SIMBAD references

Among the various kinds of A stars having a peculiar spectrum, we find the A-shell stars. Many questions are still open concerning these stars, including their evolutionary status. In the present study we have used data from the Hipparcos catalogue to examine this point. We have found that the majority of A-shell stars are well above the main sequence. No differences could be established between A-shell stars in luminosity classes III and I and those in luminosity class V as regards variability, duplicity, or the importance of the shell feature.