Tracers of chromospheric structure. I. CaII H$\&$K emission distribution of 13000 F, G and K stars in SDSS DR7 spectroscopic sample

Abstract

We present chromospheric activity index $S{}_{\mathrm{HK}}$ measurements for over 13,000 F, G and K disk stars with high signal-to-noise ratio ($>$ 60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter $\delta$S is defined as the difference between $S{}_{\mathrm{HK}}$ and a `zero' emission line fitted by several of the most inactive stars. The $S{}_{\mathrm{HK}}$ indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low resolution spectra. Cooler stars are generally more active and display a larger scatter than hotter stars. Stars associated with the thick disk are in general less active than those of the thin disk. The fraction of K dwarfs that are active drops with vertical distance from the Galactic plane. Metallicity affects $S{}_{\mathrm{HK}}$ measurements differently among F, G and K dwarfs in this sample. Using the open clusters NGC 2420, M67 and NGC6791 as calibrations, ages of most field stars in this SDSS sample range from 3-8 Gyr.

9 pages, 11 figures, AJ, 2013, 145, 140

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• Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. VI. HD 238914 and TYC 3318-01333-1 - two more Li-rich giants with planets
• Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey
• A Combined Chandra and LAMOST Study of Stellar Activity
• A Search for Planetary Nebulae With the SDSS: the outer regions of M31
• Mg II h+k Flux - Rotational Period Correlation for G-type stars
• Nearly 30,000 late-type main-sequence stars with stellar age from LAMOST DR5