Indirect probes of dark matter and globular cluster properties from dark matter annihilation within the coolest white dwarfs

Abstract

White Dwarfs (WD) capture Dark Matter (DM) as they orbit within their host halos. These captured particles may subsequently annihilate, heating the stellar core and preventing the WD from cooling. The potential wells of WDs are considerably deeper and core temperatures significantly cooler than those of main sequence stars. Consequently, DM evaporation is less important in WDs and DM with masses Mχ 100 keV and annihilation cross-sections orders of magnitude below the canonical thermal cross-section ( σav 10 −46 cm 3 /s) can significantly alter WD cooling in particular astrophysical environments. We consider WDs in globular clusters (GCs) and dwarf galaxies. If the parameters of the DM particle are known, then the temperature of the coolest WD in a GC can be used to constrain the DM density of the cluster's halo (potentially even ruling out the presence of a halo if the inferred density is of order the ambient Galactic density). Recently several direct detection experiments have seen signals whose origins might be due to low mass DM. In this paper, we show that if these claims from CRESST, DAMA, CDMS-Si, and CoGeNT could be interpreted as DM, then observations of NGC 6397 limit the fraction of DM in that cluster to be fDM 10 −3 . This would be an improvement over existing constraints of 3 orders of magnitude and clearly rule out a significant DM halo for this cluster. More generally, we show how such observations constrain combinations of DM and GC properties. Building on previous work, we also show how observations of WDs in dwarf galaxies, such as Segue I, can provide novel constraints on low mass DM or DM with very low contemporary annihilation cross-sections as may be realized in models in which s-wave annihilation is suppressed and p-wave annihilation dominates. This paper provides further motivation for high-quality observations of stellar populations as a probe of dark matter.

Last electroweak WIMP standing: pseudo-dirac higgsino status and compact stars as future probes

“…We focus on white dwarfs, although many of our conclusions should carry over to neutron stars (with rather different observational prospects). Capture of dark matter in compact stars has been discussed in the literature [94][95][96][97][98][99]. One major novelty with such objects, compared to the Sun, is kinematic: because they are very dense they have a high escape velocity.…”

The Lost Dwarfs of Centaurus a and the Formation of Its Dark Globular Clusters

“…If so, they must have lost the majority of the dark matter via dynamical processes throughout their evolution, since today there is no evidence for significant DM content in GCs (e.g. Moore 1996;Baumgardt et al 2009;Lane et al 2010;Conroy et al 2011;Feng et al 2012;Ibata et al 2013;Hurst et al 2015). For a discussion of MOND-based explanations, see Derakhshani (2014), however, MOND predictions fall orders of magnitude below what is required to explain the derive DSC dynamics (Smith & Candlish, private communication).…”

Dark matter searches with asteroseismology

“…Although the density of DM in our region of the Galaxy is estimated to be very low, ρ χ ≈ 0.4 GeV cm −3 [15], it suffices to change the internal properties of stars similar to the Sun [5]. In environments with greater DM densities, such as the center of the Milky Way and inside dwarf galaxies and globular clusters, the impact on stars could be much larger [16][17][18][19], in particular in the case of compact stars [20,21].…”