White dwarfs as dark matter detectors

Abstract

Dark matter that is capable of sufficiently heating a local region in a white dwarf will trigger runaway fusion and ignite a type Ia supernova. This was originally proposed by Graham et al. and used to constrain primordial black holes which transit and heat a white dwarf via dynamical friction. In this paper, we consider dark matter (DM) candidates that heat through the production of highenergy standard model (SM) particles, and show that such particles will efficiently thermalize the white dwarf medium and ignite supernovae. Based on the existence of long-lived white dwarfs and the observed supernovae rate, we derive new constraints on ultra-heavy DM with masses greater than 10 16 GeV which produce SM particles through DM-DM annihilations, DM decays, and DM-SM scattering interactions in the stellar medium. As a concrete example, we place bounds on supersymmetric Q-ball DM in parameter space complementary to terrestrial bounds. We put further constraints on DM that is captured by white dwarfs, considering the formation and self-gravitational collapse of a DM core which heats the star via decays and annihilations within the core. It is also intriguing that the DM-induced ignition discussed in this work provide an alternative mechanism of triggering supernovae from sub-Chandrasekhar, non-binary progenitors.

Type Ia supernovae from dark matter core collapse

“…If the DM has a small but non-zero annihilation cross section, collapse can dramatically increase the number density of the DM core, resulting in SN ignition via a large number of rapid annihilations. Both of these processes extend the previously derived constraints on DM in [3], notably to masses as low as 10 5 GeV.…”

“…λ T was numerically computed in [39] and is λ T ≈ 10 −5 cm at a number density n ion ≈ 10 32 cm −3 . One can also consider, as in [3], the critical energy E boom required to heat an entire trigger region λ 3 T to arXiv:1905.00395v1 [hep-ph] 1 May 2019 an MeV. E boom ≈ 10 16 GeV for n ion ≈ 10 32 cm −3 and sharply increases at lower WD densities-this agrees with the expectation that WDs grow closer to instability as they approach the Chandrasekhar mass.…”

“…It is also possible to deposit this energy indirectly, e.g., by DM interactions releasing SM particles into the stellar medium [3]. To this end the stopping distances of high-energy ( MeV) particles in a WD was calculated in [3], where it was shown that hadrons, photons and electrons all transfer their energies to the stellar medium within a distance of order λ T (the sole exception being neutrinos). We thus safely presume that any E E boom released into these SM products inside λ 3 T will be efficiently deposited and thermalized within this region as well.…”

Macroscopic dark matter constraints from bolide camera networks

“…ancient rocks [8,9,20]) could have been continuously exposed for up to 3 × 10 9 years, but we are unlikely to carefully examine the more than 1km 2 that would be needed to push beyond M x = 10 9 g. It will therefore require innovative thinking about astrophysical probes (eg. [16]) to probe the very highest possible macro masses.…”

“…[15]). More recently, the existence of massive white dwarfs was used to constrain a significant region of macro parameter space [16]. The region of parameter space where macros would have produced a devastating injury similar to a gunshot wound on the carefully monitored population of the western world was also recently constrainted [17].…”