This study presents multi-wavelength observational results for energetic GRB100414A 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 _ { iso } of 34.5 ^ { +2.0 } _ { -1.8 } \times 10 ^ { 52 } 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 \alpha = -2.6 \pm 0.1 .
The joint light curve with earlier Swift /UVOT observations yields a temporal break at 2.3 \pm 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 ^ { \circ } .8 , consistent with those of other well-observed long gamma-ray bursts ( GRBs ) .
The multi-wavelength analyses in this study showed that GRB100414A follows { E ^ { src } _ { peak } - E _ { iso } } and { E ^ { src } _ { peak } - E _ { \gamma } } correlations .
The late afterglow revealed a flatter evolution with significant excesses at 27.2 days .
The most straightforward explanation for the excess is that GRB100414A was accompanied by a contemporaneous supernova .
The model light curve based on other GRB - SN events is marginally consistent with that of the observed lightcurve .