BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other chromospheric activity.[1] Resultant brightness fluctuations are generally less that 0.5 magnitudes[1] on timescales equivalent to the star's rotational period, typically from a fraction of a day to several months. Some of these stars may also have flares, resulting in additional variations of the UV Ceti type. Oddly enough, Procyon the 8th brightest night-time star which is an F5 sub-giant or dwarf has also been classified as a BY Draconis variable. (Source : Schaaf, 'The Brightest Stars', Wiley, 2008.)
References
- ^ a b Lopez-Morales, Mercedes; Morrell, N. I.; Butler, R. P.; Seager, S. (2006). "Limits to Transits of the Neptune-mass planet orbiting Gl 581". Publications of the Astronomical Society of the Pacific 118. http://arxiv.org/abs/astro-ph/0609255. Retrieved 2009-04-23. "BY Draconis variable. This type of variable is characterized by quasiperiodic photometric variations over time scales from less than a day to months, and amplitudes ranging from a few hundredths of a magnitude to 0.5 mags.". (page 2 of pre-print submitted 9 September 2006)
- Samus N.N., Durlevich O.V., et al. Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.)
- Schaaf, Fred, 'The Brightest Stars', Wiley, 2008
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