Astronomy and Astrophysics, volume 318, L9-12 (1997/2-1)
An active K0 IV-V star and a hot white dwarf (EUVE J0702+129) in a wide binary.
VENNES S., CHRISTIAN D.J., MATHIOUDAKIS M. and DOYLE J.G.
Abstract (from CDS):
We present far ultraviolet and optical spectroscopy of the Extreme Ultraviolet Explorer (EUVE) survey source EUVE J0702+129 revealing a composite K0 star plus DA white dwarf spectrum. The International Ultraviolet Explorer spectra show continuum emission from a hot white dwarf (Teff=30-40,000K) and a rising contribution from the K0 star at λ>2500Å. High resolution optical spectroscopy uncovers a high level of activity with strong Hα and Ca H&K emission; application of the Wilson-Bappu relation indicates that the secondary star is slightly above the main sequence (K0 IV-V). Both objects are found at a distance of ∼130pc 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+K0 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).
binaries: general - Stars: chromospheres - Stars: evolution - white dwarfs - Stars: individual: EUVE J0702+12.9