Stellar Spots — Physical Implications
Studies of certain late-type stars have revealed evidence for appreciable changes in their photospheric radiation. These stars are rotating much more rapidly than the Sun and/or are younger, and exhibit much enhanced examples of many kinds of solar activity, such as flares. The surface brightness distributions of these stzellar photospheres are nonuniform; dark areas are called “spots” in solar analogy. Areas of up to 30% may be covered by such spots, again indicating activity on a far greater scale than typical of the Sun.
Despite the lack of definitive bolometric observations, the detection of visual light variations on the order of 30% may be translated into total luminosity variations on the order of 10% with reasonable confidence. Spots may appear or decay over timescales of days, but longer-term trends exist, with timescales of decades. No direct evidence for spot cycles on the order of 10 years in length has been found, although some stars exhibit quasi-sinusoidal variations in mean light with time-scales ~ 50 years. Other cool stars of generally greater age and slower rotation exhibit evidence for decade periods in Ca II emission.
KeywordsLight Curve Light Variation Comparison Star Physical Implication Cool Star
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- Biermann, L., 1941, Vierteljahresschr. Astron. Ges. 76, p. 194.Google Scholar
- Catalano, S., and Rodono, M., 1969, in “Nonperiodic Phenomena in Variable Stars”, ed. L. Detre (Dordrecht: Reidel), p. 435.Google Scholar
- Hall, D.S., Kreiner, J.M., and Shore, S.N., 1980, in “Close Binary Stars, IAU Symp. 73”, ed. M.J. Plavec, D.M. Popper, and R.K. Ulrich (Dordrecht: Reidel), p. 383.Google Scholar
- Hartmann, L., Dussault, M., Bopp, B.W., and Dupree, A.K. 1980, in preparation.Google Scholar
- Krzeminski, W., 1969, in “Low Luminosity Stars”, ed. S.S. Kumar (London: Gordon and Breach), p. 57.Google Scholar
- Lockwood, G.W. 1980, private communication.Google Scholar
- Ramsey, L., and Nations, H. 1980, preprint.Google Scholar
- Vogt, 1980, Astrophys. Journ., in press.Google Scholar