The Astrophysical Journal · 1975 · 69 citations · 0 references
Natural SciencesAstronomyPhysicsAstrophysicsOptical AstronomyX-ray AstronomyX-ray Background RadiationX-ray SpectroscopyFlare StarsOptical FlareStellar FlaresStellar Ultraviolet RadiationStellar X-ray RadiationX-ray Emission From Active StarsX-ray Emission LinesX-ray Line Emission
Observations that detected the first X-ray emission from flare stars are described. An X-ray flare was detected from YZ CMi at 0.28 keV and approximately 1-7 keV, although no optical or radio coverage was available. During a very large optical flare from UV Ceti, X-ray emission at (only) 0.28 keV was detected. Upper limits for X-ray emission from several small optical flares of UV Ceti are presented. Implications for X-ray flare models, the diffuse X-ray background, and low-energy cosmic-ray flux are mentioned.