http://arxiv.org/abs/1806.09693
GW170817 is the first binary neutron star merger detected in both gravitational and electromagnetic waves. To date, various models have been proposed to explain the radio and X-ray afterglows, but the data have remained inconclusive as to whether GW170817 launched a successful relativistic jet. Here we show, through Very Long Baseline Interferometry (VLBI), that the radio source associated with GW170817 is unresolved and exhibits superluminal motion between two epochs at 75 and 230 days post-merger. This measurement breaks the degeneracy between the models and indicates that, while the early-time radio emission was powered by a wider-angle outflow (cocoon), the late-time emission was most likely dominated by an energetic and narrowly-collimated jet, with opening angle <5 degrees, and observed from a viewing angle of 20+/-5 degrees. The VLBI imaging of a collimated relativistic outflow emerging from GW170817 adds substantial weight to the growing evidence linking neutron star mergers and short gamma-ray bursts.
K. Mooley, A. Deller, O. Gottlieb, et. al.
Wed, 27 Jun 18
16/54
Comments: 43 pages, 4 figures (main text), 2 figures (supplementary text), 2 tables
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