Electronic Telegram No. 1857
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://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVAE 2009gh AND 2009gi
     D. Milisavljevic, R. Fesen, and J. Parrent, Dartmouth College, report
that a low-dispersion spectrum (range 420-790 nm) of 2009gi (cf. CBET 1853),
taken on June 21.4 UT with the 2.4-m Hiltner telescope (+ CCDS) at MDM
Observatory, favors a type-II supernova classification, contrary to what was
stated on CBET 1855.  Adopting a redshift of z = 0.013, using emission lines
of H-alpha, [N II] 658.3-nm, and [S II] at 671.6 and 673.1 nm that are
observed in the host galaxy, a broad absorption feature displaying a minimum
around 619 nm in interpreted as H-alpha with a blueshifted velocity of 17000
km/s, with absorptions at 563, 640, and 677 nm interpreted as due to He I
lines at 587.6, 667.8, and 706.5 nm but blueshifted by 12500 km/s.  The
"GELATO" spectrum-comparison code (Harutyunyan et al. 2008, A.Ap. 488, 383)
provides a good fit to the type-IIb supernova 1987K at seven days past
maximum light.  Spectral fits with type-Ia templates using the SuperNova
Identification code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) produce
inconsistent redshifts and do not account for the lack of Si II 597.2-nm
line absorption typically seen near maximum brightness for type-Ia supernovae.
SNID does, however, provide a good fit and consistent redshift for the
spectrum with the type-IIb supernova 2000H at ten days past maximum.
     Also, a low-dispersion spectrum, taken as above on June 20.4, shows
2009gh (cf. CBETs 1850, 1854) to be a type-II supernova around maximum light.
Comparison with a library of supernova spectra using SNID provides a good
match with the type-IIP supernova 2004et at 6-8 days past maximum.  A strong
emission feature identified as H-alpha dominates over the corresponding
absorption component.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2009 CBAT
2009 June 23                     (CBET 1857)              Daniel W. E. Green