open cluster. Aims: We make an attempt to
determine initial conditions of the Hyades cluster at the time of its formation
in order to reproduce the present-day cumulative mass profile, stellar mass and
luminosity function (LF). Methods: We performed direct $N$-body simulations of
the Hyades in an analytic Milky Way potential that account for stellar
evolution and include primordial binaries in a few models. Furthermore, we
applied a Kroupa (2001) IMF and used extensive ensemble-averaging. Results: We
find that evolved single-star King initial models with King parameters $W_0 =
6-9$ and initial particle numbers $N_0 = 3000$ provide good fits to the
observational present-day cumulative mass profile within the Jacobi radius. The
best-fit King model has an initial mass of $1721\ M_\odot$ and an average mass
loss rate of $-2.2 \ M_\odot/\mathrm{Myr}$. The K-band LFs of models and
observations show a reasonable agreement. Mass segregation is detected in both
observations and models. If 33% primordial binaries are included the initial
particle number is reduced by 5% as compared to the model without primordial
binaries. Conclusions: The present-day properties of the Hyades can be well
reproduced by a standard King or Plummer initial model when choosing
appropriate initial conditions. The degeneracy of good-fitting models can be
quite high due to the large dimension of the parameter space. More simulations
with different Roche-lobe filling factors and primordial binary fractions are
required to explore this degeneracy in more detail.
View original:
http://arxiv.org/abs/1110.1274
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