We discuss high-speed spectrophotometric observations of DQ Herculis a
cquired with the Double Spectrograph and ''2D-FRUTTI'' detector on the
Hale 5 m telescope. Trailed spectrograms and Doppler tomograms of the
steady (unpulsed) light of Bahner, He I and He II lines reveals disk
emission, while disk absorption components appear in He I and Ca II li
nes. Balmer and Ca II emission also originate in the Roche lobe of the
secondary star; in neither case can we be certain whether the emissio
n is intrinsic or is due to irradiation of the secondary star. We dete
ct 71 s pulsations in both the continuum and in the He II lambda 4686
emission line. Our pulse-phased trailed spectrograms exhibit He II lam
bda 4686 emission moving from red to blue across the line profile but
not from blue to red, verifying with improved sensitivity and waveleng
th resolution the basic results of Chanan, Nelson, and Margon (1978).
We also find some evidence for pulsation on the red side of the Balmer
lines. For pulses arising from reprocessing of rotating X-ray beams i
rradiating an accretion disk, we are evidently seeing the reprocessing
sites on the far side but not on the near side, owing to a less favor
able viewing angle. In the context of this model, our data are largely
consistent with a single beam sweeping the disk with period 71 s, alt
hough we cannot rule out the possibility that two beams (originating a
t the two poles of a magnetic dipole) excite the pulsed optical emissi
on. The latter circumstance would imply a white dwarf spin period of 1
42 s. The pulsed component of the He II lambda 4686 light is totally e
clipsed, and the center of the source of pulsed He II lambda 4686 ligh
t is likely to be displaced or extended From the white dwarf. The He I
I lambda 4686 pulsation amplitude is strongest at +500 km s(-1) implyi
ng that the reprocessed emission is anisotropic, enhanced in the inwar
d (toward the white dwarf) add backward (opposite to the local Kepleri
an flow) directions. This anisotropy could arise through enhanced emis
sivity of the saturated He II line in the direction of acceleration, i
nward and backward in the corotating frame, as disk gas becomes thread
ed onto held lines of the more slowly rotating magnetosphere inside th
e corotation radius.