SIMBAD references

We investigate possible evidence for a spectral dip around 3.5 keV in central cluster active galactic nuclei, 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 (Δχ² = 4.2 and Δχ² = 2.5) are found by including such a dip at 3.5 keV into the spectrum. A comparable result (Δχ² = 6.5) is found reanalysing archival on-axis Chandra ACIS-S observations of the centre of the Perseus cluster.