We report on the first open-use based Atacama Large Millimeter/submm Array ( ALMA ) 345-GHz observation for the late afterglow phase of GRB131030A .
The ALMA observation constrained a deep limit at 17.1 d for the afterglow and host galaxy .
We also identified a faint submillimeter source ( ALMAJ2300-0522 ) near the GRB131030A position .
The deep limit at 345 GHz and multifrequency observations obtained using Swift and RATIR yielded forward shock modeling with a two-dimensional relativistic hydrodynamic jet simulation and described X-ray excess in the afterglow .
The excess was inconsistent with the synchrotron self-inverse Compton radiation from the forward shock .
The host galaxy of GRB131030A and optical counterpart of ALMAJ2300-0522 were also identified in the SUBARU image .
Based on the deep ALMA limit for the host galaxy , the 3- \sigma upper limits of IR luminosity and the star formation rate ( SFR ) is estimated as L _ { IR } < 1.11 \times 10 ^ { 11 } L \solar and SFR < 18.7 ( M \solar yr ^ { -1 } ) , respectively .
Although the separation angle from the burst location ( 3 \farcs 5 ) was rather large , ALMAJ2300-0522 may be one component of the GRB131030A host galaxy , according to previous host galaxy cases .