3 research outputs found
Expected Coalescence Rate of Double Neutron Stars for Ground Based Interferometers
In this paper we present new estimates of the coalescence rate of neutron
star binaries in the local universe and we discuss its consequences for the
first generations of ground based interferometers. Our approach based on both
evolutionary and statistical methods gives a galactic merging rate of 1.7
10 yr, in the range of previous estimates 10 - 10
yr. The local rate which includes the contribution of elliptical
galaxies is two times higher, in the order of 3.4 10 yr. We
predict one detection every 148 and 125 years with initial VIRGO and LIGO, and
up to 6 events per year with their advanced configuration. Our recent detection
rate estimates from investigations on VIRGO future improvements are quoted.Comment: talk given at the GWDAW9 (Annecy, 2004) to be published in CQ
Advanced VIRGO: detector optimization for gravitational waves by inspiralling binaries
For future configurations, we study the relation between the abatement of the
noise sources and the Signal to Noise Ratio (SNR) for coalescing binaries. Our
aim is not the proposition of a new design, but an indication of where in the
bandwidth or for which noise source, a noise reduction would be most efficient.
We take VIRGO as the reference for our considerations, solely applicable to the
inspiralling phase of a coalescing binary. Thus, only neutron stars and small
black holes of few solar masses are encompassed by our analysis. The
contributions to the SNR given by final merge and quasi-normal ringing are
neglected. It is identified that i) the reduction in the mirror thermal noise
band provides the highest gain for the SNR, when the VIRGO bandwidth is divided
according to the dominant noises; ii) it exists a specific frequency at which
lies the potential largest increment in the SNR, and that the enlargement of
the bandwidth, where the noise is reduced, produces a shift of such optimal
frequency to higher values; iii) the abatement of the pendulum thermal noise
provides the largest, but modest, gain, when noise sources are considered
separately. Our recent astrophysical analysis on event rates for neutron stars
leads to a detection rate of one every 148 or 125 years for VIRGO and LIGO,
respectively, while a recently proposed and improved, but still conservative,
VIRGO configuration would provide an increase to 1.5 events per year. Instead,
a bi-monthly event rate, similar to advanced LIGO, requires a 16 times gain. We
analyse the 3D (pendulum, mirror, shot noises) parameter space showing how such
gain could be achieved.Comment: Change of title (Virgo detector optimization for gravitational waves
by coalescing binaries) and partially of text. 6 figure
Expected coalescence rates of NS-NS binaries for laser beam interferometers
The coalescence rate of two neutron stars (NS) is revisited. For estimation
of the number of bound NS-NS and the probability of their coalescence in a
timescale , the galactic star formation history, directly derived from
observations, and the evolution of massive stars are considered. The newly
established galactic merging rate is ,
while the local merging rate, including the contribution of elliptical
galaxies, is about a factor of two higher, . Using
the present data basis on galaxy distribution in the local universe and the
expected sensitivity of the first generation of laser beam interferometers, we
estimate that one event should occur every 125 years for LIGO and one event
each 148 years for VIRGO. The situation is considerably improved for
advanced-LIGO since we predict that 6 events per year should be detected
whereas for a recently proposed VIRGO new configuration, the event rate might
increase up to 3 events every two years.Comment: 15 pages, 3 figures accepted for publication in IJMP