Dependence of the outer boundary condition on protoneutron star asteroseismology with gravitationalwave signatures
Abstract
To obtain the eigenfrequencies of a protoneutron star (PNS) in the postbounce phase of corecollapse supernovae (CCSNe), we perform a linear perturbation analysis of the angleaveraged PNS profiles using results from a general relativistic CCSN simulation of a 15 M_{☉} star. In this work, we investigate how the choice of the outer boundary condition could affect the PNS oscillation modes in the linear analysis. By changing the density at the outer boundary of the PNS surface in a parametric manner, we show that the eigenfrequencies strongly depend on the surface density. By comparing with the gravitational wave (GW) signatures obtained in the hydrodynamics simulation, the socalled surface g mode of the PNS can be well ascribed to the fundamental oscillations of the PNS. The frequency of the fundamental oscillations can be fitted by a function of the mass and radius of the PNS similar to the case of cold neutron stars. In the case that the position of the outer boundary is chosen to cover not only the PNS but also the surrounding postshock region, we obtain the eigenfrequencies close to the modulation frequencies of the standing accretionshock instability (SASI). However, we point out that these oscillation modes are unlikely to have the same physical origin of the SASI modes seen in the hydrodynamics simulation. We discuss possible limitations of applying the angleaveraged, linear perturbation analysis to extract the full ingredients of the CCSN GW signatures.
 Publication:

Physical Review D
 Pub Date:
 June 2019
 DOI:
 10.1103/PhysRevD.99.123024
 arXiv:
 arXiv:1906.04354
 Bibcode:
 2019PhRvD..99l3024S
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 accepted for publication in PRD