A Decline in the X-ray through Radio Emission from GW170817 Continues to Support an Off-Axis Structured Jet

Understand

We present new observations of the binary neutron star merger GW170817 at $\Delta t\approx 220-290$ days post-merger, at radio (Karl G.

• Jansky Very Large Array; VLA), X-ray (Chandra X-ray Observatory) and optical (Hubble Space Telescope; HST) wavelengths.
• These observations provide the first evidence for a turnover in the X-ray light curve, mirroring a decline in the radio emission at $\gtrsim5\sigma$ significance.
• The radio-to-X-ray spectral energy distribution exhibits no evolution into the declining phase.