2015MNRAS.451.3061F

The active galaxy NGC 1275 lies at the centre of the Perseus cluster of galaxies, which is the X-ray brightest cluster in the Sky. The nucleus shows large variability over the past few decades. We compile a light curve of its X-ray emission covering about 40 years and show that the bright phase around 1980 explains why the inner X-ray bubbles were not seen in the images taken with the Einstein Observatory. The flux had dropped considerably by 1992 when images with the ROSAT HRI led to their discovery. The nucleus is showing a slow X-ray rise since the first Chandra images in 2000. If it brightens back to the pre-1990 level, then X-ray absorption spectroscopy by ASTRO-H can reveal the velocity structure of the shocked gas surrounding the inner bubbles.