TY - JOUR

T1 - Constant circulation sequences of binary neutron stars and their spin characterization

AU - Tsokaros, Antonios

AU - Uryu, Koji

AU - Ruiz, Milton

AU - Shapiro, Stuart L.

N1 - Publisher Copyright:
© 2018 American Physical Society.

PY - 2018/12/15

Y1 - 2018/12/15

N2 - For isentropic fluids, dynamical evolution of a binary system conserves the baryonic mass and circulation; therefore, sequences of constant rest mass and constant circulation are of particular importance. In this work, we present the extension of our Compact Object CALculator (cocal) code to compute such quasiequilibria and compare them with the well-known corotating and irrotational sequences, the latter being the simplest, zero-circulation case. The circulation as a measure of the spin for a neutron star in a binary system has the advantage of being exactly calculable since it is a local quantity. To assess the different measures of spin, such as the angular velocity of the star, the quasilocal, dimensionless spin parameter J/M2, or the circulation C, we first compute sequences of single, uniformly rotating stars and describe how the different spin diagnostics are related to each other. The connection to spinning binary systems is accomplished through the concept of circulation and the use of the constant rotational velocity formulation. Finally, we explore a modification of the latter formulation that naturally leads to differentially rotating binary systems.

AB - For isentropic fluids, dynamical evolution of a binary system conserves the baryonic mass and circulation; therefore, sequences of constant rest mass and constant circulation are of particular importance. In this work, we present the extension of our Compact Object CALculator (cocal) code to compute such quasiequilibria and compare them with the well-known corotating and irrotational sequences, the latter being the simplest, zero-circulation case. The circulation as a measure of the spin for a neutron star in a binary system has the advantage of being exactly calculable since it is a local quantity. To assess the different measures of spin, such as the angular velocity of the star, the quasilocal, dimensionless spin parameter J/M2, or the circulation C, we first compute sequences of single, uniformly rotating stars and describe how the different spin diagnostics are related to each other. The connection to spinning binary systems is accomplished through the concept of circulation and the use of the constant rotational velocity formulation. Finally, we explore a modification of the latter formulation that naturally leads to differentially rotating binary systems.

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U2 - 10.1103/PhysRevD.98.124019

DO - 10.1103/PhysRevD.98.124019

M3 - Article

AN - SCOPUS:85059393900

SN - 2470-0010

VL - 98

JO - Physical Review D

JF - Physical Review D

IS - 12

M1 - 124019

ER -