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Session 80 - Central Stars of Planetary Nebulae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center

[80.03] Recent Changes in the Nucleus of the Planetary Nebulae LMC-N66

M. Peimbert, M. Peña, S. Torres-Peimbert (IAUNAM), M. T. Ruiz, J. Maza (U. Chile)

We report recent spectacular changes in the WR spectrum of the central star of the planetary nebula LMC-N66. Before 1987, it showed a weak continuum with a T_eff \geq 120\,000 K and L_bol \simeq 25\,000 L_ødot. In 1990 the star began an intense mass-loss event and in a short time the continuum increased by a large factor and the absolute visual magnitude of the star changed from +1.24 in 1987 to -2.57 in January 1995. Simultaneously it developed impressive WR features (P-Cygni profiles in N\,V \lambda1240 and C\,IV \lambda1550 lines, wide He\,II emission, etc.) typical of a Population I WN4.5 star. The ejecta consisted of highly ionized He- and N-rich material (Peña et al., 1995, ApJ, 441, 343; Peña, 1995, RevMexAASC, 3, 215). These conditions remained with some variations for more than 5 years. Recent optical and UV data obtained by us show that the mass-loss has diminished abruptly in less than three months. The fast optically-thick wind has almost disappeared and the visual brightness of the central object has diminished in 2 magnitudes. Part of the ejected material was detected at much lower velocity, emitting in He\,II \lambda\lambda 6406, 6678, and other lines that disappeared in few days. The possibility of a fast recombination and cooling of the highly ionized ejecta is discussed.

Program listing for Wednesday