Astron. Astrophys. 332, 173-188 (1998)

Formation and evolution of binary neutron stars

S.F. Portegies Zwart ¹ and L.R. Yungelson <sup>1, 2

1</sup> Astronomical Institute Anton Pannekoek, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands (spz@astro.uva.nl)
² Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya Str., 109017 Moscow, Russia (lry@inasan.rssi.ru)

Received 1 July 1997 / Accepted 7 November 1997

Abstract

The formation and evolution of binaries which contain two neutron stars or a neutron star with a black hole companion are discussed in detail. The evolution of the distributions in orbital period and eccentricity for neutron star binaries are studied as a function of time. In the model which fits the observations of high mass binary pulsars best the deposition of orbital energy into common envelopes has to be very efficient and a kick velocity distribution has to contain a significant contribution of low velocity kicks. The estimated age of the population has to be between several 100 Myr and 1 Gyr. The birthrate of neutron stars binary is yr^-1 (assuming 100% binarity) and their merger rate is yr^-1. The merger rate of neutron star binaries is consistent with the estimated rate of -ray bursts, if the latter are beamed into an opening angle of a few degrees. We argue that PSR B2303+46 is possibly formed in a scenario in which the common envelope is avoided while for the other three known high-mass binary pulsars a common envelope is required to explain their orbital period.

Key words: binaries: close stars: neutron pulsars: general Galaxy: stellar content

Send offprint requests to: S.F. Portegies Zwart

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Contents

• 1. Introduction
• 2. Formation of binary neutron stars
  • 2.1. Scenarios of formation
  • 2.2. Common envelopes
  • 2.3. The model
• 3. Results
  • 3.1. Birthrates of neutron stars and related binaries
  • 3.2. Neutron star-neutron star binaries
  • 3.3. Orbital period-eccentricity plane for neutron-star binaries
• 4. Discussion
  • 4.1. Populaton of HMBP and their merger times
  • 4.2. Merger rate in the Universe and -ray bursts
  • 4.3. Black hole plus neutron star binaries
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: March 10, 1998
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