Gravitational Waves from 3D Core-Collapse Supernova Models: the Impact of Moderate Progenitor Rotation

We present predictions for the gravitational wave (GW) emission of 3D supernova simulations performed for a 15 solar-mass progenitor with the PROMETHEUS-VERTEX code using energy-dependent, three-flavour neutrino transport. The progenitor adopted from stellar evolution calculations including magnetic fields had a fairly low specific angular momentum (j(Fe) less than or similar to 10(15) cm(2) s(-1)) in the iron core (central angular velocity Omega(Fe, c) similar to 0.2 rad s(-1)), which we compared to simulations without rotation and with artificially enhanced rotation (j(Fe) less than or similar to 2 x 10(16) cm(2) s(-1); Omega(Fe, c) similar to 0.5 rad s(-1)). Our results confirm that the time-domain GW signals of SNe are stochastic, but possess deterministic components with characteristic patterns at low frequencies (less than or similar to 200 Hz), caused by mass motions due to the standing accretion shock instability (SASI), and at high frequencies, associated with gravity-mode oscillations in the surface layer of the proto-neutron star (PNS). Non-radial mass motions in the post-shock layer as well as PNS convection are important triggers of GW emission, whose amplitude scales with the power of the hydrodynamic flows. There is no monotonic increase of the GW amplitude with rotation, but a clear correlation with the strength of SASI activity. Our slowly rotating model is a fainter GW emitter than the non-rotating model because of weaker SASI activity and damped convection in the post-shock layer and PNS. In contrast, the faster rotating model exhibits a powerful SASI spiral mode during its transition to explosion, producing the highest GW amplitudes with a distinctive drift of the low-frequency emission peak from similar to 80-100 to similar to 40-50 Hz. This migration signifies shock expansion, whereas non-exploding models are discriminated by the opposite trend.