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We present two years of Neutron star Interior Composition Explorer (NICER) X-ray observations of three energetic rotation-powered millisecond pulsars (MSPs): PSRs B1937+21, B1821-24, and J0218+4232. We fit Gaussians and Lorentzians to the…

Using observations of X-ray pulsar Her X-1 by the Imaging X-ray Polarimetry Explorer, we report on a highly significant ($>17\sigma$) detection of the polarization signal from an accreting neutron star. The observed degree of the linear…

High Energy Astrophysical Phenomena · Physics 2023-01-16 Victor Doroshenko , Juri Poutanen , Sergey S. Tsygankov , Valery F. Suleimanov , Matteo Bachetti , Ilaria Caiazzo , Enrico Costa , Alessandro Di Marco , Jeremy Heyl , Fabio La Monaca , Fabio Muleri , Alexander A. Mushtukov , George G. Pavlov , Brian D. Ramsey , John Rankin , Andrea Santangelo , Paolo Soffitta , Rüdiger Staubert , Martin C. Weisskopf , Silvia Zane , Iván Agudo , Lucio A. Antonelli , Luca Baldini , Wayne H. Baumgartner , Ronaldo Bellazzini , Stefano Bianchi , Stephen D. Bongiorno , Raffaella Bonino , Alessandro Brez , Niccolò Bucciantini , Fiamma Capitanio , Simone Castellano , Elisabetta Cavazzuti , Stefano Ciprini , Alessandra De Rosa , Ettore Del Monte , Laura Di Gesu , Niccolò Di Lalla , Immacolata Donnarumma , Michal Dovciak , Steven R. Ehlert , Teruaki Enoto , Yuri Evangelista , Sergio Fabiani , Riccardo Ferrazzoli , Javier A. Garcia , Shuichi Gunji , Kiyoshi Hayashida , Wataru Iwakiri , Svetlana G. Jorstad , Vladimir Karas , Takao Kitaguchi , Jeffery J. Kolodziejczak , Henric Krawczynski , Luca Latronico , Ioannis Liodakis , Simone Maldera , Alberto Manfreda , Frédéric Marin , Andrea Marinucci , Alan P. Marscher , Herman L. Marshall , Giorgio Matt , Ikuyuki Mitsuishi , Tsunefumi Mizuno , C. -Y. Ng , Stephen L. O'Dell , Nicola Omodei , Chiara Oppedisano , Alessandro Papitto , Abel L. Peirson , Matteo Perri , Melissa Pesce-Rollins , Maura Pilia , Andrea Possenti , Simonetta Puccetti , Ajay Ratheesh , Roger W. Romani , Carmelo Sgrò , Patrick Slane , Gloria Spandre , Rashid A. Sunyaev , Toru Tamagawa , Fabrizio Tavecchio , Roberto Taverna , Yuzuru Tawara , Allyn F. Tennant , Nicolas E. Thomas , Francesco Tombesi , Alessio Trois , Roberto Turolla , Jacco Vink , Kinwah Wu , Fei Xie

Studies of neutron stars are extremely timely given the recent detection of gravitational waves from a binary neutron star merger GW170817, and an International Space Station payload NICER currently in operation that aims to determine radii…

General Relativity and Quantum Cosmology · Physics 2024-11-15 Nan Jiang , Kent Yagi

Neutron stars harbour extremely strong magnetic fields within their solid outer crust. The topology of this field strongly influences the surface temperature distribution, and hence the star's observational properties. In this work, we…

High Energy Astrophysical Phenomena · Physics 2020-11-04 Davide De Grandis , Roberto Turolla , Toby S. Wood , Silvia Zane , Roberto Taverna , Konstantinos N. Gourgouliatos

Intermediate-mass stars are often fast rotators, and hence are centrifugally flattened and affected by gravity darkening. To analyse this kind of stars properly, one must turn to 2D models to compute the visible radiative flux and to take…

Solar and Stellar Astrophysics · Physics 2024-02-28 Axel Lazzarotto , Alain Hui-Bon-Hoa , Michel Rieutord

r-mode astroseismology provides a unique way to study the internal composition of compact stars. Due to their precise timing, recycled millisecond radio pulsars present a particularly promising class of sources. Although their thermal…

High Energy Astrophysical Phenomena · Physics 2017-01-25 Kai Schwenzer , Tuğba Boztepe , Tolga Güver , Eda Vurgun

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

The problem of computing the pulse profiles from thermally emitting spots on the surface of a neutron star in general relativity is reconsidered. We show that it is possible to extend Beloborodov (2002) approach to include (multiple) spots…

High Energy Astrophysical Phenomena · Physics 2015-06-15 R. Turolla , L. Nobili

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

Many types of stars show periodic variations of radius and brightness, which are commonly referred to as `stellar pulsations'. Observed pulsational characteristics are determined by fundamental stellar parameters. Consequently,…

Astrophysics · Physics 2016-08-30 O. Kochukhov

The method of characteristics (MOC) is widely used for neutron transport calculation in recent decades. However, the key problem determining whether MOC can be applied in highly heterogeneous geometry is how to combine an effective geometry…

Nuclear Theory · Physics 2015-06-16 Zhen-Ping Chen , Hua-Qing Zhen , Guang-Yao Sun , Jing Song , Li-Juan Hao , Li-Qin Hu , Yi-Can Wu

The hard X-ray emission from magnetars and other isolated neutron stars remains under-explored. An instrument with higher sensitivity to hard X-rays is critical to understanding the physics of neutron star magnetospheres and also the…

High precision asteroseismic data provide a unique opportunity to test input microphysics such as stellar opacities, chemical composition or equation of state. These tests are possible because pulsational frequencies as well as amplitudes…

Solar and Stellar Astrophysics · Physics 2015-06-18 Przemysław Walczak , Jadwiga Daszyńska-Daszkiewicz

We study theoretical X-ray light curves and polarization properties of accretion-powered millisecond pulsars. We assume that the radiation is produced in two antipodal spots at the neutron star surface which are associated with the magnetic…

Astrophysics · Physics 2009-11-10 Kerttu Viironen , Juri Poutanen

Time-resolved spectroscopic observations of rapidly oscillating Ap (roAp) stars show a complex picture of propagating magneto-acoustic pulsation waves, with amplitude and phase strongly changing as a function of atmospheric height. We have…

Solar and Stellar Astrophysics · Physics 2015-03-13 O. Kochukhov , E. Khomenko

In this paper, we compute a full atlas of radio, X-ray and $\gamma$-ray pulse profiles relying on the force-free magnetosphere model. Our goal is to use such data bank of multi-wavelength profiles to fit a substantial number of radio-loud…

High Energy Astrophysical Phenomena · Physics 2024-07-17 Jérôme Pétri

Understanding the existence of exotic matter phases and phase transitions within the core of neutron stars is crucial to advancing our knowledge of cold-dense matter physics. Recent multi-messenger observations, including gravitational…

High Energy Astrophysical Phenomena · Physics 2025-05-07 Chun Huang , Shashwat Sourav

Neutron stars provide a unique environment to probe the properties of dense nuclear matter. In this work, we present a comparative study between two approaches to modeling the neutron star structure: a Chiral Effective Field Theory based…

Nuclear Theory · Physics 2026-02-20 Federico Nola

In spite of the rich phenomenology of the polarization properties of radio pulsars, the rotating vector model (RVM) created 50 years ago remains the best method to determine the beam geometry of a pulsar. We apply the RVM to a sample of 854…

High Energy Astrophysical Phenomena · Physics 2023-03-08 Simon Johnston , Michael Kramer , Aris Karastergiou , Mike Keith , Lucy Oswald , Aditya Parthasarathy , Patrick Weltevrede

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