[IAUC] CBET 1796: 20090513 : SUPERNOVAE 2009ef-2009ek

[IAUC mailing list]

                                                  Electronic Telegram No. 1796
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://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVAE 2009ef-2009ek
     D. Sand, Harvard-Smithsonian Center for Astrophysics (CfA) and Las
Cumbres Observatory Global Telescope Network; M. L. Graham, University of
Victoria; R. Foley (CfA); C. Bildfell, University of Victoria; D. W. Just, S.
Herbert-Fort, and S. Sivanandam, Steward Observatory; C. J. Pritchet,
University of Victoria; H. Hoekstra, Leiden University; and D. Zaritsky,
Steward Observatory, report that six more supernovae (cf. CBET 1753) were
discovered on g'- and r'-band images obtained at the Canada-France-Hawaii
Telescope (+ Megacam).  Auxiliary imaging/photometry was obtained with the
Steward Observatory 2.3-m reflector (+ 90Prime imager).  All spectroscopy was
obtained with the MMT at Mount Hopkins using the Blue-Channel Spectrograph
on May 3 (except that the Hectrospec instrument was used on Apr. 27 for
2009eg).  The publicly available Supernova Identification code of Blondin
and Tonry (2007, Ap.J. 666, 1024) was utilized for determining spectroscopic
types.  All six objects appear to be normal type-Ia supernovae except for
2009ef, whose spectrum resembles that of the type-Ib supernova 1984L at 28
days past maximum.

 SN       2009 UT     R.A. (2000.0) Decl.       g'     r'    Offset
 2009ef   Mar. 23   15 19 12.57  + 6 21 29.2   21.8   21.1   1".97 E, 0".66 N
 2009eg   Mar. 31   14 54 15.47  +18 57 52.8   17.6   17.7   6".53 W, 1".17 N
 2009eh   Apr.  3   15 20 38.08  + 7 39 32.5   21.2   21.0   0".62 E, 2".39 S
 2009ei   Apr. 22   14 32 17.26  +25 36 15.8   20.9   20.8     --
 2009ej   Apr. 22   15 10 59.53  + 6 33 10.0   19.0   18.8   1".17 E, 2".67 S
 2009ek   Apr. 23   15 19 46.76  +48 31 50.6   20.7   20.7   1".18 E, 0".36 S

The spectrum of 2009ef reveals a redshift of z = 0.18.  Additional Megacam
magnitudes for 2009ef:  Apr. 23, g' = 22.6, r' = 21.2.  The apparent host
galaxy for 2009ef has g' = 21.7 and r' = 21.3.  The spectrum of 2009eg shows
it to be around three weeks past maximum with a redshift of z = 0.057.
Additional Megacam magnitudes for 2009eg:  Apr. 22, g' = 19.2, r' = 18.4.
The apparent host galaxy of 2009eg has g' = 16.5, r' = 15.8.
     The spectrum of 2009eh was heavily contaminated by the elliptical host
galaxy (whose redshift is z = 0.044, and which has magnitudes g' = 17.0 and
r' = 16.2); to correct for this, the host-galaxy spectral-energy distribution
(SED) was reconstructed from its broad-band photometry (Blanton et al. 2003,
A.J. 125, 2348; Blanton and Roweis, 2007, A.J. 133, 734), so that subtracting
the host-galaxy SED from the contaminated spectrum produced a residual
supernova spectrum.  A SNID analysis indicates that the residual spectrum of
2009eh is consistent with that of a type-Ia supernova at z = 0.044, roughly
90 days past maximum.  To confirm this interpretation, the supernova-
identification program "Superfit" (Howell et al. 2005, Ap.J. 634, 1190),
which accounts for host-galaxy light contamination, was used on the unaltered
spectrum of 2009eh -- with a normal type-Ia supernova roughly 70 days past
maximum providing an excellent fit.  Based on these two different codes,
2009eh appears to be roughly 2-3 months past maximum at z = 0.044.
Additional magnitudes for 2009eh:  Apr. 23, g' = 21.5, r' = 21.6.  The field
of 2009eh was last observed with Megacam in June 2008.
     The spectrum of 2009ei shows it to be around ten days past maximum at
z = 0.23.  SN 2009ei is apparently hostless down to magnitudes g' about 24.5
and r' about 24.5; further deep imaging after the supernova has faded will
put stricter limits on any possible host galaxy.  The spectrum of 2009ej
shows it to be around three weeks past maximum at z = 0.083.  The apparent
host galaxy of 2009ej has g' = 19.3, r' = 18.7.  The spectrum of 2009ek shows
it to be around one week past maximum at z = 0.21.  Additional magnitudes for
2009ek from the 90Prime imager:  Apr. 21, g' = 21.0, r' = 20.8.  The apparent
host galaxy of 2009ek has g' = 20.7, r' = 20.7.


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

                         (C) Copyright 2009 CBAT
2009 May 13                      (CBET 1796)              Daniel W. E. Green