TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2174 SUBJECT: SNeIa AS THE POSSIBLE PROGENITORS OF SHORT-DURATION GRBs. DATE: 03/04/27 17:01:23 GMT FROM: Arnon Dar at Technion-Israel Inst. of Tech Arnon Dar (Technion and CERN) and Alvaro De Rujula (CERN) report: There is mounting evidence that LONG-DURATION GRBs are produced in core-collapse (Types Ib,Ic,II) supernova (SN) explosions, as advocated in the CannonBall (CB) model. The GRB and its afterglow are both made as highly relativistic plasmoids, or CBs, (Lorentz factors gamma ~ 1000) interact with the circumstellar wind and with the interstellar medium (ISM). The CBs are emitted, as in quasars and micro-quasars, as material accretes onto the newly-born compact object, shortly after the core-collapse. The GRB and its afterglow are observable only if the supernova is viewed at an angle of order 1/gamma (i.e. within milliradians) of the CBs' flight direction [1]. It is a natural possibility, in the CB model, that SHORT-DURATION GRBs be made --in an analogous fashion-- by CBs emitted, also in an accretion-induced process, in Type Ia SN explosions. Type Ia and core-collapse SNe may have quite different environments. Less "wind" and a higher ISM circumburst density in Type Ia SNe do, in the CB model, imply a harder and shorter GRB, as well as a much faster declining (and hard-to-detect) afterglow. The Type Ia SNe perhaps responsible for short-duration GRBs may be observable, provided one looks at the GRBs' location --EVEN IN THE ABSENCE OF AN OBSERVED GRB AFTERGLOW-- around 20 (1+z) days after the explosion, when their (peak, unextinct, bolometric) luminosity is ~ 10^{43.35} erg/s. We suggest the use of the most sensitive NIR/optical telescopes to search the error box of SHORT GRBs for associated Type Ia SNe. Should such SNe be found there, they could be used to localize the short GRBs, identify their host galaxies, measure their redshifts, and dramatically increase the detection rate of cosmological supernovae. [1] S. Dado, Arnon Dar and A. De Rujula, astro-ph/0304106 and references therein.