Tellurium emission line in kilonova AT 2017gfo

Kenta Hotokezaka; Masaomi Tanaka; Daiji Kato; Gediminas Gaigalas

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arXiv · 2307.00988

Tellurium emission line in kilonova AT 2017gfo

Kenta Hotokezaka·Masaomi Tanaka·Daiji Kato·Gediminas Gaigalas

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Abstract

The late-time spectra of the kilonova AT 2017gfo associated with GW170817 exhibit a strong emission line feature at $2.1\,{\rm \mu m}$. The line structure develops with time and there is no apparent blue-shifted absorption feature in the spectra, suggesting that this emission line feature is produced by electron collision excitation. We attribute the emission line to a fine structure line of Tellurium (Te) III, which is one of the most abundant elements in the second r-process peak. By using a synthetic spectral modeling including fine structure emission lines with the solar r-process abundance pattern beyond the first r-process peak, i.e., atomic mass numbers $A\gtrsim 88$, we demonstrate that [Te III] $2.10\,\rm \mu m$ is indeed expected to be the strongest emission line in the near infrared region. We estimate that the required mass of Te III is $\sim 10^{-3}M_{\odot}$, corresponding to the merger ejecta of $0.05M_{\odot}$, which is in agreement with the mass estimated from the kilonova light curve.

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Kenta Hotokezaka, Masaomi Tanaka, Daiji Kato, Gediminas Gaigalas. 2023-07-03. Tellurium emission line in kilonova AT 2017gfo. https://arxiv.org/abs/2307.00988

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