Electronic Telegram No. 946
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 2007ay IN UGC 4310
     N. Morrell, M. Phillips, and G. Folatelli, on behalf of the Carnegie
Supernova Project, report a new spectroscopic observation (range 380-920
nm) of SN 2007ay (cf. CBETs 905, 908), obtained on Apr. 18.07 UT with the
du Pont telescope (+ WFCCD spectrograph) at Las Campanas Observatory.
The development of strong He I lines is observed in these data, although
Balmer lines are still present, fairly resembling the spectrum of the
type-IIb supernova 1993J between 34 and 45 days after explosion (source:
Filippenko 1997, ARAA 35, 309).  The 'superfit' spectrum-comparison code
(Howell et al. 2005, Ap.J. 634, 1190) provides also a good match with a
spectrum of supernova 2000H when observed 30 days after explosion.  This
indicates that 2007ay should be reclassified as a type-IIb supernova.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2007 CBAT
2007 April 26                    (CBET 946)               Daniel W. E. Green