Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817

By Masaomi Tanaka, Y. Utsumi, P. Mazzali, Nozomu Tominaga, Michitoshi Yoshida, Y. Sekiguchi, T. Morokuma, K. Motohara, K. Ohta, K. Kawabata and 35 more. 2017

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Recent detection of gravitational waves from a neutron star (NS) merger event GW170817 and identification of an electromagnetic counterpart provide a unique opportunity to study the physical processes in NS mergers. To derive properties of ejected material from the NS merger, we perform radiative transfer simulations of kilonova, optical and near-infrared emissions powered by radioactive decays of r-process nuclei synthesized in the merger. We find that the observed near-infrared emission lasting for > 10 days is explained by 0.03 Msun of ejecta containing lanthanide elements. However, the blue optical component observed at the initial phases requires an ejecta component with a relatively high electron fraction (Ye). We show that both optical and near-infrared emissions are simultaneously reproduced by the ejecta with a medium Ye of ~ 0.25. We suggest that a dominant component powering the emission is post-merger ejecta, which exhibits that mass ejection after the first dynamical ejection is quite efficient. Our results indicate that NS mergers synthesize a wide range of r-process elements and strengthen the hypothesis that NS mergers are the origin of r-process elements in the Universe.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/42a8c71930dc3a271a26742f681355f085e81ee4

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Citations in the corpus

Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “…2017; Cowperthwaite et al. 2017; Tanvir et al. 2017; Shappee et al. 2017; Kilpatrick et al. 2017; Kasliwal et al. 2017; Nicholl et al. 2017; Chornock et al. 2017; Drout et al. 2017; Mc- Cully et al. 2017; Tanvir et al. 2017; Villar et al. 2017; however, see Smartt et al. 2017; Tanaka et al. 2017).”
GW170817: Joint Constraint on the Neutron Star Equation of State from Multimessenger Observations (2017, background): “05~ of material (Chornock et al. 2017; Cowperthwaite et al. 2017; Drout et al. 2017; Nicholl et al. 2017; Perego et al. 2017; Rosswog et al. 2017; Tanaka et al. 2017; Tanvir et al. 2017; Villar et al. 2017).”
Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study (2017, background): “…simultaneously with GW170817(e.g., Abbott et al. 2017b; Arcavi et al. 2017; Coulter et al. 2017; Cowperthwaite et al. 2017; Drout et al. 2017; Kasliwal et al. 2017; Nicholl et al. 2017; Pian et al. 2017; Shappee et al. 2017; Smartt et al. 2017; Soares-Santos et al. 2017; Tanaka et al. 2017).”
A Magnetar Origin for the Kilonova Ejecta in GW170817 (2018, background): “…Wollaeger et al. 2017; Tanaka et al. 2018; also see Fernández & Metzger 2016; Metzger 2017 for reviews), a conclusion reached independently by several groups (e.g., Drout et al. 2017; Kasen et al. 2017; Kasliwal et al. 2017; Murguia-Berthier et al. 2017; Tanaka et al. 2017; Waxman et al. 2017).”
Constraining the Maximum Mass of Neutron Stars from Multi-messenger Observations of GW170817 (2017, background): “The KN following GW170817 showed evidence for two distinct emitting ejecta components (Cowperthwaite et al. 2017; Kasen et al. 2017; Tanaka et al. 2017).”
The Origin of r-process Elements in the Milky Way (2017, background): “…that NS-NS mergers can synthesize enough r-process material to be the dominant site in the Milky Way (Abbott et al. 2017a; Cowperthwaite et al. 2017; Chornock et al. 2017; Gompertz et al. 2017; Kasen et al. 2017; Rosswog et al. 2017; Tanaka et al. 2017a; Wang et al. 2017; Hotokezaka et al. 2018).”
The Combined Ultraviolet, Optical, and Near-infrared Light Curves of the Kilonova Associated with the Binary Neutron Star Merger GW170817: Unified Data Set, Analytic Models, and Physical Implications (2017, background): “We specifically explore a model with two components (“blue,” k = 0.5 cm2 g−1 and “red,” κ left as a free parameter), and with three components (“blue,” k = 0.5 cm2 g−1; “purple,” k = 3 cm2 g−1; and “red,” k = 10 cm2 g−1; Tanaka et al. 2017a).”
Gravitational waves from neutron star mergers and their relation to the nuclear equation of state (2019, background): “[26] M.”
Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way (2018, background): “The Kilonova AT 2017gfo (SSS17a) The ultraviolet, optical, and infrared emission from GW170817 suggest a significant production of r-process elements (e.g, Chornock et al. 2017; Cowperthwaite et al. 2017; Drout et al. 2017; Pian et al. 2017; Tanaka et al. 2017; Villar et al. 2017).”
AT 2017gfo: An Anisotropic and Three-component Kilonova Counterpart of GW170817 (2017, background): “Two or even three component models are necessary (Cowperthwaite et al. 2017; Tanvir et al. 2017; Tanaka et al. 2017).”
Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis (2018, background): “…ejected during and shortly after the merger (Chornock et al. 2017; Cowperthwaite et al. 2017; Drout et al. 2017; Nicholl et al. 2017; Perego et al. 2017a; Tanaka et al. 2017; Tanvir et al. 2017; Utsumi et al. 2017; Villar et al. 2017; Waxman et al. 2018; Kawaguchi et al. 2018; Metzger et al. 2018).”