Long-term spectroscopic monitoring of HD 160529

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Session 80 -- Stellar Activity II: Early Type Stars, Normal Stars
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[80.02] Long-term spectroscopic monitoring of HD 160529

T. G\"ang, C. Leitherer (STScI), C. Gummersbach, A. Kaufer, H. Mandel, O. Stahl, T. Szeifert, B. Wolf (LSW), J. Kovacs (GAO)

We have observed the galactic Luminous Blue Variable HD 160529 at the ESO-50cm telescope with a fiber-linked echelle spectrograph in 3 observing runs from 1992 to 1994. In total 188 spectra were obtained with a $S/N \approx 100$ and a resolving power of $\lambda / \Delta \lambda\approx20\,000$ in the wavelength range 4050\,\AA $ < \lambda <$ 6800\,\AA.

In our 1992 survey we detected a sharp increase in the radial velocity curve of the He\,I\,$\lambda5876$ line (from about -13 km/s to -27 km/s) which could be explained by a shell-ejection. Simultaneously a peak in the visuell brightness is observed indicating a possible correlation of photometric and spectroscopic variations.

At the same time the Si\,II\,$\lambda6347$ and Fe\,II\,$\lambda6248$ lines show significant intensity variations in their red wings. The blue wings of these lines which originate further outside of the atmosphere at higher velocities are not influenced by this feature.

The H$\alpha$ line shows a strong P Cygni profile with no $v_{\rm rad}$ variations; only the variable intensity of the emission component reflects the density variations within the envelope which are caused by the ejected shell. The maximum radial velocity of about $v_{\rm rad}(max) \approx -185$\ km/s was measured on the blue wing of the absorption component of H$\alpha$. A mass-loss rate of $\dot{M} \approx 10^{-5} \ {\rm M}_{\odot}{\rm yr}^{-1}$ was determined by fitting models to the H$\alpha$ line profile.

The sodium lines consisted of 3 absorption and 1 emission components at $v_{\rm rad}= -98, -68, -12, +34 \ {\rm km/s}$ (measured at the line peaks). By comparing the NaD lines from Wolf et al.\ (1974), Sterken et al.\ (1991) and our observations we see similar $v_{\rm rad}$ values but strongly varying intensities.

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