Supernovae and the Ap Phenomenon

We present evidence that relates the phenomenon of the chemically peculiar stars of the upper main sequence to supernovae explosions in young galactic clusters and associations. In the Upper Scorpius region of the Scorpio-Centaurus association we find that the radio shell discovered by Sancisi and Van Woerden (1970) from 21 cm observations and interpreted by them as an old supernova remnant has interacted with dense clouds. This remnant is seen clearly in the deep sky, narrow-band, H-alpha pictures of Sivan (1974). We find that the peculiar stars lie close to, or along the edges of, the interaction.