Hayes, F. , Heng, I. S. , Lamb, G., Lin, E.-T., Veitch, J. and Williams, M. J. (2023) Unpacking merger jets: a Bayesian analysis of GW170817, GW190425 and electromagnetic observations of short gamma-ray bursts. Astrophysical Journal, 954(1), 92. (doi: 10.3847/1538-4357/ace899)
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Abstract
We present a novel fully Bayesian analysis to constrain short gamma-ray burst (sGRB) jet structures associated with cocoon, wide-angle, and simple top-hat jet models, as well as the binary neutron star (BNS) merger rate. These constraints are made given the distance and inclination information from GW170817, observed flux of GRB 170817A, observed rate of sGRBs detected by Swift, and the neutron star merger rate inferred from LIGO's first and second observing runs. A separate analysis is conducted where a fitted sGRB luminosity function is included to provide further constraints. The jet structure models are further constrained using the observation of GW190425, and we find that the assumption that it produced a GRB 170817–like sGRB which went undetected due to the jet geometry is consistent with previous observations. We find and quantify evidence for low-luminosity and wide-angle jet structuring in the sGRB population, independently from afterglow observations, with log Bayes factors of 0.45–0.55 for such models when compared to a classical top-hat jet. Slight evidence is found for a Gaussian jet structure model over all others when the fitted luminosity function is provided, producing log Bayes factors of 0.25–0.9 ± 0.05 when compared to the other models. However, without considering GW190425 or the fitted luminosity function, the evidence favors a cocoon-like model with log Bayes factors of 0.14 ± 0.05 over the Gaussian jet structure. We provide new constraints to the BNS merger rates of 1–1300 Gpc⁻³ yr⁻¹ or 2–680 Gpc⁻³ yr⁻¹ when a fitted luminosity function is assumed.
| Item Type: | Articles |
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| Additional Information: | We are grateful for computational resources provided by Cardiff University, and funded by an STFC (grant No. ST/I006285/1) supporting UK Involvement in the Operation of Advanced LIGO. The authors thank Shiho Kobayashi for fruitful discussions. F.H. was supported by Science and Technology Research Council (STFC) (grant No. ST/N504075/1). J.V., I.S.H. and M.J.W. are supported by STFC (grant No. ST/V005634/1). M.J.W. was also supported by STFC (grant No. 2285031). G.P.L. is supported by a Royal Society Dorothy Hodgkin Fellowship (grant Nos. DHF-R1-221175 and DHFERE-221005). E.T.L is supported by National Science and Technology Council (NSTC) of Taiwan (grant No. 111-2112-M-007-020). |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Heng, Professor Ik Siong and Hayes, Dr Fergus and Williams, Mr Michael and Veitch, Dr John |
| Authors: | Hayes, F., Heng, I. S., Lamb, G., Lin, E.-T., Veitch, J., and Williams, M. J. |
| College/School: | College of Science and Engineering > School of Physics and Astronomy |
| Research Centre: | College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research |
| Journal Name: | Astrophysical Journal |
| Publisher: | IOP Publishing |
| ISSN: | 0004-637X |
| ISSN (Online): | 1538-4357 |
| Copyright Holders: | Copyright © 2023 The Authors |
| First Published: | First published in Astrophysical Journal 954(1):92 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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