Time-resolved spectroscopy of long-period DQ Herculis stars.

High-dispersion time-resolved spectroscopic observations of four long-period DQ Herculis stars (intermediate polars) are presented: V1223 Sgr, H2215 - 086, 3A 0729 + 103, and AO Psc. In two of these objects orbital modulations were clearly detected, permitting an investigation of dynamic parameters. The source of He II line emission appears to have a physically different location from that of hydrogen. The source of He II is placed in the hot spot or accreting stream. In all four objects short-period coherent variations in wavelength were discovered. The periods in each case turned out to be close to, and within error the same as, the photometric white-dwarf coherent periods. This lends the strongest kinematic evidence to date in support of an oblique magnetic rotator model.