Identification of A-type supergiants from LAMOST DR5

Abstract

ABSTRACT We present a new method for selecting A-type supergiants (A-SGs hereafter) in the LAMOST DR5 data set using the line indices, and identify 40 spectra of 30 A-SG candidates. Based on the analysis of the absolute magnitude of Gaia DR3, SIMBAD data base, ZTF light variation data, and spectral characteristics of A-SGs, we classified the 30 A-SG candidates into 18 A-SGs and 12 A-SG candidates with different levels of credibility. We also subclassify spectral types of 18 A-SGs and 12 A-SG candidates by using human eyes and find a good consistency between our results and those of MKCLASS for most of them. The spatial distribution of 18 A-SGs and 12 A-SG candidates indicates that they are located in the Galactic latitude smaller than 20○. In addition, the distribution of 13 A-SGs and 7 A-SG candidates with reliable Gaia DR3 kinematic parameters in the Toomre diagram indicates that they are located in the Galactic disc, which also suggests that they are young, massive stars. Our selection has worked out well, in that only one A-SG candidate and one A-SG appear to exhibit discrepant kinematics.