Continued Radio Observations of GW170817 3.5 yr Post-merger

We present new radio observations of the binary neutron star merger GW170817 carried out with Karl G. Jansky Very large Array (VLA) more than 3\,yrs after merger. Our combined dataset is derived by co-adding $\approx32$\,hours VLA time on-source, and as such provides deepest observation (rms sensitivity $\approx 0.99\,\mu$Jy) field obtained to date at 3\,GHz. find no evidence for a late-time re-brightening mean epoch $t\approx 1200$\,d since merger, in contrast 2.1\,\sigma$ excess observed X-ray wavelengths same epoch. measurements agree expectations from post-peak decay afterglow structured jet. Using these results, we constrain parameter space models that predict possibly arising high-velocity tail kilonova ejecta, which would dominate emission years (once jet fades below detection level). results point steep energy-speed distribution ejecta (with energy-velocity power law index $\alpha \gtrsim 5$). suggest possible implications our analysis, when recent tentative X-rays, highlight need continued radio-to-X-ray monitoring test different scenarios.