Detection of EUV Emission From the Low Activity Dwarf HD 4628: Evidence For a Cool Corona

M. Mathioudakis (1), J.J. Drake (1), P.W. Vedder (1), J.H.M.M. Schmitt (2), and S. Bowyer (1)

1) Center for EUV Astrophysics, 2150 Kittredge Street, University of California, Berkeley, CA 94720
2) MPE, Giessenbachstr. 1 Garching, Germany 8046

Astronomy and Astrophysics, 291, 517, 1994


We present observations of low activity late-type stars obtained with the Extreme Ultraviolet Explorer (EUVE). These stars are the slowest rotators, and acoustic heating may dominate their outer atmospheric heating process. We report detection of EUV emission from the low activity K dwarf HD 4628 during the EUVE Deep Survey in the Lexan/boron band. This detection, in conjunction with the non-detection of this object in the ROSAT PSPC all-sky survey, suggests the existence of a cool corona with a characteristic temperature of less than ~1.0E+06 K. The flux and spectral signature are consistent with current theories of acoustic heating.

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