The masses of two binary neutron star systems

Thorsett, S. E.; Arzoumanian, Zaven; McKinnon, Mark; Taylor, J. H.

doi:10.1086/186758

Cited by 120 publications

(105 citation statements)

References 21 publications

(22 reference statements)

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“…The masses of neutron stars have been determined for a number of binary radio pulsars as well as binary X-ray pulsars (see Thorsett et al 1993 and references therein). All the measurements are consistent with a mass M = (1.35 ± 0.1)M ⊙ .…”

Section: Polytropic Models For Neutron Stars -23 -mentioning

confidence: 99%

Hydrodynamic instability and coalescence of binary neutron stars

Lai¹,

Rasio²,

Shapiro³

1994

ApJ

133

166

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We study the importance of hydrodynamic effects on the evolution of coalescing binary neutron stars. Using an approximate energy functional constructed from equilibrium solutions for polytropic binary configurations, we incorporate hydrodynamic effects into the calculation of the orbital decay driven by gravitational wave emission. In particular, we follow the transition between the quasi-static, secular decay of the orbit at large separation and the rapid dynamical evolution of configurations approaching contact. We show that a purely Newtonian hydrodynamic instability can significantly accelerate the coalescence at small separation. Such an instability occurs in all close binary configurations containing sufficiently incompressible stars. Calculations are performed for various neutron star masses, radii, and spins. The influence of the stiffness of the equation of state is also explored by varying the effective polytropic index. Typically, we find that the radial infall velocity just prior to contact is about 10% of the tangential orbital velocity. Once the stability limit is reached, the final evolution only takes another orbit. Post-Newtonian effects can move the stability limit to a larger binary separation, and may induce an even larger radial velocity. We also consider the possibility of mass transfer from one neutron star to the other. We show that stable mass transfer is impossible except when the mass of one of the components is very small (M ∼ < 0.4M ⊙ ) and the viscosity is high enough to maintain corotation. Otherwise, either the two stars come into contact or the dynamical instability sets in before a Roche limit can be reached.

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Section: Polytropic Models For Neutron Stars -23 -mentioning

confidence: 99%

Hydrodynamic instability and coalescence of binary neutron stars

Lai¹,

Rasio²,

Shapiro³

1994

ApJ

133

166

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“…The observations of relativistic parameters in pulsar binary systems have presented the first application of general relativity and provided the most widely available laboratories for testing theories of gravitation (e.g. Hulse & Taylor 1975;Taylor & Weisberg 1982;Weisberg & Taylor 2003;Thorsett et al 1993;Stairs et al 2002). Mass measurements are also possible in X-ray binaries, where a neutron star X-ray pulsar and an optical companion reside.…”

Section: Introductionmentioning

confidence: 99%

Study of measured pulsar masses and their possible conclusions

Zhang

Wang

Zhao

et al. 2011

A&A

147

116

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We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 ± 0.30 M . When the 46 NSs with measured spin periods are divided into two groups at 20 milliseconds, i.e., the millisecond pulsar (MSP) group and others, we find that their mass averages are, respectively, M = 1.57 ± 0.35 M and M = 1.37 ± 0.23 M . In the framework of the pulsar recycling hypothesis, this suggests that an accretion of approximately ∼0.2 M is sufficient to spin up a neutron star and place it in the millisecond pulsar group. Based on these estimates, an approximate empirical relation between the accreting mass (ΔM) of recycled pulsar and its spin period is proposed as ΔM = 0.43 (M )(P/1 ms) −2/3 . If we focus only on the DNS, the mass average of all 18 DNSs is 1.32 ± 0.14 M , and the mass averages of the recycled DNSs and the non-recycled NS companions are, respectively, 1.38 ± 0.12 M and 1.25 ± 0.13 M . This is consistent with the hypothesis that the masses of both NSs in DNS system have been affected by accretion. The mass average of MSPs is higher than the Chandrasekhar limit 1.44 M , which may imply that most of binary MSPs form via the standard scenario by accretion recycling. If we were to assume that the mass of a MSP formed by the accretion induced collapse (AIC) of a white dwarf must be less than 1.35 M , then the portion of the binary MSPs involved in the AICs would not be higher than 20%, which imposes a constraint on the AIC origin of MSPs. With accreting mass from the companion, the nuclear matter composition of MSP may experience a transition from the "soft" equation of state (EOS) to a "stiff" EOS or even neutron to quark matter.

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“…However, for almost all stages except for the last few milliseconds of coalescence of binary systems, the timescale of change of the system due to gravitational waves, τ GW , is much longer than that of the orbital period, τ orb . Specifically, τ orb /τ GW ∼ (v/c) 5 and it is less than 1 % even for v ∼ 0.3c. At the same time, the energy radiated due to gravitational wave emission is only a few percent of the total energy even when two stars come very close.…”

Section: A Assumptionsmentioning

confidence: 96%

“…From more detailed observations of PSR1913+16, much information about neutron stars such as the mass has been obtained and at the same time many other binary pulsar systems have been found [3][4][5][6][7]. Since there are many binary systems composed of neutron stars/black holes, it is estimated that gravitational waves from binary systems will be observed directly once a year in galaxies within 200Mpc [8].…”

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confidence: 99%

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New numerical scheme to compute three-dimensional configurations of quasiequilibrium compact stars in general relativity: Application to synchronously rotating binary star systems

1999

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A new numerical scheme to compute 3D configurations of quasiequilibrium compact stars in general relativity -Application to synchronously rotating binary star systems - AbstractWe have developed a new numerical scheme to obtain quasiequilibrium structures of nonaxisymmetric compact stars such as binary neutron star systems as well as the spacetime around those systems in general relativity. Although, strictly speaking, there are no equilibrium states for binary configurations in general relativity, the timescale of orbital change due to gravitational wave radiation is so long compared with the orbital period that we can assume nonaxisymmetric systems in "quasiequilibrium" states. 1Concerning quasiequilibrium states of binary systems in general relativity, several investigations have been already carried out by assuming conformal flatness of the spatial part of the metric. However, the validity of the conformally flat treatment has not been fully analyzed except for axisymmetric configurations. Therefore it is desirable to solve quasiequilibrium states by developing totally different methods from the conformally flat scheme. In this paper we present a new numerical scheme to solve directly the Einstein equations for 3D configurations without assuming conformal flatness, although we make use of the simplified metric for the spacetime. This new formulation is the extension of the scheme which has been successfully applied for structures of axisymmetric rotating compact stars in general relativity. It is based on the integral representation of the Einstein equations by taking the boundary conditions at infinity into account. We have checked our numerical scheme by computing equilibrium sequences of binary polytropic star systems in Newtonian gravity and those of axisymmetric polytropic stars in general relativity. We have applied this numerical code to binary star systems in general relativity and have succeeded in obtaining several equilibrium sequences of synchronously rotating binary polytropes with the polytropic indices N = 0.0, 0.5 and 1.0.

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The masses of two binary neutron star systems

Cited by 120 publications

References 21 publications

Hydrodynamic instability and coalescence of binary neutron stars

Hydrodynamic instability and coalescence of binary neutron stars

Study of measured pulsar masses and their possible conclusions

New numerical scheme to compute three-dimensional configurations of quasiequilibrium compact stars in general relativity: Application to synchronously rotating binary star systems

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