A Dependence of GALEX FUV Magnitudes of F, G, and K Dwarfs Upon Stellar Activity

作者：Smith Graeme H^*; Redenbaugh Anja K

来源：Publications of the Astronomical Society of the Pacific, 2010, 122(897): 1303-1310.

DOI：10.1086/657051

The magnitudes of F, G, and K dwarf stars measured in the FUV bandpass of the GALEX satellite are found to show correlations with chromospheric activity. Values of a color (m(FUV) - B) were obtained by combining GALEX FUV and Johnson B magnitudes for a large sample of dwarfs for which published measurements of flux in the chromospheric Ca II H and K emission lines are available. Among dwarfs with (B - V) < 0.8 the photospheric flux produces a two-color relation between m(FUV) - B and B - V. A color excess Delta(m(FUV) - B), obtained by making a first-order correction for this photospheric effect, shows a correlation with chromospheric activity for stars with log R'(HK) > -4.8, where R'(HK) is the ratio between the luminosity in the H and K emission lines and the bolometric luminosity. Among dwarfs with (B - V) > 0.8 the photospheric contribution to the flux in the GALEX FUV bandpass is sufficiently low that the uncorrected m(FUV) - B color shows a clear variation with log R'(HK). The approximately linear nature of this relation indicates that the combined flux in the FUV band, which for such late-type dwarfs arises from transition-region and chromospheric emission lines, is related in a power-law manner to the flux in the Ca II H and K emission lines.

• 出版日期2010-11