Observational Inference on the Delay Time Distribution of Short GammaRay Bursts
Abstract
The delay time distribution of neutron star mergers provides critical insights into binary evolution processes and the merger rate evolution of compact object binaries. However, current observational constraints on this delay time distribution rely on the small sample of Galactic double neutron stars (with uncertain selection effects), a single multimessenger gravitational wave event, and indirect evidence of neutron star mergers based on rprocess enrichment. We use a sample of 68 host galaxies of short gammaray bursts to place novel constraints on the delay time distribution and leverage this result to infer the merger rate evolution of compact object binaries containing neutron stars. We recover a powerlaw slope of $\alpha ={1.83}_{0.39}^{+0.35}$ (median and 90% credible interval) with α < 1.31 at 99% credibility, a minimum delay time of ${t}_{\min }={184}_{79}^{+67}\,\mathrm{Myr}$ with ${t}_{\min }\gt 72\,\mathrm{Myr}$ at 99% credibility, and a maximum delay time constrained to ${t}_{\max }\gt 7.95\,\mathrm{Gyr}$ at 99% credibility. We find these constraints to be broadly consistent with theoretical expectations, although our recovered powerlaw slope is substantially steeper than the conventional value of α = 1, and our minimum delay time is larger than the typically assumed value of 10 Myr. Pairing this cosmological probe of the fate of compact object binary systems with the Galactic population of double neutron stars will be crucial for understanding the unique selection effects governing both of these populations. In addition to probing a significantly larger redshift regime of neutron star mergers than possible with current gravitational wave detectors, complementing our results with future multimessenger gravitational wave events will also help determine if short gammaray bursts ubiquitously result from compact object binary mergers.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 2022
 DOI:
 10.3847/20418213/ac91cd
 arXiv:
 arXiv:2206.02814
 Bibcode:
 2022ApJ...940L..18Z
 Keywords:

 Gammaray bursts;
 Gravitational wave sources;
 Compact binary stars;
 629;
 677;
 283;
 Astrophysics  High Energy Astrophysical Phenomena;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 13 pages, 3 figures, ApJ Letters accepted