English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The distribution of stellar $\mathrm{H}\alpha$ chromospheric activity withrespect to stellar atmospheric parameters (effective temperature$T_\mathrm{eff}$, surface gravity $\log\,g$, and metallicity $\mathrm{[Fe/H]}$)and main-sequence/giant categories is investigated for the F-, G-, and K-typestars observed by the LAMOST Medium-Resolution Spectroscopic Survey (MRS). Atotal of 329,294 MRS spectra from LAMOST DR8 are utilized in the analysis. The$\mathrm{H}\alpha$ activity index ($I_{\mathrm{H}{\alpha}}$) and the$\mathrm{H}\alpha$ $R$-index ($R_{\mathrm{H}{\alpha}}$) are evaluated for theMRS spectra. The $\mathrm{H}\alpha$ chromospheric activity distributions withindividual stellar parameters as well as in the $T_\mathrm{eff}$ -- $\log\,g$and $T_\mathrm{eff}$ -- $\mathrm{[Fe/H]}$ parameter spaces are analyzed basedon the $R_{\mathrm{H}{\alpha}}$ index data. It is found that: (1) for themain-sequence sample, the $R_{\mathrm{H}{\alpha}}$ distribution with$T_\mathrm{eff}$ has a bowl-shaped lower envelope with a minimum at about 6200K, a hill-shaped middle envelope with a maximum at about 5600 K, and an upperenvelope continuing to increase from hotter to cooler stars; (2) for the giantsample, the middle and upper envelopes of the $R_{\mathrm{H}{\alpha}}$distribution first increase with a decrease of $T_\mathrm{eff}$ and then dropto a lower activity level at about 4300 K, revealing different activitycharacteristics at different stages of stellar evolution; (3) for both themain-sequence and giant samples, the upper envelope of the$R_{\mathrm{H}{\alpha}}$ distribution with metallicity is higher for stars with$\mathrm{[Fe/H]}$ greater than about $-1.0$, and the lowest-metallicity starshardly exhibit high $\mathrm{H}\alpha$ indices. A dataset of $\mathrm{H}\alpha$activity indices for the LAMOST MRS spectra analyzed is provided with thispaper.

$\mathrm{H}\alpha$ chromospheric activity of F-, G-, and K-type stars observed by the LAMOST Medium-Resolution Spectroscopic Survey