DISCOVERY OF AN O Ⅵ-EMITTING NEBULA AROUND THE HOT WHITE DWARF KPD 0005+5106

摘要

A survey of diffuse interstellar sight lines observed with the Far Ultraviolet Spectroscopic Explorer has led to the serendipitous discovery of a high-ionization nebula around the hot white dwarf KPD 0005+5106. The nebula has an O Ⅵ λ1032 surface brightness of up to 25,000 photons s~(-1) cm~(-2) sr~(-1), making it the brightest region of extended O Ⅵ emission in our survey. Photoionization models using the incident white dwarf continuum successfully reproduce the observed O Ⅵ intensity. The O Ⅵ emission arises in the highly ionized inner region of a planetary nebula around KPD 0005+5106. This newly discovered nebula may be one member of a class of high-ionization planetary nebulae that are difficult to detect in the optical, but that can be easily identified in the ultraviolet.