Light Curves for Rapidly Rotating Neutron Stars

Annu. Rev. Astron. Astrophys.

Freire

2016

1,389

1,231

We summarize our current knowledge of neutron star masses and radii. Recent instrumentation and computational advances have resulted in a rapid increase in the discovery rate and precise timing of radio pulsars in binaries in the last few years, leading to a large number of mass measurements. These discoveries 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 M⊙ mass range. For radii, large, high quality datasets from X-ray satellites as well as significant progress in theoretical modeling led to considerable progress in the measurements, placing them in the 9.9 − 11.2 km range and shrinking their uncertainties due to a better understanding of the sources of systematic errors. The combination of the massive neutron star discoveries, the tighter radius measurements, and improved laboratory constraints of the properties of dense matter has already made a substantial impact on our understanding of the composition and bulk properties of cold nuclear matter at densities higher than that of the atomic nucleus, a major unsolved problem in modern physics.

Section: Radii Via Pulse Profile Modelingmentioning

confidence: 99%

Masses, Radii, and the Equation of State of Neutron Stars

Annu. Rev. Astron. Astrophys.

Freire

2016

1,389

1,231

“…Finally, as the spin frequency of a neutron star approaches the breakup frequency, the star becomes significantly oblate. Several authors have explored, at different levels of approximation, the effects of increasing the spin of a neutron star on several observables such as the lightcurves that arise when the surface emission on a spinning neutron star is not uniform Braje, Romani & Rauch 2000;Muno,Özel & Chakrabarty 2003;Poutanen & Gierlinski 2003;Cadeau, Leahy & Morsink 2005;Cadeau et al 2007;Morsink et al 2007), the rotational broadening of atomic lines that originate on the stellar surfaces (Özel & Psaltis 2003;Bhattacharyya, Miller & Lamb 2006;Chang et al 2006), as well as their apparent surface areas (Bauböck et al 2012). …”

Section: Observed Physical Quantitiesmentioning

confidence: 99%

Surface emission from neutron stars and implications for the physics of their interiors

2012

Rep. Prog. Phys.

124

Abstract. Neutron stars are associated with diverse physical phenomena that take place in conditions characterized by ultrahigh densities as well as intense gravitational, magnetic, and radiation fields. Understanding the properties and interactions of matter in these regimes remains one of the challenges in compact object astrophysics. Photons emitted from the surfaces of neutron stars provide direct probes of their structure, composition, and magnetic fields. In this review, I discuss in detail the physics that governs the properties of emission from the surfaces of neutron stars and their various observational manifestations. I present the constraints on neutron star radii, core and crust composition, and magnetic field strength and topology obtained from studies of their broadband spectra, evolution of thermal luminosity, and the profiles of pulsations that originate on their surfaces.

“…At moderate spin frequencies (i.e., 800 Hz), the neutron-star spacetime acquires a quadrupole moment and its surface becomes oblate. Finally, at spin frequencies near breakup (i.e., 1 kHz), higher order multipoles become important and the neutron-star spacetimes can only be calculated by numerically solving the field equations for particular equations of state (Cook et al 1994;Stergioulas & Friedman 1995;Stergioulas 2003; see also Cadeau et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Pulse Profiles From Spinning Neutron Stars in the Hartle-Thorne Approximation

Psaltis

2014

ApJ

We present a new numerical algorithm for the calculation of pulse profiles from spinning neutron stars in the Hartle-Thorne approximation. Our approach allows us to formally take into account the effects of Doppler shifts and aberration, of frame dragging, as well as of the oblateness of the stellar surface and of its quadrupole moment. We confirm an earlier result that neglecting the oblateness of the neutron-star surface leads to 5%-30% errors in the calculated profiles and further show that neglecting the quadrupole moment of its spacetime leads to 1%-5% errors at a spin frequency of 600 Hz. We discuss the implications of our results for the measurements of neutron-star masses and radii with upcoming X-ray missions, such as NASA's NICER and ESA's LOFT.