Estimates of the radius and albedo of comet-asteroid transition object 4015 Wilson-Harrington based on infrared observations

Abstract

We present simultaneous near-infrared and thermal-infrared observations of 4015 1979 VA, also known as comet P/Wilson-Harrington, which permit an estimate of its albedo and radius. If the standard thermal model (STM, highest nuclear temperature) is assumed, a radius of 1.30±0.16 km and a geometric albedo in the J bandpass of 0.10±0.02 are obtained. Although our observations of P/WH do not rule out the applicability of the STM, we believe the isothermal latitude model (ILM, lowest temperature) better describes the thermal properties of this object because of its size and rotation period. The ILM case yields a radius of 1.95±0.25 km and an albedo in the J bandpass of 0.05±0.01. We compare the nuclear characteristics of comet P/Wilson-Harrington with those of four other periodic comets observed in sufficient detail.