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Gravitational waves from supernova explosions

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Gravitational waves from supernova explosions

 

The observed supernova frequencies of different types (SN Ia, Ib, II) in different types of galaxies (E-...-S-...-Ir) (see van den Bergh and Tammann, 1991[200]) immediately provide us with the SN frequency distribution in space. We can investigate projection of this distribution onto the celestial sphere in two ways: in terms of lines of constant SN frequencies per one square degree for all galaxies from the sample (Figure 36), and in terms of constant GW amplitudes at a given SN frequency per square degree (Figure 44).

 
Figure 44: Distribution of GW amplitudes from SN events over the sky. Inside regions encircled by the lines the total SN event rate >1/30 yrtex2html_wrap_inline8935 degtex2html_wrap_inline8937 at a given level of tex2html_wrap_inline8939 (Lipunov et al., 1995a). 

Inside regions encircled by the lines of constant SN frequency in Figure 45, the total SN frequency exceeds 1 per 3, 10, 30 and 100 year per square degree, respectively. This figure represents the cross-sections of the projected mass density per square degree by mass.

 
Figure 45: The sky distribution of the total supernova frequency from nearby galaxies in terms of lines of equal frequencies per square degree. The total SN frequency exceeds 1 per 3, 10, 30 and 100 year per square degree inside regions encircled by the lines (Lipunov et al., 1995a).  

Inside regions encircled by the lines of constant tex2html_wrap_inline8939 (Figure 44), the total SN event rate at a given level of tex2html_wrap_inline8939 . In other words, the cross-sections of nearby galaxy space distribution by distance are given by this figure.

We assume after Thorne (1988)[191] the characteristic strain metric amplitude tex2html_wrap_inline8939 to be:

displaymath12336

where is a distance to the source, is the total energy radiated as GW; a conservative estimate of GW energy during SN explosion tex2html_wrap_inline89450.1 percent of the expected neutrino  luminosity is used. The characteristic frequency of the GW burst  is assumed to be 1 kHz. We must note that GW bursts produced by supernova explosions have been poorly understood so far, so only relative figures of tex2html_wrap_inline8939 may have meaning.

In Figure 46 the SN rates of different types integrated over the whole sky are plotted as a function of a given detector sensitivity in terms of the strain metric amplitude h. Clearly seen are contributions from the closest groups of galaxies and the Virgo cluster (assuming a Hubble constant of 75 km stex2html_wrap_inline8853). At better sensitivities () a power law with a slope of -3 is seen, , which reflects the almost isotropical distribution of matter beyond tex2html_wrap_inline89457 Mpc. The total rate of SN events over the sky for nearby galaxies is about 40 per year.

 

Figure 46: SNe rates of different types integrated over the whole sky as a function of a given detector sensitivity in terms of strain metric amplitude h. Contributions from some close groups of galaxies are indicated (Lipunov et al., 1995a). 


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Next: Gravitational Waves from Coalescing Up: A Gravitational Wave Map Previous: A Gravitational Wave Map

Mike E. Prokhorov
Sat Feb 22 18:38:13 MSK 1997