2021/03/31 by Arvind Balasubramanian, Alessandra Corsi, Kunal P. Mooley +6 · 49 citations
Physics and Astronomy · #Afterglow #Astrophysics and Cosmic Phenomena #Ejecta #Gamma-ray bursts and supernovae #Jansky #Kilonova #LOFAR #Neutron star #Pulsars and Gravitational Waves Research #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/abfd38
published in The Astrophysical Journal Letters 914(1), L20 (IOP Publishing) · 6 pages, 2 figures. Version published in ApJL (includes minor updates to figures, data and refs)
openalex created_date 2021/03/15 · openalex publication_date 2021/06/01 · arxiv created 2021/06/18 · arxiv updated 2021/06/22 · openalex updated_date 2026/08/05
Abstract We present new radio observations of the binary neutron star merger GW170817 carried out with the Karl G. Jansky Very large Array (VLA) more than 3 yr after the merger. Our combined data set is derived by coadding more than ≈32 hr of VLA time on-source, and as such provides the deepest combined observation (rms sensitivity ≈0.99 μ Jy) of the GW170817 field obtained to date at 3 GHz. We find no evidence for a late-time radio rebrightening at a mean epoch of t ≈ 1200 days since merger, in contrast to a ≈2.1 σ excess observed at X-ray wavelengths at the same mean epoch. Our measurements agree with expectations from the post-peak decay of the radio afterglow of the GW170817 structured jet. Using these results, we constrain the parameter space of models that predict a late-time radio rebrightening possibly arising from the high-velocity tail of the GW170817 kilonova ejecta, which would dominate the radio and X-ray emission years after the merger (once the structured jet afterglow fades below detection level). Our results point to a steep energy-speed distribution of the kilonova ejecta (with energy-velocity power-law index α ≳ 5). We suggest possible implications of our radio analysis, when combined with the recent tentative evidence for a late-time rebrightening in the X-rays, and highlight the need for continued radio-to-X-ray monitoring to test different scenarios.