[IAUC] CBET 908: 20070326 : SUPERNOVAE 2007aw, 2007ax, 2007ay

[IAUC mailing list]

                                                  Electronic Telegram No. 908
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS en CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT en CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html


SUPERNOVAE 2007aw, 2007ax, 2007ay
     N. Morrell and G. Folatelli, on behalf of the Carnegie Supernova
Project, report spectroscopic observations (range 342-961 nm) of 2007aw,
2007ax, and 2007ay obtained on Mar. 26.11, 26.06, and 26.02 UT,
respectively, with the 2.5-m du Pont telescope (+ Boller & Chivens
spectrograph) at Las Campanas Observatory.
     The spectrum of 2007aw (cf. CBET 902) shows this to be a type-Ic
supernova at one week to ten days after maximum light.  Adopting the NED
recession velocity of 3431 km/s for the host galaxy (Wegner et al. 2003,
A.J. 126, 2268), the 'superfit' spectrum-comparison code (Howell et al.
2005, Ap.J. 634, 1190) provides matches to the earliest spectrum of SN
1997dq (unknown age), and to that of the type-Ic supernova 2004fe at 8
days after maximum light.
     SN 2007ax (cf. CBET 904) is a type-Ia supernova, similar to the
subluminous supernova 1991bg at maximum light.  Assuming the NED recession
velocity of 2057 km/s for the host galaxy (Simien and Prugniel 2000, A.Ap.
Suppl. 145, 263), the absorption minimum of the Si II 635.5-nm doublet
indicates an expansion velocity of about 10000 km/s, while that of the Ca
II H-and-K doublet corresponds to 15000 km/s.
     SN 2007ay (cf. CBET 905) is a type-II supernova.  The spectrum,
although noisy, shows a blue continuum with P-Cyg profiles of Balmer lines.
Adopting the recession velocity of 4355 km/s from NED for the host galaxy
(Schneider et al. 1990, Ap.J. Suppl. 72, 245), 'superfit' provides a
good match to spectra of SN 1999em at 4 and 9 days after explosion.  The
position of the absorption minimum of H_beta corresponds to an expansion
velocity of about 11000 km/s.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2007 CBAT
2007 March 26                    (CBET 908)               Daniel W. E. Green