Spectroscopy of close visual binary components of the stable shell star 1 Del

TL;DR

This study spectroscopically resolved the close visual binary star 1 Del, revealing that the primary is a Be/shell star and the secondary is not an emission-line object, providing new insights into disk formation in such systems.

Contribution

First spectroscopic resolution of 1 Del binary components, distinguishing their spectral types and emission properties, enhancing understanding of disk formation in shell stars.

Findings

1 Del A is a Be/shell star.

1 Del B is not an emission-line object.

Spectra of both components were obtained for the first time.

Abstract

Stable shell stars are ideal objects for studying basic physical principles of the formation of disks in Be stars. If these stars have a close unresolved visual companion, its contribution toward the modelling of the disk cannot be overlooked, as is sometimes done. The study aims to spectroscopically resolve close visual binary Be (shell) star 1 Del, which up to now was only resolved by speckle or micrometric measurements. The integral field spectroscopy obtained by the SINFONI spectrograph at the VLT telescope in the European Southern Observatory (ESO) in the infrared region was used; we supplemented these observations with visual spectroscopy with the Perek Telescope at the Ondrejov Observatory. Spectra of 1 Del were successfully resolved, and, for the first time, spectra of 1 Del B were obtained. We found that 1 Del A is a Be/shell star, while 1 Del B is not an emission-line object.