A Decline in the X-Ray through Radio Emission from GW170817 Continues to Support an Off-axis Structured Jet
gravitational waves, relativistic processes
© 2018. The American Astronomical Society. All rights reserved. We present new observations of the binary neutron star merger GW170817 at Δt ≈ 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 5σ significance. The radio-to-X-ray spectral energy distribution exhibits no evolution into the declining phase. Our full multi-wavelength data set 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 ∼1000 days post-merger.
Alexander, K. D.; Margutti, R.; Blanchard, P. K.; Fong, W.; Berger, E.; Hajela, A.; Eftekhari, T.; Chornock, R.; Cowperthwaite, P. S.; Giannios, D.; Guidorzi, C.; Kathirgamaraju, A.; Macfadyen, A.; Metzger, B. D.; Nicholl, M.; Sironi, L.; Villar, V. A.; Williams, P. K.G.; Xie, X.; and Zrake, J., "A Decline in the X-Ray through Radio Emission from GW170817 Continues to Support an Off-axis Structured Jet" (2018). Physics & Astronomy Open Access Publications. 83.