Equation of state effects on gravitational waves from rotating core collapse

Abstract

Gravitational waves (GWs) generated by axisymmetric rotating collapse, bounce, and early postbounce phases of a galactic core-collapse supernova are detectable by current-generation gravitational wave observatories. Since these GWs are emitted from the quadrupole-deformed nuclear-density core, they may encode information on the uncertain nuclear equation of state (EOS). We examine the effects of the nuclear EOS on GWs from rotating core collapse and carry out 1824 axisymmetric general-relativistic hydrodynamic simulations that cover a parameter space of 98 different rotation profiles and 18 different EOS. We show that the bounce GW signal is largely independent of the EOS and sensitive primarily to the ratio of rotational to gravitational energy, T=jWj, and at high rotation rates, to the degree of differential rotation. The GW frequency (f peak ∼ 600-1000 Hz) of postbounce core oscillations shows stronger EOS dependence that can be parametrized by the core's EOS-dependent dynamical frequency ffiffiffiffiffiffiffiffi Gρ c p . We find that the ratio of the peak frequency to the dynamical frequency f peak = ffiffiffiffiffiffiffiffi Gρ c p follows a universal trend that is obeyed by all EOS and rotation profiles and that indicates that the nature of the core oscillations changes when the rotation rate exceeds the dynamical frequency. We find that differences in the treatments of lowdensity nonuniform nuclear matter, of the transition from nonuniform to uniform nuclear matter, and in the description of nuclear matter up to around twice saturation density can mildly affect the GW signal. More exotic, higher-density physics is not probed by GWs from rotating core collapse. We furthermore test the sensitivity of the GW signal to variations in the treatment of nuclear electron capture during collapse. We find that approximations and uncertainties in electron capture rates can lead to variations in the GW signal that are of comparable magnitude to those due to different nuclear EOS. This emphasizes the need for reliable experimental and/or theoretical nuclear electron capture rates and for self-consistent multidimensional neutrino radiation-hydrodynamic simulations of rotating core collapse.

Equation of state effects in the core collapse of a 20−M⊙ star

“…e main drawback of these studies is that o en the EOSs being compared were obtained with distinct approaches, used di erent prescriptions to describe low density ma er, and, with the exception of Ref. [22] which analyzed changes resulting from using 18 different EOSs in their simulations, the number of EOSs investigated was rather small. us, in many cases, it was challenging to disentangle how a parameter of the EOS contributed to a given observable.…”

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

“…In order to validate this approximate approach for studying GWs from CCSNe, we compare our results to those of Richers et al (2017), who use a CFC GR approach. We find that our simulations produce nearly identical GW bounce signals to those of Richers et al (2017). This paper is organized as follows: in Section 2 we present our methods and treatment of microphysics within our FLASH simulations.…”

“…GW strain vs. time (postbounce) for a 12 M progenitor(Woosley & Heger 2007) with Ω0 = 3 rad s −1 . Plotted in the dashed line is the GW strain fromRichers et al (2017) using the CFC CoCoNuT code, and the solid line is our result using the effective relativistic potential coupled with Newtonian dynamics. While the different grids and treatment of hydrodynamics lead to differences in the strain in the early postbounce phase, we qualitatively verify our gravitational treatment by obtaining a nearly exact bounce signal.ers et al (2017)'s simulation by using a ray-by-ray, threespecies, neutrino leakage scheme (O'Connor & Ott 2010; Couch & O'Connor 2014)…”

Detection prospects of core-collapse supernovae with supernova-optimized third-generation gravitational-wave detectors

“…We can infer various physical parameters such as the nuclear equation of state, rotation rate, pulsation frequencies, etc. from the gravitational wave signal of a CCSN once it has been detected [9][10][11]. However, gravitational waves from CCSN are yet to be observed [12,13].…”