Gravitational waves from 3D core-collapse supernova models: The impact of moderate progenitor rotation

Abstract

We present predictions for the gravitational-wave (GW) emission of three-dimensional supernova (SN) simulations performed for a 15 solar-mass progenitor with the PROMETHEUS-VERTEX code using energy-dependent, three-flavor neutrino transport. The progenitor adopted from stellar evolution calculations including magnetic fields had a fairly low specific angular momentum (j Fe 10 15 cm 2 s −1 ) in the iron core (central angular velocity Ω Fe,c ∼0.2 rad s −1 ), which we compared to simulations without rotation and with artificially enhanced rotation (j Fe 2 × 10 16 cm 2 s −1 ; Ω Fe,c ∼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 ( 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). Nonradial mass motions in the postshock 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 nonrotating model because of weaker SASI activity and damped convection in the postshock 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 ∼80-100 Hz to ∼40-50 Hz. This migration signifies shock expansion, whereas non-exploding models are discriminated by the opposite trend.

Temporal and angular variations of 3D core-collapse supernova emissions and their physical correlations

“…All three of the nonexploding models also show an m = 1 spiral SASI mode (Blondin 2005) developing ∼400 ms postbounce, after the early SASI phase, when the stalled shock radius has receded. The spiral SASI is a three-dimensional feature observed in earlier simulations (Kuroda et al 2016;Summa et al 2018;Andresen et al 2019) and cannot be seen in axisymmetric two-dimensional simulations.…”

Features of Accretion-phase Gravitational-wave Emission from Two-dimensional Rotating Core-collapse Supernovae

“…This results in a "muting" of the GW signal with increasing rotation speeds. While the origins of this muting are physical, such behavior may not be seen in full 3D simulations of CCSNe due to the appearance of spiral modes of the SASI and magnetorotational instabilities (MRI) (Cerdá-Durán et al 2007;Andresen et al 2019) .…”

Characterizing the Gravitational Wave Signal from Core-collapse Supernovae

“…However, a number of sophisticated neutrino-radiation-hydrodynamics simulations of CCSN have become available in the past several years (Tamborra et al 2013;Melson et al 2015b;Lentz et al 2015;Melson et al 2015a;Roberts et al 2016;Müller et al 2017;Ott et al 2018;Summa et al 2018;Kuroda et al 2018;O'Connor & Couch 2018;Vartanyan et al 2019;Glas et al 2019). Gravitational wave signals have been published for ten of these models (Andresen et al 2017;Yakunin et al 2017;Andresen et al 2018). However, even though these simulations exhibit some common qualitative features, it is difficult to extract general quantitative conclusions from the published data, because of the limited number of models and the variety of employed microphysical treatments and numerical setups.…”