MK-like spectral classification for hot subdwarf stars with LAMOST spectra

An MK-like spectral classification has been conducted for 1224 hot subdwarf stars with LAMOST DR9 low-resolution spectra. The whole sample was divided into four categories according to the spectral line characteristics: He-normal, He-weak, He-strong C and He-strong. Each selected spectrum was assigned a spectral class, a luminosity class and an helium class by comparing the line depth and width with standard spectra selected in LAMOST. Relationships between atmospheric parameters and spectral classification were also presented.