Central Bureau for Astronomical Telegrams
IAUC 4593: 1987A; AX Per
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Circular No. 4593
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
The GRIS collaboration (S. Barthelmy, Goddard Space Flight
Center (GSFC); N. Gehrels, GSFC; M. Leventhal, ATT/Bell Laboratories;
C. J. MacCallum, Sandia National Laboratories; B. J. Teegarden, GSFC;
and J. Tueller, GSFC) reports the detection of gamma-ray line and
continuum flux from SN 1987A. The observation was made with a high-
resolution germanium spectrometer flown on a high-altitude balloon
over Alice Springs. The supernova was observed for an 11-hour period
centered on May 1.77 UT. Additionally, a small amount of data was
taken in a second pass on May 2. The experiment alternated between
source and background pointings every 20 min. Preliminary results are
reported here in the energy range 120-2000 keV. Subsequent analysis
will extend this to the full range for this flight of 60-8000 keV.
The 56Co radioactive decay line at 1238 keV was detected at a level of
(8.1 +/- 1.7) x 10**-4 photons cm**-2 s**-1. (The error quoted is
statistical only; systematic uncertainties remain to be evaluated.)
The statistical significance of this result is 4.9 sigma. Rough
estimation indicates a centroid consistent with no doppler shift and a
width of 15-25 keV (3600-6000 km/s). The 1238-keV line width is
significantly larger than the instrumental line width, but proper
deconvolution with the instrument response function has not yet been
performed. Such a large broadening may indicate a substantial amount
of mixing of the freshly synthesized material with the overlying
mantle. The data also indicate an excess in the vicinity of the 847-
keV 56Co line. Analysis is complicated by the presence of a strong
instrumental background line at 844 keV. In addition, a strong
continuum signal was detected in the 120- to 700-keV band. Further
results on these are expected at a later date.
Visual magnitude estimates by A. C. Beresford, Adelaide, South
Australia: May 7.55 UT, 7.5; 9.39, 7.6; 10.38, 7.7.
AX PERSEI
Visual magnitude estimates: Mar. 22.77 UT, 9.2 (A. Boattini,
Florence, Italy); 24.2, 9.1 (R. Royer, Wrightwood, CA); 27.7, 9.0 (A.
Mizsar, Budapest, Hungary); 29.77, 9.3 (Boattini); Apr. 2.86, 9.3 (P.
Schmeer, Bischmisheim, West Germany); 10.88, 9.3 (Schmeer); 14.89, 9.3
(Schmeer); 18.89, 9.2 (Schmeer); 22.87, 9.2 (Schmeer); 24.89, 9.2
(Schmeer); 26.12, 9.1 (Schmeer); May 7.07, 9.1 (Schmeer).
1988 May 11 (4593) Brian G. Marsden
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