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We calculate the disk and boundary layer luminosities for accreting rapidly rotating neutron stars with low magnetic fields in a fully general relativistic manner. Rotation increases the disk luminosity and decreases the boundary layer…

Astrophysics · Physics 2007-05-23 Arun V. Thampan , Bhaskar Datta

We analyze the effects of including $\Delta(1232)$ isobars in an equation of state (EoS) for cold, $\beta$-stable neutron star matter, employing relativistic nuclear mean field theory. The selected EoS reproduces the properties of nuclear…

High Energy Astrophysical Phenomena · Physics 2019-10-09 Patricia Ribes , Angels Ramos , Laura Tolos , Claudia Gonzalez-Boquera , Mario Centelles

The back-bending phenomenon for compact stars is studied by means of analytical equations of state, for both constant-pressure phase transitions and the transitions through the mixed-phase region. We restrict ourselves to the case of normal…

Astrophysics · Physics 2007-05-23 J. L. Zdunik , M. Bejger , P. Haensel , E. Gourgoulhon

We perform the first study of the oscillation frequencies of rapidly rotating neutron stars in alternative theories of gravity, focusing mainly on the fundamental $f$-modes. We concentrated on a particular class of alternative theories -…

General Relativity and Quantum Cosmology · Physics 2017-09-13 Stoytcho S. Yazadjiev , Daniela D. Doneva , Kostas D. Kokkotas

We obtained high quality spectra of 135 stars of spectral types F and later and derived ``overall'' broadening functions in selected wavelength regions utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of the…

Astrophysics · Physics 2009-11-10 A. Reiners , J. H. M. M. Schmitt Hamburger Sternwarte

As an extension of our previous work, we investigate the dynamical instability against nonaxisymmetric bar-mode deformations of differentially rotating stars in Newtonian gravity varying the equations of state and velocity profiles. We…

Astrophysics · Physics 2009-11-07 Masaru Shibata , Shigeyuki Karino , Yoshiharu Eriguchi

Transitions of nuclear compositions in the crust of a neutron star induced by stellar spin-down are evaluated at zero temperature. We construct a compressible liquid-drop model for the energy of nuclei immersed in a neutron gas, including…

Astrophysics · Physics 2016-08-30 Kei Iida , Katsuhiko Sato

We study the effects of isovector-scalar ($\delta$)-meson on neutron star. Influence of $\delta$-meson on both static and rotating neutron star is discussed. Inclusion of $\delta$-meson in a neutron star system consisting of proton, neutron…

Nuclear Theory · Physics 2016-03-01 S. K. Biswal , Bharat Kumar , S. K. Patra

A one-armed spiral instability has been found to develop in differentially rotating stellar models that have a relatively stiff, $n=1$ polytropic equation of state and a wide range of rotational energies. This suggests that such…

Astrophysics · Physics 2008-11-26 Shangli Ou , Joel E. Tohline

Neutron stars with strong magnetic fields are considered in the framework of f(R) gravity. In order to describe dense matter in magnetic field, the model with baryon octet interacting through $\sigma$$\rho$$\omega$-fields is used. The…

General Relativity and Quantum Cosmology · Physics 2015-06-19 Artyom V. Astashenok , Salvatore Capozziello , Sergei D. Odintsov

We report on an undergraduate student project initiated in the summer semester of 2004 with the aim to establish equations of state for white dwarfs and neutron stars for computing mass-radius relations as well as corresponding maximum…

Astrophysics · Physics 2009-11-13 Irina Sagert , Matthias Hempel , Carsten Greiner , Juergen Schaffner-Bielich

Dynamical instabilities in protoneutron stars may produce gravitational waves whose observation could shed light on the physics of core-collapse supernovae. When born with sufficient differential rotation, these stars are susceptible to a…

We present a systematic study of the properties of pure hadronic and hybrid compact stars. The nuclear equation of state (EoS) for beta-equilibrated neutron star matter was obtained using density dependent effective nucleon-nucleon…

Nuclear Theory · Physics 2015-03-19 Abhishek Mishra , Partha Roy Chowdhury , D. N. Basu

Highly magnetized neutron stars are promising candidates to explain some of the most peculiar astronomical phenomena, for instance, fast radio bursts, gamma-ray bursts, and superluminous supernovae. Pulsations of these highly magnetized…

High Energy Astrophysical Phenomena · Physics 2023-03-13 Man Yin Leung , Anson Ka Long Yip , Patrick Chi-Kit Cheong , Tjonnie Guang Feng Li

At second order in perturbation theory, the $r$-modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation-reaction, the…

High Energy Astrophysical Phenomena · Physics 2018-03-07 John L. Friedman , Lee Lindblom , Keith H. Lockitch

We review the covariant density functional approach to the equation of state of the dense nuclear matter in compact stars. The main emphasis is on the hyperonization of the dense matter, and the role played by the $\Delta$-resonances. The…

Nuclear Theory · Physics 2023-02-08 Armen Sedrakian , Jia-Jie Li , Fridolin Weber

We study the nuclear isentropic equation of state for a stellar matter composed of nucleons, hyperons, and $\Delta$-resonances. We investigate different snapshots of the evolution of a neutron star, from its birth as a lepton-rich…

Nuclear Theory · Physics 2023-09-19 Adamu Issifu , Kauan D. Marquez , Mateus R. Pelicer , Débora P. Menezes

We present long-term (~10^4 M) axisymmetric simulations of differentially rotating, magnetized neutron stars in the slow-rotation, weak magnetic field limit using a perturbative metric evolution technique. Although this approach yields…

Astrophysics · Physics 2009-11-11 Zachariah B. Etienne , Yuk Tung Liu , Stuart L. Shapiro

We investigate the effect of $\Delta$ baryons on the radial oscillations of neutron and hyperon stars, employing a density-dependent relativistic mean-field model. The spin-$3/2$ baryons are described by the Rarita-Schwinger Lagrangian…

Nuclear Theory · Physics 2023-06-21 Ishfaq A. Rather , Kauan D. Marquez , Grigoris Panotopoulos , Ilidio Lopes

We investigate the correlation between nuclear neutron radii and the radius of neutron stars. We use a well-established hadronic SU(3) model based on chiral symmetry that naturally includes non-linear vector meson and scalar meson - vector…

Nuclear Theory · Physics 2009-11-07 S. Schramm