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Session 80 - Central Stars of Planetary Nebulae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
The broad profile of the nuclear C III\lambda5696A line in the WC8 nucleus of NGC 40 shows profile shape variations on time scales of hours. Relatively narrow intensity peaks and/or valleys (i.e. "features") appear first near the center of the 1400 km/s-wide line. Over the next 3 hours the features slide toward either the red or blue line edge with a Doppler Shift that increases linearly with time. The acceleration is apparently the same for all features. The size of the acceleration zone is at least 5 R(sun). The fluxes of C III and many other nuclear lines are also variable on time scales of days and months.
The optical attributes of the C IIIl5696=C5 line from the nucleus of NGC 40 are very similar to line profile variations reported in some "normal" late-type WC stars. This suggests that the same wind acceleration mechanism (which is widely believed to be radiative acceleration of ``blobs'= ' that form in an unstable outflowing wind) is an inherent property of local conditions in WR atmospheres.
Program listing for Wednesday