Central Bureau for Astronomical Telegrams
IAUC 4343: 1987A
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Circular No. 4343
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
J. Matthews, University of Western Ontario, reports: "Continuing
spectroscopy with the Cerro Tololo Interamerican Observatory
1-m telescope shows that the earlier report (IAUC 4336) of emission
at 420 nm was in error and that there is instead a broad absorption
at 413 nm that has been steadily deepening since Mar. 4. H alpha
absorption has begun to show signs of saturation, implying that the
SN shell is becoming optically thick. Decreasing emission (or perhaps
increasing absorption) is taking place on the blueward side of
the broad emission feature near 460 nm. There is also apparent
increased emission near 478 nm and pronounced absorption now at 425
and 432 nm. Absorption features at 483, 520, 543, 555, 574 and 603
nm continue to strengthen. Further radial velocities (in units of
10E km/s) derived from Balmer-line minima: Mar. 10.01, H alpha = -10.4,
H beta = -7.6, H gamma = -7.6, H delta = -8.8; 11.02, -10.9, -7.7, -8.0, -9.0;
12.04, -10.0, -7.4, -7.6, -8.4; 13.01, -9.9, -7.4, -6.9, -1.8."
W. H. Sun, University of California at Los Angeles, reports:
"Blue-enhanced Cassegrain CCD spectra (range 320-540 nm, resolution
0.42 nm) were obtained with the CTIO 1.5-m telescope on Mar.
10-12. Several spectra were taken with the red end (beyond 380
nm) deliberately saturated so as to obtain reasonable signal to
noise in the blue. To avoid the strong blue flux from the north-
west companion (IAUC 4333), exposures were made with a 1" east-
west slit positioned 2" north of the image center, at the center,
and then 2" south of image center. These samples across the SN
image show the raw counts in the blue increasing by a factor of about
10 from south limb to north limb. A cursory examination of the
spectral region shortward of 380 nm reveals no evidence of a
Balmer discontinuity. Two broad, blended emission features at 346
and 357 nm dominate this region, perhaps obscuring any absorption
edge that may be present in the spectrum. I have also detected a
moderately-weak emission feature at 372.7 nm in the south-limb
spectra. J. Matthews and I note that such an emission line has
been attributed to nebulosity surrounding earlier supernovae in
NGC 3003, 3938 and 4303."
Word received indirectly from V. Blanco, Cerro Tololo
Interamerican Observatory, casts doubt on the reality of the 'companion
about 2" to the southwest of the SN' reported on IAUC 4341.
Visual magnitude estimates by R. H. McNaught, Coonabarabran,
N.S.W.: Mar. 12.58, 4.3; 12.75, 4.3; 13.40, 4.2; 13.79, 4.0.
1987 March 14 (4343) Brian G. Marsden
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