Hubble Space Telescope FOS Observations of KPD 0005+5106: A Subluminous WN-WC Descendant with Ongoing Mass Outflow?

Abstract

The results are reported of spectroscopic observations of the ultrahigh excitation, helium-rich, prewhite-dwarf KPD 0005 + 5106 obtained with the HST Faint Object Spectrograph (FOS) in 1991 May and July with the red (FOS/RD) and blue (FOS/BL) Digicon detectors. The data reveal a rich line spectrum both in absorption and in emission with ultra-high excitation species present including O VIII, N V, possibly C V, Fe VI, Fe VII, and numerous weaker high n, low l, transitions of C IV and O VI as well as the predominant He II (3 yields n) and He II (Balmer alpha) absorption lines. There is a strong emission complex at 2981 A which is identified as primarily due to three transitions of N V commonly seen in WN Wolf-Rayet spectra. Evidence is presented that high-ionization species in emission (O VIII, N V, C IV, Si IV) and in absorption (He II, Fe VI, Fe VIII) are longward-shifted relative to the far-UV resonance (circumstellar) absorption lines by 25-50 km/s.