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IAUC 6589: 1997ab; C/1995 O1

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                                                 Circular No. 6589
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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     H.-J. Hagen and D. Reimers, Hamburg Observatory, report the
discovery of a supernova (mag 16.2) on a spectrum taken on Feb. 28.
SN 1997ab is first visible on an objective-prism plate taken on
1996 Apr. 11 with the Calar Alto 0.80-m Schmidt telescope for the
Hamburg Quasar survey; it was automatically selected on the
digitized plate as a low-redshift QSO candidate due to its
ultraviolet excess and its strong H-beta emission.  From the
objective-prism spectrum, we derive mag B = 14.7 +/- 0.5.  A CCD
image taken with the Calar Alto 2.2-m telescope shows a bright
point source 7" southwest of the galaxy center; the supernova is
located at R.A. = 9h51m00s.4, Decl. = +20o04'24" (equinox 2000.0).
The spectrograms taken with the same instrument show SN 1997ab to
be of the rare emission-line Seyfert-1 type II, similar to SN
1987F, with a blue underlying continuum.  Besides strong Balmer
lines, the spectrum shows broad Fe II emission bumps and a strong
infrared Ca II triplet.  The redshift of the parent galaxy (from
sharp, forbidden H II-region lines O III and S II) is 0.012.  SN
1997ab faded in eleven months by < 2 mag and was at least 2 mag
brighter in Apr. 1996 than the parent galaxy, which is a dwarf
irregular of mag 17.

     T. Farnham and D. Schleicher, Lowell Observatory; and S.
Lederer, University of Florida, write:  "Narrow-band photometry
obtained with the 0.79-m telescope at Lowell Observatory on Mar.
6.5 and 7.5 UT (when r = 1.02-1.01 AU) yield the following mean
Haser-model production rates: log Q(OH) = 30.24, log Q(CN) = 28.05,
log Q(C2) = 28.16.  The dust-production rate was log (Af rho) =
5.93.  Combining these results with those obtained from Lowell by
Schleicher, Farnham, and R. Millis during the previous seven weeks
at r = 1.54-1.52, 1.34, 1.23-1.20, and 1.09 AU indicates that gas
production has now leveled off and dust production is increasing at
a slower rate, as compared to the r-dependent slopes of -3 to -4
displayed by both the gas and the dust from mid-Jan. to mid-Feb.
However, this leveling off in the gas may in part be due to the
rapidly-decreasing geocentric distance yielding smaller projected
apertures, coupled with a strong aperture effect exhibited by the
various gas species.  In contrast, the derived dust production
shows little dependence with aperture size."
     Naked-eye m1 estimates:  Mar. 9.74 UT, -0.3 (K. Cernis,
Moletai Observatory, Lithuania); 12.19, -0.4 (M. V. Zanotta, San
Marco Pass, Italy); 16.44, -0.5 (G. W. Kronk, Troy, IL); 17.80,
-0.6 (P. Candy, Viterbo, Italy).

                      (C) Copyright 1997 CBAT
1997 March 17                  (6589)            Daniel W. E. Green

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