APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
An unidentified line in X-ray spectra of the Andromeda galaxy and Perseus galaxy cluster
Alexey Boyarsky, Oleg Ruchayskiy, Dmytro Iakubovskyi, Jeroen Franse
http://arxiv.org/abs/1402.4119
...Although for individual objects it is hard to exclude the possibility that the feature is due to an instrumental effect or an atomic line of anomalous brightness, it is consistent with the behavior of a line originating from the decay of dark matter particles. Future detections or non-detections of this line in multiple astrophysical targets may help to reveal its nature.
Detection of An Unidentified Emission Line in the Stacked X-ray spectrum of Galaxy Clusters
Esra Bulbul, Maxim Markevitch, Adam Foster, Randall K. Smith, Michael Loewenstein, Scott W. Randall
http://arxiv.org/abs/1402.2301
... On the origin of this line, we argue that there should be no atomic transitions in thermal plasma at this energy. An intriguing possibility is the decay of sterile neutrino, a long-sought dark matter particle candidate. ...
*by Esra Bulbul, Maxim Markevitch et alhttp://arxiv.org/abs/1410.2852
New emission line at ~3.5 keV - observational status, connection with radiatively decaying dark matter and directions for future studies Dmytro Iakubovskyi.
(Submitted on 10 Oct 2014 (v1), last revised 12 Nov 2014 (this version, v2))
Invited review for Advances in Astronomy and Space Physics.
Abstract:
Recent works of [1402.2301*,1402.4119**], claiming the detection of extra emission line with energy ~3.5 keV in X-ray spectra of certain clusters of galaxies and nearby Andromeda galaxy, have raised considerable interest in astrophysics and particle physics communities. A number of new observational studies claim detection or non-detection of the extra line in X-ray spectra of various cosmic objects. In this review I summarize existing results of these studies, overview possible interpretations of the extra line, including intriguing connection with radiatively decaying dark matter, and show future directions achievable with existing and planned X-ray cosmic missions.