Nuclear limits on gravitational waves from elliptically deformed pulsars

Abstract

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 $h_0$ 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 $0.18kpc$ to $0.35kpc$ from Earth, the {\it maximal} $h_0$ is found to be in the range of $\sim[0.4-1.5]\times 10^{-24}$. This prediction serves as the first {\it direct} nuclear constraint on the gravitational radiation. Its implications are discussed.Comment: 13 pages, 5 figures, and 2 Table. Accepted for publication in Physics Letters

Single-nucleon potential decomposition of the nuclear symmetry energy

“…For example, the density slope L of the symmetry energy at nuclear matter saturation density ρ 0 has been shown to be important in determining several critical quantities such as the size of the neutron skin in heavy nuclei [11][12][13][14][15][16][17][18][19][20], the location of the neutron drip line [21], the core-crust transition density [3,4,12,[22][23][24][25], and the gravitational binding energy [26] of neutron stars. The symmetry energy may also have significant influence on gravitational wave emission from compact stars [27][28][29][30][31]. Furthermore, knowledge on the symmetry energy might be useful for understanding the non-Newtonian gravity proposed in grand unified theories and for constraining properties of the neutral, weakly coupled, light spin-1 gauge U boson originating from supersymmetric extensions of the standard model [10,[32][33][34][35].…”

Density matrix expansion for the isospin- and momentum-dependent MDI interaction

“…The resulting symmetry energy has further been used to impose constraints on both the parameters in the Skyrme effective interactions and the neutron skin thickness of heavy nuclei [7]. The MDI interaction with the constrained isospin dependence has also been used to study the properties of hot asymmetric nuclear matter [8] as well as those of neutron stars [9][10][11][12][13][14], including the transition density that separates their liquid core from their inner crust [15]. New constraints on the masses and radii of neutron stars were then obtained from comparing the resulting crustal fraction of the moment of inertia of neutron stars with that of the Vela pulsar extracted from its glitches [15].…”

Gravitational waves from pulsars in the context of magnetic ellipticity

“…For a matter of comparison, some authors argue that a fiducial upper limit for the ellipticity would be around ε ∼ 10 −6 , considering asymmetries supported by anisotropic stress built up during the crystallization period of the crust (see, e.g., [3], and references therein).…”