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FLOYDS Classification of DLT17cd/AT 2017fzw and ATLAS17jiv/AT 2017gah as Young Subluminous Type Ia Supernovae

ATel #10639; G. Hosseinzadeh (Las Cumbres Obs./UCSB), S. Valenti (UC Davis), D. A. Howell, I. Arcavi, C. McCully (Las Cumbres Obs./UCSB)
on 14 Aug 2017; 21:49 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Iair Arcavi (iarcavi@lcogt.net)

Subjects: Optical, Supernovae

We obtained spectra of DLT17cd/AT 2017fzw (ATel #10629) and ATLAS17jiv/AT 2017gah (ATel #10633) on 2017 August 13.8 and 13.6 UT, respectively, with the robotic FLOYDS instrument mounted on the Las Cumbres Observatory 2-meter telescope in Siding Spring, Australia. Using Superfit (Howell et al. 2005, ApJ, 634, 1190) and SNID (Blondin & Tonry 2007, ApJ, 666, 1024), we find good fits between AT 2017fzw and several 91bg-like Type Ia supernovae at the redshift of its proposed host galaxy (z=0.005; De Vaucouleurs et al. 1991, "Third Reference Catalog of Bright Galaxies" via NED). We measure a Si II velocity of ~17,000 km/s, indicating the supernova is well before maximum light. We find good fits between AT 2017gah and several Type Ia supernovae at the redshift of its proposed host galaxy (z=0.009; Lauberts & Valentijn 1989, "The Surface Photometry Catalogue of the ESO-Uppsala Galaxies" via NED). We measure a Si II velocity of ~14,000 km/s, indicating the supernova is well before maximum light. The silicon ratio suggests it may be subluminous.