Lanthanide Features in Near-infrared Spectra of Kilonovae

Understand

The observations of GW170817/AT2017gfo have provided us with evidence that binary neutron star mergers are sites of $r$-process nucleosynthesis.

• However, the observed signatures in the spectra of GW170817/AT2017gfo have not been fully decoded especially in the near-infrared (NIR) wavelengths.
• In this paper, we investigate the kilonova spectra over the entire wavelength range with the aim of elemental identification.
• We systematically calculate the strength of bound-bound transitions by constructing a hybrid line list that is accurate for important strong transitions and complete for weak transitions.