A Gamma-Ray Burst Remnant in Our Galaxy: HESS J1303-631

We present the results of our investigation of the multiwavelength data onHESS J1303-631, an unidentified TeV source serendipitously discovered in theGalactic plane by the HESS collaboration. These results strongly suggest theidentification of this particular source as the remnant of a Gamma-Ray Burst(GRB) that happened some few tens of thousands years ago in our Galaxy at adistance on the order of 10 kpc from us. We show, through detailed calculationsof particle diffusion, interaction and radiation processes of relativisticparticles in the interstellar medium, that it is possible for a GRB remnant(GRBR) to be a strong TeV emitter with no observable synchrotron emission. Wepredict spectral and spatial signatures that would unambiguously distinguishGRBRs from ordinary supernova remnants, including: (1) large energy budgetsinferred from their TeV emission, but at the same time, (2) suppressed fluxesin the radio through GeV wavebands; (3) extended center-filled emission with anenergy-dependent spatial profile; and (4) a possible elongation in thedirection of the past pair of GRB jets. While GRBRs can best be detected byground-based gamma-ray detectors, the future GLAST mission will play a crucialrole in confirming the predicted low level of GeV emission.Comment: Replaced by the version accepted in ApJ Letters (to appear in April/May 2006); 4 pages, 3 figure