The spectral variability or line profile variations (LPV) of otherwise single WR objects has been known for a long time (Wilson 1948) but has been the subject of detailed investigation only with the advent of linear detectors (Ebbets 1979). More recently LPVs have been recognized as very common (Moffat & Robert 1991; Robert 1994). Recently LPVs have been studied in detail for several WR stars: HD 50896 (Morel et al. 1998), HD 191765 (Morel et al. 1999) and HD 4004 (Niedzielski 2000). In spite of a long list of possible processes which may possibly result in the observed spectral variability, the question of the nature of LPVs in WR stars remains open.
The first photometric observation of HD 4004 was reported by Hiltner (1956). Moffat & Shara (1986) reported its weak photometric variability for the first time. Line profile variations in HD 4004 were first observed by Niedzielski (1995). An more extended review on HD 4004 can be found in Niedzielski (1998).
Recently Morel et al. (1999) presented an extensive photometric and spectroscopic study of HD 4004 and confirmed the spectral variability reported by Niedzielski (1995). They also presented evidence for unique, short lasting (3-4 days) photometric brightening of this object but found only marginal photometric variability in an additional 11 day photometric monitoring. Morel el al. (1999) were not able to find any periodicity in their data.
Niedzielski (2000) presented results of optical spectroscopic monitoring of HD 4004. He was able to describe the amplitude of observed variations in emission lines of different ions in terms of wind ionization stratification. Niedzielski (2000) excluded a binarity scenario both with a degenerate and non-degenerate object, as possible explanations of observed variations in the optical spectrum of HD 4004.
In this paper we present results of complete analysis of HD 4004 from two observing runs performed in lower resolution than in Niedzielski (2000) but covering much larger wavelength range, from 4350 to 5700 . We aim to extend the correlation of variability in HeII lines reported by Niedzielski (1996) through a comparison of variability observed simultaneously in several lines.
© European Southern Observatory (ESO) 2000
Online publication: October 30, 19100