Revisiting the Galactic Double Neutron Star merger and LIGO detection rates

TL;DR

This paper refines the Galactic double neutron star merger rate estimates by incorporating detailed beam shape and viewing geometry, resulting in more accurate predictions for LIGO detection rates.

Contribution

It introduces a new method that uses actual beam shape data of pulsars to improve merger rate estimates, reducing systematic uncertainties.

Findings

The joint Galactic DNS merger rate is estimated at 32^{+19}_{-9} Myr^{-1}.

The LIGO detection rate is estimated at 3.5^{+2.1}_{-1.0} Myr^{-1}.

Methodology aligns well with previous estimates, confirming its robustness.

Abstract

We revisit the merger rate for Galactic double neutron star (DNS) systems in light of recent observational insight into the longitudinal and latitudinal beam shape of the relativistic DNS PSR J1906$+$0746. Due to its young age and its relativistic orbit, the pulsar contributes significantly to the estimate of the joint Galactic merger rate. We follow previous analyses by modelling the underlying pulsar population of nine merging DNS systems and study the impact and resulting uncertainties when replacing simplifying assumptions made in the past with actual knowledge of the beam shape, its extent and the viewing geometry. We find that the individual contribution of PSR J1906$+$0746 increases to $R = 6^{+28}_{-5}$ Myr$^{-1}$ although the values is still consistent with previous estimates given the uncertainties. We also compute contributions to the merger rates from the other DNS systems by applying a generic beam shape derived from that of PSR J1906+0746, evaluating the impact of previous assumptions. We derive a joint Galactic DNS merger rate of $R^{\rm{gen}}_{\rm{MW}} = 32^{+19}_{-9}$Myr$^{-1}$, leading to a LIGO detection rate of ${R}^{\rm{gen}}_{\rm{LIGO}} = 3.5^{+2.1}_{-1.0}$Myr$^{-1}$ (90% conf. limit), considering the upcoming O3 sensitivity of LIGO. As these values are in good agreement with previous estimates, we conclude that the method of estimating the DNS merger and LIGO detection rates via the study of the radio pulsar DNS population is less prone to systematic uncertainties than previously thought.