Binaries With Black Holes

Black holes in binary systems spiral together, as they emit gravitational waves, just as binary neutron stars do. The gravitational waves from, and the dynamics of, the coalescence will be quite different, however. 

The merger and ringdown of the black hole will produce a burst of gravitational radiation that is in the HF band for stellar-mass black holes, or in the LF band for supermassive black holes. Typically, the black holes will 

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Coalescing neutron star binaries. Coalescing of neutron stars (or black holes) is foreseen to be the the most powerful source of detectable gw. The frequency of such events is estimated to be ly D/200 Mpc) and their amplitude will allow detection of sources as far as 50 Mpc. We are thus waiting for about one event every 60 years with the current sensitivity of detectors. 

Black holes. One great achievement of gravitational wave astronomy would be the first detection of a signal coming directly from a black hole. Just like with neutron stars, black holes can emit gw either alone or in binary systems. 

In these considerations, it must be kept in mind that there is a stellar spike around the black hole at the Galactic Center. The steepness of this stellar spike is however not very well know. With large uncertainties, Genzel et al.(2003) estimate the slope of the stellar spike to be 7stars 1.3-1.4. This means that the current stellar spike is probably shallow. We may think that the stellar spike is our best proxy for the dark matter spike. If so, also the dark matter spike would also be shallow, and thus inconsequential for neutralino signals. However, the dark matter and stellar spikes follow very different evolution histories, because contrary to the dark matter, binary collisions of stars and coalescence of two stars into one at collisions effectively relax the stellar system to a shallower spike. 

The analysis of nucleosynthesis in hypernovae suggests a possible classification scheme of supernova explosions [111]. In this scheme, core collapse in stars with initial main sequence masses Mms < 25 — 30M leads to the formation of neutron stars, while more massive stars end up with the formation of black holes. Whether or not the collapse of such massive stars is associated with powerful hypernovae ( Hypernova branch ) or faint supernovae ( Faint SN branch ) can depend on additional ( hidden ) physical parameters, such as the presupernova rotation, magnetic fields. [39], or the GRB progenitor being a massive binary system component [145, 117]. The need for other parameters determining the outcome of the core collapse also follows from the continuous distribution of C+O cores of massive stars before the collapse, as inferred from observations, and strong discontinuity between masses of compact remnants (the mass gap between neutron stars and black holes) [28]2. 

The end-over-end tumble of binary star systems is an excellent source of gravitational waves in both the LF and HF bands. The gravitational wave frequency increases with the total mass of the system, and is inversely proportional to the separation of the binary elements. Thus, compact binaries composed of neutron stars and/or stellar-mass black holes radiate at the highest frequencies since the elements can get very close together without merging. 

FIGURE 2 The intensity of some astrophysical sources. CB, compact binaries WDB, white dwarf binaries CBC, compact binary coalescence SN, supernovae a, coalescence of binary black holes with 10 /W b, black hole formations with 10 Mq c, black hole binary with 10 M d, black hole-black hole with 10 /W . 

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