Ongoing magnetospheric accretion in the multiring transitional disc of HD 141569A

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ABSTRACT We present the results of long-term spectroscopic monitoring of the Herbig Ae star HD 141569A. The analysis is based on spectra obtained at the Shamakhy Astrophysical Observatory during 2017–2023 together with archival Ultraviolet and Visual Echelle Spectrograph spectra acquired with the European Southern Observatory Very Large Telescope in 2007. Using synthetic model atmospheres, we investigated the emission structure of the hydrogen Balmer lines in the presence of strong photospheric absorption. The H $\alpha$ and H $\delta$ emission profiles exhibit double-peaked structures with central depressions, indicating that the emitting gas is in Keplerian rotation within the circumstellar disc. Peak velocities were used to estimate the emission radii of several hydrogen lines. We find an increase in the linear gas velocity together with a gradual decrease in the peak intensity ratio ($I_{\rm V}/I_{\rm R}$) from the outer to the inner disc regions. The Na i D, Ca ii K, and metallic absorption lines reveal outflowing gas with a velocity of approximately $-13\pm 1.5$ km s$^{-1}$. Their narrow widths, significantly smaller than the stellar rotational velocity, suggest formation within an optically thick circumstellar wind. The hydrogen, Na i, and He i $\lambda 5876$ lines show spectroscopic signatures of ongoing accretion onto the star. Accretion rates derived from the H $\gamma$ and H $\delta$ lines yield the most reliable lower limit to the mass accretion rate, $\dot{M}_{\rm acc}\approx (0.85\!-\!0.93)\times 10^{-8}\, M_\odot \, {\rm yr}^{-1}$. These findings demonstrate that magnetospheric accretion onto HD 141569A remains active despite its highly evolved multiring transitional disc.

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