TITLE: GCN CIRCULAR NUMBER: 22211 SUBJECT: LIGO/Virgo GW170817: X-ray observations confirm prediction made from radio data DATE: 17/12/08 21:30:16 GMT FROM: Kunal Mooley at Oxford U K. P. Mooley (Oxford, NRAO/Caltech) et al. report The X-ray flux of GW170817 on December 03-06 (reported by Troja et al. 2017, GCN 22201; Margutti et al. 2017, GCN 22203, Haggard et al. 2017, GCN 22206 based on the Chandra observations) is exactly as predicted last week by Mooley et al. 2017 (http://arxiv.org/abs/1711.11573) based on radio spectral indices. This suggests that the radio and X-ray emission both arise from a mildly relativistic wide-angle outflow, consistent with the cocoon model (see also Gottlieb et al. 2017, Hallinan et al. 2017, Kasliwal et al. 2017). A relativistic jet core, if it exists, is either too weak (having a sub-dominant contribution to the radio light curve early on) or too strong (such that its electromagnetic signatures will be observed in the future). See Mooley et al. 2017 for details.