tokens: the evolution after 18.25 days but underpredicts the millimeter-band data and the observations above ≈10 GHz before 8.55 days. Figure 10. Same as Figure 8 , but now including energy injection between 0.15 and 0.26 days (Section 4.3 ), a standard RS contributing to the optical/NIR light curve before 2 × 10 −3 days and to the radio at 1.5 days (Section 5.1 ), and a refreshed RS contributing to the millimeter-band light curve (Section 5.3 ). Figure 11. Same as Figure 9 , but for the model (solid) shown in Figure 10 decomposed into FS (dashed) and RS (dotted) contributions. The two RS components are best distinguished at 1.5 days, where the lower-frequency component arises from an RS in the original shell producing the GRB, while the higher-frequency component arises from the collision of two shells at 0.15 days, which also produces the X-ray rebrightening. The red shaded regions represent the expected variability due to scintillation. To summarize, the continued high flux density of the X-ray detections after ≈1 day suggests that the X-ray excess at ≈0.26 days is not due to late-time central engine activity, but is caused by a rebrightening of the FS radiation. The multiband data are consistent with a wind-like circumburst medium, requiring a single episode of energy injection at ≈0.2 days. The resultant model fits the optical and X-ray evolution and matches the radio SED after 18 days. However, this model underpredicts the CARMA light curve, as well as the 5–83 GHz SED at 1.5 and 8.55 days. To account for these deficits, we next investigate the effect of including emission from additional components. We delineate the evidence for their presence and consider their possible physical origins. 5. Multicomponent Models 5.1. Reverse Shock In Section 3.2 , we discussed the apparent multicomponent structure of the radio SEDs between 1.5 and 18.2 days. In the previous section, we have shown that while a single FS model can reproduce the gross features of the radio light curves, such a model cannot explain the multiple peaks in the SED at 1.5 days, the ≈14 GHz peak at 4.5 days, and the SED at 8.55 days. Of these, the greatest discrepancy between data and model arises in the radio SEDs at 1.5 and 4.55 days. We now consider whether each spectral peak at 1.5 days can in turn be ascribed to radiation from an RS. An RS propagating into GRB ejecta is expected to produce synchrotron radiation with its own set of characteristic frequencies, ν a,r , , and ν c,r , and peak flux . These quantities are related to those of the FS at the deceleration time, ec , when the RS just crosses the ejecta, and the relation between the two sets of break frequencies and fluxes allows for a determination of the ejecta Lorentz factor and magnetization. After the RS crosses the ejecta, the flux above ν c,r declines rapidly, 16 16 The angular time delay effect prevents abrupt disappearance of flux above ν c,r ; instead, we expect (Kobayashi Zhang 2003 ). as no electron is
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