Kilonova from post-merger ejecta as an optical and near-Infrared counterpart of GW170817

Masaomi Tanaka, Yousuke Utsumi, Paolo A. Mazzali, Nozomu Tominaga, Michitoshi Yoshida, Yuichiro Sekiguchi, Tomoki Morokuma, Kentaro Motohara, Kouji Ohta, Koji S. Kawabata, Fumio Abe, Kentaro Aoki, Yuichiro Asakura, Stefan Baar, Sudhanshu Barway, Ian A. Bond, Mamoru Doi, Takuya Fujiyoshi, Hisanori Furusawa, Satoshi HondaYoichi Itoh, Miho Kawabata, Nobuyuki Kawai, Ji Hoon Kim, Chien Hsiu Lee, Shota Miyazaki, Kumiko Morihana, Hiroki Nagashima, Takahiro Nagayama, Tatsuya Nakaoka, Fumiaki Nakata, Ryou Ohsawa, Tomohito Ohshima, Hirofumi Okita, Tomoki Saito, Takahiro Sumi, Akito Tajitsu, Jun Takahashi, Masaki Takayama, Yoichi Tamura, Ichi Tanaka, Tsuyoshi Terai, Paul J. Tristram, Naoki Yasuda, Tetsuya Zenko

Research output: Contribution to journalArticlepeer-review

241 Citations (Scopus)


Recent detection of gravitationalwaves from a neutron star (NS)merger event GW170817 and identification of an electromagnetic counterpart provide a unique opportunity to study the physical processes in NS mergers. To derive properties of ejected material from the NS merger, we perform radiative transfer simulations of kilonova, optical and near-infrared emissions powered by radioactive decays of r-process nuclei synthesized in the merger. We find that the observed near-infrared emission lasting for >10 d is explained by 0.03M⊙ of ejecta containing lanthanide elements. However, the blue optical component observed at the initial phases requires an ejecta component with a relatively high electron fraction (Ye). We show that both optical and near-infrared emissions are simultaneously reproduced by the ejecta with a medium Ye of ~0.25. We suggest that a dominant component powering the emission is post-merger ejecta, which exhibits that the mass ejection after the first dynamical ejection is quite efficient. Our results indicate that NS mergers synthesize a wide range of r-process elements and strengthen the hypothesis that NS mergers are the origin of r-process elements in the Universe.

Original languageEnglish
Article number102
JournalPublication of the Astronomical Society of Japan
Issue number6
Publication statusPublished - 2017 Dec 1


  • Abundances
  • Gravitational waves
  • Nuclear reactions
  • Nucleosynthesis
  • Stars: neutron


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