Stationary components of HeI in strong magnetic fields - a tool to identify magnetic DB white dwarfs

In only three of the 61 known magnetic white dwarfs helium has been identif ied unambiguously while about 20% of all non-magnetic stars of this class a re known to contain He I or He II. One reason for this discrepancy is that the identification of peculiar objects as magnetic white dwarfs is based ei ther on the presence of hydrogen line components in strong magnetic fields {for which atomic data exist since 1984 {or the polarization of the corresp onding radiation which has not been measured for many objects. Until recent ly, data for He I data were available only for magnetic fields below 20 MG. This changed with the publication of extensive data by the group in Heidel berg. The corresponding calculations have now been completed for the energe tically lowest five states of singlet and triplet symmetry for the subspace s with \m\ less than or equal to 3; selected calculations have been perform ed for even higher excitations. In strongly magnetized white dwarfs only li ne components are visible whose wavelengths vary slowly with respect to the magnetic field, particularly stationary components which have a wavelength minimum or maximum in the range of the magnetic fields strengths on the st ellar surface. In view of the many ongoing surveys finding white dwarfs we want to provide the astronomical community with a tool to identify helium i n white dwarfs for fields up to 5.3 GG. To this end we present all calculat ed helium line components whose wavelengths in the UV, optical, and near IR vary slowly enough with respect to the field strength to produce visible a bsorption features. We also list all stationary line components in this spe ctral range. Finally, we find series of minima and maxima which occur as a result of series of extremal transitions to increasingly higher excitations . We estimated the limits for 8 series which can possibly give rise to addi tional absorption in white dwarf spectra; one strong absorption feature in GD229 which is yet unexplained by stationary components is very close to tw o estimated series limits.