We explore fluorescence and reflection models of the companion to SN 1987A observed by speckle interferometry, recalling a 1901 precedent. The apparent small angular size of the companion is a severe constraint. A fluorescence model cannot reach the observed brightness unless the ultraviolet burst from the supernova contained as many as 2 x 10^58^ ionizing photons. This is ~ 25 times stronger than generous current models. Even then the expected line ratios and widths do not fit the observations. The absence of narrow Hα and Hβ lines in the supernova spectrum, the ratio of fluxes of the companion in Hα and [N II] filters, the invisibility of the companion at λ4861 (Hβ), and its detection at λ5330 fail to agree with theory. A dust-reflection model is more promising, and the color can be reddened by the evaporation of small grains, but the model still falls >~ 1 mag short in brightness. Furthermore, a dust reflection should have increased in relative brightness in 1987 May-June, rather than disappearing as the mystery spot did. If all the observations are correct, neither model is likely to work.
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Felten et al. (1989) studied this question.