A catalog of early-type H{\alpha} emission line stars and 58 newly confirmed Herbig Ae/Bes from LAMOST DR7

TL;DR

This paper presents a comprehensive catalog of early-type emission-line stars from LAMOST DR7, introduces a new method to distinguish Herbig Ae/Be stars from classical Be stars, and confirms 58 new Herbig Ae/Be stars, expanding the known population.

Contribution

It provides a large, classified catalog of early-type emission-line stars, proposes updated criteria to differentiate Herbig Ae/Be stars, and confirms new candidates using multi-wavelength data.

Findings

Catalog includes 30,048 spectra of 25,886 stars, with 3,922 having prior records.

Identified 66 confirmed Herbig Ae/Be stars, 58 of which are newly discovered.

Most confirmed Herbig Ae/Be stars are distant, located beyond 1 Kpc.

Abstract

We derive a catalog of early-type emission-line stars including 30,048 spectra of 25,886 stars from LAMOST DR7, in which 3,922 have Simbad records. The sample is obtained using K-Nearest Neighbor and Random Forest methods and visually inspected. The spectra are classified into 3 morphological types (10 subtypes) based on H$\alpha$ emission line profiles. Some spectra contaminated by nebula emission lines such as from HII regions are flagged in the catalog. We also provide a specific sub-catalog of 101 stars with the stellar wind by calculating stellar wind or accretion flow velocities based on P Cygni or inverse P Cygni profiles, in which 74\% of them having velocities below 400km/s. More important, with two color-color diagrams (H-K, K- W1) and (H-K, J-H) of a collection of known Herbig Ae/Be stars (HAeBes) and classical Ae/Be stars (CAeBes), we propose an updated criterion to separate HAeBes from CAeBes. By the criterion, we select 201 HAeBes candidates and 5,547 CAeBes candidates from the sample. We confirmed 66 of the 201 HAeBes by using both WISE images and LAMOST spectra and present a specific HAeBe sub-catalog, in which 58 are newly identified. In addition, the WISE colors (W1-W2, W1- W3, and W1-W4) show the distribution consistency between our confirmed HAeBes and that of the known HAeBes. Most of the 66 confirmed HAeBes locate in the lower edge of the main sequence of hot end in the HR diagram, while the distances of about 77\% exceed 1Kpc, which enlarges the number of far distant known HAeBes.