We have carried out an analysis of the HST STIS archival spectra of the
magnetic white dwarf in the Hyades eclipsing-spectroscopic, post-common
envelope binary V471 Tauri, time resolved on the orbit and on the X-ray
rotational phase of the magnetic white dwarf. An HST STIS spectrum obtained
during primary eclipse reveals a host of transition region/chromospheric
emission features including N V (1238, 1242), Si IV (1393, 1402), C IV (1548,
1550) and He II (1640). The spectroscopic characteristics and emission line
fluxes of the transition region/chromosphere of the very active, rapidly
rotating, K2V component of V471 Tauri, are compared with the emission
characteristics of fast rotating K dwarfs in young open clusters. We have
detected a number of absorption features associated with metals accreted onto
the photosphere of the magnetic white dwarf from which we derive radial
velocities. All of the absorption features are modulated on the 555s rotation
period of the white dwarf with maximum line strength at rotational phase 0.0
when the primary magnetic accretion region is facing the observer. The
photospheric absorption features show no clear evidence of Zeeman splitting and
no evidence of a correlation between their variations in strength and orbital
phase. We report clear evidence of a secondary accretion pole. We derive C and
Si abundances from the Si IV and C III features. All other absorption lines are
either interstellar or associated with a region above the white dwarf and/or
with coronal mass ejection events illuminated as they pass in front of the
white dwarf.Comment: The Astrophysical Journal, May 10, 2012 issue - 16 figure