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Inspiralling neutron stars |
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© AEI/ZIB |
Simulations of inspiralling neutron stars and black holes provide insights into the possible structure of gravitational wave signals. They significantly increase the probability of identifying gravitational waves in the detector data. The article focuses on the last few orbits before coalescence of binary neutron star systems and their experimental observation (which is expected in the coming years) by the network of gravitational wave detectors LIGO, GEO600 and Virgo - LIGO is in the United States, GEO600 is the German-British gravitational wave detector in Ruthe near Hannover, operated by the Albert Einstein Institute and Virgo is the French-Italian detector installed in Cascina, near Pisa.
By exploiting the computational power of supercomputers and by performing the most extended and accurate calculations of this process, a team of scientists from Germany, France, the U.S. and Japan was able to improve a simplified but analytical description of the inspiral stage, when the two stars are still separate but their orbit is shrinking because of the large emission of gravitational waves. The refinement of the analytic description via accurate numerical calculations has shown that it can be used with success also to describe objects with finite dimensions, such as neutron stars, extending its validity beyond the much simpler case of binary black holes. “We found out how to introduce corrections in simplified models of binary neutron stars, so that they can reproduce the results of complex numerical simulations”, says Professor Luciano Rezzolla, head of the numerical relativity group at the Albert Einstein Institute/AEI in Potsdam. This breakthrough opens the way to a large-scale modelling of the gravitational signal emitted by the last orbits of a system of two neutron stars with a precision adequate for detection.
An insight into neutron stars
In addition, the work provides important evidence that the detection of this type of signal will allow one to measure the ratio between the mass and radius of neutron stars. This measurement is potentially very important because it will give access to new information on the equation of state of ultra-dense nuclear matter, of which neutron stars are made, and which remains essentially unknown.
The article is the result of a collaboration between a team of numerical and analytical theorists of Relativistic gravity: Luca Baiotti (Osaka Universities, Japan), Thibault Damour (IHÉS, France), Bruno Giacomazzo (NASA Goddard, USA), Alessandro Nagar (IHÉS, France) and Luciano Rezzolla (Albert Einstein Institute, Germany).
More information on the group, as well as images and animations of the simulations can be found on the group web page:
Bibliography
L. Baiotti, T. Damour, B. Giacomazzo, A. Nagar and L. Rezzolla, Physical Review Letters, Vol.105, No. 26
arXiv:1009.0521v2 [gr-qc]
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