Avoided crossing in gravitational wave spectra from protoneutron star

Understand

The ramp up signals of gravitational waves appearing in the numerical simulations could be important signals to estimate parameters of the protoneutron star (PNS) at supernova explosions.

• To identify the signals with PNS oscillations, we make a linear perturbation analysis and compare the resultant eigenfrequencies with the ramp up signals obtained via the two-dimensional numerical simulations.
• Then, we find that the ramp up signals correspond well to the $g_1$-mode in the early phase and to the $f$-mode, to which the $g_1$-mode is exchanged via the avoided crossing.
• We also confirm that the $f$- and $g_1$-modes are almost independent of the selection of the PNS surface density in the later phase after core bounce.