2009CBET.1796....1S

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.