36 research outputs found
Detectability of f-mode Unstable Neutron Stars by the Schenberg Spherical Antenna
The Brazilian spherical antenna (Schenberg) is planned to detect high
frequency gravitational waves (GWs) ranging from 3.0 kHz to 3.4 kHz. There is a
host of astrophysical sources capable of being detected by the Brazilian
antenna, namely: core collapse in supernova events; (proto)neutron stars
undergoing hydrodynamical instability; f-mode unstable neutron stars, caused by
quakes and oscillations; excitation of the first quadrupole normal mode of 4-9
solar mass black holes; coalescence of neutron stars and/or black holes; exotic
sources such as bosonic or strange matter stars rotating at 1.6 kHz; and
inspiralling of mini black hole binaries. We here address our study in
particular to the neutron stars, which could well become f-mode unstable
producing therefore GWs. We estimate, for this particular source of GWs, the
event rates that in principle can be detected by Schenberg and by the Dutch
Mini-Grail antenna.Comment: 7 pages, 3 figures; Classical and Quantum Gravity (in press
Silicon emissivity as a function of temperature
In this paper we present the temperature-dependent emissivity of a silicon sample, estimated from its cool-down curve in a constant low temperature environment ( ~ 82K). The emissivity value follow a linear dependency in the 120–260 K temperature range. This result is of great interest to the LIGO Voyager gravitational wave interferometer project since it would mean that no extra high thermal emissivity coating on the test masses would be required in order to cool them down to 123 K. The results presented here indicate that bulk silicon itself can have sufficient thermal emissivity in order to cool the 200 kg LIGO Voyager test masses only by radiation in a reasonable short amount of time (less than a week). However, it is still not clear if the natural emissivity of silicon will be sufficient to maintain the LIGO Voyager test masses at the desired temperature (123 K) while removing power absorbed by the test masses. With the present results, a black coating on the barrel surface of the test masses would be necessary if power in excess of 6 W is delivered. However, the agreement we found between the hemispherical emissivity obtained by a theory of semi-transparent Silicon and the obtained experimental results makes us believe that the LIGO Voyager test masses, because of their dimensions, will have effective emissivities around 0.7, which would be enough to remove about 8.6 W (7.5 W) for a shield at 60 K (80 K). This hypothesis may be confirmed in the near future with new measurements
Possible Strong Gravitational Wave Sources for the LISA Antenna
Recently Fuller & Shi proposed that the gravitational collapse of
supermassive objects () could be a cosmological source
of -ray bursts (GRBs). The major advantage of their model is that
supermassive object collapses are far more energetic than solar mass-scale
compact mergers. Also, in their proposal the seeds of supermassive black holes
(SMBHs) thus formed could give rise to the SMBHs observed at the center of many
galaxies. We argue here that, besides the generation of GRBs, there could well
occur a strong generation of gravitational waves (GWs) during the formation of
SMBHs. As a result, the rate of such GW bursts could be as high as the rate of
GRBs in the model by Fuller & Shi. In this case, the detection of GRBs and
bursts of GWs should occur with a small time difference. We also argue that the
GWs produced by the SMBHs studied here could be detected when the Laser
Interferometric Space Antenna (LISA) becomes operative.Comment: 10 pages (AAS Latex macros v5.0.2), 2 eps figures. The Astrophysical
Journal (accepted
Astrophysics from data analysis of spherical gravitational wave detectors
The direct detection of gravitational waves will provide valuable
astrophysical information about many celestial objects. Also, it will be an
important test to general relativity and other theories of gravitation. The
gravitational wave detector SCHENBERG has recently undergone its first test
run. It is expected to have its first scientific run soon. In this work the
data analysis system of this spherical, resonant mass detector is tested
through the simulation of the detection of gravitational waves generated during
the inspiralling phase of a binary system. It is shown from the simulated data
that it is not necessary to have all six transducers operational in order to
determine the source's direction and the wave's amplitudes.Comment: 8 pages and 3 figure
Response of the Brazilian gravitational wave detector to signals from a black hole ringdown
It is assumed that a black hole can be disturbed in such a way that a
ringdown gravitational wave would be generated. This ringdown waveform is well
understood and is modelled as an exponentially damped sinusoid. In this work we
use this kind of waveform to study the performance of the SCHENBERG
gravitational wave detector. This first realistic simulation will help us to
develop strategies for the signal analysis of this Brazilian detector. We
calculated the signal-to-noise ratio as a function of frequency for the
simulated signals and obtained results that show that SCHENBERG is expected to
be sensitive enough to detect this kind of signal up to a distance of .Comment: 5 pages, 4 figures, Amaldi 5 Conference Proceedings contribution.
Submitted to Class. Quantum Gra