Документ взят из кэша поисковой машины. Адрес оригинального документа : http://star.arm.ac.uk/~ambn/abstract260.html Дата изменения: Tue Jan 7 12:12:34 1997 Дата индексирования: Tue Oct 2 00:18:58 2012 Кодировка: Поисковые слова: ultraviolet

We present far ultraviolet and optical spectroscopy of the Extreme Utraviolet Explorer (EUVE) survey source EUVE J0702+129 revealing a composite KO star plus DA white dwarf spectrum. The International Ultraviolet Explorer spectra show continuum emission from a hot white dwarf (T_{eff} = 30 - 40,000 K) and a rising contribution from the KO star at lambda \geq 2500 A. High resolution optical spectroscopy uncovers a high level of activity with strong H alpha and Ca H&K emission; application of the Wilson-Bappu relation indicates that the secondary star is slightly above the main sequence (KO IV-V). Both objects are found at a distance of ~ 130 pc and they likely constitute a physical pair. The EUV emission is dominated by the white dwarf, but the late-type star certainly contributes at higher energy. An interesting parallel is drawn with other DA+KO pairs with moderately active secondaries such as HD 18131 and HR 1608. The present discovery as well as other recent ones demonstrate the existence of a large population of white dwarfs hidden by evolved companions (III-IV).