We investigate possible evidence for a spectral dip around 3.5 keV in central cluster AGNs , motivated by previous results for archival Chandra observations of the Perseus cluster and the general interest in novel spectral features around 3.5 keV that may arise from dark matter physics .
We use two deep Chandra observations of the Perseus and Virgo clusters that have recently been made public .
In both cases , mild improvements in the fit ( \Delta \chi ^ { 2 } = 4.2 and \Delta \chi ^ { 2 } = 2.5 ) are found by including such a dip at 3.5 keV into the spectrum .
A comparable result ( \Delta \chi ^ { 2 } = 6.5 ) is found re-analysing archival on-axis Chandra ACIS-S observations of the centre of the Perseus cluster .