Astrophysical tests of strong-field gravity: pulse profile modeling and boundary conditions in neutron stars
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Data
2025-03-14
Autores
Costa, Tulio Ottoni Ferreira da
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Universidade Federal do Espírito Santo
Resumo
We live in a golden age to explore gravity in the strong field regime of compact objects. Present and future multimessenger experiments will allow precision tests with high-energy electromagnetic radiation and gravitational waves, probing the relativistic environment of compact objects. This thesis comprises two main parts and explores the strong gravity of neutron stars (NS). In the first part, we compute bolometric light curves from emitting hot spots on the surface of pulsars in the context of the Scalar-Tensor theory of gravity. This calculation considers several relativistic ingredients that affect the observed flux, such as Doppler shift, light bending, and time delay. We show that highly compact NSs, with compactness close to GM/Rc2 ∼ 0.284, are ideal astrophysical laboratories to seek deviations of General Relativity (GR) because of the light curve’s sensitivity to the gravity theory. In the second part, we explore the possibility of non-rigid rotation of NSs, studying a toy model that captures the main idea of a stratified rotation. We show the impact of different parts of the NS rotating with different angular velocities on the moment of inertia, exploring some of its astrophysical consequences. Our study aims to call attention to possible systematics when performing inference of NS parameters by techniques such as the timing of radio pulses or pulse profile modeling when assuming that the star rotates rigidly.
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Astrofísica , Relatividade geral , Teoria de campos