An extensive $\Delta a$-photometric survey of southern B and A type bright stars

摘要: Photoelectric photometry of 803 southern BS objects in the a-system as detection tool for magnetic chemically peculiar (=CP2) stars has been carried out and compared to published spectral types. The statistical yield such detected by both techniques is practically same. We show that there are several factors which contaminate search these stars, but this contami- nation only order 10% techniques. nd a smooth transition from normal stars. Our sample exhibits largest fraction CP2 at their bluest colour interval, i.e. all range 0:19 B V< 0 :10 or 0:10 b y< :05. No based on a-criterion were found bluer colours. Towards red side drops about 3% positive values V y with limits roughly corresponding type A5. photometric behaviour other stars: Am, HgMn, Del, Boo, He abnormal well Be/shell supergiants shows some slight, def- inite deviations Spectroscopic vi- sual binaries not distinguished behaviour. results work justify larger (e.g. open clusters) employing more time-saving photo- metric methods (CCD).