We present Very Large Array ( VLA ) and Atacama Large Millimeter/sub-millimeter Array ALMA radio observations of GW 170817 , the first Laser Interferometer Gravitational-wave Observatory ( LIGO ) /Virgo gravitational wave ( GW ) event from a binary neutron star merger and the first GW event with an electromagnetic ( EM ) counterpart .
Our data include the first observations following the discovery of the optical transient at both the centimeter ( 13.7 hours post merger ) and millimeter ( 2.41 days post merger ) bands .
We detect faint emission at 6 GHz at 19.47 and 39.23 days after the merger , but not in an earlier observation at 2.46 d. We do not detect cm/mm emission at the position of the optical counterpart at frequencies of 10-97.5 GHz at times ranging from 0.6 to 30 days post merger , ruling out an on-axis short gamma-ray burst ( SGRB ) for energies \gtrsim 10 ^ { 48 } erg .
For fiducial SGRB parameters , our limits require an observer viewer angle of \gtrsim 20 ^ { \circ } .
The radio and X-ray data can be jointly explained as the afterglow emission from an SGRB with a jet energy of \sim 10 ^ { 49 } -10 ^ { 50 } erg that exploded in a uniform density environment with n \sim 10 ^ { -4 } -10 ^ { -2 } cm ^ { -3 } , viewed at an angle of \sim 20 ^ { \circ } -40 ^ { \circ } from the jet axis .
Using the results of our light curve and spectral modeling , in conjunction with the inference of the circumbinary density , we predict the emergence of late-time radio emission from the deceleration of the kilonova ( KN ) ejecta on a timescale of \sim 5 - 10 years that will remain detectable for decades with next-generation radio facilities , making GW 170817 a compelling target for long-term radio monitoring .