Central Bureau for Astronomical Telegrams
IAUC 4943: 1987A
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Circular No. 4943
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
J. Wampler, S. D'Odorico, C. Gouiffes, M. Tarenghi and L.-F. Wang,
European Southern Observatory, report: "Images of the nebulosity near
SN 1987A were obtained on 1989 Dec. 18 using the 3.5-m NTT telescope
and a CCD camera system that sampled the data with a spatial resolution
of 0".152/pixel; the diameters of isolated star images on the CCD
frames lay between 0".4 and 0".5 FWHM. Narrow-band filters were
centered on wavelengths corresponding to [O III] 500.7 nm and [N II]
658.4 nm and to the continuum redward of these. The emission nebula is
strikingly similar morphologically to the Galactic planetary nebula NGC
7009. The majority of the forbidden-line emission is concentrated in a
central, 2".5 by 2".1 ring nebula with its major axis aligned east-
west. Faint filamentary structures extend to 2".7 north and to 2".2
south of the supernova and form dipole-like structures connecting the
nebula's eastern and western ends; a third, even fainter, filament
extends from the western end and curves northwest to a distance of at
least 4".3. These arms and the central nebula are seen both in the
continuum and line filters and therefore contain a mixture of gas and
dust. Spatially resolved spectra were obtained on Dec. 9 using the
Cassegrain echelle spectrograph attached to the 3.6-m telescope.
Velocity determinations from [O III] 500.7 nm show that, relative to
the central nebula's mean velocity, the northern arm is approaching at
5 km/s, and the southern arm is receding at 3 km/s. The eastern
end of the central nebula is receding, and the western end is
approaching, at 5 km/s; the expansion velocity in the center of the
nebula is about 10 km/s. This planetary-nebula-like, gas-rich
structure is embedded in a 'light echo', gas-poor nebula with
approximately uniform surface brightness comparable to that of the
brighter portions of the large outer rings detected earlier (Crotts
1988, Ap.J. 333, L51; Gouiffes et al. 1988, A.Ap. 198, L9). The
morphology of this inner, reflection nebula is similar to the
silhouette of 'Napoleon's hat' seen face on, the top of the hat's
'crown' being 6" north of the supernova. There is very little
nebulosity south of the southern gaseous filament. The hat's east-west
tips, which are separated by about 15" and lie along an east-west line
passing within a few arcsec of the supernova, blend smoothly into a
filamentary emission nebula that defines the east and west rims of a
large, dark V-shaped bay seen against the diffuse background radiation
of the LMC. The echoes of the outer ring disappear as they cross this
bay, which extends southeastward from its apex at the supernova's position."
1990 January 16 (4943) Brian G. Marsden
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