The Pickering Series in O Type Stars

Abstract

IF the Pickering series, consisting of the lines 5411, 4542, 4200, etc., in stellar spectra, is due to ionised helium, it is known from the investigations of Fowler and from Bohr's theory that there must be additional lines which appear as violet components of the Balmer series of hydrogen. As these components have an average separation of 2 Å. they should be readily seen in the spectra of O type stars. Unfortunately, there are two unfavourable circumstances: first, the O type stars are all faint, and, secondly, the lines of both the Balmer and the Pickering series are in general so diffuse as to be hopelessly blended.