Core collapse supernovae are among the most energetic explosions in the modern Universe and one of the long-standing riddles of stellar astrophysics. According to the standard paradigm of the neutrino-driven mechanism of such explosion, the energy transfer by the intense neutrino flux can be the decisive agents for powering the supernova outburst. We expect the next generation of neutrino telescopes (KM3NeT, Icecube-Gen2, HyperKamiokande) to be able to discriminate the core collapse supernova signal from the noise with high accuracy. The collapse of the iron core of a massive star is expected to produce also gravitational waves in addition to neutrinos. While neutrinos carry information about the mode amplitude in the outer region of the core, gravitational waves probe deeper in. To enhance the detection efficiency of core collapse supernova signals we present a novel multi-messenger method that takes advantage of the information coming from the neutrino signal and try to extract evidence for core collapse supernova simulated features embedded in Gaussian noise with spectral behaviour of the gravitational wave detectors (Advanced LIGO and Virgo). Using this new approach we can classify signal from noise and identify the signal more efficiently with the aim to increase the detectability distance of such type of source.
The numerical study of the dynamics of core-collapse supernovae allowed in the recent decades to identify specific hydrodynamics mechanisms which control the evolution of the shock wave. Among these dynamics, one that is expected to produce signatures both in the neutrino and the gravitational wave emission is the Standing Accretion Shock Instability (SASI) .
SASI is a hydrodynamical mode with a typical frequency, phase and possibly varying amplitude that develops when a deformed stalled shock front precedes around the newly formed proto-neutron star (PNS). Such precession in turn induces an asymmetric accretion onto the PNS, resulting in fluctuations in the luminosity of the emitted neutrinos, and the emission of gravitational waves (GW).
At this moment, SASI is a hypothesis supported by numerical simulations that awaits observational tests. Neutrinos and GW are the only messengers that can, for a future Galactic supernova, directly probe this phenomenon and provide measurements of the relevant parameters. Such measurements will clarify the properties of the PNS, the nuclear equation of state (EOS), ultimately the yet-uncertain supernova explosion mechanism.
In this project we advance the topic to a more quantitative level, by establishing a framework which is new in the context of gravitational wave and neutrino data analyses. This methodology is an implementation of the maximum likelihood principle, and uses the probability density function distributions of the observed power at different frequencies. By using core-collapse simulations of [1] as test bed for the method, we will identify the SASI and constrain the astronomical distance at which a CCSNe could be identified with the existing detectors: the horizon for our research. As part of the likelihood-based analysis we will also try to address the question of parameter estimation and compare the results for the parameter variances to the optimally possible variance.
The present proposal is intended as a first step towards a joint description of the problem for neutrinos and gravitational waves.
[1] T. Kuroda, K. Kotake, K. Hayama, and T. Takiwaki, Astrophys. J. 851, 62 (2017).