A New Catalog of Am-type Chemically Peculiar Stars Based on LAMOST

Abstract

A total of about 21,600 Am candidates were detected with the MKCLASS code based on the low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Data Releases 8 (v1.0), 9 (v0), and 10 (v0), which greatly expands the database of Am-type stars. By crossmatching the known catalogs of Am stars and our Am candidates with the AAVSO International Variable Star Index catalog, a catalog of the largest eclipsing Am binaries was obtained, which includes 754 binaries and provides a substantial sample with which to study Am stars. Fundamental information, including atmospheric parameters of the two kinds of candidates, are collected and listed in the catalogs, such as temperature, log g, and metallicity. We further carried out statistical analysis of the types of parameters. In our new catalog, there are some Am candidates with a temperature lower than 7000 K and some eclipsing Am binary candidates with a period of less than 1 day, which poses challenges to the slow rotation of stars classified as type Am observed in previous research. These candidates are significant and provide a great opportunity to explore the real relationship between Am-type stars’ peculiarity and slow stellar rotation. The Hertzsprung–Russell diagram of Am stars and the primary stars of eclipsing Am binary candidates indicate that a majority of the Am stars and almost all primary stars of binaries are in or around the main-sequence evolution stage.