Long-term spectroscopic monitoring of the Luminous Blue Variable HD 160529^*

¹ Landessternwarte Königstuhl, 69117 Heidelberg, Germany
² L-3 Communications, NASA/GSFC, Greenbelt, MD 20771, USA
³ Astronomy Group, Vrije Universiteit Brussel, Pleinlan 2, 1050 Brussels, Belgium
⁴ European Southern Observatory, 85748 Garching, Karl-Schwarzschild-Str. 2, Germany

Corresponding author: O. Stahl, O.Stahl@lsw.uni-heidelberg.de

Received: 7 November 2002
Accepted: 19 December 2002

Abstract

We have spectroscopically monitored the galactic Luminous Blue Variable HD 160529 and obtained an extensive high-resolution data set that covers the years 1991 to 2002. During this period, the star evolved from an extended photometric minimum phase towards a new visual maximum. In several observing seasons, we covered up to four months with almost daily spectra. Our spectra typically cover most of the visual spectral range with a high spectral resolution ( 20 000 or more). This allows us to investigate the variability in many lines and on many time scales from days to years. We find a correlation between the photospheric Hei lines and the brightness of the star, both on a time scale of months and on a time scale of years. The short-term variations are smaller and do not follow the long-term trend, strongly suggesting different physical mechanisms. Metal lines also show both short-term and long-term variations in strength and also a long-term trend in radial velocity. Most of the line-profile variations can be attributed to changing strengths of lines. Propagating features in the line profiles are rarely observed. We find that the mass-loss rate of HD 160529 is almost independent of temperature, i.e. visual brightness.