Constraints on millicharged dark matter and axionlike particles from timing of radio waves

Abstract

We derive constraints on millicharged dark matter and axionlike particles using pulsar timing and fast radio burst observations. For dark matter particles of charge $\ensuremath{\epsilon}e$, the constraint from time of arrival (TOA) of waves is $\ensuremath{\epsilon}/{m}_{\mathrm{milli}}\ensuremath{\lesssim}{10}^{\ensuremath{-}8}\text{ }\text{ }{\mathrm{eV}}^{\ensuremath{-}1}$, for masses ${m}_{\mathrm{milli}}\ensuremath{\gtrsim}{10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{eV}$. For axionlike particles, the polarization of the signals from pulsars yields a bound in the axial coupling $g/{m}_{a}\ensuremath{\lesssim}{10}^{\ensuremath{-}13}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}/({10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV})$, for ${m}_{a}\ensuremath{\lesssim}{10}^{\ensuremath{-}19}\text{ }\text{ }\mathrm{eV}$. Both bounds scale as $(\ensuremath{\rho}/{\ensuremath{\rho}}_{\mathrm{dm}}{)}^{1/2}$ for fractions of the total dark matter energy density ${\ensuremath{\rho}}_{\mathrm{dm}}$. We make a precise study of these bounds using TOA from several pulsars, FRB 121102, and polarization measurements of PSR $\mathrm{J}0437\ensuremath{-}4715$. Our results rule out a new region of the parameter space for these dark matter models.