Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1976
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976a%26a....48...19b&link_type=abstract
Astronomy and Astrophysics, vol. 48, no. 1, Apr. 1976, p. 19-25. Research supported by the Consiglio Nazionale delle Ricerche o
Astronomy and Astrophysics
Astrophysics
22
Chromosphere, Hertzsprung-Russell Diagram, K Lines, Radiant Flux Density, Stellar Spectra, Emission Spectra, Giant Stars, K Stars, Main Sequence Stars, Spectrum Analysis, Stellar Atmospheres, Stellar Temperature
Scientific paper
Absolute energy fluxes in the K emission line of Ca II are determined from spectrograms for 31 F5-K7 main-sequence stars and 172 G2-M5 giants. The reduction procedure is discussed with specific reference to error estimates for the derived fluxes. It is found that the K-line flux of giant stars is about 100,000 erg/sq cm per sec for early G types and decreases by two orders of magnitude from G2 to M5. Flux differences are observed for giants earlier than K0, and the average flux of giants is found to be an order of magnitude lower than that of main-sequence stars of the same spectral type. The ratio of K-line flux to bolometric flux is shown to have a maximum at an effective temperature of about 4500 K for the giants and at about 5000 K for the main-sequence stars. All the stars with measured fluxes are plotted on an H-R diagram (bolometric magnitude vs effective temperature). The results show that stars with higher photospheric temperatures have greater chromospheric emission and confirm that photospheric temperature is an important parameter in K-line emission.
Blanco Cristina
Catalano Santo
Marilli Ettore
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