SPECTRAL VARIABILITY OF SUPERGIANT HD21389

Abstract

Late B- and early A-type supergiants are interesting evolved stars exhibiting photometric variability accompanied by spectral changes. Particularly interesting is a group of pulsating stars named after Deneb as α Cyg variables. Deneb-type variables are known for decades to show variability in both brightness and radial velocities. Despite this group of stars undergoing continuous
observations, the mechanism responsible for such changes is not yet well understood. In order to better understand and possibly describe this mechanism, the continuous spectral monitoring of early-type supergiants is still a topical task. The main goal of our work is to characterize the spectral variability of one of the Deneb-type variables – HD21389. We carried out the spectral variability
analysis of its spectra taken within 6 years from 2017 up to now.

Radial velocities and lines’ profiles of HD 21389 show variability across the whole observational period with the most prominent variability in the Hα line. Among other things, we captured the final phase of the High-Velocity Absorption event (HVA) which HD 21389 underwent in 2018, and observed broad emission features around Balmer lines.