A catalogue of early-type emission-line stars and H{\alpha} line
  profiles from LAMOST DR2
  We present a catalogue including 11,204 spectra for 10,436 early-type
emission-line stars from LAMOST DR2, among which 9,752 early-type emission-line
spectra are newly discovered. For these early-type emission-line stars, we
discuss the morphological and physical properties from 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 view
of physical classification, which include classical Be stars, Herbig Ae/Be
stars, close binaries and spectra contaminated by HII regions. The majority of
Herbig Ae/Be stars and classical Be stars are identified and separated using
the (H-K, K-W1) color-color diagram. We also discuss thirty one binary systems
as listed in SIMBAD on-line catalogue and identify 3,600 spectra contaminated
by HII regions after cross matching with positions in the Dubout-Crillon
catalogue. 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 FeII emission lines and roughly calculate stellar wind velocities for
seven spectra with P-Cygni profiles.
