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

Abstract

We present a catalogue including 11,204 spectra for 10,436 early-type emissionline 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 Hα emission profiles display a wide variety of shapes. Based on the Hα 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 Hα 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 H II 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 H II regions after crossmatching 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 Hα 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.

On the kinematics of a runaway Be star population

“…Although we have not fully resolved the contribution of the post-mass-transfer channel to the Be star population with the TGAS data, we are optimistic about the road ahead. The second and later Gaia data releases will increase the sample of Be stars with accurate kinematics by at least an order of magnitude; for instance, Hou et al (2016) present a catalogue of 5187 Be stars in LAMOST, all of which will have proper-motions and parallaxes in Gaia DR2. The Bayesian approach developed in this work to tackle the kinematics of a large population lays the foundation for the full exploitation of this future dataset.…”

“…We consider three datasets which satisfy this requirement. The first is from Berger & Gies (2001), the second is a cross-match between the Be Star Spectra database (BeSS) with SIMBAD and the Tycho-Gaia Astrometric Solution (TGAS), and the third is a cross-match of the Be catalogue of Hou et al (2016) from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) with TGAS. We then combine and clean these datasets by removing any duplicates, as well as stars with anomalously high radial velocities.…”

Spectroscopically Identified Cataclysmic Variables from the LAMOST Survey. I. The Sample

“…In the spectra of these CVs, low-order Balmer lines such as Hα and Hβ always show emissions in the cores, and higher order of Balmer series show broad absorption lines. Therefore, we firstly pick up spectra with Hα in emission from more than 470,000 O/B/A, white dwarf and CV spectra using the method proposed by Hou et al (2016). The method aims to figure out two different profile shapes of strong Hα emission lines as well as weak emission lines lying in the deep Hα absorption profiles in spectra.…”

WEDA: A Weak Emission-Line Detection Algorithm Based on the Weighted Ranking

“…A considerable amount of meaningful information can be mined from the massive amounts of data. Spectral data with Hα emission line in LAMOST [26] can be chosen for use in WEDA. Previous work has found data with Hα emission line and used these spectral data, for example, to study peculiar A-type stars [27] and to search for classical Be stars [28].…”