Aims. We analyze the properties of VIRGO detector with the aim of studying its ability to search for coalescing black hole binaries. We focus on the remnants of the Population III stars, which currently should be massive black holes (∼100−1000 M ), some of them bound in binary systems. The coalescence of such binaries due to emission of gravitational waves may be currently observable. Methods. We use a binary population synthesis to model the evolution of Population III binaries. Results. We calculate the signal to noise ratios of gravitational waves emitted by the system in each of the coalescence phase: inspiral, merger and ringdown, and provide simple formulae for the signal to noise ratio as a function of masses of the binaries. We estimate the detection rates for the VIRGO interferometer and also compare them with the estimates for the current LIGO. We show that these expected rates are similar to, or larger than the expected rates from coalescences of Population I and II compact object binaries.

Possible astrophysical consequences of the Hořava quantum gravity theory have been recently studied by several authors. They usually employ the Kehagias-Sfetsos (KS) spacetime which is a spherically symmetric vacuum solution of a specific version of Hořava's gravity. The KS metric has several unusual geometrical properties that in the present article we examine by means of the often used technique of embedding diagrams. We pay particular attention to the transition between naked singularity and black-hole states, which is possible along some particular sequences of the KS metrics.

No abstract