X-ray line signal from 7 keV axino dark matter decay

Understand

Recently a weak X-ray emission around E ~ 3.5 keV was detected in the Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster but its source has been unidentified.

• Axino, the superpartner of axion, with a mass 2E is suggested as a possible origin of the line with R-parity violating decay into photon and neutrino.
• Moreover, most of parameter space is consistent with recent observation by the BICEP2 experiment.