Central Bureau for Astronomical Telegrams
IAUC 5927: 1987A; KR Aur
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Circular No. 5927
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
L.-F. Wang, Beijing Observatory; and E. J. Wampler, European
Southern Observatory, report: "Observations of SN 1987A with the
ESO 3.5-m New Technology Telescope in 1992 Jan. and in 1993 Jan.
and Dec. indicate that, while the integrated brightness of the ring-
shaped nebulosity surrounding SN 1987A has decreased by about 20
percent during this 2-yr period, the distribution of light along
the ring has changed dramatically from early observations. The
ring is increasing in brightness at several locations. Following
image deconvolution to achieve an effective resolution of 0".2, the
1993 Dec. frames show that the ring emission regions are now highly
clumped and have a somewhat different structure when seen in
H-alpha, [N II], or [O III]. Overall, the ring is brightening in
the northwest, while continuing to fade in the south. The major
new patches coincide roughly with the radio structure reported by
Staveley-Smith et al. (1993, Nature 366, 136). These changes may
herald the beginning of the interaction between the supernova ejecta
and the nebular material surrounding SN 1987A. But significant
amounts of SN 1987A envelope gas have not yet reached the ring,
since spectra show that the nebular lines are still narrow. Perhaps
the interactions between the expanding SN envelope and the
residual gas interior to the ring that are producing the radio
(Staveley-Smith et al. 1993) and x-ray (Beuermann et al. 1994, A.Ap.
281, L45) emissions also generate sufficient ultraviolet photons to
reionize patches of gas in the ring. Near-infrared images now
resolve the inner photosphere of SN 1987A. A comparison between the
image profile of SN 1987A and those of field stars in deconvolved
Gunn i frames with an effective resolution of 0".3 shows a resolved
image with FWHM diameter 0".37."
KR AURIGAE
A. Antov and V. Popov, Department of Astronomy and National
Astronomical Observatory, Bulgarian Academy of Sciences, Sofia,
report that this object has faded from B = 13.8 in Dec. 1993 to B =
14.5 on 1994 Jan. 20, and that further fading to mag 17-18 can be
expected. Spectroscopic and high-speed-photometric monitoring during
the minimum state could be helpful in determining if the
cessation of accretion is the reason for brightness dips.
1994 January 27 (5927) Daniel W. E. Green
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