A catalog of early-type emission-line stars and Hα line profiles from LAMOST DR2

We present a catalog including 11 204 spectra of 10 436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these early type emission-line stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the H alpha emission profiles display a wide variety of shapes. Based on the H alpha line profiles, these spectra are categorized into five distinct classes: single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the H alpha line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H (II) regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a (H-K, K-W1) color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by H (II) regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of H alpha profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fe (II) emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.