Nuclear limits on gravitational waves from elliptically deformed pulsars

Gravitational radiation is a fundamental prediction of General Relativity. Elliptically deformed pulsars are among the possible sources emitting gravitational waves (GWs) with a strain-amplitude dependent upon the star's quadrupole moment, rotational frequency, and distance from the detector. We show that the gravitational wave strain amplitude h₀$h_0$ depends strongly on the equation of state of neutron-rich stellar matter. Applying an equation of state with symmetry energy constrained by recent nuclear laboratory data, we set an upper limit on the strain-amplitude of GWs produced by elliptically deformed pulsars. Depending on details of the EOS, for several millisecond pulsars at distances 0.18 kpc to 0.35 kpc from Earth, the maximal  h₀$h_0$ is found to be in the range of ∼[0.4–1.5]×¹⁰⁻²⁴$\sim [0.4\text{–}1.5]\times {10}^{\mathrm{-24}}$. This prediction serves as the first direct nuclear constraint on the gravitational radiation. Its implications are discussed.