Testing the origin of ~3.55 keV line in individual galaxy clusters
  observed with XMM-Newton
  If the unidentified emission line at ~3.55 keV previously found in spectra of
nearby galaxies and galaxy clusters is due to radiatively decaying dark matter,
one should detect the signal of comparable strength from many cosmic objects of
different nature. By studying existing dark matter distributions in galaxy
clusters we identified top-19 of them observed by XMM-Newton X-ray cosmic
mission, and analyzed the data for the presence of the new line. In 8 of them,
we identified > 2 sigma positive line-like residuals with average position 3.52
+/- 0.08 keV in the emitter's frame. Their observed properties are unlikely to
be explained by statistical fluctuations or astrophysical emission lines;
observed line position in M31 and Galactic Center makes an additional argument
against general-type systematics. Being interpreted as decaying dark matter
line, the new detections correspond to radiative decay lifetime tau_dm ~
(3.5-6) x 10^27 s consistent with previous detections.
