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Raytracing computations for light emitted from the surface of a rapidly rotating neutron star are carried out in order to construct light curves for accreting millisecond pulsars. These calculations are for realistic models of rapidly…

Astrophysics · Physics 2007-05-23 D. Leahy , S. Morsink , C. Cadeau

In order to examine the pulse profile from a pulsar, we derive the formula for describing the flux from antipodal hot spots with any static, spherically symmetric spacetime. We find that the pulse profiles are almost independent of the…

High Energy Astrophysical Phenomena · Physics 2017-11-17 Hajime Sotani , Umpei Miyamoto

We present raytracing computations for light emitted from the surface of a rapidly-rotating neutron star in order to construct light curves for X-ray pulsars and bursters. These calculations are for realistic models of rapidly-rotating…

Astrophysics · Physics 2011-02-11 Coire Cadeau , Sharon M. Morsink , Denis Leahy , Sheldon S. Campbell

The Neutron Star Interior Composition Explorer (NICER) mission has provided a unique opportunity to constrain the equation of state of neutron stars by using the technique of pulse-profile modelling. This technique requires accurate and…

General Relativity and Quantum Cosmology · Physics 2021-05-12 G. André Oliva , Francisco Frutos-Alfaro

We present a Bayesian method to constrain the masses and radii of neutron stars (NSs) using the information encoded in the X-ray pulse profiles of accreting millisecond pulsars. We model the shape of the pulses using "oblate Schwarzschild"…

High Energy Astrophysical Phenomena · Physics 2018-10-31 T. Salmi , J. Nättilä , J. Poutanen

The Neutron star Interior Composition Explorer (NICER) is currently observing the x-ray pulse profiles emitted by hot spots on the surface of rotating neutron stars allowing for an inference of their radii with unprecedented precision. A…

High Energy Astrophysical Phenomena · Physics 2021-05-06 Hector O. Silva , George Pappas , Nicolás Yunes , Kent Yagi

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…

High Energy Astrophysical Phenomena · Physics 2015-06-16 Dimitrios Psaltis , Feryal Ozel

Gravitational light bending by compact stars is an important astrophysical phenomenon. The bending angle depends on the stellar compactness, which is the ratio of stellar mass $M$ to radius $R$. In this paper, we investigate the pulse…

High Energy Astrophysical Phenomena · Physics 2018-08-29 Hajime Sotani , Umpei Miyamoto

The equation of state of cold supra-nuclear-density matter, such as in neutron stars, is an open question in astrophysics. A promising method for constraining the neutron star equation of state is modelling pulse profiles of thermonuclear…

High Energy Astrophysical Phenomena · Physics 2016-12-28 A. L. Stevens , J. D. Fiege , D. A. Leahy , S. M. Morsink

We describe the model of surface emission from a rapidly rotating neutron star that is applied to Neutron Star Interior Composition Explorer X-ray data of millisecond pulsars in order to statistically constrain the neutron star mass-radius…

We consider the effect of rapid rotation on the light curves of neutron stars with hot polar caps. For $P \approx 3$ms spin periods, the pulse fractions can be as much as an order of magnitude larger than with simple slowly-rotating…

Astrophysics · Physics 2009-10-31 Timothy M. Braje , Roger W. Romani , Kevin P. Rauch

Millisecond pulsars are rapidly rotating neutron stars where general relativity plays a strong role in the propagation of light from the neutron star to observer. The observed X-ray pulse shapes carry information on the mass, radius and…

High Energy Astrophysical Phenomena · Physics 2010-03-29 Denis Leahy

Modeling the amplitudes and shapes of the X-ray pulsations observed from hot, rotating neutron stars provides a direct method for measuring neutron-star properties. This technique constitutes an important part of the science case for the…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Dimitrios Psaltis , Feryal Ozel , Deepto Chakrabarty

The Oblate Schwarzschild (OS) approximation is a method often used to compute the flux of X-rays emitted from a rapidly rotating neutron star. In this approximation, the oblate shape of the rotating star is embedded in the Schwarzschild…

High Energy Astrophysical Phenomena · Physics 2025-12-01 Zsombor Jakab , Sharon Morsink

We systematically study pulsar light curves, taking into account the special relativistic effect, i.e., the Doppler factor due to the fast spin of the neutron stars, together with the time delay, which comes from the difference of the…

High Energy Astrophysical Phenomena · Physics 2018-12-05 Hajime Sotani , Umpei Miyamoto

Pulse profile modelling using X-ray data from NICER permits the inference of mass and radius for rotation-powered millisecond pulsars. This in turn constrains the equation of state of cold dense matter. Previous studies indicate that the…

High Energy Astrophysical Phenomena · Physics 2025-04-02 Erik Bootsma , Serena Vinciguerra , Anna L. Watts , Yves Kini , Tuomo Salmi

We calculate stationary configurations of rapidly rotating compact stars in general relativity, to study the properties of circular orbits of test particles in the equatorial plane. We search for simple, but precise, analytical formulae for…

Solar and Stellar Astrophysics · Physics 2011-06-14 M. Bejger , J. L. Zdunik , P. Haensel

A photon emitted near a compact object at an angle $\alpha$ with respect to the radial direction escapes to infinity at a different angle $\psi>\alpha$. This bending of light is caused by a strong gravitational field. We show that, in a…

Astrophysics · Physics 2009-11-07 Andrei M. Beloborodov

We calculate the effects of spot size on pulse profiles of moderately rotating neutron stars. Specifically, we quantify the bias introduced in radius measurements from the common assumption that spots are infinitesimally small. We find that…

High Energy Astrophysical Phenomena · Physics 2016-08-17 Michi Baubock , Dimitrios Psaltis , Feryal Ozel

We present an analytical study of light curves of slowly rotating radio pulsars with emphasis on the chromatic effects derived from the presence of a plasma environment; analyzing the effects of the compactness, the metric model, and the…

High Energy Astrophysical Phenomena · Physics 2023-02-27 Gastón Briozzo , Emanuel Gallo
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