Nature of stellar active regions

Journal Article · Thu Dec 01 04:00:00 EST 1983 · Publ. Astron. Soc. Pac.; (United States)

DOI:https://doi.org/10.1086/131286· OSTI ID:6591746

Observational estimates of chromospheric radiative loss rates in Ca II H and K in main-sequence F, G, and K dwarfs are used to compare stars that span a range of activity levels with each other and with the sun. For stars with spectral types similar to that of the sun, it is found that chromospheric radiative losses in stars with active chromospheres exceed the flux emitted by plages on the sun at solar maximum by about a factor of 6. If this difference is due primarily to a difference in the fraction of the stellar surface covered by plage-like material, and not to a change in the character of the emission-line regions, then more than half of the stellar surface in stars with large chromospheric radiative loss rates must be covered by active regions. It is also possible to show that active regions in young solar-type stars extend at least to latitudes + or - 25 deg from the rotational equator and that a typical individual region contributes no more than 2 percent - 3 percent of the total H and K emission. In Kappa Cet, observations show that the rotational modulation persisted in both phase and amplitude for at least 100 days (12 rotation cycles). 23 references.

• Research Organization: Univ. of Hawaii, Honolulu
• OSTI ID: 6591746
• Journal Information: Publ. Astron. Soc. Pac.; (United States), Journal Name: Publ. Astron. Soc. Pac.; (United States) Vol. 95; ISSN PASPA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALKALI METALS
ALKALINE EARTH METALS
ATMOSPHERES
CALCIUM
DWARF STARS
ELEMENTS
EMISSION SPECTRA
FACULAE
FLUX DENSITY
HYDROGEN
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
METALS
NONMETALS
POTASSIUM
RADIANT FLUX DENSITY
RADIATION TRANSPORT
SOLAR ACTIVITY
SPECTRA
STAR MODELS
STARS
STELLAR ATMOSPHERES
SUN