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تسجيل مستخدم جديدComment on Probing the Dark Matter-Electron Interactions via Hydrogen-Atmosphere Pulsating White Dwarfs
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In Phys. Rev. D 98, 103023 (2018), a novel scenario was proposed to probe the interactions between dark matter (DM) particles and electrons, via hydrogen-atmosphere pulsating white dwarfs (DAVs) in globular clusters. The estimation showed that the scenario could hopefully test the parameter space: $5 mathrm{GeV} le m_{chi} le 10^{4} mathrm{GeV}$ and $sigma_{chi,e} ge 10^{-40} mathrm{cm}^{2}$, where $m_{chi}$ is the DM particles mass and $sigma_{chi,e}$ is the elastic scattering cross section between DM and electron. In this comment, we have determined the exact lower limit of the testable DM particle mass $sim 1.38 - 1.58 mathrm{GeV}$, which depends on $sigma_{chi,e}$. This gives us a credible lower limit of the testable DM particle mass in above scenario, and provide a clear upper limit of the DM particle mass which we should consider in future research.
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White dwarfs, the most abundant stellar remnants, provide a promising means of probing dark matter interactions, complimentary to terrestrial searches. The scattering of dark matter from stellar constituents leads to gravitational capture, with impor
tant observational consequences. In particular, white dwarf heating occurs due to the energy transfer in the dark matter capture and thermalisation processes, and the subsequent annihilation of captured dark matter. We consider the capture of dark matter by scattering on either the ion or the degenerate electron component of white dwarfs. For ions, we account for the stellar structure, the star opacity, realistic nuclear form factors that go beyond the simple Helm approach, and finite temperature effects pertinent to sub-GeV dark matter. Electrons are treated as relativistic, degenerate targets, with Pauli blocking, finite temperature and multiple scattering effects all taken into account. We also estimate the dark matter evaporation rate. The dark matter-nucleon/electron scattering cross sections can be constrained by comparing the heating rate due to dark matter capture with observations of cold white dwarfs in dark matter-rich environments. We apply this technique to observations of old white dwarfs in the globular cluster Messier 4, which we assume to be located in a DM subhalo. For dark matter-nucleon scattering, we find that white dwarfs can probe the sub-GeV mass range inaccessible to direct detection searches, with the low mass reach limited only by evaporation, and can be competitive with direct detection in the $1-10^4$ GeV range. White dwarf limits on dark matter-electron scattering are found to outperform current electron recoil experiments over the full mass range considered, and extend well beyond the $sim 10$ GeV mass regime where the sensitivity of electron recoil experiments is reduced.
White dwarfs (WDs) are the most promising captors of dark matter (DM) particles in the crests that are expected to build up in the cores of dense stellar clusters. The DM particles could reach sufficient densities in WD cores to liberate energy throu
gh self-annihilation. The extinction associated with our Galactic Centre, the most promising region where to look for such effects, makes it impossible to detect the potential associated luminosity of the DM-burning WDs. However, in smaller stellar systems which are close enough to us and not heavily extincted, such as $omega-$Cen, we may be able to detect DM-burning WDs. We investigate the prospects of detection of DM-burning WDs in a stellar cluster harbouring an IMBH, which leads to higher densities of DM at the centre as compared with clusters without one. We calculate the capture rate of WIMPs by a WD around an IMBH and estimate the luminosity that a WD would emit depending on its distance to the center of the cluster. Direct-summation $N-$body simulations of $omega-$Cen yield a non-negligible number of WDs in the range of radii of interest. We apply our assumption to published HST/ACS observations of stars in the center of $omega-$Cen to search for DM burning WDs and, although we are not able to identify any evident candidate because of crowding and incompleteness, we proof that their bunching up at high luminosities would be unique. We predict that DM burning will lead to a truncation of the cooling sequence at the faint end. The detection of DM burning in future observations of dense stellar clusters, such as globular clusters or ultra-compact dwarf galaxies could allow us to probe different models of DM distributions and characteristics such as the DM particle scattering cross section on nucleons. On the other hand, if DM-burning WDs really exist, their number and properties could give hints to the existence of IMBHs.
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