Central Bureau for Astronomical Telegrams
IAUC 4366: 1987A; 1982i
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Circular No. 4366
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
G. Sonneborn, IUE Observatory, Goddard Space Flight Center,
and R. Kirshner, Center for Astrophysics, report: "New astrometric
data from pre-outburst plates, which clearly demonstrate the existence
of a third star in the Sk -69 202/SN 1987A field (IAUC 4356),
has prompted further analysis of IUE 120-200 nm spectra taken during
Mar. The two stellar sources detected in far-ultraviolet spectra
of the SN (IAUC 4333) have been deconvolved by fitting the
spatially-resolved spectra with a skewed-gaussian model of the IUE
point-spread function. The stellar spectra are fit extremely well
by two point-sources separated by 4".13 +/- 0".35 in an image taken on
Mar. 13, when the IUE 10"x20"-aperture position angle was 152 deg.
This separation is in agreement with that expected for stars 2 and
3 (IAUC 4356) and inconsistent with the separation of either stars
1 and 2 or stars 1 and 3. There is no evidence for a third point-
source shortward of 160 nm (where the best IUE spatial resolution
is obtained). In spectra taken on Mar. 3, however, when the SN
flux was still detected above the stellar continua at 190 nm, the
SN signal was located between the stellar spectra, about 2".9 +/- 0".2
from the northern stellar component. We identify the northern component
with star 2 and the southern component with star 3 and conclude
that star 1, Sk -69 202, has disappeared. The star 2 identification
was confirmed by successfully obtaining its spectrum through
the 3"-diameter aperture, offset 3".0 to the northwest (p.a. 321 deg)
from the SN's center of light. The ultraviolet spectrum of star 2
has the appearance of an early- to mid-B spectral type with a flux
level of 4.5 x 10E-14 erg/cm**2/s/A at 130 nm. The flatness of the
spectrum from 125 to 185 nm implies a visual magnitude fainter than
14.0, assuming moderate LMC extinction. Star 3 also appears to be
an early-type star, with a flux level of 1.9 x 10E-14 erg/cm**2/s/A at
130 nm. Star 3 is fainter than star 2 at all wavelengths shortward
of 185 nm."
Visual magnitude estimates: Apr. 10.36 UT, 3.2 (M. Morel,
Rankin Park, N.S.W.); 10.78, 3.5 (R. McNaught, Siding Spring Obs.).
PERIODIC COMET HALLEY (1982i)
Total visual magnitude estimates: Mar. 26.21 UT, 12.9 (C. S.
Morris, Lockwood Valley, CA, 0.26-m reflector); 27.26, 13.4 (R.
Keen, Mt. Thorodin, CO, 0.32-m reflector); Apr. 2.29, 12.9 (A.
Hale, Las Cruces, NM, 0.20-m reflector).
1987 April 13 (4366) Daniel W. E. Green
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