2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/2673The optical light curve of the afterglow following the gamma-ray burst GRB990712 is re-examined. Recently published polarization measurements of that source require a collimated outflow geometry that in turn predicts a break in the light curve. We show that the V-band light curve is consistent with such a break and that the post-break light curve evolution is dominated by a supernova contribution.4 pages, 1 figure, accepted for publication in ApJLAstrophysicstext