Doppler Tomography of the Be Star HD 698

Ilfa A. Gabitova, Sergey V. Zharikov, А. С. Мирошниченко, A. C. Carciofi, Azamat A. Khokhlov, Aldiyar T. Agishev, Peter Prendergast

Galaxies, 2025

Full text Open access: Gold Metadata (CSL-JSON)

DOI 10.3390/galaxies13040080

Data confidence 70 medium

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Abstract

We present a Doppler tomography study of the Be star HD 698, recently resolved via interferometry as a post-mass-transfer binary system consisting of a Be star and a stripped, pre-subdwarf companion. Based on 76 high-resolution optical spectra obtained between 2014 and 2023, we analyze the Hα and Hβ emission lines and apply Doppler tomography to map the structure of the circumstellar disk. The Hα line reveals an asymmetric, multi-component velocity distribution, with an emission feature closely following the orbital motion of the companion. V/R variations in both Hα and Hβ lines are phase-locked with the companion’s orbital motion, indicating a tidally induced disk asymmetry. We discuss possible origins of the companion-centered Hα emission, including a circumsecondary disk, a transient mass-transfer stream, and stellar wind.