2021RAA....21..202D

The molecular-rich atmospheres of M type stars complicate our understanding to their atmospheric properties. Recently, great progress has been made in atmospheric modeling of M-type stars, and we take advantage of the updated BT-Settl model grid to develop a pipeline LASPM to measure atmospheric parameters (Teff, log g, [M/H]) of M-type stars from low-resolution spectra. The pipeline was applied to the sixth and seventh data release (DR6 & DR7) of Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which released atmospheric parameters for 610 419 and 680 185 M-type spectra, respectively. The key algorithm is to find the best-matching for templates in the synthetic spectral library for an observed spectrum, and then minimizing χ2 through a linear combination of five best-matching templates. The intrinsic precisions of the parameters were estimated by using the multiple epoch observations for the same stars, which are 118 K, 0.20 dex, 0.29 dex for Teff, log g, and [M/H] respectively. The Teff and log g are consistent with the spectral and luminosity classifications by LAMOST 1D pipeline, and the loci of giants and dwarfs both on spectral index and color-magnitude diagrams show the validity. The metallicities of LASPM are also checked with the selected members of four open clusters (NGC 2632, Melotte 22, ASCC_16, and ASCC_19), which are consistent without any bias. Comparing the results between LASPM and the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP), there is a scatter of 73 K, 0.22 dex, 0.21 dex for Teff, log g, and [M/H], respectively.