SIMBAD references

Compact objects undergoing mass transfer exhibit significant (and double-peaked) H_α emission lines. Recently, new methods have been developed to identify black hole X-ray binaries and calculate their systematic parameters using H_α line parameters, such as the full width at half-maximum (FWHM), equivalent width (EW), and separation of double peaks. In addition, the FWHM-EW plane from spectroscopy and the H_α color-color diagram from photometry can be used for rapid stellar classification. We measure the H_α and H_β profiles (e.g., FWHM and EW) using the LAMOST DR9 low- and medium-resolution spectra, and calculate the systematic parameters (e.g., velocity semiamplitude of the donor star, mass ratio, inclination angle, and mass of the accretor). A new correlation between FWHM and K₂, K₂ = 0.205(18) FWHM, is obtained for cataclysmic variables (CVs) in our sample. Both the FWHM-EW plane and the H_α color-color diagram can distinguish CVs with FWHM ≳ 1000 km s^–1 from Be stars and young stellar objects to some extent. To improve classification accuracy and enhance the selection of compact objects, we propose a new set of idealized filters with effective widths of 30, 130, and 400 Å for the narrow H_α filter, broad H_α filter, and r-band filter, respectively.