Abstract
For decades, gamma-ray bursts (GRBs) have been broadly divided into long- and short-duration bursts, lasting more or less than 2 s, respectively. However, this dichotomy does not perfectly map to the two progenitor channels that are known to produce GRBs: mergers of compact objects (merger GRBs) or the collapse of massive stars (collapsar GRBs). In particular, the merger GRB population may also include bursts with a short, hard <2 s spike and subsequent longer, softer extended emission. The recent discovery of a kilonova—the radioactive glow of heavy elements made in neutron star mergers—in the 50-s-duration GRB 211211A further demonstrates that mergers can drive long, complex GRBs that mimic the collapsar population. Here we present a detailed temporal and spectral analysis of the high-energy emission of GRB 211211A. We demonstrate that the emission has a purely synchrotron origin, with both the peak and cooling frequencies moving through the γ-ray band down to X-rays, and that the rapidly evolving spectrum drives the extended emission signature at late times. The identification of such spectral evolution in a merger GRB opens avenues to diagnostics of the progenitor type.
| Original language | English |
|---|---|
| Pages (from-to) | 67-79 |
| Number of pages | 13 |
| Journal | Nature Astronomy |
| Volume | 7 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2023 |
Bibliographical note
Publisher Copyright:© 2022, The Author(s), under exclusive licence to Springer Nature Limited.
Funding
We thank A. Goldstein for his insights into fitting GBM data, S. Barthelmy, D. Palmer, A. Lien and D. Tak for discussions on the performance of BAT and G. Ghisellini for fruitful discussions on emission physics. The work makes use of data supplied by the UK Swift Science Data Centre at the University of Leicester and the Neil Gehrels Swift Observatory. This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center Online Service provided by the NASA/Goddard Space Flight Center, and specifically this work has made use of public Fermi-GBM data. B.P.G. and M.N. are supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 948381, to M.N.). M.N. acknowledges a Turing Fellowship. A.J.L. and D.B.M. are supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 725246, to A.J.L.). The Cosmic Dawn Center is funded by the Danish National Research Foundation under grant no. 140. B.D.M. is supported in part by the National Science Foundation (grant nos AST-2009255 and AST-2002577). The Flatiron Institute is supported by the Simons Foundation. G.P.L. is supported by the UK Science Technology and Facilities Council under grant no. ST/S000453/1. The Fong Group at Northwestern acknowledges support by the National Science Foundation under grant nos AST-1814782, AST-1909358 and CAREER grant no. AST-2047919. W.F. gratefully acknowledges support from the David and Lucile Packard Foundation. P.A.E. and K.L.P. acknowledge funding from the UK Space Agency. We thank A. Goldstein for his insights into fitting GBM data, S. Barthelmy, D. Palmer, A. Lien and D. Tak for discussions on the performance of BAT and G. Ghisellini for fruitful discussions on emission physics. The work makes use of data supplied by the UK Swift Science Data Centre at the University of Leicester and the Neil Gehrels Swift Observatory. This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center Online Service provided by the NASA/Goddard Space Flight Center, and specifically this work has made use of public Fermi-GBM data. B.P.G. and M.N. are supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 948381, to M.N.). M.N. acknowledges a Turing Fellowship. A.J.L. and D.B.M. are supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 725246, to A.J.L.). The Cosmic Dawn Center is funded by the Danish National Research Foundation under grant no. 140. B.D.M. is supported in part by the National Science Foundation (grant nos AST-2009255 and AST-2002577). The Flatiron Institute is supported by the Simons Foundation. G.P.L. is supported by the UK Science Technology and Facilities Council under grant no. ST/S000453/1. The Fong Group at Northwestern acknowledges support by the National Science Foundation under grant nos AST-1814782, AST-1909358 and CAREER grant no. AST-2047919. W.F. gratefully acknowledges support from the David and Lucile Packard Foundation. P.A.E. and K.L.P. acknowledge funding from the UK Space Agency.
| Funders | Funder number |
|---|---|
| Flatiron Institute | |
| National Science Foundation | AST-2009255, AST-2002577 |
| David and Lucile Packard Foundation | |
| National Aeronautics and Space Administration | |
| Simons Foundation | |
| Goddard Space Flight Center | |
| Horizon 2020 Framework Programme | 948381, 725246 |
| UK Space Agency | |
| Science and Technology Facilities Council | AST-2047919, AST-1909358, ST/S000453/1, AST-1814782 |
| University of Leicester | |
| European Commission | |
| Danmarks Grundforskningsfond | 140 |