IR speckle-interferometry of SN1987a

The speckle-interferometry of SN1987a in the near IR λ λ 2-5 μ m revealed the presence of faint sources of emission which lay up to about 60 milliarcsec (mas) from the supernova on June 17-22 and at 350 mas on August 6, 1987. The corresponding velocity scale and the colour temperature of the emission indicate that we were observing a light echo from dust clumps. The clumps were presumably formed in the region where the fast wind of the blue supergiant (BSG) progenitor Sk-690202 interacts with the relict red supergiant (RSG) wind material. The first detection of the light echo on day 113 after the explosion implies that the RSG wind ceased to blow less than 4600 (10 km.s-1/vd) yr, where vd is the velocity at which the relict dust flows out from the supernova