Free access article

Issue A&A Volume 406, Number 2, August I 2003 Page(s) L33 - L37 Section Letters DOI 10.1051/0004-6361:20030855

A&A 406, L33-L37 (2003)
DOI: 10.1051/0004-6361:20030855

Letter

Evidence for supernova signatures in the spectrum of the late-time bump of the optical afterglow of GRB 021211

M. Della Valle¹, D. Malesani², S. Benetti³, V. Testa⁴, M. Hamuy^{5, 1}, L. A. Antonelli⁴, G. Chincarini^{6, 7}, G. Cocozza^{4, 8}, S. Covino⁶, P. D'Avanzo⁶, D. Fugazza⁹, G. Ghisellini⁶, R. Gilmozzi¹⁰, D. Lazzati¹¹, E. Mason¹⁰, P. Mazzali¹² and L. Stella<sup>4

1</sup>  INAF, Osservatorio Astrofisico di Arcetri, largo E. Fermi 5, 50125 Firenze, Italy
²  International School for Advanced Studies (SISSA/ISAS), via Beirut 2-4, 34016 Trieste, Italy
³  INAF, Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁴  INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone (Roma), Italy
⁵  Carnegie Observatories, 813 Santa Barbara Street, Pasadena, California 91101, USA
⁶  INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (Lc), Italy
⁷  University of Milano-Bicocca, Department of Physics, Piazza delle Scienze 3, 20126 Milano, Italy
⁸  University of Roma "Tor Vergata", Department of Physics, via della Ricerca Scientifica 1, 00133 Roma, Italy
⁹  INAF, Telescopio Nazionale Galileo, Roque de Los Muchachos, PO box 565, 38700 Santa Cruz de La Palma, Spain
¹⁰  ESO, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago, Chile
¹¹  Institute of Astrophysics, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
¹²  INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy

(Received 25 April 2003 / Accepted 9 June 2003)

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 Å, which we have identified with Ca II blueshifted by ~  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.

Key words: gamma rays: bursts -- supernovae

Offprint request: M. Della Valle, massimo@arcetri.astro.it

SIMBAD Objects

© ESO 2003

What is OpenURL?