Electronic Telegram No. 302
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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SUPERNOVA 2005gj
     J. Prieto, Ohio State University (OSU); P. Garnavich,
University of Notre Dame; and D. DePoy, J. Marshall, J. Eastman,
and S. Frank, OSU, on behalf of the SDSS-II Supernova
Collaboration, report that spectra (range 390-730 nm; resolution
0.31 nm/pixel) of SN 2005gj (cf. CBET 247, IAUC 8616) were
obtained with the MDM 2.4-m telescope (+ CCDS) approximately
once per week since its discovery.  The supernova was discovered
by the SDSS-II supernova search and initially classified as a
type-IIn event based on the presence of resolved Balmer emission.
The spectrum has evolved to show broad absorption features at
around 440, 475, 510, and 610 nm (rest-frame for z = 0.062),
while the Balmer emission lines remain.  The spectrum obtained on
Nov. 12.3 UT is remarkably similar to the spectrum of the
peculiar type-Ia supernova 2002ic (cf. IAUC 8019, 8151, 8157,
8161) obtained on 2002 Dec. 27 (Hamuy et al. 2003, Nature, 424,
651).  It is concluded that SN 2005gj is a 1991T-like type-Ia
event interacting with circumstellar material and giving rise to
the resolved emission lines on top of the characteristic type-Ia
spectrum.  This is the second clear detection of hydrogen in the
spectrum of a type-Ia supernova.  The preliminary SDSS-II light
curve indicates that it has just passed maximum light (at
magnitude r about 17.2).  The study of SN 2005gj throughout the
electromagnetic spectrum is urged, as it could yield data to
help to understand better the nature of the progenitors of
thermonuclear supernovae.  A plot comparing the spectrum of SN
2005gj with that of SN 2002ic has been posted at
http://www.astronomy.ohio-state.edu/~prieto/sn05gj_compar.ps


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2005 CBAT
2005 November 23                 (CBET 302)               Daniel W. E. Green