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Related papers: Constraining the Neutron Star Mass--Radius Relatio…

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The NASA Neutron star Interior Composition Explorer (\emph{NICER}) mission measures the X-ray pulse profiles of select millisecond pulsars and uses sophisticated pulse profile modeling (PPM) techniques to constrain their masses ($M$) and…

High Energy Astrophysical Phenomena · Physics 2026-04-14 Ryan O'Connor , Chun Huang , Alexander Y. Chen

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

Rotation-powered "recycled" millisecond pulsars are a variety of rapidly-spinning neutron stars that typically show thermal X-ray radiation due to the heated surface of their magnetic polar caps. Detailed numerical modeling of the…

High Energy Astrophysical Phenomena · Physics 2016-03-23 Slavko Bogdanov

Four neutron star radius measurements have already been obtained by modeling the X-ray pulses of rotation-powered millisecond pulsars observed by the Neutron Star Interior Composition ExploreR (NICER). We report here the radius measurement…

NICER observed several rotation-powered millisecond pulsars to search for or confirm the presence of X-ray pulsations. When broad and sine-like, these pulsations may indicate thermal emission from hot polar caps at the magnetic poles on the…

In the last few years, the NICER collaboration has provided mass and radius inferences, via pulse profile modeling, for two pulsars: PSR J0030+0451 and PSR J0740+6620. Given the importance of these results for constraining the equation of…

High Energy Astrophysical Phenomena · Physics 2024-01-09 Serena Vinciguerra , Tuomo Salmi , Anna L. Watts , Devarshi Choudhury , Yves Kini , Thomas E. Riley

One very promising technique for measuring the dense matter Equation of State exploits hotspots that form on the neutron star surface due to the pulsar mechanism, accretion streams, or during thermonuclear explosions in the neutron star…

High Energy Astrophysical Phenomena · Physics 2019-09-04 Anna L. Watts

The observation of neutron stars enables the otherwise impossible study of fundamental physical processes. The timing of binary radio pulsars is particularly powerful, as it enables precise characterization of their (three-dimensional)…

We report the detection of X-ray pulsations from the rotation-powered millisecond-period pulsars PSR J0740+6620 and PSR J1614-2230, two of the most massive neutron stars known, using observations with the Neutron Star Interior Composition…

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

In the last few years, NICER data has enabled mass and radius inferences for various pulsars, and thus shed light on the equation of state for dense nuclear matter. This is achieved through a technique called pulse profile modeling. The…

High Energy Astrophysical Phenomena · Physics 2026-03-25 Mariska Hoogkamer , Yves Kini , Tuomo Salmi , Anna L. Watts , Johannes Buchner

We present an analysis of the effects of uncertainties in the atmosphere models on the radius, mass, and other neutron star parameter constraints for the NICER observations of rotation-powered millisecond pulsars. To date, NICER has applied…

We report Bayesian inference of the mass, radius and hot X-ray emitting region properties - using data from the Neutron Star Interior Composition ExploreR (NICER) - for the brightest rotation-powered millisecond X-ray pulsar PSR…

The Neutron-star Interior Composition ExploreR (NICER) is collecting data to measure the radii of neutron stars by observing the pulsed emission from their surfaces. The primary targets are isolated, rotation-powered pulsars, in which the…

High Energy Astrophysical Phenomena · Physics 2019-02-27 Michi Baubock , Dimitrios Psaltis , Feryal Ozel

In recent years our understanding of the dense matter equation of state (EOS) of neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and from nuclear physics…

High Energy Astrophysical Phenomena · Physics 2021-09-28 G. Raaijmakers , S. K. Greif , K. Hebeler , T. Hinderer , S. Nissanke , A. Schwenk , T. E. Riley , A. L. Watts , J. M. Lattimer , W. C. G. Ho

Accurate and precise measurements of neutron star radii provide invaluable information about the cold, dense matter in neutron star cores. Analyses of synthetic X-ray pulse waveform data similar to the data obtained from non-accreting…

High Energy Astrophysical Phenomena · Physics 2025-11-24 Isiah M. Holt , M. Coleman Miller , Alexander J. Dittmann , Frederick K. Lamb

The Neutron Star Interior Composition Explorer (NICER) is an X-ray astrophysics payload on the International Space Station. It enables unprecedented high-precision timing of millisecond pulsars without the pulse broadening and delays due to…

The NICER collaboration recently published a joint estimate of the mass and the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling. Raaijmakers et al. (2019) explored the implications of this measurement for the dense matter…

High Energy Astrophysical Phenomena · Physics 2020-04-20 G. Raaijmakers , S. K. Greif , T. E. Riley , T. Hinderer , K. Hebeler , A. Schwenk , A. L. Watts , S. Nissanke , S. Guillot , J. M. Lattimer , R. M. Ludlam

In the past few years, new observations of neutron stars and neutron-star mergers have provided a wealth of data that allow one to constrain the equation of state of nuclear matter at densities above nuclear saturation density. However,…

High Energy Astrophysical Phenomena · Physics 2021-11-18 Peter T. H. Pang , Ingo Tews , Michael W. Coughlin , Mattia Bulla , Chris Van Den Broeck , Tim Dietrich