Dust Production of Comet 21P/Giacobini-Zinner Throughout its 2018 Apparition

Abstract

We present the results of a long term telescopic observation campaign of comet 21P/Giacobini-Zinner, parent body of the Draconid meteor shower, spanning $\sim 240$ days during its 2018 apparition. Determinations of comet 21P's dust production rate through the $Af\rho$ parameter derived from these images show that the comet had a highly asymmetric dust production rate that peaked $\sim 10-30$ days before perihelion, when the comet was at a heliocentric distance of $\sim 1.02 - 1.08 \thinspace \mathrm{AU}$. The single highest $Af\rho$ measurement occurred on 2018-Aug-14 (27 days before perihelion), and had a measured value of $Af\rho = 1594 \thinspace \mathrm{cm}$. The comet's $Af\rho$ profile is well described by a double-exponential model that rises rapidly during ingress and declines even more rapidly during its egress. These results are fully consistent with observations of comet 21P's dust and gas production rates during past apparitions, and suggest that the double-exponential model we have derived provides a reasonable and stable approximation for the comet's activity over the past thirty to forty years.