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Abstract

We compare gravitational-wave (GW) signals from eight three-dimensional
simulations of core-collapse supernovae from Glas et al. (2019), using two
different progenitors with zero-age main sequence masses of 9 and 20 solar
masses. The collapse of each progenitor was simulated four times, at two
different grid resolutions and with two different neutrino transport methods,
using the Aenus-Alcar code. The main goal of this study is to assess the
validity of recent concerns that the so-called "Ray-by-Ray+" (RbR+)
approximation is problematic in core-collapse simulations and can adversely
affect theoretical GW predictions. Therefore, signals from simulations using
RbR+ are compared to signals from corresponding simulations using a fully
multidimensional (FMD) transport scheme. The 9 solar-mass progenitor
successfully explodes, whereas the 20 solar-mass model does not. Both the
standing accretion shock instability and hot-bubble convection develop in the
postshock layer of the non-exploding models. In the exploding models,
neutrino-driven convection in the postshock flow is established around 100 ms
after core bounce and lasts until the onset of shock revival. We can,
therefore, judge the impact of the numerical resolution and neutrino transport
under all conditions typically seen in non-rotating core-collapse simulations.
We find excellent qualitative agreement in all GW features and mostly very
satisfactory quantitative agreement between simulations using the different
transport schemes. Overall, resolution-dependent differences in the
hydrodynamic behaviour of low-resolution and high-resolution models turn out to
have a greater impact on the GW signals than consequences of the different
transport methods. Furthermore, increasing the resolution decreases the
discrepancies between models with different neutrino transport.