[vsnet-grb-info 23482] GRB 190829A: Follow up VLA and VLBI radio observations urged

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25581
SUBJECT: GRB 190829A: Follow up VLA and VLBI radio observations urged
DATE:    19/08/30 20:21:02 GMT
FROM:    Arnon Dar at Technion-Israel Inst. of Tech  <arnon at physics.technion.ac.il>

S. Dado and A. Dar report,

The long duration, low luminosity GRB190829A [1] at redshift z=0.0785 [2] 
with Ep=130 +/- 20 keV and Eiso~1.8E50 erg, most probably, is an ordinary 
narrowly beamed GRB being viewed from far off-axis -it satisfies well the 
correlation (1+z)Ep propto (Eiso)^{1/3}, predicted [3] by the cannonball 
model of GRBs, as can be seen from figure 3 of [4].  Like in SHB 170817A
[5], VLA and VLBI follow up observations of the radio afterglow of
GRB190829A may resolve its compact superluminal source and measure its 
apparent superluminal velocity, Vapp ~ 2c/theta, from which  its far 
off-axis viewing angle theta  can be determined [6]. We urge such follow 
up VLA and VLBI radio observations of its afterglow.

[1] S. Lesage et al.,  GCN 25575.
[2] A. F. Valeev et al., GCN  25565.
[3] A. Dar & A. De R'ujula, arXiv:astro-ph/0012227 (Eq. 40).
[4] S. Dado & A. Dar, arxiv:1908.05116.
[5] K. P. Mooley, et al., Nature, 561, 355 (2018) [arXiv:1806.09693].
[6] A. Dar & A. De R'ujula, arXiv:astro-ph/0008474.