Central Bureau for Astronomical Telegrams
IAUC 4356: 1987A
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Circular No. 4356
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. M. West, A. Lauberts, and H.-E. Schuster, European Southern
Observatory; and H. E. Joergensen, Copenhagen University Observatory,
report: "Accurate positions have been determined for SN 1987A
and the 3 components of the Sanduleak -69 202 system, by means of
16 ESO Schmidt plates (8 taken during 1976-1982, 8 taken 1987 Feb.
25-27), one 3.6-m triplet plate, and 30 CCD frames obtained with the
Danish 1.5 m telescope. Based on about 30 Perth standards, we find for
SN 1987A: R.A. = 5h35m49s.992, Decl. = -69 17'58.08 (equinox 1950.0); the
accuracy, about 0".2 in each coordinate, is mainly determined by the
Perth system. The other positions (equinox 1950.0) are: star 1, R.A.
= 5h35m49.983, Decl. = -69 17'57.99; star 2, 5h35m49.543, -69 17'56.10;
star 3, 5h35m50.232, -69 17'58.44. The offset (SN - star 1) is Delta-R.A.
= +0".05 +/- 0".06, Delta-Decl. = -0".09 +/- 0".09. For star 2 we find U =
14.5 +/- 0.5 and R = 16.5 +/- 1.0. The R mag of star 3 is about that of
star 2, but its spectral type must be later. Supposing that the
spectral type of star 2 is B0 V, that E(B-V) = 0.2 and extinction A(V)
= 0.6, and subtracting star 2 from the measured UBVRI magnitudes of
Sanduleak -69 202 (Rousseau et al. 1978, A. Ap. Suppl. 31, 243;
Blanco, IAUC 4349), we find for star 1: V(0) = 11.70, or M(V) =
-6.8 at (m-M) = 18.5. This and the dereddened colors of star 1
agree extremely well with the standard values for a B3 Ia star (cf.
Johnson 1966, Ann. Rev. Astr. Ap. 4, 193) and we therefore see no
photometric evidence of a fourth star. In particular, the presence
of an M I-III star seems to be excluded."
T. Girard and W. van Altena, Astronomy Department, Yale
University, report that they have measured the position of Sanduleak
-69 202 on blue and yellow plates taken on 1973 Jan. 9 with the
Yale Southern Observatory's 0.5-m double astrograph at El Leoncito.
The positions (equinox 1950.0), with respect to 36 Perth 70 stars, are:
blended image on blue plate, R.A. = 5h35m49.807 +/- 0s.057; Decl. =
-69 17'57.61 +/- 0".34; star 1 (yellow plate), 5h35m49.991 +/- 0s.045;
-69 17'58.06 +/- 0".20; star 2 (yellow plate), 5h35m49.714 +/- 0s.045;
-69 17 56.66 +/- 0".20. The yellow image was marginally resolved,
with a 1-2 mag difference between stars 1 and 2.
Further visual magnitude estimates: Mar. 29.54 UT, 3.9 (A.
Beresford, Adelaide, S. Australia); 30.40, 3.7 (R. H. McNaught,
Siding Spring Observatory); 30.40, 3.6 (D. A. J. Seargent, The
Entrance, N.S.W.); 30.51, 3.9 (Beresford); 31.39, 3.8 (McNaught);
31.40, 3.5 (Seargent); 31.41, 3.6 (G. Garradd, Tamworth, N.S.W.).
1987 April 1 (4356) Daniel W. E. Green
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