Sakurai's Object (V4334 Sgr): evolution of the dust shell from 1999 to 2001

We present fits to 1–5 μm spectra of the dust shell around Sakurai's Object (V4334 Sgr) obtained over the period 1999 May to 2001 September, using the dusty modelling program. We find that the emission is consistent with carbon dust grains for which the optical properties are predominantly graphitic, and for which sizes range from ∼0.005 to ∼1–2 μm with a size distribution n(a) da∝a−3 da. We further find an increase in the mass-loss rate, and in the angular diameter of the dust shell, which may now be resolvable in the mid-infrared with an 8–10 m class telescopes. We also determine the time dependence of the stellar luminosity and radius, and find consistency with recent evolutionary modelling.