Abstract
THE 8–13-μm flux from supernova 1987A has increased substantially1 since around May 1988 (∼ 450 days after the explosion), and the 8–13-μm source has been resolvable1, having a full width at half maximum of ∼1.5" in September 1988. This is attributed1 to re-radiation by an asymmetric circumstellar dust cloud, located mainly behind the supernova at a distance of ∼200 light days. This cloud may be related to the gas shell inferred from ultraviolet lines2,3. Here we extend the calculations of Roche et al.1 and consider the further implications of such a cloud. We conclude the following: the expected optical echo from the cloud (V-band magnitude mv ≲ 12) should be resolvable, and this, rather than an internal energy source (such as a pulsar), may cause the observed4–6 slowdown in dimming of the supernova; the reflected light may contribute substantially to the current optical luminosity; observations should be made as soon as possible, for the phenomenon may be evanescent; and the dust spectrum suggests that the dust is carbonaceous rather than silicaceous, although the circumstellar region is thought2 to be carbon-poor. This cloud behind the supernova may be truly interstellar.
Published Version
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