Electronic Telegram No. 1765
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CBAT@CFA.HARVARD.EDU (science)
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SUPERNOVA 2009dd IN NGC 4088
     N. Elias-Rosa and S. D. Van Dyk, Spitzer Science Center, California
Institute of Technology; I. Agnoletto, Universita' di Padova; and S. Benetti,
Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova,
report that a spectrogram (range 340-800 nm, resolution 1.8 nm) of 2009dd (cf.
CBET 1764), obtained on Apr. 15.19 UT with the Nordic Optical Telescope (+
ALFOSC), shows it to be a young type-II supernova.  Assuming a recession
velocity of 757 km/s (Verheijen and Sancisi 2001, A.Ap. 370, 765; via NED)
for the host galaxy, the "GELATO" spectrum-comparison code (Harutyunyan et al.
2008, A.Ap. 488, 383; available at https://gelato.tng.iac.es) provides good
fits to spectra of type-II supernovae at several days after explosion.  The
expansion velocity deduced from the H-alpha absorption is about 9900 km/s.
The spectrum shows an intense (equivalent width 0.28 nm) absorption due to
the Na I D doublet, which might indicate a somewhat-high interstellar
absorption suffered by the supernova light inside the parent galaxy.
     H. Yamaoka, Kyushu University, forwards the following pre-discovery
magnitude estimates of 2009dd obtained by K. Itagaki (Yamagata, Japan)
from unfiltered CCD images taken with a 0.60-m reflector:  Apr. 2.558 UT,
[18.0: (limit determination is rather difficult due to the neighboring
bright galaxy nucleus); 9.581, 14.5; 10.720, 14.4; 13.567, 14.3.


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                         (C) Copyright 2009 CBAT
2009 April 15                    (CBET 1765)              Daniel W. E. Green