Physics

Galaxy

Jet (fluid)

Optics

Astronomy

Stars

Light curve

Circumbinary planet

Neutron star

Radio galaxy

Hubble space telescope

Astrophysics

Jansky

Spectral energy distribution

Wavelength

Thermodynamics

The Astrophysical Journal Letters

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. Our full multi-wavelength dataset is consistent with the predicted behavior of our previously published models of a successful structured jet expanding into a low-density circumbinary medium, but pure cocoon models with a choked jet cannot be ruled out. If future observations continue to track our predictions, we expect that the radio and X-ray emission will remain detectable until $\sim 1000$ days post-merger.

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