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D. G. Schleicher (Lowell Obs.), P. V. Birch (Perth Obs.)
We present analysis and results from narrowband photometry of Comets LINEAR (2000 WM1) and Ikeya-Zhang (2002 C1) during their recent apparitions. We began monthly photometric observations of LINEAR in August 2001 (r = 2.7 AU) using the Hall 1.1-m telescope at Lowell Observatory, and these continued until mid-December, when LINEAR became a southern hemisphere object and observations proceeded from Perth Observatory near perihelion (0.6 AU). LINEAR again became available from the north in March 2002, and was followed outward until July (2.9 AU). Over this range of distances, gas production rates varied by more than 150x, but followed a canonical water vaporization curve inside of about 2.4 AU, consistent with an active area of about 10 km2 and a lower limit of the effective nucleus radius of about 0.9 km. Measurements of Ikeya-Zhang began in February from Perth (0.9 AU) and continued from Lowell beginning in April (0.7 AU) and are on-going, with the most recent observations obtained in July (2.1 AU). Gas production r-dependences for I-Z are slightly steeper than a canonical vaporization model, and imply an active area of about 16 km2, or a minimum effective radius of 1.1 km. Both comets have moderately high gas-to-dust ratios. These and other results for each comet will be presented. This research is supported by NASA.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.