Central Bureau for Astronomical Telegrams
IAUC 4741: 1987A; 1989B
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Read IAUC 4742
Circular No. 4741
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
A. Crotts, Goddard Space Flight Center and McDonald Observatory;
and W. E. Kunkel, Las Campanas Observatory, Carnegie Institute of
Washington, write: "CCD images from the 2.5-m and 1.0-m telescopes
at Las Campanas Observatory taken in 1988 Oct. and Dec. show that the
feature reported on IAUC 4733 and 4739 is indeed a light echo. Such a
feature is seen clearly in V data from Dec. 15 data from the 2.5-m
telescope as a peak in surface brightness with a centroid in radius of
8".40 +/- 0".08 from the supernova (accounting for the wings of the
supernova image). The same feature can be found in Oct. 6 data from
the 1.0-m telescope at a radius of 7".97 +/- 0".12. This is consistent
with the expected expansion of 0".52, showing that the feature is an
echo. It would appear that the echo brightened considerably between
Oct. and Dec. It should also be noted that these data would predict a
radius of 8".7 for the period Jan. 24-Feb. 5 covered by the two
previous Circulars, assuming the echo reflects from a thin sheet. The
Dec. 15 data were also used to set limits on the extent of deviations
by the SN 1987A image from a stellar source, as might be expected from
a circumstellar light echo. In V the brightest possible nonstellar
residual remaining, once a stellar image is subtracted, is no more
than 2 percent as bright as SN 1987A at that time (for radii interior
to 5"). This puts extremely stringent limits on the extinction caused
by any dust associated with gas producing the narrow emission lines
reported on IAUC 4739, assuming the lines are emitted due to recombination
soon after irradiation by the supernova's ultraviolet pulse."
SUPERNOVA 1989B IN NGC 3627
P. Appleton, Iowa State University; and I. Robson, Lancashire
Polytechnic, report: "We observed NGC 3627 with the IRCAM infrared
camera of the U.K. Infrared Telescope on Feb. 14.34 UT and measured
the brightness of SN 1989B to be J = 12.2, H = 11.6, K = 11.5 in a
7".2 software aperture. Corresponding magnitudes of an adjacent
aperture located on the spiral arm were 13.1, 12.3, and 12.3."
Further visual magnitude estimates: Feb. 13.20 UT, 11.9 (A.
Pereira, Cabo da Roca, Portugal); 13.95, 12.5 (A. Boattini, Florence,
Italy); 14.88, 12.1 (P. Schmeer, Bischmisheim, West Germany); 16.12,
12.5 (M. Dionisi, Anzio, Italy); 16.92, 12.4 (J. Shanklin, Cambridge,
England).
1989 February 17 (4741) Daniel W. E. Green
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