In general, the signal at bounce is strongest for the rotating (and most asymmetric) explosions. The
strong bounce signal is possible in AICs, low-mass collapse and normal core-collapse supernovae. The rest of
the signals in Figures 32 and 33
are only appropriate for normal core-collapse supernovae. Except in the
fastest-rotating cases, the signals from AICs, low-mass collapse and normal supernovae are only observable
if they occur within local group galaxies. We are unable to observe stellar collapse in the nearby Virgo
cluster. A detection of a stellar collapse in this cluster would argue that either extreme rotation does occur
in stars or that bar modes exist in these cores.
If bar modes do develop in the proto neutron star, the GW signal may be orders of magnitude higher
amplitude than that produced in the bounce or convective phase. Figure 23 shows the signal for bar-mode
sources assuming the source is at 10 Mpc instead of the 10 kpc. Dynamical bar modes could be easily
detected out to the Virgo cluster. Even secular bar modes should be detected out to Virgo. If such modes
are produced in even 1/10th of all stellar collapses, advanced LIGO should detect multiple GW outbursts
per year as soon as it reaches its design specifications. Non-detections place limits on the spin rate of
stars.
Black hole forming systems have the potential to form stronger GWs. But the fragmentation claimed in
many results did not occur in the 3-dimensional models by Rockefeller et al. [250]. Their predicted GW
signal was on par with the upper limits to rotational collapse shown in Figure 32. Like normal
stellar collapse, black-hole–forming objects are unlikely to be observed as far out as the Virgo
cluster.
Although the signal for very massive stars () is expected to be much larger than other
black-hole–forming systems, these objects are believed to only form in the early universe (modest
metallicities cause these stars to lose most of their mass in winds, in case they behave more like lower-mass
black-hole–forming systems). At such distances, these collapses will be difficult to observe. However, if the
rate of these objects is high, it may be that future detectors such as the DECi-hertz Interferometer
Gravitational wave Observatory (DECIGO) and the Big Bang Observer (BBO) may be able to detect GW
emission from these objects [298].
The possible exception for detectable GW emission from black-hole formation is the formation of
SMBHs. SMBHs exist. If they are formed in the collapse of an SMS, a number of observational sources
should allow us to observe these objects with LISA (Figure 30).
http://www.livingreviews.org/lrr-2011-1 |
Living Rev. Relativity 14, (2011), 1
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