All Figures

$\begin{figure} \par\includegraphics[angle=90,width=7.3cm,clip]{5055fg01.eps} \end{figure}$ Figure 1: High dispersion IUE spectra of the ${\lambda }$ 1640 wavelength region of the sharp-lined stars $\tau$ Sco (B0.2 V) and HR 1886 (B1 V). The spectra partially resolve the He II 1640.4 Å line from the blend of Ni III/Fe II blend near 1640.0 Å. The wavelength range depicted corresponds approximately to the velocity range exhibited in most of the figures in this paper. The "Reseaux'' title notes the presence of a fiducial marker in the focal plane of the detector of the SWP camera.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.5cm,clip]{5055fg02.eps} \end{figure}$ Figure 2: The equivalent width contributions to the He II ${\lambda }$ 1640 blend as a function of stellar effective temperature, computed from both LTE (solid line) and non-LTE (dashed) model atmospheres and measured over the wavelength interval $\lambda \lambda$ 1638.7-1641.5. Pairs of solutions are shown for the unrotated and broadened ( $V_{\rm rot}\sin~i$ = 300 km s^-1) profiles. The lower group of lines correspond to the equivalent widths found for the He II transitions alone. Normal compositions and a microturbulent velocity of 5 km s^-1 are assumed.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg03.eps} \end{figure}$ Figure 3: IUE spectra of ${\lambda }$ Eri obtained from observations during the epochs 1993.7-1994.1 and 1995.8 for the He II and Si IV doublet. The 1993-4 spectra are smoothed over 2 points in this plot. The shaded areas indicate the variations of the photospheric components; significance on He II is for this shaded area. In all plots, we assume a centroid wavelength 1640.3 for the ${\lambda }$ 1640 aggregate feature. In this convention the He II feature centroid will correspond to a velocity of about +55 km s^-1. Unless otherwised noted, the velocity system for the C IV doublet is referenced to the ${\lambda }$ 1550.8 component.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.85cm,clip]{5055fg04.eps} \end{figure}$ Figure 4: Comparison of IUE observations SWP 29272 and 29301 (2.0 days later) on ${\lambda }$ Eri for He II, Si IV ${\lambda }$ 1394 line and the C IV doublet in the spectra. The comb indicates the velocity range over which there are correlated variations.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg05.eps} \end{figure}$ Figure 5: Comparison of IUE observations SWP 39904 and 39911 (19 h later) for He II, the C IV doublet and the Si IV ${\lambda }$ 1394 line in ${\lambda }$ Eri. This figure shows typical rapid weakenings of the He II line in this star.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.5cm,clip]{5055fg06.eps} \end{figure}$ Figure 6: Comparison of IUE observations SWP 32228 and 32232 (3.9 h later) for the He II, the C IV, and Si IV ${\lambda }$ 1394 lines in ${\lambda }$ Eri. This figure shows typical rapid filling in of the red wing of the He II line in this star. The X-marked features in all three features are instrumental ("missing minor frames'').
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg07.eps} \end{figure}$ Figure 7: IUE observations of ${\omega }$ Ori during 1983 that show variations of the He II, Si IV and C IV lines. The interval between the solid and dashed line observations is 16 days. The dotted line (He II only) shows the observation SWP 21159 13 days after the second observation. The significances quoted is for differences between the first and second, second and third, and first and third He II observations, respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg08.eps} \end{figure}$ Figure 8: IUE observations of ${\omega }$ Ori over a 12 h interval in 1983, exhibiting variations of the He II, Si IV and C IV lines. Errors on He II are taken in the interval 0-350 km s^-1.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg09.eps} \end{figure}$ Figure 9: A comparison of ${\mu }$ Cen's He II and C IV lines in 1980 and 1982 for ${\mu }$ Cen. Note the weak red wing emission. Errors on He II refer to blue and red halves of the profile, respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.5cm,clip]{5055fg10.eps} \end{figure}$ Figure 10: A comparison of the He II and the C IV lines for the interval April 1986-February 1989 for ${\mu }$ Cen. Note the weakening of the He II line coincident with the formation of red wing emission in C IV. Errors on He II refer to blue/central and red portions of profile (see comb).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg11.eps}\end{figure}$ Figure 11: A comparison 6 Cep's He II and C IV lines for epochs 1989.0 and 1990.5. Note the inactivity of the red wing emission in the C IV line. The wind was in a different state during 1982-86 (C IV, dotted line).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=8.1cm,clip]{5055fg12.eps}\end{figure}$ Figure 12: A montage of four variations of the C IV and He II lines in 1983, 1986, 1994.7, and 1994.9 for HD 67536. The dashed line represents the mean of the available 22 spectra. The photospheric components of the C IV doublet of observation SWP 27503 (bold line) are nearly completely filled in. The average spectra (dashed plot) are binned to 4 instead of 2 pixels. Note the slightly sharp, red displaced features (in the first three cases in emission) in these lines. "5.1 $\sigma$ '' (panel b, fourth spectrum) refers only to the variation of the sharp absorption.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.45cm,clip]{5055fg13.eps} \end{figure}$ Figure 13: The comparison of the stronger than unusual He II and C IV spectra for $\psi ^1$ Ori obtained at 1987.2 relative to mean profiles.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.45cm,clip]{5055fg14.eps} \end{figure}$ Figure 14: A comparison of the He II and C IV spectra for $\psi ^1$ Ori at the epoch 1980.0 relative to the mean profiles. The single spectrum shows a weak sharp absorption feature at 100 km s^-1.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg15.eps} \end{figure}$ Figure 15: A comparison of the He II and C IV spectra during the 1991.2 campaign on ${\eta }$ Cen. Notice the variation of the blue wings over over a 7.4 h interval. Our significance acceptance criterion was relaxed in this one case because of the correlation with the strong C IV variation.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg16.eps} \end{figure}$ Figure 16: A comparison of the He II and C IV lines during the 1991.2 campaign on ${\eta }$ Cen. Note the variation of the red wings over a 3.9 h interval.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg17.eps} \end{figure}$ Figure 17: A comparison of the He II and C IV spectra between epochs 1979.5 and 1979.8 for ${\pi }$ Aqr.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg18.eps} \end{figure}$ Figure 18: A comparison of the He II and C IV spectra between epochs 1988.4 and 1993.9 for ${\pi }$ Aqr. Errors on He II are given for the blue wing (comb interval) and red wing, respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg19.eps} \end{figure}$ Figure 19: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 line spectra between epochs 1989 (SWP 36329) and 1992 for 2 Vul. The comb shows the region of differences of the profiles, which are also shared by the Si III ${\lambda }$ 1206 line (not shown).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg20.eps} \end{figure}$ Figure 20: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 spectra for 2 Vul for the epochs 1983 and 1992. Although not shown, the Si III line exhibits similar variations.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg21.eps} \end{figure}$ Figure 21: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 spectra for a mean and an observation of 19 Mon during 1994.2. The significance on He II refers to the whole profile. Thus, the significance of the variation of the blue wing exceeds 6.0 $\sigma$ .
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7.85cm,clip]{5055fg04.eps} \end{figure}$	Figure 4: Comparison of IUE observations SWP 29272 and 29301 (2.0 days later) on ${\lambda }$ Eri for He II, Si IV ${\lambda }$ 1394 line and the C IV doublet in the spectra. The comb indicates the velocity range over which there are correlated variations.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg05.eps} \end{figure}$	Figure 5: Comparison of IUE observations SWP 39904 and 39911 (19 h later) for He II, the C IV doublet and the Si IV ${\lambda }$ 1394 line in ${\lambda }$ Eri. This figure shows typical rapid weakenings of the He II line in this star.
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$\begin{figure} \par\includegraphics[angle=90,width=7.5cm,clip]{5055fg06.eps} \end{figure}$	Figure 6: Comparison of IUE observations SWP 32228 and 32232 (3.9 h later) for the He II, the C IV, and Si IV ${\lambda }$ 1394 lines in ${\lambda }$ Eri. This figure shows typical rapid filling in of the red wing of the He II line in this star. The X-marked features in all three features are instrumental ("missing minor frames'').
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg08.eps} \end{figure}$	Figure 8: IUE observations of ${\omega }$ Ori over a 12 h interval in 1983, exhibiting variations of the He II, Si IV and C IV lines. Errors on He II are taken in the interval 0-350 km s^-1.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg09.eps} \end{figure}$	Figure 9: A comparison of ${\mu }$ Cen's He II and C IV lines in 1980 and 1982 for ${\mu }$ Cen. Note the weak red wing emission. Errors on He II refer to blue and red halves of the profile, respectively.
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$\begin{figure} \par\includegraphics[angle=90,width=7.5cm,clip]{5055fg10.eps} \end{figure}$	Figure 10: A comparison of the He II and the C IV lines for the interval April 1986-February 1989 for ${\mu }$ Cen. Note the weakening of the He II line coincident with the formation of red wing emission in C IV. Errors on He II refer to blue/central and red portions of profile (see comb).
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$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg11.eps}\end{figure}$	Figure 11: A comparison 6 Cep's He II and C IV lines for epochs 1989.0 and 1990.5. Note the inactivity of the red wing emission in the C IV line. The wind was in a different state during 1982-86 (C IV, dotted line).
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$\begin{figure} \par\includegraphics[angle=90,width=7.45cm,clip]{5055fg13.eps} \end{figure}$	Figure 13: The comparison of the stronger than unusual He II and C IV spectra for $\psi ^1$ Ori obtained at 1987.2 relative to mean profiles.
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$\begin{figure} \par\includegraphics[angle=90,width=7.45cm,clip]{5055fg14.eps} \end{figure}$	Figure 14: A comparison of the He II and C IV spectra for $\psi ^1$ Ori at the epoch 1980.0 relative to the mean profiles. The single spectrum shows a weak sharp absorption feature at 100 km s^-1.
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$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg15.eps} \end{figure}$	Figure 15: A comparison of the He II and C IV spectra during the 1991.2 campaign on ${\eta }$ Cen. Notice the variation of the blue wings over over a 7.4 h interval. Our significance acceptance criterion was relaxed in this one case because of the correlation with the strong C IV variation.
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$\begin{figure} \par\includegraphics[angle=90,width=7.7cm,clip]{5055fg16.eps} \end{figure}$	Figure 16: A comparison of the He II and C IV lines during the 1991.2 campaign on ${\eta }$ Cen. Note the variation of the red wings over a 3.9 h interval.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg17.eps} \end{figure}$	Figure 17: A comparison of the He II and C IV spectra between epochs 1979.5 and 1979.8 for ${\pi }$ Aqr.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg18.eps} \end{figure}$	Figure 18: A comparison of the He II and C IV spectra between epochs 1988.4 and 1993.9 for ${\pi }$ Aqr. Errors on He II are given for the blue wing (comb interval) and red wing, respectively.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg19.eps} \end{figure}$	Figure 19: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 line spectra between epochs 1989 (SWP 36329) and 1992 for 2 Vul. The comb shows the region of differences of the profiles, which are also shared by the Si III ${\lambda }$ 1206 line (not shown).
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg20.eps} \end{figure}$	Figure 20: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 spectra for 2 Vul for the epochs 1983 and 1992. Although not shown, the Si III line exhibits similar variations.
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$\begin{figure} \par\includegraphics[angle=90,width=7.65cm,clip]{5055fg21.eps} \end{figure}$	Figure 21: A comparison of the He II, C IV, and Si IV ${\lambda }$ 1394 spectra for a mean and an observation of 19 Mon during 1994.2. The significance on He II refers to the whole profile. Thus, the significance of the variation of the blue wing exceeds 6.0 $\sigma$ .
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