Multimessenger observations of core-collapse supernovae: Exploiting the standing accretion shock instability

The gravitational wave (GW) and neutrino signals from core-collapse supernovae (CCSNe) are expected to carry pronounced imprints of the standing accretion shock instability (SASI). We investigate whether the correlation between the SASI signatures in the GW and neutrino signals could be exploited to enhance the detection efficiency of GWs. We rely on a benchmark full-scale three-dimensional CCSN simulation with zero-age main sequence mass of $27M_{\odot }$. Two search strategies are explored: 1. the inference of the SASI frequency range and/or time window from the neutrino event rate detectable at the IceCube Neutrino Observatory; 2. the use of the neutrino event rate to build a matched filter template. We find that incorporating information from the SASI modulations of the IceCube neutrino event rate can increase the detection efficiency compared to standard GW excess energy searches up to 30% for nearby CCSNe. However, we do not find significant improvements in the overall GW detection efficiency for CCSNe more distant than 1.5 kpc. We demonstrate that the matched filter approach performs better than the unmodeled search method, which relies on a frequency bandpass inferred from the neutrino signal. The improved detection efficiency provided by our matched filter method calls for additional work to outline the best strategy for the first GW detection from CCSNe.

Figure 1

Gravitational wave strain (left column, in blue) and IceCube event rate for ${\overline{\nu }}_e$ (no flavor conversion, in red) and ${\overline{\nu }}_x$ (full flavor conversion, in green) (right column) for our benchmark CCSN model, assuming a CCSN at 10 kpc. The observer directions are selected for strong (top plots), intermediate (middle plots) and weak (bottom plots) neutrino SASI modulations, respectively. The subpanels in the left plots show the cross (top) and plus (bottom) polarization modes of the GW signal. The bottom panels, labeled “Filtered,” show the GW (left) and neutrino signals (right) after low-pass and high-pass band filters have been applied. The filters remove any part of the signal below 50 Hz and above 300 Hz. The filtered GW and neutrino signals show a certain degree of correlation in their modulations.

Figure 2

Flowchart of the novel matched filter pipeline proposed in this paper to search for GWs by relying on the SASI signatures detectable in the neutrino signal.

Figure 3

Detection efficiency for our three selected waveforms and different detection strategies. The top panel shows the MF method where the filter was constructed by relying on the SASI time periods reconstructed from neutrino signal. The middle panel shows the MF method, with a band pass filter. The bottom panel compares the best performing MF curves of the top and middle panel to the standard EP method. The black curve represents the fiducial cWB search, while the gray curve represents a cWB search where we have restricted the frequency range to be [50, 300] Hz. The solid lines refer to the scenario with no flavor mixing, while the dashed lines represent the case of full-flavor conversion. All efficiencies are calculated at a $\mathrm{FAR}\approx 1/\mathrm{year}$ and a distance of 0.5 kpc. Note that the $y$-axis in the bottom panel differs from the other two.

Figure 4

Detection efficiency as a function of the CCSN distance for the MF and EP methods. The top, middle, and bottom panels represent the detection efficiency for waveform 1, 2, and 3, respectively. For CCSNe occurring beyond 1.5 kpc, the efficiency of the MF methods rapidly degrades, and the EP approach tends to perform better.