Central Bureau for Astronomical Telegrams
IAUC 7061: 1998ew; 1998ex
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Circular No. 7061
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998ew IN NGC 6943
J. Maza, Department of Astronomy, University of Chile, reports
the discovery by R. Antezana, on a T-Max 400 film taken by L. E.
Gonzalez with the Maksutov telescope at Cerro El Roble on Nov.
23.02 UT, of a supernova (B about 14) located at R.A. = 20h44m32s.1,
Decl. = -68o43'37" (equinox 2000.0), which is 5" west and 73" north
of the nucleus of NGC 6943. The object was confirmed by R.
Gonzalez on Nov. 24.07 with the same telescope at Cerro El Roble.
SN 1998ew is not visible on films obtained with the Cerro El Roble
telescope on Nov. 11.06 (B > 19.5).
F. Patat, European Southern Observatory (ESO); N. Christlieb,
Hamburger Sternwarte; and J. Sollerman, Stockholm Observatory,
report that a full reduction of a CCD spectrogram (range 400-900 nm,
resolution 2.0 nm) obtained with the ESO-Danish 1.54-m telescope (+
DFOSC) on Nov. 27.05 UT shows that a few lines, accompanied by very
weak P-Cyg profiles, are superimposed on a blue and otherwise
featureless continuum, and they are identified as H-alpha, H-beta,
H-gamma, and He I at 587.6 nm. The spectral features and the blue
continuum are consistent with a supernova of type II, roughly
around maximum light. The expansion velocities deduced from the
minima of H-beta, H-gamma, and He 587.6-nm are 8200, 8500, and 7900
km/s, respectively. The magnitudes of SN 1998ew were V about 15.2
and R about 14.9. Using a recession velocity of 3085 km/s for NGC
6943 (Da Costa et al. 1991, Ap.J. Suppl. 75, 935) and H_0 = 65 km
sE-1 MpcE-1, the absolute magnitude is V about -18.2, which is
somewhat brighter than that seen in normal type-II supernovae.
There may be some resemblance to bright type-II supernovae, such as
SN 1979C (Branch et al. 1981, Ap.J. 224, 780).
SUPERNOVA 1998ex IN MCG +11-10-16
J. Mueller reports her discovery of a supernova (mag about
18.5) on a red plate taken by herself with the 1.2-m Oschin Schmidt
Telescope on Nov. 25 UT in the course of the second Palomar Sky
Survey. SN 1998ex is located at R.A. = 7h41m42s.28, Decl. =
+64o44'02".3 (equinox 2000.0), which is 5".1 west and 10".1 north
of the center of MCG +11-10-16. R. Gal obtained CCD images of SN
1998ex with the 1.5-m Palomar telescope on Nov. 26, and he
provided the positional information. There is no object at this
position on either the Digital Sky Survey or on an overlapping red
sky-survey plate taken on 1989 Dec. 23. A spectrum taken on Nov.
26 by I. Smail and A. Dressler with the Hale 5-m telescope shows it
to be a type-Ia supernova. A preliminary measurement of the
redshift of the supernova is 11~200 km/s.
(C) Copyright 1998 CBAT
1998 November 27 (7061) Daniel W. E. Green
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