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IAUC 6980: 1998de; 1998dh; C/1997 J2; SGR 1627-41

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IAUC number

                                                 Circular No. 6980
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html
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     P. Garnavich, S. Jha, and R. Kirshner, Harvard-Smithsonian
Center for Astrophysics, report that a spectrum of SN 1998de (cf.
IAUC 6977) was obtained with the Tillinghast 1.5-m telescope on
July 25.4 UT by M. Calkins.  A broad absorption feature of Si II is
seen at 618.5 nm, implying that this is a type-Ia supernova.
Correcting for the host-galaxy redshift of 5023 km/s (from the NASA
Extragalactic Database), the photospheric expansion velocity is
13 300 km/s.  The blue end of the spectrum shows Ti II absorption,
characteristic of the sub-luminous SNe 1991bg and 1986G, and the
very strong Si II at 580 nm also suggests that this will be a fast-
declining type-Ia event.

SUPERNOVA 1998dh IN NGC 7541
     Garnavich et al. also write:  "A spectrum of SN 1998dh (cf.
IAUC 6978) was obtained with the Tillinghast 1.5-m telescope on
July 26.4 UT by P. Berlind.  The spectrum is clearly that of a
normal type-Ia supernova before maximum.  Broad Si II is observed
at 613.21 nm, implying a photospheric velocity of 13 400 km/s
(assuming a redshift for the host galaxy of 2678 km/s from the NASA
Extragalactic Database).  Interstellar absorption lines of Na I are
seen from our galaxy with an equivalent width (EW) of 0.1 nm and
from NGC 7541 with an EW of 0.04 nm.  SN 1998dh should reach a
visual magnitude of about 13.8."

     Total visual magnitude estimates:  June 20.37 UT, 11.7 (R.
Keen, Mt. Thorodin, CO, 0.32-m reflector); 28.44, 11.4 (N. Biver,
Oahu, HI, 0.26-m reflector); July 2.90, 10.8 (K. Hornoch,
Lelekovice, Czech Republic, 0.35-m reflector); 16.95, 11.6 (R. J.
Bouma, Groningen, The Netherlands, 0.25-m reflector); 19.16, 10.9
(J. Bortle, Stormville, NY, 0.41-m reflector); 22.98, 11.3 (A.
Baransky, Kiev, Ukraine, 0.20-m reflector); 26.90, 10.9 (M.
Reszelski, Szamotuly, Poland, 0.25-m reflector).

SGR 1627-41
     Corrigendum.  IAUC 6962 titled this object incorrectly.

                      (C) Copyright 1998 CBAT
1998 July 27                   (6980)            Daniel W. E. Green

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