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Low-frequency View of GW170817/GRB 170817A with the Giant Metrewave Radio Telescope

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posted on 2019-06-25, 10:56 authored by L Resmi, S Schulze, CH Ishwara-Chandra, K Misra, J Buchner, M De Pasquale, R Sanchez-Ramirez, S Klose, S Kim, NR Tanvir, PT O'Brien
The short gamma-ray burst (GRB) 170817A was the first GRB associated with a gravitational-wave event. Due to the exceptionally low luminosity of the prompt γ-ray and the afterglow emission, the origin of both radiation components is highly debated. The most discussed models for the burst and the afterglow include a regular GRB jet seen off-axis and the emission from the cocoon encompassing a “choked” jet. Here, we report low radio frequency observations at 610 and 1390 MHz obtained with the Giant Metrewave Radio Telescope. Our observations span a range of ∼7 to ∼152 days after the burst. The afterglow started to emerge at these low frequencies about 60 days after the burst. The 1390 MHz light curve barely evolved between 60 and 150 days, but its evolution is also marginally consistent with an Fν ∝ t 0.8 rise seen in higher frequencies. We model the radio data and archival X-ray, optical, and high-frequency radio data with models of top-hat and Gaussian structured GRB jets. We performed a Markov Chain Monte Carlo analysis of the structured-jet parameter space. Though highly degenerate, useful bounds on the posterior probability distributions can be obtained. Our bounds of the viewing angle are consistent with that inferred from the gravitational-wave signal. We estimate the energy budget in prompt emission to be an order of magnitude lower than that in the afterglow blast wave.


We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. We thank Avishay Gal-Yam and Doron Kushnir for using the high-performance computing (HPC) facility WEXAC at the Weizmann Institute of Science. The Weizmann HPC facility is partly supported by the Israel Atomic Energy Commission—The Council for Higher Education—Pazi Foundation and partly by a research grant from The Abramson Family Center for Young Scientists. Development of the BOXFIT code was supported in part by NASA through grant NNX10AF62G issued through the Astrophysics Theory Program and by the NSF through grant AST-1009863. Simulations for BOXFIT version 2 have been carried out in part on the computing facilities of the Computational Center for Particle and Astrophysics (C2PAP) of the research cooperation "Excellence Cluster universe" in Garching, Germany. This work made use of the IAA-CSIC high-performance (HPC) and throughput (HTC) computing infrastructure. R.L. acknowledges support from the grant EMR/2016/007127 from Department of Science and Technology, India. R.L. thanks M. Govindankutty (IIST, Trivandrum) for generously providing computing facilities and ICTS, Bangalore for hospitality and computing facilities. J.B. acknowledges support from the CONICYT-Chile grant Basal-CATAPFB-06/2007 and FONDECYT Postdoctorados 3160439. R.S.-R. acknowledges support from ASI (Italian Space Agency) through the contract No. 2015-046-R.0 and from European Union Horizon 2020 Programme under the AHEAD project (grant agreement No. 654215). S.S. acknowledges support from the Feinberg Graduate School. R.S.-R. is grateful for the excellent support and advice from Rafael Parra (Computing Center, IAA-CSIC).



Astrophysical Journal, 2018, 867 (1)

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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American Astronomical Society, IOP Publishing





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