Blue horizontal-branch stars from LAMOST

Accurate atmospheric parameters of BHB stars are essential for investigating the formation and evolution of the Galaxy. In this work, a data-driven technique named Stellar Label Machine (SLAM) is used to estimate the atmospheric parameters of Large Sky Area Multi-Object Fiber Spectroscopic Telescope low-resolution spectra for BHB stars with a set of A-type theoretical spectra as the training data set.

We add color indexes ((BP-G), (G-RP), (BP-RP), (J-H)) during the training process to constrain the stellar temperature further. Finally, we derive the atmospheric parameters (Teff, logg, [Fe/H]) for 5355 BHB stars. Compared to existing literature results, our results are more robust, and after taking the color index into account the resulting precision of Teff and logg is significantly improved, especially for the spectrum with a low signal-to-noise ratio (S/N).