P. D'Avanzo, A. Melandri (INAF-OAB), L. Tomasella, S. Benetti, E. Cappellaro, A. Pastorello (INAF-OAPd), E. Brocato (INAF-OAR), M. Branchesi (Urbino University/INFN Firenze), E. Pian (SNS-Pisa), L.Amati (INAF-IASF Bo), L. A. Antonelli, (INAF-OAR), P. Astone (INFN-Roma), S. Campana, S. Covino ((INAF-OAB), V. D'Elia (INAF-ASDC), F. Getman (INAF-OAC), G. Giuffrida (INAF-ASDC), A.Grado (INAF-OAC), G.Greco (Urbino University/INFN Firenze), L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), S. Marinoni, P. Marrese (INAF-ASDC), L. Nicastro, E. Palazzi (INAF-IAFS Bo), S. Piranomonte, L. Pulone (INAF-OAR), F. Ricci (Sapienza University), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), P. Blay (IAC/NOT, Canary Island, Spain) on behalf of the INAF Gravitational Astronomy group report:
We report the spectroscopic observation of the optical candidates reported by Smith et al. (GCN Circ. 18786) PS15dpu (aka ASASSN-15un) and PS15dou with the Nordic Optical Telescope (Canary Islands, Spain) equipped with ALFOSC (gm4, range 320-910 nm) starting on Jan 09.88 UT.
For PS15dpu aka ASASSN-15un, we confirm the main findings of Seibert et al. 2016, Atel#8526, that the object is a very young type II SN. The spectrum shows prominent P-Cygni lines of H and He I. The ejecta velocity obtained from the position of the Halpha minimum is about 9000 km/s.
The low S/N spectrum of PS15dou is consistent with those of evolved type II SNe, showing the presence of P-Cygni H lines, Na ID, Ca II H&K and several Fe II lines. The best match is found with SN 1996L (Benetti et al. 1999, MNRAS 305, 811) around 2 month after explosion. Classification was done with GELATO (Harutyunyan et al. 2008, A&A, 488, 383) and SNID (Blondin and Tonry 2007, ApJ, 666, 1024).
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