The dust envelope of the Herbig AE star, AB Aur.

Abstract

Ultraviolet low resolution observations of a Herbig Ae star, AB Aur, when compared with a theoretical energy distribution for the same spectral type, show the existence of an anomalous extinction, which is believed to be due to a circumstellar dust envelope surrounding the star. The study of this anomalous extinction allows the author to determine the properties of the grains responsible for it. These properties can then be tested by comparing a computed infrared energy distribution with infrared calibrated observations. It is found that small grains of silicates can be responsible for both ultraviolet extinction and infrared excess near 10 μ, but that the infrared excess between 1 and 4 μ is probably due to a free-free emission mechanism in a 15,000K chromosphere.