Dark Matter and Neutron Stars

Abstract

Neutron stars and fast radio bursts (FRBs) serve as powerful, complementary probes of dark matter models that lie beyond the reach of laboratory experiments. This thesis investigates neutron stars and their role in dark matter search strategies. In the first part, the thesis demonstrates a new method to look for inelastic dark matter. We show that inelastic dark matter captured by neutron stars can remain in long-lived orbits and annihilate outside the stellar volume. By modeling this exterior annihilation process in the Galactic center, we derive gamma-ray and neutrino flux predictions that translate into limits on the inelastic dark matter-nucleon cross section of σχn ≲3×10^−46 cm^-2 for dark matter masses ranging between mχ ∼ 10^2 −10^5 GeV, with next-generation observatories expected to improve sensitivity by an order of magnitude. Shifting focus from the Galactic Center to our own backyard, we refine the solar neighborhood’s free electron density map by combining pulsar parallax measurements with Gaussian process interpolation. This empirically calibrated ne(r) sharpens dispersion-measure-based neutron star distance estimates and identifies the most promising nearby neutron star targets for infrared searches of dark matter induced heating signatures. Finally, we expand our approach to cosmological transients. It has been appreciated for some time that asymmetric dark matter can cause neutron stars to implode and form black holes. These implosions have been linked to fast radio bursts. For the first time, this thesis obtains predictions for fast radio burst dispersion measure distributions arising from neutron star implosions triggered by accumulated asymmetric dark matter cores or primordial black hole capture in spiral, elliptical and dwarf galaxy hosts. Together, these investigations show that through high-energy annihilation signals, thermal heating, and fast radio burst signatures of dark matter induced collapse, neutron stars serve as a useful means for determining or bounding dark matter's interactions.