Electronic Telegram No. 425
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)
URL http://cfa-www.harvard.edu/iau/cbat.html


SUPERNOVA 2006T IN NGC 3054
     S. Blondin, M. Modjaz, R. Kirshner, and P. Challis,
Harvard-Smithsonian Center for Astrophysics; and T. Matheson,
National Optical Astronomy Observatory, report that a spectrum
(range 350-740 nm) of SN 2006T (cf. IAUC 8666), obtained on Feb.
22.31 UT by P. Berlind with the F. L. Whipple Observatory 1.5-m
telescope (+ FAST), shows this supernova to have developed
conspicuous lines of He I (rest wavelengths 587.6, 667.8, 706.5 nm)
and is very similar to spectra of the type-IIb SN 1993J at 30-40
days past explosion (Matheson et al. 2000, A.J. 120, 1487; cf.
http://www.cfa.harvard.edu/oir/Research/supernova/spectra/sn2006T_vs_sn1993J.gif
SN 2006T was classified as a probable type-IIb supernova on CBET
386.  The appearance of He lines was confirmed in two subsequent
spectra, obtained on Mar. 2.31 by M. Calkins and on Mar. 9.28 by
E. Falco with the same telescope.  SN 2006T is thus a definite
type-IIb supernova.  Adopting a recession velocity of 2194 km/s for
the host galaxy (de Vaucouleurs et al. 1991, Third Ref. Cat. of
Bright Galaxies, ver 3.9), the blueshift of the maximum absorption
in the H_alpha line has evolved from 14500 km/s on Feb. 2.36
(cf. CBET 386) to 10500 km/s on Mar. 9.28.  The absorption maxima
in the three He I lines are blueshifted by approximately 6000 km/s
in the Mar. 2.31 spectrum.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2006 CBAT
2006 March 9                     (CBET 425)               Daniel W. E. Green