Searching for dark matter with neutron star mergers and quiet kilonovae

Abstract

We identify new astrophysical signatures of dark matter that implodes neutron stars (NSs), which could decisively test whether NS-imploding dark matter is responsible for missing pulsars in the Milky Way galactic center, the source of some r-process elements, and the origin of fast-radio bursts. First, NSimploding dark matter forms ∼10 −10 solar mass or smaller black holes inside neutron stars, which proceed to convert neutron stars into ∼1.5 solar mass black holes (BHs). This decreases the number of neutron star mergers seen by LIGO/Virgo (LV) and associated merger kilonovae seen by telescopes like DES, BlackGEM, and ZTF, instead producing a population of "black mergers" containing ∼1.5 solar mass black holes. Second, dark matter-induced neutron star implosions may create a new kind of kilonovae that lacks a detectable, accompanying gravitational signal, which we call "quiet kilonovae." Using DES data and the Milky Way's r-process abundance, we constrain quiet kilonovae. Third, the spatial distribution of neutron star merger kilonovae and quiet kilonovae in galaxies can be used to detect dark matter. NS-imploding dark matter destroys most neutron stars at the centers of disc galaxies, so that neutron star merger kilonovae would appear mostly in a donut at large radii. We find that as few as ten neutron star merger kilonova events, located to ∼1 kpc precision could validate or exclude dark matter-induced neutron star implosions at 2σ confidence, exploring dark matter-nucleon cross-sections 4-10 orders of magnitude below current direct detection experimental limits. Similarly, NS-imploding dark matter as the source of fast radio bursts can be tested at 2σ confidence once 20 bursts are located in host galaxies by radio arrays like CHIME and HIRAX.

Science case for the Einstein telescope

“…Dark matter accumulating in neutron stars and interacting through Yukawa-like interactions in the dark sector could affect the orbital dynamics of a neutron star binaries, and therefore the corresponding waveform, in a way detectable by ET [174], whose low-frequency sensitivity makes it an especially sensitive probe to dark matter mediated forces between neutron stars. In some models [175,176], the accumulation of dark matter may lead to the formation of a black hole inside a neutron star, which then accretes the remaining neutron star matter, leading to black holes of (1 − 2) M that could be observed by ET.…”

Type Ia supernovae from dark matter core collapse

“…Note that R χχ as defined is trivially smaller than R th if conditions (41) and (43) are satisfied. The expression for R χχ depends on whether this takes place during the viscous or inertial drag regimes, or in the inelastic scattering regime (27). Written in terms of the annihilation cross-section σ χχ v col , this scales as:…”

Supernovae sparked by dark matter in white dwarfs

“…See Appendix A for an extended discussion of bounds obtained from different white dwarfs, including those in old globular clusters [14]. Also displayed are the bounds obtained from the Xenon-1T experiment (blue) [51] and neutron star implosions (yellow) [29]. 10 10 K [64].…”

“…Dark matter's non-gravitational interactions with ordinary matter may also be detected using astrophysical systems. The impact of dark matter interactions can be observed in solar fusion [1][2][3][4], cooling gas cloud temperatures [5][6][7][8], stellar emission [9][10][11], white dwarfs [12][13][14][15][16][17][18][19], and neutron stars [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. In particular, due to the enormous density of white dwarfs and neutron stars, these objects serve as effective natural laboratories for testing dark matter models.…”