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We consider a relativistic radiating spherical star in conformally flat spacetimes. In particular we study the junction condition relating the radial pressure to the heat flux at the boundary of the star which is a nonlinear partial…

General Relativity and Quantum Cosmology · Physics 2014-12-23 G. Abebe , K. S. Govinder , S. D. Maharaj

Simple spherical, non-rotating stellar models are inadequate when describing real stars in the limit of very fast rotation: Both the observable spectrum and the geometrical shape of the star deviate strongly from simple models. We attempt…

Solar and Stellar Astrophysics · Physics 2015-05-30 T. H. Dall , L. Sbordone

We investigate static and spherically symmetric stars disformally coupled to a scalar field. The scalar field is assumed to be shift symmetric, and hence the conformal and disformal factors of the metric coupled to matter are dependent only…

General Relativity and Quantum Cosmology · Physics 2021-11-17 Tact Ikeda , Aya Iyonaga , Tsutomu Kobayashi

Classical Be stars are introduced as object class and their particular potential for space based photometry is highlighted. A brief summary of the various types of variability observed in Be stars makes clear that an interpretation of every…

Solar and Stellar Astrophysics · Physics 2016-10-25 Thomas Rivinius , Dietrich Baade , Alex C. Carciofi

Stars are not perfectly spherically symmetric. They are deformed by rotation and magnetic fields. Until now, the study of stellar shapes has only been possible with optical interferometry for a few of the fastest-rotating nearby stars. We…

Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because…

High Energy Astrophysical Phenomena · Physics 2017-12-01 Vasileios Paschalidis , Nikolaos Stergioulas

Aether Scalar-Tensor theory is a relativistic alternative gravity model that behaves like cold dark matter on cosmological scales while predicting the MOND force-law in astrophysical systems. The theory correctly predicts the cosmic…

General Relativity and Quantum Cosmology · Physics 2025-05-07 Christopher Reyes , Jeremy Sakstein

In this paper we review the basics of magneto-rotational properties of neutron stars focusing on spin-up/spin-down behavior at different evolutionary stages. The main goal is to provide equations for the spin frequency changes in various…

High Energy Astrophysical Phenomena · Physics 2024-02-08 P. Abolmasov , A. V. Biryukov , S. B. Popov

We give a brief overview of where we stand with respect to some old and new questions bearing on how massive stars evolve and end their lifetime. We focus on the following key points that are further discussed by other contributions during…

Solar and Stellar Astrophysics · Physics 2017-11-15 Georges Meynet , André Maeder , Cyril Georgy , Sylvia Ekström , Patrick Eggenberger , Fabio Barblan , Han Feng Song

In this work we consider the thermal evolution of rigidly rotating neutron stars. In order to perform such study we first calculate the structure of rotating objects, which is considerably more complicated than that of spherical objects.…

High Energy Astrophysical Phenomena · Physics 2013-07-30 Rodrigo Negreiros , Stefan Schramm , Fridolin Weber

Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence, and are key probes of the evolutionary properties of galaxies. The focus of this review is on the broad patterns in…

Astrophysics · Physics 2012-08-27 Robert C. Kennicutt,

We study continuous phase spaces of single spins and develop a complete description of their time evolution. The time evolution is completely specified by so-called star products. We explicitly determine these star products for general spin…

Quantum Physics · Physics 2019-01-11 Bálint Koczor , Robert Zeier , Steffen J. Glaser

We have found some new exact static spherically symmetric interior solutions of metric $f(R)$ gravitational theories describing the equilibrium configuration of a star. Then the solution is matched to the exterior solution and thus gives a…

General Relativity and Quantum Cosmology · Physics 2015-05-30 Ali Shojai , Fatimah Shojai

The present work investigates the numerical evolution of linearized oscillations of non-rotating, spherically symmetric neutron stars within the framework of general relativity. We derive the appropriate equations using the (3+1)-formalism.…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Johannes Ruoff

It is shown, for the self-consistent system of scalar, electro-magnetic and gravitational fields in general relativity, that the equations of motion admit a special kind of solutions with spherical or cylindrical symmetry. For these…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Yu. P. Rybakov , B. Saha , G. N. Shikin

Stars and their exoplanets evolve together. Depending on the physical characteristics of these systems, such as age, orbital distance and activity of the host stars, certain types of star-exoplanet interactions can dominate during given…

Solar and Stellar Astrophysics · Physics 2020-09-30 A. A. Vidotto

We investigate the neutron stars spin evolution (breaking, inclination angle evolution and radiative precession), taking into account the superfluidity of the neutrons in the star core. The neutron star is treated as a two-component system…

High Energy Astrophysical Phenomena · Physics 2013-03-25 D. P. Barsukov , O. A. Goglichidze , A. I. Tsygan

Neutron stars are highly compact astrophysical objects and therefore of utmost relevance to learn about theories of gravity. Whereas the proper equation of state of the nuclear matter inside neutron stars is not yet known, and a wide range…

General Relativity and Quantum Cosmology · Physics 2022-04-28 Jutta Kunz

The rotation rate of a star has important implications for the detectability, characterisation and stability of any planets that may be orbiting it. This chapter gives a brief overview of stellar rotation before describing the methods used…

Earth and Planetary Astrophysics · Physics 2018-12-05 P. F. L. Maxted

We are interested in the global dynamics of a massive scalar field evolving under its own gravitational field and, in this paper, we study spherically symmetric solutions to Einstein's field equations coupled with a Klein-Gordon equation…

General Relativity and Quantum Cosmology · Physics 2022-12-29 Philippe G. LeFloch , Filipe C. Mena , The-Cang Nguyen