Observational Inference on the Delay Time Distribution of Short Gamma-ray Bursts

Understand

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 $r$-process enrichment.
• We use a sample of 68 host galaxies of short gamma-ray 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 power-law slope of $\alpha = -1.83^{+0.35}_{-0.39}$ (median and 90% credible interval) with $\alpha < -1.31$ at 99% credibility, a minimum delay time of $t_\mathrm{min} = 184^{+67}_{-79}~\mathrm{Myr}$ with $t_\mathrm{min} > 72~\mathrm{Myr}$ at 99% credibility, and a maximum delay time constrained to $t_\mathrm{max} > 7.95~\mathrm{Gyr}$ at 99% credibility.