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IAUC 5630: 1992bc; 1978K; 1992ba

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                                                  Circular No. 5630
Central Bureau for Astronomical Telegrams
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

SUPERNOVA 1992bc IN ESO 300-G9
     M. Hamuy, Cerro Tololo Interamerican Observatory; and J. Maza,
University of Chile, report the discovery by R. Antezana (University
of Chile) of a supernova located about 15" east and 5" north of
the nucleus of the spiral galaxy ESO 300-G9 (R.A. = 3h03m22s.2,
Decl. = -39 45'15", equinox 1950.0).  The supernova, of mpg about
15, was found on a 20-min unfiltered IIa-O plate taken by C. Muena
and G. Valladares with the CTIO Curtis Schmidt telescope on Oct.
4.364 UT.  A spectrogram (range 320.0-750.0 nm), obtained by Maza
on Oct. 6.1 with the CTIO 4-m telescope, shows the characteristic
Si II 635.5-nm feature of type-Ia supernovae.  The minimum of the
Si II absorption yields an expansion velocity of about 13 000 km/s
with respect to the galaxy's rest frame.  This spectrum shows
resemblance to that of the type-Ia SN 1989B, 7 days before maximum
light.  The spectrum of the galaxy's nucleus yields a redshift of z
= 0.019.

     A. V. Filippenko, University of California at Berkeley,
writes:  "Careful consideration of the available data strongly
supports the suggestion of Ryder et al. (IAUC 5615) that the suspected
nova in NGC 1313 (IAUC 4950) is actually a supernova.  The x-ray
luminosity exceeds 10E40 erg/s, and the nonthermal radio luminosity
is over 200 times that of Cas A, the brightest Galactic supernova
remnant.  It is probable that the progenitor was a very massive
star having a dense, slow stellar wind with a mass-loss rate
exceeding 10E-4 solar masses per year.  The observed properties
resemble those of SN 1986J in NGC 891, and perhaps of SN 1961V in NGC
1058.  Based on its measured brightness, SN 1978K is extinguished
by roughly 4-6 mag at optical wavelengths, possibly due to the
dense circumstellar gas.  Further study of this object, which will
help characterize the growing subclass of radio- and x-ray-luminous
type-II supernovae, is encouraged."

SUPERNOVA 1992ba IN NGC 2082
     A. C. Gilmore reports the following position of SN 1992ba,
measured by P. M. Kilmartin from films taken by Gilmore with the
0.6-m f/14 Cassegrain telescope and 0.15-m f/15 astrographs at Mt.
John University Observatory on Oct. 4.62 UT:  R.A. = 5h41m31s.88,
Decl. = -64 19'21".0 (equinox 1950.0, uncertainty about 1" in each

1992 October 6                 (5630)            Daniel W. E. Green

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