The Late-time Radio Behavior of Gamma-ray Burst Afterglows: Testing the Standard Model

Abstract We examine a sample of 21 gamma-ray burst (GRB) afterglow light curves at radio frequencies and compare them to the X-ray and/or optical properties afterglows predictions standard jet/fireball model. Our includes every Swift GRB with an curve indicating jet break published curve, as well several other targets observed or and/optical breaks. late-time decline each attempt fit analytical model based on equations data set. show that most events in our are incompatible light-curve behavior predicted by conventional theory. Many exhibit post-break afterglow. Only one this sample, any time, shows eventually expected ∼ t −2 , although two others it their millimeter curve. Several remain consistent if such began after observations. The alone does not, however, indicate whether can be modeling code. Indeed, well-fit GRBs may only appear so due lack multiwavelength data. While second source emission account for some anomalous behavior, tests is often not case unless main component simultaneously suppressed.