Central Bureau for Astronomical Telegrams
IAUC 4330: 1987A
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Read IAUC 4331
Circular No. 4330
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
R. Garrison, University of Toronto, informs us that the last
Las Campanas prediscovery plate that did not show the supernova
(cf. IAUC 4316) was exposed by I. Shelton during Feb. 23.059-
23.101 UT. He also communicates the following report from Shelton
and B. Madore: "The evolution of the U-B, B-V, two-color diagram
is closely following that of the type II supernova 1959D in NGC
7331 (Arp 1961, Ap.J. 133, 833). Adopting Arp's intrinsic colors
for SN 1959D, the color excess of SN 1987A is E(B-V) = 0.3. The
rate of color evolution is quite different in the two cases. SN
1987A moves in the two-color plot at a rate that is about five
times that of SN 1959D. Assuming identical velocity evolution,
the radius of SN 1987A would be five times smaller than SN 1959D
at any given color. The luminosity is therefore estimated to be
25 times smaller, which gives a magnitude at maximum light that is
3.5 times fainter than the classical type II SN 1959D. That would
place it at mag 4+, which is what we are now observing."
A. Cassatella, W. Wamsteker, L. Sanz and C. Gry, on behalf of
the European IUE SN Team, report: "Further observations with the
IUE Observatory show that the spectral changes longward of 250 nm
continue, but at a considerably slower rate than before. The
overall spectral shape on Mar. 3.29 UT was quite similar to that on
Mar. 1.17 between 250 and 320 nm. In the long-wavelength range the
similarity with spectra of SN 1983N mentioned before persists. The
spectrum of SN 1987A on Mar. 2 is nearly indistiguishable from that
of the SN 1983N on 1983 July 19 (somewhat after maximum at similar
phase in the lightcurve). The only difference appears to be that
a feature at 297 nm with a width of 5.2 nm is in emission in SN
1983N (Type Ib), while it seems to be in absorption in SN 1987A.
At shorter wavelengths the features at 187.2, 202.4 and 239.2 nm
are still present although much weaker, narrower and slightly shifted
in wavelength. The decrease in brightness as measured around
290 nm seems to have slowed down slightly since Mar. 2. It is now
about 0.2 mag/hr, compared with the earlier reported rate of 0.3 mag/hr
at this wavelength. The halt in the SWP range is fully confirmed
by the Mar. 3 data. A more detailed comparison with spectra from
the IUE Archive in the range 120-165 nm confirms the similarity of
the recent spectra with an early-type supergiant in the LMC."
1987 March 4 (4330) Brian G. Marsden
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