paper

Models of Kilonova/macronova emission from black hole-neutron star mergers

arXiv:1601.07711 · doi:10.3847/0004-637X/825/1/52

Abstract

Black hole-neutron star mergers are among the promising gravitational-wave sources for ground-based detectors, and gravitational waves from black hole-neutron star mergers are expected to be detected in the next few years. Simultaneous detection of electromagnetic counterparts with gravitational-wave detection provides rich information about the merger events. Among the possible electromagnetic counterparts from the black hole-neutron star merger, the emission powered by the decay of radioactive r-process nuclei, so called kilonova/macronova, is one of the best targets for follow-up observation. We derive fitting formulas for the mass and the velocity of ejecta from a generic black hole-neutron star merger based on recently performed numerical relativity simulations. We combined these fitting formulas with a new semi-analytic model for a black hole-neutron star kilonova/macronova lightcurve which reproduces the results of radiation-transfer simulations. Specifically, the semi-analytic model reproduces the result of each band magnitude obtained by the radiation transfer simulations within ~1 mag. By using this semi-analytic model, we found that, at 400 Mpc, the kilonova/macronova is as bright as 22-24 mag for the cases with a small chirp mass and a high black hole spin, and >28 mag for a large chirp mass and a low black hole spin. We also apply our model to GRB130603B as an illustration, and show that a black hole-neutron star merger with a rapidly spinning black hole and a large neutron star radius is favored.

12 pages, 9 figures, 2 tables, published in ApJ. Online lightcurve calculator of our model is available at http://www2.yukawa.kyoto-u.ac.jp/~kyohei.kawaguchi/kn_calc/main.html

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