We present our broadband study of GW170817 from radio to hard X-rays, including NuSTAR and Chandra observations up to 165 days after the merger, and a multi-messenger analysis including LIGO constraints. The data are compared with predictions from a wide range of models, providing the first detailed comparison between non-trivial cocoon and jet models. Homogeneous and power-law shaped jets, as well as simple cocoon models are ruled out by the data, while both a Gaussian shaped jet and a cocoon with energy injection can describe the current dataset for a reasonable range of physical parameters, consistent with the typical values derived from short GRB afterglows. We propose that these models can be unambiguously discriminated by future observations measuring the post-peak behaviour, with slope -1.0 for the cocoon and -2.5 for the jet model.
@article{arxiv.1801.06516,
title = {The outflow structure of GW170817 from late time broadband observations},
author = {E. Troja and L. Piro and G. Ryan and H. van Eerten and R. Ricci and M. H. Wieringa and S. Lotti and T. Sakamoto and S. B. Cenko},
journal= {arXiv preprint arXiv:1801.06516},
year = {2018}
}
Comments
6 pages, 4 figures, accepted by MNRAS Letters. Minor changes to match the accepted version