The results of Fryer, Woosley, and Heger suggest that the collapse remnant (prior to black hole formation) is susceptible to the development of a secular bar-mode instability. However, at , the GW emission would be redshifted out of LIGO-II’s frequency range. At , , with a corresponding frequency of [86, 88]. Even if such a signal persists for a hundred cycles, it probably would be undetectable by LIGO-II. Note that these signal strengths are orders of magnitude lower than the qualitative estimates of signal strength given in Carr, Bond, and Arnett .
LIGO-II may be able to detect the GW emission from binary clumps formed via a fragmentation instability. If such a signal is emitted at and persists for 10 cycles, would be , over a frequency range of [86, 88]. The likelihood of the development of a fragmentation instability is diminished by the fact that the off-center density maxima present in the simulations of Fryer, Woosley, and Heger are not very pronounced.
The “ring-down” of the black hole remnant will likely be strong because Fryer, Woosley, and Heger observe a high accretion rate after collapse. FHH estimate that for a source located at , the GWs would be redshifted out of LIGO-II’s bandwidth. However, for a source at , and the frequency range is . This signal may be marginally detectable with LIGO-II (see Figure 2).
© Max Planck Society and the author(s)