J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817

Yousuke Utsumi, Masaomi Tanaka, Nozomu Tominaga, Michitoshi Yoshida, Sudhanshu Barway, Takahiro Nagayama, Tetsuya Zenko, Kentaro Aoki, Takuya Fujiyoshi, Hisanori Furusawa, Koji S. Kawabata, Shintaro Koshida, Chien Hsiu Lee, Tomoki Morokuma, Kentaro Motohara, Fumiaki Nakata, Ryou Ohsawa, Kouji Ohta, Hirofumi Okita, Akito TajitsuIchi Tanaka, Tsuyoshi Terai, Naoki Yasuda, Fumio Abe, Yuichiro Asakura, Ian A. Bond, Shota Miyazaki, Takahiro Sumi, Paul J. Tristram, Satoshi Honda, Ryosuke Itoh, Yoichi Itoh, Miho Kawabata, Kumiko Morihana, Hiroki Nagashima, Tatsuya Nakaoka, Tomohito Ohshima, Jun Takahashi, Masaki Takayama, Wako Aoki, Stefan Baar, Mamoru Doi, Francois Finet, Nobuyuki Kanda, Nobuyuki Kawai, Ji Hoon Kim, Daisuke Kuroda, Wei Liu, Kazuya Matsubayashi, Katsuhiro L. Murata, Hiroshi Nagai, Tomoki Saito, Yoshihiko Saito, Shigeyuki Sako, Yuichiro Sekiguchi, Yoichi Tamura, Masayuki Tanaka, Makoto Uemura, Masaki S. Yamaguchi

Research output: Contribution to journalArticlepeer-review

121 Citations (Scopus)

Abstract

GW170817 is the first detected gravitational wave source from a neutron star merger. We present the Japanese collaboration for gravitational-wave electro-magnetic (J-GEM) follow-up observations of SSS17a, an electromagnetic counterpart of GW170817. SSS17a shows a 2.5mag decline in the z band during the period between 1.7 and 7.7 d after the merger. Such a rapid decline is not comparable with supernovae light curves at any epoch. The color of SSS17a also evolves rapidly and becomes redder during later epochs: the z - H color has changed by approximately 2.5mag during the period between 0.7 and 7.7 d. The rapid evolutions of both the color and the optical brightness are consistent with the expected properties of a kilonova that is powered by the radioactive decay of newly synthesized r-process nuclei. Kilonova models with Lanthanide elements can reproduce the aforementioned observed properties well, which suggests that r-process nucleosynthesis beyond the second peak takes place in SSS17a. However, the absolute magnitude of SSS17a is brighter than the expected brightness of the kilonova models with an ejectamass of 0.01M⊙, which suggests a more intensemass ejection (~0.03M⊙) or possibly an additional energy source.

Original languageEnglish
Article number101
JournalPublications of the Astronomical Society of Japan
Volume69
Issue number6
DOIs
Publication statusPublished - 2017

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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