High-resolution coronagraphy of the circumstellar environment of SN 1987A

A coronagraph with broad-band B and R filters was used to image a 23 x 36 arcsec region centered on SN 1987A with a resolution of 0.8 arcsecs about 300 days after eruption to search for evidence of a light echo from circumstellar dust. All of the identifiable sources of radiation in these bands in the region corresponded to objects observed before the eruption. A stringent upper limit of 22.5 mag/sq arcsec is set on the B-band brightness of an echo-like, largely azimuthally symmetric feature located anywhere between 4 arcsecs from the supernova out to the edge of the observed field. This implies an upper bound of 10 to the 18th H atoms/cu cm to the column density of any circumstellar shell of gas of average galactic properties located on the ellipsoid of equal delay points between about 2 and 20 pc from the supernova. 17 refs