Metastable Neutron Stars as Transient-Rate Detectors of Heavy Dark Matter

Abstract

Metastable neutron stars can undergo catastrophic conversion to quark-containing stars when a localized energy deposition nucleates a critical bubble. We show that dark-matter-induced conversions can be constrained by the present transient rate of the neutron star population, rather than by the survival of any individual hadronic star as often assumed in previous literature. Population depletion makes the present transition rate nonmonotonic: weak triggering produces few transitions, whereas sufficiently rapid triggering predominantly converts stars formed in the past. Consequently, transient observations can exclude a finite interval of interaction rates, qualitatively different from conventional one-sided survival bounds. Using the beaming-corrected short gamma ray burst rate as a benchmark, we derive constraints on dark matter annihilation, decay, inelastic particle scattering, and elastic scattering of macroscopic dark matter, including parameter space not covered by existing probes. Transient demographics thus provide a new population level probe of dark sector interactions and the phase structure of ultradense matter.