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

The localization of the short-duration, hard-spectrum GRB 050509b was a watershed event. Thanks to the nearly immediate relay of the GRB position by Swift, we began imaging the GRB field 8 minutes after the burst and continued for the following 8 days. No

ClosinginonaShort-HardBurstProgenitor:ConstraintsfromEarly-TimeOpticalImagingandSpectroscopyofaPossibleHostGalaxyofGRB050509bJ.S.Bloom1,J.X.Prochaska2,D.Pooley1,3,C.H.Blake4,R.J.Foley1,S.Jha1,E.Ramirez-Ruiz5,2,3,J.Granot6,5,A.V.Filippenko1,S.Sigurdsson7,A.J.Barth8,H.-W.Chen9,M.C.Cooper1,E.E.Falco4,R.R.Gal10,B.F.Gerke11,M.D.Gladders12,J.E.Greene4,J.Hennanwi1,13,L.C.Ho12,K.Hurley14,B.P.Koester15,W.Li1,L.Lubin10,J.Newman16,13,D.A.Perley1,G.K.Squires17,andW.M.Wood-Vasey4

arXiv:astro-ph/0505480v2 5 Sep 200512DepartmentofAstronomy,601CampbellHall,UniversityofCalifornia,Berkeley,CA94720-3411.UniversityofCaliforniaObservatories/LickObservatory,UniversityofCalifornia,SantaCruz,CA95064.34ChandraFellow.Harvard-SmithsonianCenterforAstrophysics,60GardenStreet,Cambridge,MA02138.56InstituteforAdvancedStudy,OldenLane,Princeton,NJ08540.KIPAC,StanfordUniversity,P.O.Box20450,MailStop29,Stanford,CA94309.7DepartmentofAstronomy&Astrophysics,525DaveyLaboratory,PennsylvaniaStateUniversity,UniversityPark,PA16802.8DepartmentofPhysics&Astronomy,4129FrederickReinesHall,UniversityofCalifornia,Irvine,CA92697-4575.9CenterforSpaceResearch,MassachusettsInstituteofTechnology,Cambridge,MA02139-430710DepartmentofPhysics,OneShieldsAve.,UniversityofCalifornia,Davis,CA95616-8677.11DepartmentofPhysics,366LeConteHall,UniversityofCalifornia,Berkeley,CA94720-7300.12CarnegieObservatories,813SantaBarbaraStreet,Pasadena,CA91101.13HubbleFellow.14UCBerkeley,SpaceSciencesLaboratory,7GaussWay,Berkeley,CA94720-7450.

15DepartmentofPhysics,UniversityofMichigan,AnnArbor,MI48109-1090.

16InstituteforNuclearandParticleAstrophysics,LawrenceBerkeleyNationalLaboratory,Berkeley,CA

94720.

17SpitzerScienceCenter,CaliforniaInstituteofTechnology314-6,Pasadena,CA91125.

ABSTRACT

Thelocalizationoftheshort-duration,hard-spectrumgamma-rayburstGRB050509bbythe

Swiftsatellitewasawatershedevent.NeverbeforehadamemberofthismysterioussubclassofclassicGRBsbeenrapidlyandpreciselypositionedinaskyaccessibletothebevyofground-basedfollow-upfacilities.ThankstothenearlyimmediaterelayoftheGRBpositionbySwift,webeganimagingtheGRB eld8minutesaftertheburstandcontinuedforthefollowing8days.ThoughtheSwiftX-rayTelescope(XRT)discoveredanX-rayafterglowofGRB050509b,the rsteverof