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IAUC 3921: Poss. SN IN NGC 4246; 1983n

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                                                  Circular No. 3921
Central Bureau for Astronomical Telegrams
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

     J. Maza, Department of Astronomy, University of Chile,
telexes that L. E. Gonzalez has found at Cerro El Roble a possible
supernova 33" east and 14" south of the nucleus of NGC 4246 (R.A. =
12h15m4, Decl. = +7deg28', equinox 1950.0).  On Mar. 2 mpg = 18.0.

     M. Festou, Institut d'Astrophysique, Paris, reports: "
Spectroscopic observations of P/Crommelin were made on Feb. 25.4 UT in
the range 120-340 nm.  The short-wavelength camera was exposed for
60 min on the comet's nucleus and revealed emissions of O I 130 nm
(170 R), C I 166 nm (40 R) and S I 181 nm (145 R).  There is some
indication that C I 193-nm emission was present.  The long-
wavelength camera was exposed for 52 min at a point 66" from the
nucleus in a direction nearly perpendicular to the sun-comet line.
All three bands of OH were easily observed.  Assumption that the
OH cloud has spherical symmetry leads to a gas-production rate of
water of 3 x 10**28 s**-1.  The observed resonance line of H I of ~  8
kR is consistent with that figure.  The sulphur production rate
can be estimated as 4.2 x 10**25 s**-1, leading to a sulphur-to-water
production-rate ratio of 0.0014.  This value, slightly above
previously observed values, might indicate either a surge in sulphur
production near the time of observation or an asymmetric OH cloud.
The present evaluation of the gas production of water, together
with recent visual observations, indicate that predictions made by
both Festou and Morris (IHW Newsletter No. 3) were pessimistic far
from perihelion and optimistic near perihelion and that the
lightcurve is shallower than anticipated."

     S. Larson, Lunar and Planetary Laboratory, reports that direct
and spectroscopic (range 300-560 nm) observations on Mar. 1 and 2
with the 1.5-m reflector at the Catalina Station showed emissions
of OH, NH, C3, CH, C2 and NH2.  The continuum was confined to
within 2" of the nucleus and the coma was slightly asymmetric.

     Total visual magnitude estimates: Mar. 3.02 UT, 8.3 (D. W. E.
Green, Harvard, MA, 0.20-m reflector); 4.16, 8.4 (C. S. Morris,
Mount Gleason, CA, 20 x 80 binoculars); 5.80, 8.2 (J.-C. Merlin,
Le Creusot, France, 0.26-m reflector); 6.79, 8.1 (Merlin).

1984 March 8                   (3921)              Brian G. Marsden

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