RADIATIVE TRANSFER SIMULATIONS OF NEUTRON STAR MERGER EJECTA

作者：Masaomi Tanaka, Kenta Hotokezaka · 发表于：The Astrophysical Journal · 年份：2013 · DOI：10.1088/0004-637x/775/2/113 · 被引用次数：478 · 研究领域：Gamma-ray bursts and supernovae、Pulsars and Gravitational Waves Research、Astrophysical Phenomena and Observations

Mergers of binary neutron stars (NSs) are among the most promising gravitational wave (GW) sources. Next generation GW detectors are expected to detect signals from NS mergers within about 200 Mpc. The detection of electromagnetic wave (EM) counterparts is crucial to understanding the nature of GW sources. Among the possible EM emission from the NS merger, emission powered by radioactive r -process nuclei is one of the best targets for follow-up observations. However, predictions so far have not taken into account detailed r -process element abundances in the ejecta. We perform for the first time radiative transfer simulations of the NS merger ejecta including all the r -process elements from Ga to U. We show that the opacity of the NS merger ejecta is about κ = 10 cm 2 g −1 , which is higher than that of Fe-rich Type Ia supernova ejecta by a factor of ∼100. As a result, the emission is fainter and lasts longer than previously expected. The spectra are almost featureless due to the high expansion velocity and bound–bound transitions of many different r -process elements. We demonstrate that the emission is brighter for a higher mass ratio of the two NSs and a softer equation of state adopted in the merger simulations. Because of the red color of the emission, follow-up observations in red optical and near-infrared (NIR) wavelengths will be the most efficient. At 200 Mpc, the expected brightness of the emission is i = 22–25 AB mag, z = 21–23 AB mag, and 21–24 AB mag in the NIR...