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M. J. Wolff (SSI), A. D. Code (U. Wisconsin)
We present observations of the central stars of four high excitation planetary nebulae (IC~2165, Me~2-1, NGC~2440, NGC~7027) taken with the Wide Field Camera and the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. For each of these stars, most of the flux is in the ultraviolet resulting in low visual brightness against a background of high nebular surface brightness. As a result even the detection of these objects is difficult and determinations of the visual magnitude of the central stars have been very divergent. The high angular resolution of the HST instruments and the choice of filters, including several ultraviolet bandpasses, has provided reliable magnitudes and, for the first time, direct determination of the amount of dust extinction present along the respective lines of sight. We find EB-V values of 0.40 (IC~2165), 0.15 (Me~2-1), 0.15 (NGC~2440), and 1.10 (NGC~7027). We also determine V (and B, not listed here) magnitudes for the four central stars of 17.47±.06 (IC~2165), 18.40±.05 (Me~2-1), 17.63±.16 (NGC~2440), and 16.04±.04 (NGC~7027). The advantage of using narrow band or medium bandwidth filters in the V region as well as the gain from higher spatial resolution is illustrated by comparison with ground-based and HST measurements made with V (or very similar) filter bandpasses (e.g., Ciardullo et al. 1999, AJ, 118, 488).
This research was supported by NASA Grant NAG5-1611 ``Extension of Wide Field Planetary Camera: Post-Launch Science and Engineering Activities.''
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The author(s) of this abstract have provided an email address for comments about the abstract: wolff@colorado.edu