Cuckoo’s eggs in neutron stars: can LIGO hear chirps from the dark sector?

Abstract

We explore in detail the possibility that gravitational wave signals from binary inspirals are affected by a new force that couples only to dark matter particles. We discuss the impact of both the new force acting between the binary partners as well as radiation of the force carrier. We identify numerous constraints on any such scenario, ultimately concluding that observable effects on the dynamics of binary inspirals due to such a force are not possible if the dark matter is accrued during ordinary stellar evolution. Constraints arise from the requirement that the astronomical body be able to collect and bind at small enough radius an adequate number of dark matter particles, from the requirement that the particles thus collected remain bound to neutron stars in the presence of another neutron star, and from the requirement that the theory allows old neutron stars to exist and retain their charge. Thus, we show that any deviation from the predictions of general relativity observed in binary inspirals must be due either to the material properties of the inspiraling objects themselves, such as a tidal deformability, to a true fifth force coupled to baryons, or to a nonstandard production mechanism for the dark matter cores of neutron stars. Viable scenarios of the latter type include production of dark matter in exotic neutron decays, or the formation of compact dark matter objects in the early Universe that later seed star formation or are captured by stars.

Hidden-sector modifications to gravitational waves from binary inspirals

“…The amount of dark matter inside neutron stars is subject to considerable theoretical uncertainty, since this does depend, not only on the dark matter model, but also on the formation and entire lifetime of the neutron star. Estimates of the fraction of the neutron star mass in dark matter range from a few percent [56] to one part in 10 15 [51]. Remarkably, in this work we find that gravitational wave observations can probe dark matter even at mass fractions below the latter estimate.…”

“…Future gravitational wave observations should also be sensitive probes of other modifications to General Relativity, such as large extra-dimensions [15,16], timevarying fundamental constants [17], parity violation [12][13][14], Lorentz violation [18,19], scalar-tensor gravity [20][21][22][23][24], and dark matter [32][33][34][35][36][37][38][39][40][41][42][43][44][45][49][50][51] (see also [31]). These modifications can by probed by precise interferometer measurements of the gravitational waves emitted by compact binary mergers, though to do so requires building analytic templates of the modified waves and a detailed statistical analysis.…”

“…If the dark sector includes a light force mediator, then this naturally leads to an additional force between neutron stars, similar to that experienced by compact objects in scalartensor gravity, where the role of accumulated mass is played by a scalar field-dependent modulation of the inertial mass. This additional force modifies the gravitational wave signal from neutron star binary mergers, which can potentially probe the underlying dark matter model [49][50][51][52] (see also [53]). We emphasize that this conclusion is completely general and it does not depend on a specific dark matter model.…”

Primordial Black Holes as a Dark Matter Candidate Are Severely Constrained by the Galactic Center 511 keVγ-Ray Line

“…The direct detection of gravitational waves have started vigorous activities in the field of gravitational wave astroparticle physics. These observations have prompted many new ideas like searches of long range forces in the dark sector and many other novel research directions in this nascent field [84]. This discovery has also led to renewed interest in PBHs as dark matter candidate.…”

New probe of dark matter-induced fifth force with neutron star inspirals

“…A light scalar (again not necessarily the main DM) can also be efficiently radiated if each NS carries different scalar charge-to-mass ratio, forming a scalar-charge dipole [7,20]. This dipole radiation is qualitatively different from the GW quadrupole radiation, thus can be tested with GW waveform evolution [20][21][22]. It is efficient for any light scalars with long enough Compton wavelength 1/m φ 10 km.…”