Prospects for detecting neutron star-white dwarf mergers with decihertz gravitational-wave observatories

TL;DR

This paper evaluates the potential of upcoming decihertz gravitational-wave observatories to detect neutron star-white dwarf mergers, enabling early warnings and precise localizations that could identify their electromagnetic counterparts and origins.

Contribution

It provides detection rate estimates, localization accuracy, and highlights the importance of early warnings for multimessenger observations of NS-WD mergers.

Findings

Detection rates: 1500-1900 for DO-Optimal, 33000-46000 for DECIGO.

Most mergers localized within 0.01 deg^2.

Early warnings enable electromagnetic follow-up and origin identification.

Abstract

Based on different neutron star-white dwarf (NS-WD) population models, we investigate the prospects of gravitational-wave (GW) detections for NS-WD mergers, with the help of early warnings from two space-borne decihertz GW observatories, DO-Optimal and DECIGO. We not only give quick assessments of the GW detection rates for NS-WD mergers with the two decihertz GW detectors, but also report systematic analyses on the characteristics of GW-detectable merger events using the method of Fisher matrix. With a sufficient one-day early-warning time, the yearly GW detection number for DO-Optimal is in the range of $ (1.5$-$1.9) \times 10^{3}$, while it is $ (3.3$-$4.6) \times 10^{4}$ for DECIGO. More importantly, our results show that most NS-WD mergers can be localized with an uncertainty of $O(10^{-2})\,\mathrm{deg}^2$. Given the NS-WD merger as a possible origin for a peculiar long-duration gamma-ray burst, GRB 211211A, followed with kilonova-like emissions, we further suggest that the GW early-warning detection would allow future electromagnetic telescopes to get prepared to follow-up transients after some special NS-WD mergers. Based on our analyses, we emphasize that such a feasible "wait-for" pattern can help to firmly identify the origin of GRB 211211A-like events in the future and bring excellent opportunities for the multimessenger astronomy.