Author/Authors :
Covino، S. نويسنده , , Stella، L. نويسنده , , Testa، V. نويسنده , , Lazzati، D. نويسنده , , Ghisellini، G. نويسنده , , Fugazza، D. نويسنده , , Malesani، D. نويسنده , , Chincarini، G. نويسنده , , Benetti، S. نويسنده , , Antonelli، L. A. نويسنده , , Valle، M. Della نويسنده , , Hamuy، M. نويسنده , , Cocozza، G. نويسنده , , DAvanzo، P. نويسنده , , Gilmozzi، R. نويسنده , , Mason، E. نويسنده , , Mazzali، P. نويسنده ,
Abstract :
We present photometric and spectroscopic observations of the gamma-ray burst GRB 021211 obtained during the late stages of its afterglow. The light curve shows a rebrightening occurring ~ 25 days after the GRB. The analysis of a VLT spectrum obtained during the bump (27 days after the GRB) reveals a suggestive resemblance with the spectrum of the prototypical type-Ic SN 1994I, obtained ~ 10 days past maximum light. Particularly we have measured a strong, broad absorption feature at 3770 (angstrom), which we have identified with Ca II blueshifted by ~ 14400 km s^-1, thus indicating that a supernova (SN) component is indeed powering the "bump" in the afterglow decay. Assuming SN 1994I as a template, the spectroscopic and photometric data together indicate that the SN and GRB explosions were at most separated by a few days. Our results suggest that GRBs might be associated also to standard type-Ic supernovae.
