TITLE: GCN CIRCULAR NUMBER: 14095 SUBJECT: GRB 121217A theoretical estimate of redshift and of supernova occurrence DATE: 12/12/18 12:28:55 GMT FROM: Remo Rufinni at ICRA R. Ruffini, L. Izzo, G.B. Pisani, C.L. Bianco, on behalf of a larger collaboration, report: GRB 121217A, following our theoretical considerations based on the Induced Gravitational Collapse scenario for GRBs-SNe, allows also for a different solution with a cosmological redshift of z=0.8 (+- 0.1). We base this result on a preliminary analysis of the superposition of the late X-ray afterglow emission, considering GRB 090618 as the prototype of the class. We have considered the first 75 ks of the X-ray afterglow light curve of GRB 121217A in this preliminary analysis. More details on the model will appear soon on the arXiv. We also predict a presence of a SN emerging after about 18 (+- 3) days from the GRB trigger, e.g. in the first days of January 2013. Assuming an interstellar extinction obtained from the Schlegel et al. (1998) extinction map and a supernova emission similar to the 1998bw one, we estimate an observed magnitude of +24.5 (+- 0.5) in the J filter. We further notice that, given the galactic latitude less than 5 deg (-4.89 deg), the calculated extinction value can differ at least of 1 mag. Follow-up photometric and possibly spectroscopical observations are strongly requested.