  The Extreme Ultraviolet Explorer (EUVE) satellite was used for three days
beginning on 1997 Mar 26.96 UT to obtain photometric and spectroscopic
observations of the eclipsing SU UMa-type dwarf nova OY Carinae in
superoutburst. Because of the longer time on source (143 ks), the larger number
of eclipses observed (17), and the higher count rate in the detector (0.5-2.2
counts/s), we are able to significantly strengthen previous reports that there
is little or no eclipse by the secondary of the EUV emission region of OY Car
in superoutburst. The mean EUVE spectrum extends from 70 to 190 A and contains
broad (FWHM~1 A) emission lines of N V, O V-O VI, Ne V-Ne VII, Mg IV-Mg VI, Fe
VI-Fe VIII, and possibly Fe XXIII. Good fits of the observed spectrum are
obtained with a model (similar to that of Seyfert 2 galaxies) wherein radiation
from the boundary layer and accretion disk is scattered into the line of sight
by the system's photoionized accretion disk wind. It is possible to trade off
continuum luminosity for wind optical depth, but reasonable models have a
boundary layer temperature T_{bl}=90-130 kK and a boundary layer and accretion
disk luminosity L_{bl}=L_{disk} ~4x10^{34} erg/s ~ 10 Lsun, corresponding to a
mass-accretion rate Mdota~10^{-8} Msun/yr; an absorbing column density
N_H=1.6-3.5x10^{19} cm^{-2}; and a wind mass-loss rate Mdotw~10^{-10} Msun/yr ~
0.01 Mdota. Because radiation pressure alone falls an order of magnitude short
of driving such a wind, magnetic forces must also play a role in driving the
wind of OY Car in superoutburst.
