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IAUC 6783: 1997ef

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                                                 Circular No. 6783
Central Bureau for Astronomical Telegrams
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SUPERNOVA 1997ef IN UGC 4107
     J. Y. Hu, Y. L. Qiu, Q. Y. Qiao, and J. Y. Wei, Beijing
Astronomical Observatory (BAO), report that the possible supernova
in UGC 4107 reported on IAUC 6778 is being monitoring
photometrically and spectroscopically at BAO.  The object did not
appear on CCD images (limiting mag 18.5) taken on Nov. 16.  CCD
images taken with the 0.60-m telescope show that it brightened from
Nov. 28 to Dec. 8; available CCD magnitudes:  Nov. 28.70 UT, 16.8;
Dec. 7.74, 16.3; 8.72, 16.2.  The low-dispersion spectra obtained
with 2.16-m telescope on Nov. 28, Dec. 4, and 7, show that the
spectra still show the features reported by Garnavich et al. (IAUC
6778), but the peaks are shifted redward.  The peak at 510 nm
reported by Garnavich et al. shifted to 520, 535, and 545 nm in
spectra obtained on Nov. 28, Dec. 4, and 7, respectively.  The Na D
absorption lines in SN 1997ef show the same redshift as does the
H-alpha from UGC 4107, implying that the object is located in the
host galaxy.
     A. V. Filippenko, University of California at Berkeley (UCB),
reports that he has examined a spectrum (range 470-1020 nm,
resolution 1.5 nm) of SN 1997ef, obtained by E. L. Martin (UCB) on
Dec. 10 with the 3-m Shane reflector at Lick Observatory:  "The
spectrum superficially resembles that of a supernova but in detail
is unlike that of any known type of supernova; the features are
unusually broad (FWHM 50 nm).  The strongest emission line is at
rest wavelength 540 nm; if identified with [O I] 557.7 nm, its
blueshift is presumably due to obscuration of the object's back
side.  A smaller peak at 639 nm is then consistent with H-alpha
blueshifted by the same amount.  Weak peaks are visible at 777 nm
(possibly unshifted O I 777.4 nm), 850 nm (slightly shifted Ca II?),
and 909 nm (shifted O I 926 nm?).  All of the maxima listed by
Garnavich et al. (IAUC 6778) have moved substantially to the red.
If this offset is applied to their reported peak at 440 nm, the
feature would now be roughly consistent with unshifted Mg I] 457.1
nm.  Aside from the tentative H-alpha identification (which may
instead be unshifted [O I]), the spectrum vaguely resembles what
might be expected from a denuded O-Ne-Mg (or perhaps C-O) core.
Thus, the object could be a previously unobserved, extreme example
of a stripped (type-Ic-like) supernova, though other
interpretations are possible.  The great breadth of the lines
suggests a low mass for the ejecta.  Further observations of this
unique object are encouraged."
     Unfiltered CCD magnitude estimates:  Nov. 8 UT, [17.5: (W. D.
Li, R. R. Treffers, Filippenko, and M. Modjaz, Lick Observatory);
Dec. 2.4, 16.5: (Li et al.); 7.98, 16.7 (S. Moretti and S.
Tomaselli, Forli, Italy).

                      (C) Copyright 1997 CBAT
1997 December 10               (6783)            Daniel W. E. Green

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