Optical spectroscopy of Be stars: Peak separation of Balmer emission lines.

The Be stars display variable optical emission lines originating in the circumstellar disc. Here we analyze high resolution spectroscopic observations of Be stars and the distance between the peaks of Hα$$ \mathrm{H}\alpha $$, Hβ$$ \mathrm{H}\beta $$, and Hγ$$ \mathrm{H}\gamma $$ emission lines (ΔVα$$ \Delta {V}_{\alpha } $$,ΔVβ$$ \Delta {V}_{\beta } $$, and ΔVγ$$ \Delta {V}_{\gamma } $$ respectively). Combining published data, spectra from the ELODIE archive (obtained in the period 1998–2003) and Rozhen spectra (obtained 2015–2023) of 93 Be stars, we find a set of relations connecting ΔVα$$ \Delta {V}_{\alpha } $$, ΔVβ$$ \Delta {V}_{\beta } $$ and ΔVγ$$ \Delta {V}_{\gamma } $$. They are effective for 30≤ΔVα≤500kms−1$$ 30\le \Delta {V}_{\alpha}\le 500\kern0.3em \mathrm{km}\kern0.3em {\mathrm{s}}^{-1} $$, 80≤ΔVβ≤600kms−1$$ 80\le \Delta {V}_{\beta}\le 600\kern0.3em \mathrm{km}\kern0.3em {\mathrm{s}}^{-1} $$, and 40≤ΔVγ≤300kms−1$$ 40\le \Delta {V}_{\gamma}\le 300\kern0.3em \mathrm{km}\kern0.3em {\mathrm{s}}^{-1} $$. The new equations are in the form y=ax+b$$ y= ax+b $$ and are valid for a wider velocity range than in previous studies. [ABSTRACT FROM AUTHOR]