  We propose different scenarios where a keV dark matter annihilates to produce
a monochromatic signal. The process is generated through the exchange of a
light scalar of mass of order 300 keV - 50 MeV coupling to photon through loops
or higher dimensional operators. For natural values of the couplings and
scales, the model can generate a gamma-ray line which can fit with the recently
identified 3.5 keV X-ray line.

High Energy Physics - Phenomenology;High Energy Astrophysical Phenomena;High Energy Physics - Theory