An optimal envelope ejection efficiency for merging neutron stars

Abstract

We use the rapid binary stellar evolution code BINARY_C to estimate the rate of merging neutron stars with numerous combinations of envelope ejection efficiency and natal kick dispersion. We find a peak in the local rate of merging neutron stars around $\alpha \approx 0.3$$-$$0.4$, depending on the metallicity, where $\alpha$ is the efficiency of utilising orbital energy to unbind the envelope. The peak height decreases with increasing electron-capture supernova kick dispersion ${\sigma }_{\mathrm{ECSN}}$. We explain the peak as a competition between the total number of systems that survive the common-envelope phase increasing with $\alpha$ and their separation, which increases with $\alpha$ as well. Increasing $\alpha$ reduces the fraction of systems that merge within a time shorter than the age of the Universe and results in different mass distributions for merging and non-merging double neutron stars. This offers a possible explanation for the discrepancy between the Galactic double neutron star mass distribution and the observed massive merging neutron star event GW190425. Within the $\alpha$$-$${\sigma }_{\mathrm{ECSN}}$ parameter space that we investigate, the rate of merging neutron stars spans several orders of magnitude up to more than $1\times 10^3{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ and can be higher than the observed upper limit or lower than the observed lower limit inferred thus far from merging neutron stars detected by gravitational waves. Our results stress the importance of common-envelope physics for the quantitative prediction and interpretation of merging binary neutron star events in this new age of gravitational wave astronomy.

16 pages, 10 figures, this is an author-produced version of an article accepted for publication in MNRAS following peer review. The version of record is now available online at https://doi.org/10.1093/mnras/stad971 . (N.b. the tables are better formatted in the arXiv article.) Our data are available online at https://zenodo.org/record/7811486#.ZDJt6I5BzJU

References in corpus (27)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Cosmic Star Formation History
• Binary interaction dominates the evolution of massive stars
• Tests of general relativity from timing the double pulsar
• Formation of Double Neutron Star Systems
• Timing Measurements of the Relativistic Binary Pulsar PSR B1913+16
• Metallicity Evolution of Damped Lyman-alpha Systems out to z~5
• The observed velocity distribution of young pulsars
• Double neutron stars: merger rates revisited
• Evolution of magnetized, differentially rotating neutron stars: Simulations in full general relativity
• The impact of companions on stellar evolution
• Measurement of Orbital Decay in the Double Neutron Star Binary PSR B2127+11C
• Asymmetric Accretion Flows within a Common Envelope
• Winds from stripped low-mass Helium stars and Wolf-Rayet stars
• Multi-telescope timing of PSR J1518+4904
• Binary stars in the Galactic thick disc
• On the role of recombination in common-envelope ejections
• Advanced LIGO Constraints on Neutron Star Mergers and R-Process Sites
• The High Time Resolution Universe Pulsar Survey XII : Galactic plane acceleration search and the discovery of 60 pulsars
• The binary pulsar PSR J1811-1736: evidence of a low amplitude supernova kick
• PSR J1930-1852: a pulsar in the widest known orbit around another neutron star
• Modelling Neutron Star-Black Hole Binaries: Future Pulsar Surveys and Gravitational Wave Detectors
• Effects of winds on the leftover hydrogen in massive stars following Roche lobe overflow
• Electron Capture Supernovae From Close Binary Systems
• PSR J1753-2240: A mildly recycled pulsar in an eccentric binary system
• Energizing the last phase of common envelope removal
• X-ray binaries and their descendants: binary radio pulsars; evidence for three classes of neutron stars?