X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity
Abstract The strong gravitational potential of neutron stars (NSs) makes them ideal astrophysical objects for testing extreme gravity phenomena. We explore the potential of NS X-ray pulsed light curve observations to probe deviations from general relativity (GR) within the scalar–tensor theory (STT)...
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| Language: | English |
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SpringerOpen
2024-12-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-024-13721-6 |
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| author | Tulio Ottoni Jaziel G. Coelho Rafael C. R. de Lima Jonas P. Pereira Jorge A. Rueda |
| author_facet | Tulio Ottoni Jaziel G. Coelho Rafael C. R. de Lima Jonas P. Pereira Jorge A. Rueda |
| author_sort | Tulio Ottoni |
| collection | DOAJ |
| description | Abstract The strong gravitational potential of neutron stars (NSs) makes them ideal astrophysical objects for testing extreme gravity phenomena. We explore the potential of NS X-ray pulsed light curve observations to probe deviations from general relativity (GR) within the scalar–tensor theory (STT) of gravity framework. We compute the flux from a single, circular, finite-size hot spot, accounting for light bending, Shapiro time delay, and Doppler effect. We focus on the high-compactness regime, i.e., close to the critical GR value $$GM/(c^2 R)=0.284$$ G M / ( c 2 R ) = 0.284 , over which multiple images of the spot appear and impact crucially the light curves. Our investigation is motivated by the increased sensitivity of the pulse to the scalar charge of the spacetime in such high compactness regimes, making these systems exceptionally suitable for scrutinizing deviations from GR, notably phenomena such as spontaneous scalarization, as predicted by STT. We find significant differences in NS observables, e.g., the flux of a single spot can differ up to 80% with respect to GR. Additionally, reasonable choices for the STT parameters that satisfy astrophysical constraints lead to changes in the NS radius relative to GR of up to approximately 10%. Consequently, scalar parameters might be better constrained when uncertainties in NS radii decrease, where this could occur with the advent of next-generation gravitational wave detectors, such as the Einstein Telescope and LISA, as well as future electromagnetic missions like eXTP and ATHENA. Thus, our findings suggest that accurate X-ray data of the NS surface emission, jointly with refined theoretical models, could constrain STTs. |
| format | Article |
| id | doaj-art-f41148d355d844bf924860d847f9a1b7 |
| institution | Kabale University |
| issn | 1434-6052 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | European Physical Journal C: Particles and Fields |
| spelling | doaj-art-f41148d355d844bf924860d847f9a1b72025-02-02T12:39:10ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60522024-12-01841211410.1140/epjc/s10052-024-13721-6X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravityTulio Ottoni0Jaziel G. Coelho1Rafael C. R. de Lima2Jonas P. Pereira3Jorge A. Rueda4PPGCosmo, Universidade Federal do Espírito SantoNúcleo de Astrofísica e Cosmologia (Cosmo-Ufes) and Departamento de Física, Universidade Federal do Espírito SantoDepartamento de Física, Universidade do Estado de Santa CatarinaNúcleo de Astrofísica e Cosmologia (Cosmo-Ufes) and Departamento de Física, Universidade Federal do Espírito SantoICRANet-Ferrara, Dipartimento di Fisica e Scienze della Terra, Università degli Studi di FerraraAbstract The strong gravitational potential of neutron stars (NSs) makes them ideal astrophysical objects for testing extreme gravity phenomena. We explore the potential of NS X-ray pulsed light curve observations to probe deviations from general relativity (GR) within the scalar–tensor theory (STT) of gravity framework. We compute the flux from a single, circular, finite-size hot spot, accounting for light bending, Shapiro time delay, and Doppler effect. We focus on the high-compactness regime, i.e., close to the critical GR value $$GM/(c^2 R)=0.284$$ G M / ( c 2 R ) = 0.284 , over which multiple images of the spot appear and impact crucially the light curves. Our investigation is motivated by the increased sensitivity of the pulse to the scalar charge of the spacetime in such high compactness regimes, making these systems exceptionally suitable for scrutinizing deviations from GR, notably phenomena such as spontaneous scalarization, as predicted by STT. We find significant differences in NS observables, e.g., the flux of a single spot can differ up to 80% with respect to GR. Additionally, reasonable choices for the STT parameters that satisfy astrophysical constraints lead to changes in the NS radius relative to GR of up to approximately 10%. Consequently, scalar parameters might be better constrained when uncertainties in NS radii decrease, where this could occur with the advent of next-generation gravitational wave detectors, such as the Einstein Telescope and LISA, as well as future electromagnetic missions like eXTP and ATHENA. Thus, our findings suggest that accurate X-ray data of the NS surface emission, jointly with refined theoretical models, could constrain STTs.https://doi.org/10.1140/epjc/s10052-024-13721-6 |
| spellingShingle | Tulio Ottoni Jaziel G. Coelho Rafael C. R. de Lima Jonas P. Pereira Jorge A. Rueda X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity European Physical Journal C: Particles and Fields |
| title | X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity |
| title_full | X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity |
| title_fullStr | X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity |
| title_full_unstemmed | X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity |
| title_short | X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity |
| title_sort | x ray pulsed light curves of highly compact neutron stars as probes of scalar tensor theories of gravity |
| url | https://doi.org/10.1140/epjc/s10052-024-13721-6 |
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