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The Diversity of Kilonova Emission in Short Gamma-Ray Bursts

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posted on 10.09.2019, 15:13 by BP Gompertz, AJ Levan, NR Tanvir, J Hjorth, S Covino, PA Evans, AS Fruchter, C Gonzalez-Fernandez, ZP Jin, JD Lyman, SR Oates, PT O'Brien, K Wiersema
The historic first joint detection of both gravitational-wave and electromagnetic emission from a binary neutron star merger cemented the association between short gamma-ray bursts (SGRBs) and compact object mergers, as well as providing a well-sampled multi-wavelength light curve of a radioactive kilonova (KN) for the first time. Here, we compare the optical and near-infrared light curves of this KN, AT 2017gfo, to the counterparts of a sample of nearby (z < 0.5) SGRBs to characterize their diversity in terms of their brightness distribution. Although at similar epochs AT 2017gfo appears fainter than every SGRB-associated KN claimed so far, we find three bursts (GRBs 050509B, 061201, and 080905A) where, if the reported redshifts are correct, deep upper limits rule out the presence of a KN similar to AT 2017gfo by several magnitudes. Combined with the properties of previously claimed KNe in SGRBs this suggests considerable diversity in the properties of KN drawn from compact object mergers, despite the similar physical conditions that are expected in many NS–NS mergers. We find that observer angle alone is not able to explain this diversity, which is likely a product of the merger type (NS–NS versus NS–BH) and the detailed properties of the binary (mass ratio, spins etc.). Ultimately disentangling these properties should be possible through observations of SGRBs and gravitational-wave sources, providing direct measurements of heavy element enrichment throughout the universe.


B.G., A.J.L., N.R.T., and K.W. have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 725246, TEDE; PI: Levan). A.J.L. and J.D.L. acknowledge support from STFC via grant ST/P000495/1. N.R.T. and K.W. acknowledge support from STFC via grant ST/N000757/1. J.H. was supported by a VILLUM FONDEN Investigator grant (project number 16599). S.C. acknowledges partial funding from Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica grant I/004/11/3. S.R.O. gratefully acknowledges the support of the Leverhulme Trust Early Career Fellowship. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.



The Astrophysical Journal, 2018, 860:62

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


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