Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars
Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star–black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1 post-Newtonian (1PN) order, it was found that O(20) sources would suffice to distinguish between a stiff, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOSs and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses.
© 2015 American Physical Society. (Received 19 March 2015; published 28 July 2015) M. A., J. M., M. T., C. V. D. B., and J. V. were supported by the research program of the Foundation for Fundamental Research on Matter (FOM), which is partially supported by the Netherlands Organisation for Scientific Research (NWO). J. V. was also supported by the UK Science and Technology Facilities Council Grant No. ST/K005014/1. S. V. acknowledges the support of the National Science Foundation and the LIGO Laboratory. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation and operates under Cooperative Agreement No. PHY-0757058. The work was funded in part by a Leverhulme Trust research project grant. The authors would like to acknowledge the LIGO Data Grid clusters, without which the simulations could not have been performed. Specifically, these include the computing resources supported by National Science Foundation Grants No. PHY-0923409 and No. PHY-0600953 to the University of Wisconsin–Milwaukee. Also, we thank the Albert Einstein Institute in Hannover, Germany, supported by the Max-Planck-Gesellschaft, for use of the Atlas high-performance computing cluster. It is a pleasure to thank Brynmor Haskell for the useful input on the "I-Love-Q" relations and Benjamin D. Lackey for the useful discussions.
Submitted - 1503.05405v2.pdf
Published - PhysRevD.92.023012.pdf