ACTIVITY AND THE ROTATION PERIOD OF COMET HYAKUTAKE (1996-B2)

Narrowband photometry of Comet Hyakutake (1996 B2) revealed periodic v ariability in the production of dust and gas during the comet's close approach to Earth in March 1996. The photometry alone was insufficient to unambiguously discriminate among several possible periods, but a u nique period determination was possible by utilizing repeating morphol ogical features in CCD images obtained simultaneously with the photome try on the nights of March 23-25. In particular, a large puff or blob of material was seen to be released in the sunward direction every 6.2 3 +/- 0.03 h. This periodic release of material, presumably from a sin gle dominant active region on the surface, was the source of the obser ved lightcurve variations, A second, much smaller morphological featur e also repeats each cycle, confirming the value of 6.23 h for Hyakutak e's synodic rotational period. (C) 1998 Academic Press.