S. Benetti, L. Tomasella, E. Cappellaro, (INAF-OAPd), E. Brocato (INAF-OAR), M. Branchesi (Urbino University/INFN Firenze), L. A. Antonelli, (INAF-OAR), P. Astone (INFN-Roma), S. Campana, S. Covino, P. D'Avanzo (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 (INAF-ASDC), P. Marrese (INAF-ASDC), A. Melandri (INAF-OAB), L. Nicastro (INAF-IASF Bo), E. Palazzi (INAF-IAFS Bo), E. Pian (SNS-Pisa), S. Piranomonte, L. Pulone (INAF-OAR), F. Ricci (Sapienza University), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR) on behalf of the INAF Gravitational Astronomy group report:
We have re-analysed the spectra of PTF15dkv and PTF15dld taken on 2015 Nov 4 with the Asiago 1.82 m Copernico Telescope + AFOSC, for which preliminary information were reported in Tomasella et al. (GCN18561).
After careful minimisation of the strong background contamination, low S/N spectra of supernovae emerge. In particular:
The spectrum of PTF15dkv, given the redshift reported in GCN18561 (z=0.081), is consistent with those shown by Type Ia Supernovae, about a week after the B maximum light.
More interesting, the spectrum of PTF15dld, given the redshift (z=0.046), is consistent with those of broad-line Type Ic Supernovae, close to maximum light. In particular, the spectrum closely resembles that of SN 2006aj (Pian et al 2006, Nature 442, 1011), which has been associated with the GRB 060218 (Campana et al. 2006, Nature 442, 1008). These are rare events (<1% of all core collapse SNe) and are likely associated to jet-like core collapse.
For the latter object follow-up observations have been activated.