| Abstract
| - R band CCD photometric observations of short period Jupiter family comets in the heliocentric region of 2.11 AU $\leq R_{\rm h}\leq 5.63$ AU were performed using the 4.2 m William Herschel Telescope on La Palma in December 1998. 22 comets were targeted, including the comet-asteroid transition object 49P/Arend-Rigaux. Out of a total of ten detected comets, six were seen to display substantial outgassing (48P, 65P, 74P, 103P, 128P, and 139P), with the remaining four comets (7P, 9P, 22P, and 49P) being stellar in appearance. Nuclear radius measurements and relative dust production rates in terms of $Af\rho$ were measured for these comets, along with upper limits for the remaining twelve undetected comets (6P, 44P, 51P, 54P, 57P, 63P, 71P, 73P, 79P, 86P, 87P, and 100P). The inactive comets had nuclear radii in the range 1.8 km $\leq r_{\rm N}\leq 4.4$ km, while upper limits for the active and undetected comets (assuming they all lay within the field of view) were between 0.6 km and 12.7 km, for an assumed albedo of 0.04. Even if one applies the previously measured maximum axis ratio of 2.6:1 and the minimum measured albedo of 0.02 to the undetected comets, their projected semi-major axes are all constrained to below 8 km. For the active comets, photometric profiles of their dust comae were measured and are consistent with those of steady state coma models.
|
