X-ray line signal from 7 keV axino dark matter decay
  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. 
Kyoungchul Kong, Jong-Chul Park, Seong Chan Park
hep-ph astro-ph.CO astro-ph.GA astro-ph.HE