2012ApJ...748L...4U

This study presents multi-wavelength observational results for energetic GRB 100414A with GeV photons. The prompt spectral fitting using Suzaku/WAM data yielded spectral peak energies of E ^src_peak of 1458.7^+132.6_- 106.6_ keV and E_isoof 34.5^+2.0_- 1.8_x 10⁵² erg with z = 1.368. The optical afterglow light curves between 3 and 7 days were effectively fitted according to a simple power law with a temporal index of α = -2.6±0.1. The joint light curve with earlier Swift/UVOT observations yields a temporal break at 2.3±0.2 days. This was the first Fermi/LAT detected event that demonstrated the clear temporal break in the optical afterglow. The jet opening angle derived from this temporal break was 5°.8, consistent with those of other well-observed long gamma-ray bursts (GRBs). The multi-wavelength analyses in this study showed that GRB 100414A follows E ^src_peak-E_iso and E ^src_peak-E_γcorrelations. The late afterglow revealed a flatter evolution with significant excesses at 27.2 days. The most straightforward explanation for the excess is that GRB 100414A was accompanied by a contemporaneous supernova. The model light curve based on other GRB-SN events is marginally consistent with that of the observed light curve.