The emergence of a lanthanide-rich kilonova following the merger of two neutron stars

Tanvir, N. R., Levan, A. J., González-Fernández, C., Korobkin, O., Mandel, I., Rosswog, S., Hjorth, J., D?Avanzo, P., Fruchter, A. S., Fryer, C. L., Kangas, T., Milvang-Jensen, B., Rosetti, S., Steeghs, D., Wollaeger, R. T., Cano, Z., Copperwheat, C. M., Covino, S., D?Elia, V., de Ugarte Postigo, A., Evans, P. A., Even, W. P., Fairhurst, Stephen ORCID: https://orcid.org/0000-0001-8480-1961, Jaimes, R. Figuera, Fontes, C. J., Fujii, Y. I., Fynbo, J. P. U., Gompertz, B. P., Greiner, J., Hodosan, G., Irwin, M. J., Jakobsson, P., Jørgensen, U. G., Kann, D. A., Lyman, J. D., Malesani, D., McMahon, R. G., Melandri, A., O?Brien, P. T., Osborne, J. P., Palazzi, E., Perley, D. A., Pian, E., Piranomonte, S., Rabus, M., Rol, E., Rowlinson, A., Schulze, S., Sutton, Patrick ORCID: https://orcid.org/0000-0003-1614-3922, Thöne, C. C., Ulaczyk, K., Watson, D., Wiersema, K. and Wijers, R. A. M. J. 2017. The emergence of a lanthanide-rich kilonova following the merger of two neutron stars. The Astrophysical Journal 848 (2) , L27. 10.3847/2041-8213/aa90b6

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Abstract

We report the discovery and monitoring of the near-infrared counterpart (AT2017gfo) of a binary neutron-star merger event detected as a gravitational wave source by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo (GW170817) and as a short gamma-ray burst by Fermi Gamma-ray Burst Monitor (GBM) and Integral SPI-ACS (GRB 170817A). The evolution of the transient light is consistent with predictions for the behavior of a "kilonova/macronova" powered by the radioactive decay of massive neutron-rich nuclides created via r-process nucleosynthesis in the neutron-star ejecta. In particular, evidence for this scenario is found from broad features seen in Hubble Space Telescope infrared spectroscopy, similar to those predicted for lanthanide-dominated ejecta, and the much slower evolution in the near-infrared ${K}_{{\rm{s}}}$-band compared to the optical. This indicates that the late-time light is dominated by high-opacity lanthanide-rich ejecta, suggesting nucleosynthesis to the third r-process peak (atomic masses $A\approx 195$). This discovery confirms that neutron-star mergers produce kilo-/macronovae and that they are at least a major—if not the dominant—site of rapid neutron capture nucleosynthesis in the universe.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Publisher:	IOP
ISSN:	20418213
Date of First Compliant Deposit:	2 November 2017
Date of Acceptance:	29 September 2017
Last Modified:	03 May 2023 16:53
URI:	https://orca.cardiff.ac.uk/id/eprint/106133

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