TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2133 SUBJECT: Superluminal motion in GRB 030329 (Correction) DATE: 03/04/10 17:19:52 GMT FROM: Arnon Dar at Technion-Israel Inst. of Tech Arnon Dar (Technion) and Alvaro De Rujula (CERN) report: We use the infamous Cannonball model (CB model) of GRBs to predict the superluminal motion of the source of the radio afterglow (AG) of GRB 030329 (GCN 1985, 1997), potentially observable with the VLBA (see, e.g. GCN 2129). The CB model has been succesful in describing GRB 030329 and its AG, in predicting the supernova (SN) contribution to the AG, and even the date at which the SN was to be convincingly seen [1]. In the CB model, the cannonballs responsible for the GRB and the AG light move superluminally in the sky, as they travel away from their projenitor SN. THIS MOTION MAY BE OBSERVABLE IN THE RADIO AG, IF ITS LOCATION IS FOLLOWED AS A FUNCTION OF TIME [2]. The SN cannot be currently seen in the radio, so that it is the motion of the radio-AG source (the CB) that one may try to observe. In the case of GRB 030329 there were two CBs, one of which dominates the AG after t ~ 1 day. Using the parameters of this CB determined in [1] (initial Lorentz factor 1477, viewing angle 2 mrad, and deceleration parameter 476 kpc) and Eqs. (30, 31, 41) of [3] we obtain the angular distances "alpha" (in mas) of the dominant CB to the SN as a function of "t" (observer's time in days). For the current cosmology (Omega_Lambda=0.7, Omega_Matter=0.3, H_0=75 km/s/Mpc; and for z=0.1685, so that the angular distance is 0.64 Gpc) some representative results are: (t, alpha): (0,0); (1,0.22); (2.7,0.49); (5,0.74); (10,1.1); (30,1.9). This means that from day 2.7 to day 10 the radio source may have moved 0.6 mas, and from day 10 to day 30 it may move an extra 0.8 mas. Such motion may be observable with the VLBA. * mrad in GCN 2132 was corrected to mas [1] Dado et al. astro-ph/0304106. [2] Dar and De Rujula, astro-ph/0008474. [3] Dado et al. 2003 A&A 401, 243.