Abstract

The recent detection of gravitational waves (GWs) from a system of binary neutron stars (BNS) in coincidence with electromagnetic observations has launched a new era of multimessenger astrophysics. In light of the complementary knowledge to be gained through simultaneous observations, BNS mergers are one of the main targets for terrestrial GW interferometric detectors. These observations may prove critical in understanding the equation of state (EOS) of the nuclear matter inside the neutron star core, which is still poorly constrained given current observations. Understanding the neutron star (NS) EOS is critical for binary parameter estimation, and will hopefully aid in the prediction and detection of additional GW signals for systems with varying NS masses. While configurations of binary neutron stars having mass ratios far from unity are of great interest because of their potential observational signatures, generating accurate initial data for such systems has historically proven to be difficult, and relatively limited work has been done to date in simulating unequal-mass BNS because of a variety of numerical difficulties. In this work, we have modified the publicly available LORENE binary initial data code to advance our ability to construct unequal-mass BNS initial data, and used our results to initiate dynamical evolutions of BNS mergers performed using the Einstein Toolkit. We have investigated the quality of the initial data produced by our modified version of \texttt{LORENE} by evaluating a number of metrics, particularly the conservation of the Hamiltonian constraint when data are interpolated onto a grid for use in dynamical simulations. \\ Here we discuss the process by which we generate initial data and use it for launching dynamical simulations, as well as our analysis of the dynamics of the merger for varying mass ratios and different EOSs represented as simple polytropes and piecewise polytropes. In particular, we analyze the relationship between the BNS mass ratio, EOS, and the ejected mass during the merger, and classify the fate of the merger remnant produced in each case.

Library of Congress Subject Headings

Neutron stars; Double stars--Evolution; Equations of state

Publication Date

12-12-2022

Document Type

Dissertation

Student Type

Graduate

Degree Name

Astrophysical Sciences and Technology (Ph.D.)

Department, Program, or Center

School of Physics and Astronomy (COS)

Advisor

Joshua Faber

Advisor/Committee Member

Nathaniel Barlow

Advisor/Committee Member

Joel Kastner

Campus

RIT – Main Campus

Plan Codes

ASTP-PHD

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