CCD PHOTOMETRY OF COMET 46P WIRTANEN

CCD observations of 46P/Wirtanen obtained in February 1992, when the c omet was at a post-perihelion heliocentric distance of R=1.93 AU are a nalysed. At this time the comet possessed a weak dust coma extending > 5000 km from the nucleus. The observed brightness distribution reveal s no sign of any central nucleus, and results in a firm upper limit to the radius of the nucleus of r(e) < 2.8 km (assuming an albedo of 4%) , similar to that found by Jorda and Rickman (Planet. Space Sci. 43, 5 75-579, 1995) and consistent with the reported detection by Boehnhardt et al. (Astron. Astrophys. 1997, in press). Wirtanen was also searche d for in June 1995 and August 1995, but this was unsuccessful in detec ting the comet. An upper limit to the nucleus size of 8.2 km was obtai ned from these data consistent with the values above. (C) 1997 Elsevie r Science Ltd.