Improved Treatment of Bosonic Dark Matter Dynamics in Neutron Stars: Consequences and Constraints

TL;DR

This paper models bosonic dark matter accumulation in neutron stars, dynamically determining Bose-Einstein condensate formation, and derives new constraints on dark matter properties based on neutron star observations and future telescope prospects.

Contribution

It introduces a dynamic method for BEC formation in neutron stars considering specific DM parameters, refining constraints on DM-neutron interactions and annihilation cross-sections.

Findings

BEC forms for DM mass below 10 TeV with low annihilation cross-section.

Constraints on DM-neutron cross-section vary with DM mass and BEC formation.

Future JWST observations could probe higher DM interaction cross-sections.

Abstract

It is conceivable that a bosonic dark matter (DM) with non-gravitational interactions with SM particles will be accumulated at the center of a neutron star (NS) and can lead to black hole formation. In contrast to previous works with a fixed NS temperature, we dynamically determine the formation of Bose-Einstein condensate (BEC) for a given set of DM parameters, namely the DM-neutron scattering cross-section ($\sigma_{\chi n}$), the thermal average of DM annihilation cross-section ($\langle\sigma v\rangle$) and the DM mass ($m_\chi$). For both non-annihilating and annihilating DM with $\langle\sigma v \rangle \lesssim 10^{-26}{~\rm cm^3~ s^{-1}}$, the BEC forms for $m_\chi \lesssim 10$ TeV. In case of non-annihilating DM, observations of old NS allows $\sigma_{\chi n}\lesssim 10^{-52}~{\rm cm^2}$ for $10 {~\rm MeV} \leq m_{\chi} \lesssim 10 {~\rm GeV}$ (with BEC) and $\sigma_{\chi n}\lesssim 10^{-47}~{\rm cm^2}$ for $5 {~\rm TeV} \lesssim m_\chi \lesssim 30 {~\rm PeV} $ (without BEC). This analysis shows that the electroweak mass window, $10 {~\rm GeV} \lesssim m_\chi \lesssim 5 {~\rm TeV}$ is essentially unconstrained by NS observations and therefore is subject only to direct detection experiments. In the annihilating DM scenario, the exclusion limits on DM parameters become weaker and even vanish for typical WIMP annihilation cross-section. However, the late-time heating of the NS enables us to probe the region with $\sigma_{\chi n}\gtrsim 10^{-47}~{\rm cm^2}$, using the James Webb Space Telescope in the foreseeable future. When our results are viewed in the context of indirect searches of DM, it provides a lower limit on the $\langle\sigma v\rangle$, which is sensitive to the DM thermal state.