The Identification of New Herbig Ae/Be Stars from LAMOST DR7

Abstract Herbig Ae/Be stars (HAeBes) are critical tracers of intermediate- and high-mass star formation, yet their census remains incomplete compared to low-mass young stellar objects like T-Tauri stars. To expand the known population, we systematically searched for HAeBes in LAMOST DR7 low-resolution spectra. Following Sun et al., we applied Uniform Manifold Approximation and Projection for dimensionality reduction and Support Vector Machine classification, identifying ∼240,000 spectra with potential H α emission. After removing contaminants (nonstellar objects, extragalactic sources, cataclysmic variables, and Algol systems) and restricting to B/A-type stars, we obtained 1835 candidates through 2MASS/WISE visual inspection. Spectral energy distribution analysis confirmed 143 sources with infrared excess ( J band or longer wavelengths), including 92 known HAeBes. From the remaining 51 candidates, we classified 26 with strong infrared excess as new HAeBes. Color-index analysis of confirmed HAeBes and classical Ae/Be stars (CAeBes) revealed that the ( K − W 1) 0 versus ( W 2 − W 3) 0 diagram effectively separates these populations: CAeBes predominantly occupy ( K − W 1) 0 ≤ 0.5 and ( W 2 − W 3) 0 ≤ 1.1, while other regions trace transition disks (( K − W 1) 0 < 0.5 and ( W 2 − W 3) 0 > 1.1), globally depleted disks (( K − W 1) 0 > 0.5 and ( W 2 − W 3) 0 < 1.1), and Class I/Flat/II HAeBes (( K − W 1) 0 > 0.5 and ( W 2 − W 3) 0 > 1.1). More importantly, the HAeBes exhibit a clear evolutionary gradient on this diagram, with those in the Class III, Class II, Flat-SED, and Class I evolutionary stages being effectively distinguished by concentric ellipses that are roughly centered at (0, 0) with semimajor axes of a = 1.5, a = 3.0, and a = 4.0, and a semimajor to semiminor axis ratio of 1.6:1.