BY Draconis variable
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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 than 0.5 magnitudes[1] on timescales equivalent to the star's rotational period, typically from a fraction of a day to several months. 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.)
Some of these stars may exhibit flares, resulting in additional variations of the UV Ceti type.[2] Likewise, the spectra of BY Dra variables (particularly in their H and K lines) are similar to RS CVn stars, which are another class of variable stars that have active chromospheres.[3]
[edit] 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, arXiv:astro-ph/0609255, Bibcode 2006PASP..118.1506L, doi:10.1086/508904, "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."
- ^ Schrijver, Carolus J.; Zwaan, Cornelis (2000), Solar and stellar magnetic activity, Cambridge astrophysics series, 34, Cambridge University Press, p. 343, ISBN 0521582865, http://books.google.com/books?id=Ik0nNfABUrMC&pg=PA343
- ^ Jaschek, Carlos; Jaschek, Mercedes (1990), The Classification of Stars, Cambridge University Press, p. 374, ISBN 0521389968, http://books.google.com/books?id=DCA0PIjqSpQC&pg=PA374
[edit] Further reading
- 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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| Pulsating |
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Cepheids and
cepheid-like
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Blue-white with
earlyspectra
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Other
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| Eruptive |
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Giants and
supergiants
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Eruptive binary
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Cataclysmic
or explosive
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| Rotating |
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Non-spherical
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Stellar spots
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- FK Comae Berenices
- BY Draconis
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Magnetic fields
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| Eclipsing |
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