Closing in on a Short-Hard Burst Progenitor Constraints from Early-Time Optical Imaging and(21)

Theaboveargumentssuggestthattheenergyintheout owejectedbyGRB050509bwas～Eγ,iso≈10erg,ifitwasspherical.Ontheotherhand,ifitwascollimatedintoanarrowjetofhalf-openingangle

2θ0,thenthetrueenergywouldbesmallerbyafactoroffb=(1 cosθ0)≈θ0/2.Sinceasigni canto -axis

viewingangleisnotlikely,thetrueenergyprobablydoesnotexceedEγ,iso.AhigherredshiftwouldincreaseEγ,isoandwithittheestimatefortheenergyreleaseinthisevent;however,itwouldstillremainsigni cantly48.5