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IAUC 6378: C/1996 B2; 1992ad

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                                                  Circular No. 6378
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     C. G. Mason, R. D. Gehrz, T. J. Jones, J. Mergen, and D.
Williams, University of Minnesota, report additional photometric
magnitudes (cf. IAUC 6365) obtained on Apr. 10.1 UT, using a 27"
circular aperture with a throw of 83" between the source and
reference beams (uncertainties < 10 percent):  [1.2 microns] =
+4.45, [1.6 microns] = +4.26, [2.3 microns] = +4.06, [3.6 microns]
= +1.62, [4.9 microns] = -0.04, [7.8 microns] = -2.93, [8.7
microns] = -3.36, [9.8 microns] = -3.84, [10.3 microns] = -3.88,
[11.6 microns] = -4.31, [12.5 microns] = -4.16, [18 microns] =
-4.26.  Infrared spectral energy distributions show that the dust
temperature is about 20 percent higher than would be expected for
small black spheres at the same heliocentric distance.  The 10- and
20-micron silicate emission features are very weak.
     A. T. Tokunaga, University of Hawaii; T. Y. Brooke, Jet
Propulsion Laboratory; H. A. Weaver, Applied Research Corporation;
and J. Crovisier and D. Bockelee-Morvan, Observatory of Paris,
Meudon, report the detection with the NASA Infrared Telescope
Facility of the P3 and P5 lines of the nu3 fundamental near 3.04
microns from C2H2 (acetylene) emission on Apr. 8.2 UT.  A very
preliminary range for the production rate of acetylene is 0.5-1.0 x
10E27 molecules/s (or 0.1-0.4 percent of the water abundance,
assuming a water-production rate of 2.4-4.8 x 10E29 molecules/s).

     S. D. Van Dyk, University of California at Berkeley; R. A.
Sramek, National Radio Astronomy Observatory; K. W. Weiler and M.
J. Montes, Naval Research Laboratory; and N. Panagia, Space
Telescope Science Institute, European Space Agency, report:
"Observations of the type-II SN 1992ad made on 1992 Aug. 25.81 UT
with the Very Large Array telescope show the first detection of
radio emission at wavelength 3.6 cm (8.4 GHz) with a flux density
of 0.294 +/- 0.035 mJy at R.A. = 12h26m49s.593, Decl. =
+8o52'38".72 (equinox J2000.0; +/- 0".2 in R.A., Decl.).  This is
coincident (to within 1") with the optical position given on IAUC
5552 (position end figures for equinox J2000.0:  49s.62, 38".4).
SN 1992ad was also observed at 3.6 cm on 1993 Feb. 2.49, at a flux
density of 0.312 +/- 0.057 mJy, and again at 3.6 cm on 1993 Oct.
25.69, when the source had risen in flux density to 0.787 +/- 0.101
mJy.  This behavior over the course of more than one year is
consistent with the source's being a radio supernova that is still
optically thick to its radio emission.  Radio monitoring is
continuing at this and other wavelengths."

                      (C) Copyright 1996 CBAT
1996 April 11                  (6378)            Daniel W. E. Green

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