Infrared studies of Eta Carinae - I. Spectroscopy and a composite dust model

We report spectral observations of ƞ Carinae between 8 and 13 µm which compare the central peak of the homunculus with its periphery. The spectra not only show a lower effective temperature for the outer regions but also that the grains here have a different emissivity function. This has been shown to be consistent with the presence of large grains (Mitchell & Robinson) and here the modelling is extended to that of a spherical core containing small grains (⁠|$a\cong 0.2\,\mu \text{m}$|⁠) and a disc of larger grains (⁠|$a\cong 2.0\,\mu \text{m}$|⁠); the model predictions are consistent with observations.