Stellar parameters from LAMOST MRS DR8

By performing a fitting with MARCS model atmospheric theoretical synthetic spectra combined with a domain-adaptation method, we estimate the fundamental stellar parameters (Teff, logg, [Fe/H], vmic, and vmac) and 11 chemical abundances for 1.38 million FGKM-type stars of the Medium-Resolution Spectroscopic Survey (MRS) from LAMOST-II DR8.

The domain-adaptation method, CYCLE-STARNET, is employed to reduce the gap between observed and synthetic spectra, and the L-BFGS algorithm is used to search the best-fit synthetic spectra. By combining the Two Micron All Sky Survey photometric survey data, Gaia EDR3 parallax, and MIST isochrones, the surface gravities of the stars are constrained after estimating their bolometric luminosities. The accuracy of Teff, logg, and [Fe/H] can reach 150K, 0.11dex, and 0.15dex, evaluated by the PASTEL catalog, asteroseismic samples, and other spectroscopic surveys.