Bounds on the Compactness of Neutron Stars from Brightness Oscillations during X-Ray Bursts
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In this paper, the maximum fractional rms amplitude of a star during X-ray bursts was derived as a function of stellar compactness, and the dependence of the oscillation amplitude on the compactness of the star, on the angular dependence of emission from the surface and on the rotational velocity at the stellar surface, and whether there are one or two emitting spots.Abstract:
The discovery of high-amplitude brightness oscillations at the spin frequency or its first overtone in six neutron stars in low-mass X-ray binaries during type I X-ray bursts provides a powerful new way to constrain the compactness of these stars and hence to constrain the equation of state of the dense matter in all neutron stars. Here we report general relativistic calculations of the maximum fractional rms amplitudes that can be observed during bursts, as a function of stellar compactness. We compute the dependence of the oscillation amplitude on the compactness of the star, on the angular dependence of the emission from the surface, on the rotational velocity at the stellar surface, and on whether there are one or two emitting spots. We show that color oscillations caused by the spectral variation with the angle of emission, the rotation of the star, and the limited bandwidth of the detector all tend to increase the observed amplitude of the oscillation. Nevertheless, if two spots are emitting, as appears to be the case in 4U 1636-536 and KS 1731-26, very restrictive bounds on the compactness of the star can be derived.read more
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Journal ArticleDOI
Masses, Radii, and the Equation of State of Neutron Stars
Feryal Özel,Paulo C. C. Freire +1 more
TL;DR: In this paper, the authors summarize the current knowledge of neutron-star masses and radii and show that the distribution of neutron star masses is much wider than previously thought, with three known pulsars now firmly in the 1.9-2.0-M⊙ mass range.
Journal ArticleDOI
Masses, Radii, and Equation of State of Neutron Stars
Feryal Özel,Paulo C. C. Freire +1 more
TL;DR: In this paper, the authors summarize the current knowledge of neutron star masses and radii and show that the neutron star mass distribution is much wider than previously thought, with 3 known pulsars now firmly in the 1.9-2.0 Msun mass range.
Journal ArticleDOI
A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation
Thomas E. Riley,Anna L. Watts,Slavko Bogdanov,Paul S. Ray,Renee M. Ludlam,Sebastien Guillot,Sebastien Guillot,Zaven Arzoumanian,Charles Baker,Anna V. Bilous,Deepto Chakrabarty,Keith C. Gendreau,Alice K. Harding,Wynn C. G. Ho,Wynn C. G. Ho,James M. Lattimer,Sharon M. Morsink,Tod E. Strohmayer +17 more
TL;DR: In this paper, the mass and equatorial radius of the millisecond pulsar PSR J0030+0451 were estimated based on a relativistic ray-tracing of thermal emission from hot regions of the pulsar surface.
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Millisecond Oscillations in X-Ray Binaries
TL;DR: The end of at least one cable is connected to a float and the other end exerts a tractive effort on one or a number of collecting vehicles which land on the bottom at predetermined points with respect to the point of landing of the ballast.
Journal ArticleDOI
A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation.
Thomas E. Riley,Anna L. Watts,Slavko Bogdanov,Paul S. Ray,Renee M. Ludlam,Sebastien Guillot,Sebastien Guillot,Zaven Arzoumanian,Charles Baker,Anna V. Bilous,Deepto Chakrabarty,Keith C. Gendreau,Alice K. Harding,Wynn C. G. Ho,Wynn C. G. Ho,James M. Lattimer,Sharon M. Morsink,Tod E. Strohmayer +17 more
TL;DR: In this article, the mass and equatorial radius of the millisecond pulsar PSR J0030$+$0451 were estimated from the ICER X-ray spectral-timing event data.
References
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