The Dying Wind around HD 56126, a Post–Asymptotic Giant Branch Carbon Star

Abstract

We have used the Keck I telescope to resolve at mid-infrared wavelengths the dust emission from HD 56126 (IRAS 07134+1005), a post-asymptotic giant branch carbon star with a detached dust shell. The gross morphology of the image can be explained by a strong wind that started to die about 1500 yr ago. If the star had an effective temperature T* near 2600 K when it was losing ~3 × 10-5 M☉ yr-1, then during the past 1500 yr, the average value of dT*/dt has been 2.2 K yr-1. With such a time variation of the effective temperature, the 11.7 μm image can be approximately reproduced if the mass-loss rate varied as T, as proposed in recent models for dust-driven winds. Since the mass-loss rate appears to be very sensitive to the effective temperature of the star, we speculate that the observed deviations from spherical symmetry of the dust shell can be explained by plausible variations in the surface temperature of the mass-losing star caused by rotation and/or magnetic fields.