Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817


B. P. Abbott, California Institute of Technology
R. Abbott, California Institute of Technology
T. D. Abbott, Louisiana State University
F. Acernese, Università degli Studi di Salerno
K. Ackley, University of Florida
C. Adams, LIGO Livingston
T. Adams, Université Savoie Mont Blanc
P. Addesso, Università degli Studi del Sannio
R. X. Adhikari, California Institute of Technology
V. B. Adya, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
C. Affeldt, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
M. Afrough, University of Mississippi
B. Agarwal, University of Illinois Urbana-Champaign
M. Agathos, University of Cambridge
K. Agatsuma, FOM-Institute of Subatomic Physics - NIKHEF
N. Aggarwal, LIGO, Massachusetts Institute of Technology
O. D. Aguiar, Instituto Nacional de Pesquisas Espaciais
L. Aiello, Gran Sasso Science Institute
A. Ain, Inter-University Centre for Astronomy and Astrophysics India
P. Ajith, Tata Institute of Fundamental Research, Mumbai
B. Allen, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
G. Allen, University of Illinois Urbana-Champaign
A. Allocca, Università di Pisa
P. A. Altin, The Australian National University
A. Amato, IN2P3 Institut National de Physique Nucleaire et de Physique des Particules
A. Ananyeva, California Institute of Technology
S. B. Anderson, California Institute of Technology
W. G. Anderson, University of Wisconsin-Milwaukee
S. V. Angelova, University of the West of Scotland
S. Antier, Laboratoire de l'Accélérateur Linéaire
S. Appert, California Institute of Technology
K. Arai, California Institute of Technology
M. C. Araya, California Institute of Technology

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The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long electromagnetic (EM) counterpart had a signature indicative of an r-process-induced optical transient known as a kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses inferred from the GW measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution (without the effects of wind ejecta) to the corresponding kilonova light curves from various models. The distributions of dynamical ejecta mass range between Mej = 10-3 - 10-2 M⊙ for various equations of state, assuming that the neutron stars are rotating slowly. In addition, we use our estimates of the dynamical ejecta mass and the neutron star merger rates inferred from GW170817 to constrain the contribution of events like this to the r-process element abundance in the Galaxy when ejecta mass from post-merger winds is neglected. We find that if ≳10% of the matter dynamically ejected from binary neutron star (BNS) mergers is converted to r-process elements, GW170817-like BNS mergers could fully account for the amount of r-process material observed in the Milky Way.

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Astrophysical Journal Letters

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