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Followup observations of SN 2017ivv with Asiago telescopes

ATel #11072; S. Benetti, P. Ochner, E. Cappellaro, L. Tomasella, M. Turatto (INAF OAPd) and L. Colombo (UniPd DFA)
on 18 Dec 2017; 11:59 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stefano Benetti (stefano.benetti@oapd.inaf.it)

Subjects: Optical, Supernovae

Followup observations of SN 2017ivv (Atel #11063) were obtained with the Asiago Copernico+AFOSC and Galileo+B&C instruments. The three spectra obtained on Dec. 15, 16 and 17 show a slow evolution with the emergence of a broad Halpha emission. This confirms our early Type II classification (Atel #11063). However, we recognise that the narrow emission lines attributed to Balmer lines seen in our first spectrum were due to cosmic ray contamination.

Lacking narrow lines from the host galaxy, a new redshift estimation is based only on the best fit of SN features obtained with GELATO (Harutyunyan et al. 2008, A&A, 488, 383) and SNID (Blondin and Tonry 2007, ApJ, 666, 1024) . We obtain z~0.01 with a 50% uncertainty.

The broad P-Cygni emission components of Halpha, Hbeta, Hgamma and HeI 587.6nm peak close to their rest frame positions, again suggest a low redshift.

With the revised redshift the object remains moderately bright at discovery (~-18.5 mag), but not as extreme as claimed in Atel #11063.