Central Bureau for Astronomical Telegrams
IAUC 5086: 1990c; 1987A
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Read IAUC 5087
Circular No. 5086
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
COMET LEVY (1990c)
P. Schloerb and W. Ge, University of Massachusetts, report the
detection at the Caltech Submillimeter Observatory of the 354.5-GHz HCN
J=4-3 and the 351.8-GHz H2CO J=5(1,5)-4(1,4) transitions. With an
antenna temperature of 0.7 K, the strength of the HCN J=4-3 line is
comparable to that of the J=3-2 transition reported on IAUC 5081. The
rotational temperature obtained by combining these results is 33 +/- 1
K, which is substantially greater than that predicted under conditions
of pure fluorescence equilibrium and requires significant collisional
excitation of HCN in the coma. The H2CO line area is 0.43 +/- 0.06 K km
s-1, which would yield an H2CO production rate of 5 x 10**26 under the
assumption that the H2CO originates from the nucleus and is in local
thermodynamic equilibrium at a temperature of 50 K. They also carried
out a search for lines of CH3OH in its J=5-4 band near 241.8 GHz and
obtained marginal detections of several lines at the level of 50 mK
antenna temperature.
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
A. J. Turtle and D. Campbell-Wilson, School of Physics, University
of Sydney; and R. N. Manchester, L. Staveley-Smith and M. J. Kesteven,
Australia Telescope National Facility, CSIRO, report the reappearance of
SN 1987A as a radio source. Observations at 843 MHz using the Molonglo
Observatory Synthesis Telescope (MOST) detected a source with a flux
density of about 2 mJy at the supernova position on 1990 July 5. Eight
more observations up to Sept. 1 show that the source flux density is
increasing at about 45 microJy per day and was about 4.5 mJy in mid-
August. The source was also detected using the Australia Telescope
Compact Array (ATCA) at 4790 MHz and 1472 MHz on 1990 Aug. 15 and 16,
respectively, within 0".5 of the SN position and with flux densities of
0.7 and 2.0 mJy at the two frequencies. Observations with the MOST made
over the previous two years at roughly three-month intervals up to 1990
Apr. 8 give upper limits of 1.5 mJy for a source at the SN position.
Upper limits have also been obtained using the ATCA at 4790 MHz on
several occasions over the past year, with the best limit of 0.2 mJy
being from observations on 1990 July 21. The radio emission from SN
1987A has therefore increased substantially over the past two months
and has a spectral index that appears to be changing.
1990 September 3 (5086) Brian G. Marsden
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