The dying wind around HD 56126, a post-asymptotic giant branch carbon star

We have used the Keck I telescope to resolve at mid-infrared wavelengths th e dust emission from HD 56126 (IRAS 07134+1005), a post-asymptotic giant br anch carbon star with a detached dust shell. The gross morphology of the im age 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 losi ng similar to3 x 10(-5) M-. yr(-1), then during the past 1500 yr, the avera ge value of dT(*)/dt has been 2.2 K yr(-1). With such a time variation of t he effective temperature, the 11.7 pm image can be approximately reproduced if the mass-loss rate varied as T-*(-8.26), as proposed in recent models f or 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 d eviations from spherical symmetry of the dust shell can be explained by pla usible variations in the surface temperature of the mass-losing star caused by rotation and/or magnetic fields.