S22B0049
S22B0049
Observations of “kilonova" from neutron star (NS) merger GW170817 provided the first evidence that the NS merger is a production site of r-process elements. Although the observed spectra of the kilonova have multipe broadly overlapped features especially in near-infrared (NIR) wavelengths, most of them are not yet decoded. We find that lines of doubly ionized Ce (Z=58), one of the lanthanide elements, are promising candidates for the absorption features in NIR wavelengths. This identification is, however, still not yet conclusive because the proposed NIR lines of Ce III have never been confirmed in any other star and their transition probabilities are not experimentally measured. To make this identification conclusive, we propose high-resolution NIR spectroscopic observations of two chemically peculiar (Ap type) stars with enhanced Ce abundances. By this observation, we identify the proposed Ce III lines in Galactic stars for the first time, and measure their transition probabilities. This enables the firm element identification in kilonova spectra, which opens a new way to directly measure the abundances of lanthanide elements produced by NS mergers.
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