Heavy concerns about the light axino explanation of the 3.5 keV X-ray line

Understand

An unidentified 3.5 keV line from X-ray observations of galaxy clusters has been reported recently.

• Although still under scrutiny, decaying dark matter could be responsible for this signal.
• We investigate whether an axino with a mass of 7 keV could explain the line, keeping the discussion as model independent as possible.
• We point out several obstacles, which were overlooked in the literature, and which make the axino an unlikely candidate.