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Title

The long and the short of it: modelling double neutron star and collapsar galactic dynamics

Author(s)

Kiel, Paul D.;  Hurley, Jarrod R.;  Bailes, Matthew

Abstract

Understanding the nature of galactic populations of double compact binaries (where both stars are a neutron star or black hole) has been a topic of interest for many years, particularly the coalescence rate of these binaries. The only observed systems thus far are double neutron star systems containing one or more radio pulsars. However, theorists have postulated that short-duration gamma-ray bursts may be evidence of coalescing double neutron star or neutron star-black hole binaries, while long-duration gamma-ray bursts are possibly formed by tidally enhanced rapidly rotating massive stars that collapse to form black holes (collapsars). The work presented here examines populations of double compact binary systems and tidally enhanced collapsars. We make use of binpop and binkin, two components of a recently developed population synthesis package. Results focus on correlations of both binary and spatial evolutionary population characteristics. Pulsar and long-duration gamma-ray burst observations are used in concert with our models to draw the conclusions that (i) double neutron star binaries can merge rapidly on time-scales of a few million years (much less than that found for the observed double neutron star population), (ii) common-envelope evolution within these models is a very important phase in double neutron star formation and (iii) observations of long gamma-ray burst projected distances are more centrally concentrated than our simulated coalescing double neutron star and collapsar Galactic populations. Better agreement is found with dwarf galaxy models although the outcome is strongly linked to the assumed birth radial distribution. The birth rate of the double neutron star population in our models ranges from 4 to 160 Myr-1 and the merger rate ranges from 3 to 150 Myr-1. The upper and lower limits of the rates result from including electron-capture supernova kicks to neutron stars and decreasing the common-envelope efficiency, respectively. Our double black hole merger rates suggest that black holes should receive an asymmetric kick at birth.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Monthly Notices of the Royal Astronomical Society, Vol. 406, no. 1 (Jul 2010), pp. 656-672

Publication year

2010

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Close binaries;  Gamma-ray bursts;  Neutron stars;  Pulsars;  Stellar evolution;  Stellar content

Publisher

Wiley-Blackwell

ISSN

1365-2966

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2010.16717.x

Copyright

Copyright © 2010 The Authors. Journal compilation copyright © 2010 Royal Astronomical Society. The accepted manuscript of the paper is reproduced here in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Full text

Peer reviewed