8 Summary

We have described the spectra of 14 Ae and A type shell stars in three different spectral regions observed during one observing run at the OHP in 1996. We discuss the behavior over time of the 14 stars and conclude that at least 57% show spectrum variability. For several stars there exist now well documented changes from a normal phase to a shell phase.

We analysed the binarity of our sample and found that a large percentage of the objects belong to double or triple systems. Further stars with clear indications of a shell tend to have characteristics of the Paschen series similar to giants, rather than to the dwarf stars they really are. Such a behavior is confirmed by the overbrightness of the A shell stars which reaches $\rm 1^m35$ magnitude, implying that the emitting surface is larger by a factor of about three than that of a normal dwarf.

Acknowledgements

We thank Mr. J. Marcout from the Strasbourg Observatory for drawing Figs. 1 and 2. We thank also the referee, Dr. S. Adelman, for improving the manuscript.