Central Bureau for Astronomical Telegrams
IAUC 4319: 1987A
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Circular No. 4319
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, European Southern Observatory, communicates: "A
1-s exposure with the CCD camera at the Danish 1.5-m telescope was
obtained by B. Reipurth and H. E. Jorgensen on Feb. 26.3 UT. They
were able to determine the relative positions of the supernova and
12 stars within about 1'.5 to an accuracy of about 0.5 pixel (1 pixel =
0".47). I find that the proposed supernova progenitor (= Sanduleak
-69 202) is seen to be double on one very good 60-min ESO Schmidt
plate (U, IIa-O + UG1, 1977 Dec. 9) and is possibly double on
short-exposure blue plates. Moreover, it is clearly resolved into
two stars on an early (slightly comatic) 60-min ESO 3.6-m triplet
plate (R, 098-04 + RG630, 18".9/mm, 1979 Dec. 8); a rough visual
estimate indicates that the primary component (star 1) is 3 or
more magnitudes brighter in red than the secondary (star 2). The
ultraviolet difference is smaller, probably around 1 mag. Thus
star 2 is rather bluer than star 1. The CCD position of SN 1987A,
by transfer via eight nearby Perth standards to the surrounding
stars, is R.A. = 5h35m49s.942, Decl. = -69 17'57".60 (equinox 1950.0). The
triplet positions of the two components are: R.A. = 5h35m49s.904, Decl. =
-69 17'57".36 (star 1) and R.A. = 5h35m49s.548, Decl. = -69 17'55".45 (star
2). The Schmidt positions agree to within 1".0 but are less
certain because of the smaller plate scale. The formal errors are
about +/- 0".2 in both coordinates. This shows that the supernova
progenitor cannot be star 2, and is most likely to be star 1."
M. Cropper and J. A. Bailey, Anglo-Australian Observatory;
T. I. Peacock, AAO and Hatfield Polytechnic; and D. T. Wickramasinghe,
Australian National University, report optical and infrared
photometry and polarimetry of SN 1987A taken with the Hatfield
polarimeter on the AAT. On Feb. 25.274 UT they measured J = 3.8,
H = 4.0, K = 3.6, L' = 2.4. During Feb. 25.340-25.442 UT they
measured U = 4.5, polarization 1.01 +/- 0.10 percent in p.a. 34 +/-
3 deg; B = 4.6, 0.97 +/- 0.06 in 36 +/- 2; V = 4.5, 0.83 +/- 0.08 in 46
+/- 4; R = 4.1, 0.86 +/- 0.06 in 44 +/- 3; I = 4.0, 0.81 +/- 0.04 in
41 +/- 2; J, 0.62 +/- 0.06 in 43 +/- 3; H, 0.52 +/- 0.07 in 50 +/- 4;
K, 0.49 +/- 0.12 in 44 +/- 8. They add: "The U band may be slightly
nonstandard because of neutral density filters. The polarization
is higher than the expected galactic foreground polarization, and
the object is therefore either intrinsically polarized and/or
polarized by interstellar dust in the LMC. The observed wavelength
dependence of the polarization does not appear to be in agreement
with that expected from interstellar dust."
1987 February 26 (4319) Brian G. Marsden
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