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Superluminal motion of a relativistic jet in the neutron star merger GW170817

Mooley, K. P. and Deller, A. T. and Gottlieb, O and Nakar, E. and Hallinan, G. and Bourke, S. and Frail, D. A. and Horesh, A. and Corsi, A. and Hotokezaka, K. (2018) Superluminal motion of a relativistic jet in the neutron star merger GW170817. Nature, 561 (7723). pp. 355-359. ISSN 0028-0836.

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[img] Image (JPEG) (Extended Data Table 1 Log of VLBI (HSA) observations) - Supplemental Material
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[img] Image (JPEG) (Extended Data Table 2 The initial set-ups of models A–D) - Supplemental Material
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The binary neutron-star merger GW170817 was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of about 41 megaparsecs from Earth. The radio and X-ray afterglows of GW170817 exhibited delayed onset, a gradual increase in the emission with time (proportional to t^(0.8)) to a peak about 150 days after the merger event, followed by a relatively rapid decline9. So far, various models have been proposed to explain the afterglow emission, including a choked-jet cocoon and a successful-jet cocoon (also called a structured jet). However, the observational data have remained inconclusive as to whether GW170817 launched a successful relativistic jet. Here we report radio observations using very long-baseline interferometry. We find that the compact radio source associated with GW170817 exhibits superluminal apparent motion between 75 days and 230 days after the merger event. This measurement breaks the degeneracy between the choked- and successful-jet cocoon models and indicates that, although the early-time radio emission was powered by a wide-angle outflow (a cocoon), the late-time emission was most probably dominated by an energetic and narrowly collimated jet (with an opening angle of less than five degrees) and observed from a viewing angle of about 20 degrees. The imaging of a collimated relativistic outflow emerging from GW170817 adds substantial weight to the evidence linking binary neutron-star mergers and short γ-ray bursts.

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access Paper Correction ReadCube access - Author Correction
Mooley, K. P.0000-0002-2557-5180
Deller, A. T.0000-0001-9434-3837
Gottlieb, O0000-0003-3115-2456
Nakar, E.0000-0002-4534-7089
Hallinan, G.0000-0002-7083-4049
Horesh, A.0000-0002-5936-1156
Corsi, A.0000-0001-8104-3536
Hotokezaka, K.0000-0002-2502-3730
Additional Information:© 2018 Springer Nature Limited. Received 19 June 2018; Accepted 07 August 2018; Published 05 September 2018. We are grateful to the VLBA, VLA and GBT staff, especially M. Claussen, A. Mioduszewski, T. Minter, F. Ghigo, W. Brisken, K. O’Neill and M. McKinnon, for their support with the HSA observations. We thank V. Dhawan and P. Demorest for help with observational issues with the VLBI system at the VLA. K.P.M. thanks A. Mioduszewski, E. Momjian, E. Greisen, T. Pearson and S. Kulkarni for discussions. We thank M. Kasliwal for providing comments on the manuscript. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities. K.P.M. is currently a Jansky Fellow of the National Radio Astronomy Observatory. K.P.M. acknowledges support from the Oxford Centre for Astrophysical Surveys, which is funded through the Hintze Family Charitable Foundation, for some initial work presented here. E.N. acknowledges the support of an ERC starting grant (GRB/SN) and an ISF grant (1277/13). A.T.D. is the recipient of an Australian Research Council Future Fellowship (FT150100415). G.H. acknowledges the support of NSF award AST-1654815. A.H. acknowledges support by the I-Core Program of the Planning and Budgeting Committee and the Israel Science Foundation. A.C. acknowledges support from the NSF CAREER award number 1455090 titled ‘CAREER: Radio and gravitational-wave emission from the largest explosions since the Big Bang’. Author contributions: K.P.M., A.T.D., S.B., G.H. and D.A.F. coordinated the VLBI observations. A.T.D. and K.P.M. performed the VLBI data processing. O.G. and E.N. carried out the theoretical study, including analytic calculations and numerical simulations, with some input from K.H. K.P.M., A.T.D., E.N., G.H. and D.A.F. wrote the paper. A.C. and A.H. compiled the references. A.H., A.D. and K.P.M. compiled Methods. O.G., A.T.D., A.H. and K.P.M. prepared the figures. All co-authors discussed the results and provided comments on the manuscript. The authors declare no competing interests. Code availability: The hydrodynamic simulations were done using the publicly available code PLUTO. Radio data processing software used were AIPS, DIFMAP and CASA. Data availability: All relevant (VLBI) data are available from the corresponding authors on request. The VLA data (presented in Fig. 2) are currently being readied for public release.
Errata:In Extended Data Fig. 1 of this Letter, panel a should have been marked b and vice versa. This error has been corrected online.
Funding AgencyGrant Number
National Radio Astronomy ObservatoryUNSPECIFIED
Hintze Family Charitable FoundationUNSPECIFIED
European Research Council (ERC)UNSPECIFIED
Israel Science Foundation1277/13
Australian Research CouncilFT150100415
I-CORE Program of the Planning and Budgeting CommitteeUNSPECIFIED
Subject Keywords:General relativity and gravity; High-energy astrophysics; Time-domain astronomy; Transient astrophysical phenomena
Issue or Number:7723
Record Number:CaltechAUTHORS:20180730-094902750
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88349
Deposited By: George Porter
Deposited On:31 Jul 2018 18:00
Last Modified:23 Dec 2019 16:18

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