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

Abstract

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, H𝛽, and H𝛾 emission lines (ΔV 𝛼 ,ΔV 𝛽 , and ΔV 𝛾 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 ΔV 𝛼 , ΔV 𝛽 and ΔV 𝛾 . They are effective for 30 ≤ ΔV 𝛼 ≤ 500 km s −1 , 80 ≤ ΔV 𝛽 ≤ 600 km s −1 , and 40 ≤ ΔV 𝛾 ≤ 300 km s −1 . The new equations are in the form y = ax + b and are valid for a wider velocity range than in previous studies.