Is there a 1998 bw - like supernova in the afterglow of gamma ray burst 011121 ?

We use the very simple and successful Cannonball Model (CB) of gamma ray bursts (GRBs) and their afterglows (AGs) to analyze the observations of the strongly extinct optical AG of the relatively nearby GRB 011121, which were made with ground-based telescopes at early times, and with the HST at later time. We show that GRB 011121 was indeed associated with a 1998bw-like supernova at the GRB's redshift, as we had specifically predicted for this GRB before the supernova could be observed. The identity of the progenitors of gamma ray bursts is still unknown, but it is becoming clearer and clearer. It has been suggested that GRBs are produced by highly therein). Possible evidence for a SN1998bw-like contribution to a GRB afterglow (Dar 1999a; Castro-Tirado & Gorosabel 1999) was first found by Bloom et al. (1999a) for GRB 980326, but its unknown redshift prevented a definite conclusion. The AG of GRB 970228 (located at redshift z = 0.695) appears to be overtaken by a light curve akin to that of SN1998bw (located at z bw = 0.0085), when properly scaled by their differing red-Unlike supernovae of type Ia (SNe Ia), core-collapse supernovae (SNe II/Ib/Ic) are far from being standard candles. But if their explosions are fairly asymmetric —as they would be if a fair fraction of them emit two opposite jets of cannonballs— much of the variability could be a reflection of the varying angles from which we see their non-spherically 2 S. Dado, A. Dar & A. De Rújula: The afterglow of GRB 011121 expanding shells. Exploiting this possibility to its extreme, i.e., using SN1998bw as an ansatz standard candle, Dar and De Rújula (2000), Dado et al. (2001a) and De Rújula (2002) have shown that the optical AG of all relatively nearby GRBs with known redshift (all the ones with z < 1.12) contain evidence or clear hints for a SN1998bw-like contribution to their optical AG, suggesting that most —and perhaps all— of the long duration GRBs are associated with 1998bw-like supernovae (in the more distant GRBs, the ansatz standard candle could not be seen, and it was not seen). However, in several of the above cases, lack of spectral information and multicolour photometry and the uncertain extinction in the host galaxy prevented a firm conclusion. Thus, every new instance is still interesting, it will take a few more clear cases to reach a generally accepted conclusion. localized by …