Is there a 1998 bw - like supernova in the afterglow of gamma ray burst 010921 ?

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 GRB 010921 with ground-based telescopes at early times, and with the HST at later time. We show that GRB 010921 was indeed associated with a 1998bw-like supernova at the GRB's redshift. The identity of the progenitors of gamma ray bursts is still debated. It has been suggested that GRBs are produced by highly relativistic jets (e. and De Rújula 2000 and references therein). 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 the unknown redshift prevented a quantitative analysis. 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 redshifts Dar and De Rújula (2000) and Dado et al. (2001a) have shown that the optical AG of all relatively nearby GRBs with known redshift (all the ones with z < 1.12) contain evidence or 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, but more cases are needed before a firm conclusion can be reached. references therein) have shown that the GRB is located in a relatively nearby host galaxy with redshift z = 0.451 (Djorgovski et al. 2001) and that its optical afterglow exhibits a fast temporal decline and has a large spectral slope, −2.22 ± 0.23, after correcting for extinction in our galaxy, (E(B-V)=0.148; Schlegel et al. 1998), in the direction of the GRB. Due to its relative proximity and fast temporal decline, the AG of GRB 010921 should have shown an SN1998bw-like contribution, after subtraction of its host galaxy contribution, if it was associated with a supernova akin to 1998bw, located at z = 0.451. Price et al. (2002b). From a fireball-model analysis of these observations, these authors identified a break in the optical light-curve around day 35 which they argued is due to the collimated ejecta, and concluded that the existence of a SN with a luminosity greater than 20% of SN 1998bw at z = 0.451 is ruled out. However, in this note, using the …