DARK MATTER LINE EMISSION CONSTRAINTS FROM NuSTAR OBSERVATIONS OF THE BULLET CLUSTER

Some dark matter candidates, e.g., sterile neutrinos, provide observable signatures in the form of mono-energetic line emission. We present the first search for dark matter line emission in the 3-80 keV range in a pointed observation of the Bullet Cluster with NuSTAR. We do not detect any significant line emission and instead we derive upper limits (95% CL) on the flux, and interpret these constraints in the context of sterile neutrinos and more generic dark matter candidates. NuSTAR does not have the sensitivity to constrain the recently claimed line detection at 3.5 keV, but improves on the constraints for energies of 10-25 keV.