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IAUC 6700: 1997cx; 1997cw; BL Lac

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                                                 Circular No. 6700
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1997cx IN NGC 3057
     Michael Schwartz, Cottage Grove, OR, reports his discovery of
a supernova (mag about 15) located about 20" south of the center of
NGC 3057 (R.A. = 10h05m.7, Decl. = +80o17', equinox 2000.0) on a
CCD image taken with the 0.35-m automated Tenagra Observatory
supernova patrol telescope on July 12.33 UT (with a confirming
image taken an hour later).
     S. Jha, P. Garnavich, P. Challis, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, report that a spectrogram
taken by P. Berlind at the Whipple Observatory 1.5-m telescope on
July 14.2 UT indicates that SN 1997cx is a type-II supernova past
maximum, showing P-Cyg Balmer lines, He I (587.5 nm), and Fe II.
The expansion velocity measured from the H-alpha profile is 7000
km/s.  Images taken concurrently by C. W. Hergenrother at the 1.2-m
telescope yield magnitude R = 15.4 and the following position: R.A.
= 10h05m37s.43, Decl. = +80o17'27".6 (equinox 2000.0).

     Garnavich, Jha, Kirshner, and Challis also report that spectra
of SN 1997cw were obtained by P. Berlind with the Whipple
Observatory 1.5-m telescope on July 14.5 UT, confirming that this
is a type-Ia supernova.  However, the depth of the broad Na I
absorption and Fe II lines shortward of 550 nm suggest that the
supernova is at least two weeks past maximum brightness,
significantly older than reported on IAUC 6699.  The Si II 615.0-nm
absorption is indeed weak, and the spectrum is similar to that of
SN 1991T taken 15 days past maximum (Phillips et al. 1992, A.J.
103, 1632).  Images taken near the time of the spectra, by
Hergenrother at the 1.2-m telescope, yield magnitude V = 16.4.
     Corrigendum.  On IAUC 6699, line 14, for  3.7 nm)  read  0.37

     M. Maesano, E. Massaro, and R. Nesci, Astronomical Institute,
University 'La Sapienza', Rome, report that BL Lac is still in
outburst (cf. IAUC 6693), exhibiting rapid and strong variations
[Delta(V) = 1.54 over 1 day].  Johnson B and V and Cousins R and I
magnitudes:  July 12.93 UT, 15.42, 14.52, 13.88, 13.10; July 13.96,
13.84, 12.98, 12.36, 11.65.

                      (C) Copyright 1997 CBAT
1997 July 14                   (6700)            Daniel W. E. Green

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