A Study of H$\alpha$ Line Profile Variations in $\beta$ Lyr

TL;DR

This study analyzes over 160 archival Hα spectra of the binary system β Lyr, revealing complex line profile variations and exploring potential physical origins such as accretion streams and circumbinary material.

Contribution

It provides detailed observational analysis of Hα line profile variations in β Lyr and evaluates different models to explain the observed spectral features.

Findings

The Hα emission is double-peaked and asymmetric with a persistent blueshifted absorption.

The blueshifted feature varies in velocity and is not always present.

An accretion stream model shows some promise in explaining the observations.

Abstract

We examine over 160 archival H$\alpha$ spectra from the Ritter Observatory for the interacting binary $\beta$~Lyr obtained between 1996 and 2000. The emission is characteristically double-peaked, but asymmetric, and with an absorption feature that is persistently blueshifted. Using a set of simplifying assumptions, phase varying emission line profiles are calculated for H$\alpha$ formed entirely in a Keplerian disk, and separately for the line formed entirely from an off-center bipolar flow. However, a dynamic spectrum of the data indicate the blueshifted feature is not always present, and the data are even suggestive of a drift of the feature in velocity shift. We explore whether a circumbinary envelope, hot spot on the accretion disk, or accretion stream could explain the observations. While none are satisfactory, an accretion stream explanation is somewhat promising.