Dark Kinetic Heating of Neutron Stars and An Infrared Window On WIMPs,
  SIMPs, and Pure Higgsinos
  We identify a largely model-independent signature of dark matter interactions
with nucleons and electrons. Dark matter in the local galactic halo,
gravitationally accelerated to over half the speed of light, scatters against
and deposits kinetic energy into neutron stars, heating them to infrared
blackbody temperatures. The resulting radiation could potentially be detected
by the James Webb Space Telescope, the Thirty Meter Telescope, or the European
Extremely Large Telescope. This mechanism also produces optical emission from
neutron stars in the galactic bulge, and X-ray emission near the galactic
center, because dark matter is denser in these regions. For GeV - PeV mass dark
matter, dark kinetic heating would initially unmask any spin-independent or
spin-dependent dark matter-nucleon cross-sections exceeding $2 \times 10^{-45}$
cm$^2$, with improved sensitivity after more telescope exposure. For
lighter-than-GeV dark matter, cross-section sensitivity scales inversely with
dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter,
it scales linearly with mass as a result of needing multiple scatters for
capture. Future observations of dark sector-warmed neutron stars could
determine whether dark matter annihilates in or only kinetically heats neutron
stars. Because inelastic inter-state transitions of up to a few GeV would occur
in relativistic scattering against nucleons, elusive inelastic dark matter like
pure Higgsinos can also be discovered.
