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# The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars

Title: The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars
Author:

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Date: 2017-10-16
Language: English
Scope: L27
University/Institute: Háskóli Íslands
University of Iceland
School: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Department: Raunvísindastofnun (HÍ)
Science Institute (UI)
Series: The Astrophysical Journal Letters;848(2)
ISSN: 2041-8205
2041-8213 (eISSN)
DOI: 10.3847/2041-8213/aa90b6
Subject: Gravitational waves; Nuclear reactions; Nucleosynthesis, abundances; Stars: neutron; Hubblessjónaukinn; Stjörnufræði; Stjarneðlisfræði
URI: https://hdl.handle.net/20.500.11815/526

### Citation:

Tanvir, N. R., Levan, A. J., González-Fernández, C., Korobkin, O., Mandel, I., Rosswog, S., . . . Wijers, R. A. M. J. (2017). The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars. The Astrophysical Journal Letters, 848(2), L27. doi:10.3847/2041-8213/aa90b6

### 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.

### Rights:

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