Mergers of two carbon-oxygen white dwarfs have long been suspected to be
progenitors of Type Ia Supernovae. Here we present our modifications to the
cosmological smoothed particle hydrodynamics code Gadget to apply it to stellar
physics including but not limited to mergers of white dwarfs. We demonstrate a
new method to map a one-dimensional profile of an object in hydrostatic
equilibrium to a stable particle distribution. We use the code to study the
effect of initial conditions and resolution on the properties of the merger of
two white dwarfs. We compare mergers with approximate and exact binary initial
conditions and find that exact binary initial conditions lead to a much more
stable binary system but there is no difference in the properties of the actual
merger. In contrast, we find that resolution is a critical issue for
simulations of white dwarf mergers. Carbon burning hotspots which may lead to a
detonation in the so-called violent merger scenario emerge only in simulations
with sufficient resolution but independent of the type of binary initial
conditions. We conclude that simulations of white dwarf mergers which attempt
to investigate their potential for Type Ia supernovae should be carried out
with at least 10^6 particles.Comment: 11 pages, 6 figures, accepted for publication in MNRA
