Central Bureau for Astronomical Telegrams
IAUC 6552: 1997X
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Circular No. 6552
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1997X IN NGC 4691
S. Nakano, Sumoto, Japan, reports the discovery of a supernova
(mag 13.6) by Masakatsu Aoki (Tsukioka-cho, Toyama) on nine
unfiltered CCD frames taken around Feb. 1.76 UT with a 0.43-m f/6
reflector. Y. Kushida (Yatsugatake South Base Observatory)
provides his measurement of SN 1997X (mag 13.5) from an unfiltered
CCD image taken by R. Kushida with a 0.40-m f/5 reflector on Feb.
1.816: R.A. = 12h48m14s.28, Decl. = -3 19'58".5 (equinox 2000.0),
which is about 7".2 east and 0".3 north of the center of NGC 4691
(this offset is necessarily uncertain due to the irregular nature
of the galaxy's nucleus). No star was present at the location of
SN 1997X on Aoki's most recent previous patrol films of this galaxy
taken on Jan. 16, nor was there anything on Kushida's most recent
patrol frame from Jan. 6.
N. B. Suntzeff, Cerro Tololo Interamerican Observatory (CTIO),
reports: ''A reduction by A. Clocchiatti, M. M. Phillips, and
Suntzeff of a spectrum (resolution 600; range 410--750 nm) obtained
by D.-W. Kim, Harvard-Smithsonian Center for Astrophysics (CfA) on
Feb. 4.3 UT with the CTIO 1.5-m telescope shows that SN 1997X is
probably a type-Ic supernova shortly after maximum light. A strong
absorption feature (FWHM 19.4 nm) centered at 566 nm resembles the
blend of Na I D and He I 587.6-nm in SN 1994I, 10 days after
maximum. A weaker absorption centered at about 645 nm might
correspond to He I 667.8-nm, indicating that He I lines in this
object are stronger than in SN 1994I. Narrow Na I D interstellar
lines are weak or absent. R. Covarrubias (CTIO) obtained BVI
photometry of the supernova on Feb. 4.3 with the CTIO 0.9-m
telescope, yielding preliminary photometry (+/- 0.05): B = 14.75,
V = 13.71, I = 12.85. SN 1997X is located 8".6 east and 1".3 north
of the galaxy's nucleus; note that there is also a bright nuclear
knot situated 3".2 west and 1".2 north of the galaxy's center,
which could be confused with the supernova as it fades."
P. Garnavich and R. Kirshner, CfA, report that spectra of SN
1997X were obtained on Feb. 4.47 UT with the 1.5-m Tillinghast
telescope by P. Berlind. The spectra show a fairly red continuum
with deep, broad features indicative of a supernova past maximum.
The lack of a prominent H-alpha feature or deep Si II (615 nm)
implies that this is a type-Ib/c supernova. Features with observed
minima at 567.5 and 623.0 nm are likely to be Na I and Si II,
respectively. The overall spectrum is similar to that of the type-
Ic SN 1987M (Filippenko 1992, Ap.J. 384, L37) except that the
absorption lines indicate a larger ejection velocity in SN 1997X.
(C) Copyright 1997 CBAT
1997 February 4 (6552) Daniel W. E. Green
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