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arXiv · 2206.13705

Appearance of an Infalling Star in Black Holes with Multiple Photon Spheres

Yiqian Chen·Guangzhou Guo·Peng Wang·Houwen Wu·Haitang Yang
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Abstract

Photon spheres play a pivotal role in the imaging of luminous objects near black holes. In this paper, we examine observational appearances of a star freely falling in hairy black holes, which can possess one or two photon spheres outside the event horizon. When there exists a single photon sphere, the total luminosity measured by distant observers decreases exponentially with time at late times. Due to successive arrivals of photons orbiting around the photon sphere different times, a specific observer would see a series of light flashes with decreasing intensity, which share a similar frequency content. Whereas in the case with two photon spheres, photons temporarily trapped between the photon spheres can cause a peak of the total luminosity, which is followed by a slow exponential decay, at late times. In addition, these photons lead to one more series of light flashes seen by the specific observer.

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Yiqian Chen, Guangzhou Guo, Peng Wang, Houwen Wu, Haitang Yang. 2022-06-28. Appearance of an Infalling Star in Black Holes with Multiple Photon Spheres. https://arxiv.org/abs/2206.13705

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