Astronomical Probes of Ultra Light Dark Matter

Abstract

Ultra light particles of mass \(m\lesssim 10^{-19}\mathrm {eV}\) can be probed from binary pulsar timing experiments if they are radiated from compact binary systems such as neutron star-neutron star (NS-NS) and neutron star-white dwarf (NS-WD) binary systems. The orbital period decay of the compact binary system is mainly due to gravitational wave radiation which matches with the observational data to within one percent accuracy. Ultra light particles can also emit from the compact binary systems and contribute to about one percent of the observed orbital period decay. For radiation, the mass of the ultra light particles should be less than the orbital frequency of the binary system. In this paper, we consider massless scalar or ultralight pseudoscalar axion like particles radiate from compact binary systems and put bounds on the coupling constant from pulsar timing data. These ultra light particles can be a candidate of fuzzy dark matter (FDM) and from the constraints of NS-WD, we conclude that if ALPs are FDM, then they do not couple with quarks. Astrophysical objects like neutron stars contain muons and they can mediate long range \(L_\mu -L_\tau \) force between the compact binary systems. The ultra light vector gauge bosons can also radiate from the binary systems and contribute to the orbital period decay.