Astron. Astrophys. 338, 535-555 (1998)

Colliding neutron stars

Gravitational waves, neutrino emission, and gamma-ray bursts

M. Ruffert ^{* 1} and H.-Th. Janka <sup>** 2

1</sup> Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
² Max-Planck-Institut für Astrophysik, Postfach 1523, D-85740 Garching, Germany

Received 15 April 1998 / Accepted 21 July 1998

Abstract

Three-dimensional hydrodynamical simulations are presented for the direct head-on or off-center collision of two neutron stars, employing a basically Newtonian PPM code but including the emission of gravitational waves and their back-reaction on the hydrodynamical flow. A physical nuclear equation of state is used that allows us to follow the thermodynamical evolution of the stellar matter and to compute the emission of neutrinos. Predicted gravitational wave signals, luminosities and waveforms, are presented. The models are evaluated for their implications for gamma-ray burst scenarios. We find an extremely luminous outburst of neutrinos with a peak luminosity of more than for several milliseconds. This leads to an efficiency of about 1% for the annihilation of neutrinos with antineutrinos, corresponding to an average energy deposition rate of more than and a total energy of about deposited in electron-positron pairs around the collision site within 10 ms. Although these numbers seem very favorable for gamma-ray burst scenarios, the pollution of the pair-plasma cloud with nearly of dynamically ejected baryons is 5 orders of magnitude too large. Therefore the formation of a relativistically expanding fireball that leads to a gamma-ray burst powered by neutrino emission from colliding neutron stars is definitely ruled out.

Key words: gamma rays: bursts gravitational waves elementary particles hydrodynamics stars: binaries: close stars: neutron

* e-mail: mruffert@ast.cam.ac.uk
** e-mail: thj@mpa-garching.mpg.de

Send offprint requests to: H.-Th. Janka

© European Southern Observatory (ESO) 1998

Online publication: September 14, 1998

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