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arXiv · 1802.07732

Is the macronova in GW170817 powered by the central engine?

Tatsuya Matsumoto·Kunihito Ioka·Shota Kisaka·Ehud Nakar
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Abstract

The gravitational wave event GW170817 from a binary neutron star (NS) merger is accompanied by electromagnetic counterparts, and the optical and near-infared 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 the 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 ($\sim10^{-4}-0.01\,\Msun$) 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 the power-law slope of $\sim-1.3$. The required lanthanoid fraction for the opacity can be also consistent with the Galactic one. Early or late multi-wavelength observations are crucial for revealing the central engine of short gamma-ray bursts and the r-process nucleosynthesis.

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Tatsuya Matsumoto, Kunihito Ioka, Shota Kisaka, Ehud Nakar. 2018-05-18. Is the macronova in GW170817 powered by the central engine?. https://doi.org/10.3847/1538-4357%2Faac4a8

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