科研之友
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摘要
We present chromospheric activity index S-HK measurements for 119 995 F, G and K stars with high signal-to-noise ratio (S/N > 80) spectra, extracted from LAMOST DR1 in SDSS g band. The index delta S for each of these stars is calculated by the difference between its S-HK value and the baseline determined from very inactive stars. The effect of metallicity on measurement of delta S varies with stellar T-eff. No evident Vaughan-Preston gap appears in our sample. The relation between delta S and vertical distance from the Galactic plane is determined for stars with T-eff < 5500K. Stars with higher delta S tend to be closer to the Galactic plane. Two open clusters in the DR1 sample, M45 and M67, exhibit the expected general trend that delta S decays with age. For stars with T-eff > 5500K, similar delta S levels appear in both young and old cluster stars, which supports Pace's suggestion that caution should be exercised when deriving the age of a single star by using its chromospheric activity. Finally, we investigate the relation between delta S and the kinematics of our sample.
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