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Both the mass and radius of the millisecond pulsar PSR J0030+0451 have been inferred via pulse-profile modeling of X-ray data obtained by NASA's NICER mission. In this Letter we study the implications of the mass-radius inference reported…

Recent Chandra and XMM-Newton observations of a number of X-ray ``dim'' pulsating neutron stars revealed quite unexpected features in the emission from these sources. Their soft thermal spectrum, believed to originate directly from the star…

Astrophysics · Physics 2009-11-13 Silvia Zane , Roberto Turolla

The properties of X-ray radiation from the polar caps predicted by the radio pulsar models depend on the surface chemical composition, magnetic field and star's mass and radius as well as on the cap temperature, size and position. Fitting…

Astrophysics · Physics 2008-02-03 G. G. Pavlov , V. E. Zavlin

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…

High Energy Astrophysical Phenomena · Physics 2016-10-05 Feryal Ozel , Paulo Freire

Observations of thermal radiation from neutron stars allow one to measure the surface temperatures and confront them with cooling scenarios. Detection of gravitationally redshifted spectral lines can yield the mass-to-radius ratio. In the…

Astrophysics · Physics 2007-05-23 G. G. Pavlov , V. E. Zavlin

Neutron star Interior Composition Explorer (NICER) data have been used to estimate the masses and radii of the rotation-powered millisecond pulsars PSR J0030$+$0451, PSR J0740$+$6620, PSR J0437$-$4715, PSR J1231$-$1411, and PSR…

Approximate analytical formulae are derived for the pulse profile produced by small hot spots on a rapidly rotating neutron star. Its Fourier amplitudes and phases are calculated. The proposed formalism takes into account gravitational…

Astrophysics · Physics 2008-11-26 Juri Poutanen , Andrei M. Beloborodov

We review the state of the art for measuring the X-ray polarization of neutron stars. We discuss how valuable precision measurements of the degree and position angle of polarization as a function of energy and, where relevant, of pulse…

Astrophysics · Physics 2007-05-23 M. C. Weisskopf , R. F. Elsner , D. Hanna , V. M. Kaspi , S. L. O'Dell , G. G. Pavlov , B. D. Ramsey

We study the pulse morphologies and pulse amplitudes of thermally emitting neutron stars with ultrastrong magnetic fields. The beaming of the radiation emerging from a magnetar was recently shown to be predominantly non-radial, with a small…

Astrophysics · Physics 2009-11-07 Feryal Ozel

We report a revised analysis for the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, studied previously with joint fits to NICER and XMM-Newton data by Riley et al. (2021) and Miller et al. (2021). We…

NASA's Neutron Star Interior Composition Explorer (NICER) observed X-ray emission from the pulsar PSR J0030+0451 in 2018. Riley et al. reported Bayesian parameter measurements of the mass and the star's radius using pulse-profile modeling…

High Energy Astrophysical Phenomena · Physics 2024-02-02 Chaitanya Afle , Patrick R. Miles , Silvina Caino-Lores , Collin D. Capano , Ingo Tews , Karan Vahi , Ewa Deelman , Michela Taufer , Duncan A. Brown

The interiors of neutron stars reach densities and temperatures beyond the limits of terrestrial experiments, providing vital laboratories for probing nuclear physics. While the star's interior is not directly observable, its pressure and…

High Energy Astrophysical Phenomena · Physics 2024-02-13 Delaney Farrell , Pierre Baldi , Jordan Ott , Aishik Ghosh , Andrew W. Steiner , Atharva Kavitkar , Lee Lindblom , Daniel Whiteson , Fridolin Weber

This article gives a very brief introduction about measuring the mass and radius of neutron star from X-ray observations. The masses and radii of neutron stars can be determined from photospheric radius expansion bursts in low-mass X-ray…

High Energy Astrophysical Phenomena · Physics 2015-12-23 Zhaosheng Li

Neutron star matter is investigated in a hadronic chiral model approach using the lowest flavor-SU(3) multiplets for baryons and mesons. The parameters are determined to yield consistent results for saturated nuclear matter as well as for…

Astrophysics · Physics 2008-11-26 V. Dexheimer , S. Schramm , H. Stoecker

Measuring the spin of Accreting Neutron Stars is important because it can provide constraints on the Equation of State of ultra-dense matter. Particularly crucial to our physical understanding is the discovery of sub-millisecond pulsars,…

High Energy Astrophysical Phenomena · Physics 2011-01-28 Alessandro Patruno

We discuss millisecond period brightness oscillations and surface atomic spectral lines observed during type I X-ray bursts from a neutron star in a low mass X-ray binary system. We show that modeling of these phenomena can constrain models…

Model spectra of neutron star atmospheres are nowadays widely used to fit the observed thermal X-ray spectra of neutron stars. This fitting is the key element in the method of the neutronstar radius determination. Here, we present the basic…

High Energy Astrophysical Phenomena · Physics 2016-03-23 V. F. Suleimanov , J. Poutanen , D. Klochkov , K. Werner

The masses and radii of low-magnetic field neutron stars can be measured by combining different observable quantities obtained from their X-ray spectra during thermonuclear X-ray bursts. One of these quantities is the apparent radius of…

High Energy Astrophysical Phenomena · Physics 2012-02-22 Tolga Guver , Dimitrios Psaltis , Feryal Ozel

The rapid increase in the number and precision of astrophysical probes of neutron stars in recent years allows for the inference of their equation of state. Observations target different macroscopic properties of neutron stars which vary…

High Energy Astrophysical Phenomena · Physics 2022-03-31 Isaac Legred , Katerina Chatziioannou , Reed Essick , Philippe Landry

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