Physical Characteristics of Near-Earth Asteroids from Thermal Infrared Spectrophotometry

Abstract

Thermal infrared spectrophotometric observations of the near-Earth asteroids 433 Eros, 1980 Tezcatlipoca, and 3671 Dionysus are presented and their implications for the physical characteristics of the objects discussed. Sizes and albedos are derived on the basis of published thermal models and comparison of the infrared data with optical observations. The results for 433 Eros are in very good agreement with radar and other earlier findings and demonstrate the accuracy achievable with one of the thermal models used. The new data, together with earlier results from literature, suggest the surface thermal inertia of 433 Eros is no larger than three times that of the Moon. The derived effective diamter and optical albedo of 1980 Tezcatlipoca (around lightcurve maximum) are D=6.7±1.0 km and pv=0.15±0.05, and for 3671 Dionysus D=1.0±0.2 km and pv=0.40±0.15. These diameters are significantly different from previous estimates. The thermal continua of Texcatlipoca and Dionysus are indicative of high surface thermal inertias. A near-infreared spectrum of Dionysus, coupled with the high albedo, suggests an M or E classification. Such taxonomic types are relatively rare amongst near-Earth asteroids.