# Optical spectroscopy of Be stars: peak separation of Balmer emission lines

## TL;DR

This study analyzes high-resolution spectra of 93 Be stars to establish new linear relations between the peak separations of Balmer emission lines, extending the velocity range of previous models.

## Contribution

It provides new empirical equations linking peak separations of Balmer lines in Be stars, applicable over a broader velocity range than prior research.

## Key findings

- Derived linear relations between $\Delta V_eta$ and $\Delta V_eta$
- Established validity of equations for wider velocity ranges
- Analyzed spectra from multiple archives and time periods

## Abstract

The Be stars display variable optical emission lines originating in the circumstellar disc. Here we analyse high resolution spectroscopic observations of Be stars and the distance between the peaks of H-alpha, H-beta, and H-gamma emission lines ($\Delta V_\alpha$, $\Delta V_\beta$, and $\Delta V_\gamma$ 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 $\Delta V_\alpha$, $\Delta V_\beta$ and $\Delta V_\gamma$. They are effective for $30 \le \Delta V_\alpha \le 500$ km s$^{-1}$, $80 \le \Delta V_\beta \le 600$ km s$^{-1}$, and $40 \le \Delta V_\gamma \le 300$ 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.