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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2411.04001 |
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| _version_ | 1866917939846840320 |
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| author | Zhu, Qing-Hua |
| author_facet | Zhu, Qing-Hua |
| contents | The efforts to probe the horizon-scale structure of black holes, such as Event Horizon Telescope and GRAVITY interferometer, might provide valuable insights into the strong-field regime of Einstein's theory of gravity. In the near field region of a black hole, the observational signatures of moving hotspots might potentially reveal the mechanism causing the flares, or reflect the spacetime geometries. This paper develops a ray tracing scenario to study higher-order images of moving hotspots in a thin disk around a spherical black hole. Our ray-tracing scenario establishes a one-to-one mapping between emission locations and observer's sky. It enables us to perform infinite-precision simulations for the images, because the emission sources are projected directly onto the image plane. Furthermore, we show that a source located anywhere outside the black hole can be repeatedly mapped onto the observer's sky, from primary to higher-order images. We investigate the observational signatures of hotspots, focusing on temporal fluxes and flux centroids from the primary to sixth-order images. The hotspots are considered to be moving in circular, escape, and plunging orbits. Our results find that the higher-order images can be categorized into two types. Within each type, the temporal fluxes exhibit a self-similar profile. Furthermore, as the hotspots approach the event horizon of a black hole, the fluxes from higher-order images alternately dominate the observed flux, which subsequently result in the flux decaying with time in an oscillatory manner. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2411_04001 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Observational signatures from higher-order images of moving hotspots in accretion disks Zhu, Qing-Hua General Relativity and Quantum Cosmology The efforts to probe the horizon-scale structure of black holes, such as Event Horizon Telescope and GRAVITY interferometer, might provide valuable insights into the strong-field regime of Einstein's theory of gravity. In the near field region of a black hole, the observational signatures of moving hotspots might potentially reveal the mechanism causing the flares, or reflect the spacetime geometries. This paper develops a ray tracing scenario to study higher-order images of moving hotspots in a thin disk around a spherical black hole. Our ray-tracing scenario establishes a one-to-one mapping between emission locations and observer's sky. It enables us to perform infinite-precision simulations for the images, because the emission sources are projected directly onto the image plane. Furthermore, we show that a source located anywhere outside the black hole can be repeatedly mapped onto the observer's sky, from primary to higher-order images. We investigate the observational signatures of hotspots, focusing on temporal fluxes and flux centroids from the primary to sixth-order images. The hotspots are considered to be moving in circular, escape, and plunging orbits. Our results find that the higher-order images can be categorized into two types. Within each type, the temporal fluxes exhibit a self-similar profile. Furthermore, as the hotspots approach the event horizon of a black hole, the fluxes from higher-order images alternately dominate the observed flux, which subsequently result in the flux decaying with time in an oscillatory manner. |
| title | Observational signatures from higher-order images of moving hotspots in accretion disks |
| topic | General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2411.04001 |