Is the Macronova in GW170817 Powered by the Central Engine?

Tatsuya Matsumoto, Kunihito Ioka, Shota Kisaka, Ehud Nakar

Research output: Contribution to journalArticlepeer-review

Abstract

The gravitational wave event GW170817 from a binary neutron star merger is accompanied by electromagnetic counterparts, and the optical and near-infrared emission is called a macronova (or kilonova). Although the radioactivity of synthesized r-process elements is widely discussed as an energy source, its decisive evidence is not clearly shown yet. We discuss a macronova powered by central engine activities such as jet activities and X-rays from the matter fallback and show that the engine model allows much broader parameter spaces, in particular, smaller ejecta mass (∼10-4 - 1.01 M), than the r-process model. The blue and red macronovae are naturally explained by various combinations of the ejecta, such as a cocoon and merger ejecta with the energy sources of jets and X-rays. The required energy injection is very similar to the X-ray excess observed in GRB 130603B, with a power-law slope of ∼ -1.3. The required lanthanoid fraction for the opacity can also be consistent with the Galactic one. Early or late multiwavelength observations are crucial for revealing the central engine of short gamma-ray bursts and the r-process nucleosynthesis.

Original languageEnglish
Article number55
JournalAstrophysical Journal
Volume861
Issue number1
DOIs
StatePublished - 1 Jul 2018

Keywords

  • gravitational waves
  • stars: black holes

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