[IAUC] CBET 587: 20060726 : SUPERNOVAE 2006di, 2006dr, 2006dv, 2006dw, 2006dy

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                                                  Electronic Telegram No. 587
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 2006di, 2006dr, 2006dv, 2006dw, 2006dy
     R. J. Foley, J. S. Bloom, D. A. Perley, and N. R. Butler, University
of California, Berkeley, report that inspection of CCD spectra (range
330-920 nm), obtained on July 25 UT with the Keck I 10-m telescope (+
LRIS) show that SNe 2006di (IAUC 8726) and 2006dv (IAUC 8733) are both
of type Ia.  The spectrum of 2006di is consistent with a type-Ia
supernova approximately 40 days after maximum light.  SN 2006dv has a
spectral-feature age (Riess et al. 1997, A.J. 114, 722) of 1.5 +/- 2.0
days relative to maximum light; adopting a recession velocity of 9940
km/s, found from weak Na D absorption, the minimum of the Si II 635.5-nm
absorption is found to be blueshifted by 11200 km/s.
     Spectra obtained on July 26 show that SNe 2006dr (cf. IAUC 8731),
2006dw (cf. IAUC 8733), and 2006dy (cf. CBET 586) are also all type-Ia
supernovae.  SN 2006dw has a spectral-feature age of -0.6 +/- 2.0 days
relative to maximum light.  Adopting a recession velocity of 8107 km/s
(from Sloan Digital Sky Survey Data Release 3; Abazajian et al. 2005,
A.J. 129, 1755), the minimum of the Si II 635.5-nm absorption is found
to be blueshifted by 11300 km/s.  In addition, two velocity components
are seen for both Ca H and K and the Ca infrared triplet.  The minima
of the Ca H and K absorption are blueshifted to 11900 and 18600 km/s,
while the minima of the Ca II infrared triplet is blueshifted to a
significantly smaller 9000 and 13600 km/s (gf-weighted rest wavelength
of 857.9 nm; Thomas et al. 2004, Ap.J. 601, 1019).  The Ca II infrared
triplet velocities are smaller than that found in other type-Ia
supernovae at a similar age with multiple velocity components (for
example, SN 1999ee; see Mazalli et al. 2005, MNRAS 357, 200).  The
spectrum of 2006dw also appears to have a large near-ultraviolet
(blueward of the Ca H and K absorption) excess.  In light of the
current brightness of SN 2006dw, its age, and its high-velocity
features, spectropolarimetry is encouraged.
     SN 2006dy has a spectral-feature age of -9.4 +/- 2.0 days relative
to maximum light; adopting a recession velocity of 2420 km/s, found from
weak Na D absorption, the minimum of the Si II 635.5-nm absorption is
found to be blueshifted by 13000 km/s.  SN 2006dr has a spectral-feature
age of 6.5 +/- 2.0 days relative to maximum light; adopting a recession
velocity of 4640 km/s, found from weak Na D absorption, the minimum of
the Si II 635.5-nm absorption is found to be blueshifted by 10200 km/s.


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                         (C) Copyright 2006 CBAT
2006 July 26                     (CBET 587)               Daniel W. E. Green