Stellar Spots — Physical Implications

  • L. Hartmann
Conference paper
Part of the NATO Advanced Study Institutes Series book series (ASIC, volume 68)


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.


Light Curve Light Variation Comparison Star Physical Implication Cool Star 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© D. Reidel Publishing Company 1981

Authors and Affiliations

  • L. Hartmann
    • 1
  1. 1.Harvard-Smithsonian Center for AstrophysicsUSA

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