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Shadows of naked singularity in Brans–Dicke gravity.

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Title: Shadows of naked singularity in Brans–Dicke gravity.
Authors: Puttasiddappa, Prajwal Hassan1,2 (AUTHOR) prajwal.puttasiddappa@edu.ufes.br, Rodrigues, Davi C.3,4 (AUTHOR), Mota, David F.2 (AUTHOR)
Source: European Physical Journal C -- Particles & Fields. Sep2025, Vol. 85 Issue 9, p1-7. 7p.
Subjects: Event Horizon Telescope, Compact objects (Astronomy), Mathematical singularities, Astrophysics, Ray tracing algorithms
Abstract: We investigate exact vacuum solutions in Brans–Dicke (BD) gravity, focusing on their implications for black hole shadow imaging. Motivated by the Event Horizon Telescope (EHT) observations, we revisit a class of BD solutions that exhibit a naked singularity. These solutions, despite lacking a conventional event horizon, exhibit photon spheres and produce shadow-like features. We analyze null geodesics and perform ray-tracing simulations under an optically thin accretion disk model to generate synthetic images. Our results show that BD naked singularities can cast shadows smaller than those of Schwarzschild black holes of equivalent mass. This requires, however, negative values for the BD parameter ω (in the range - 3 / 2 < ω < 0 ). The lower bound on ω is compatible with the absence of ghosts. Although such ω range is outside the Solar System bounds, our results are relevant for a larger class of modified gravity models whose local behaviour can be approximated by Brans–Dicke gravity. These findings suggest that BD naked singularities are possible candidates for compact astrophysical objects. [ABSTRACT FROM AUTHOR]
Copyright of European Physical Journal C -- Particles & Fields is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: We investigate exact vacuum solutions in Brans–Dicke (BD) gravity, focusing on their implications for black hole shadow imaging. Motivated by the Event Horizon Telescope (EHT) observations, we revisit a class of BD solutions that exhibit a naked singularity. These solutions, despite lacking a conventional event horizon, exhibit photon spheres and produce shadow-like features. We analyze null geodesics and perform ray-tracing simulations under an optically thin accretion disk model to generate synthetic images. Our results show that BD naked singularities can cast shadows smaller than those of Schwarzschild black holes of equivalent mass. This requires, however, negative values for the BD parameter ω (in the range - 3 / 2 &lt; ω &lt; 0 ). The lower bound on ω is compatible with the absence of ghosts. Although such ω range is outside the Solar System bounds, our results are relevant for a larger class of modified gravity models whose local behaviour can be approximated by Brans–Dicke gravity. These findings suggest that BD naked singularities are possible candidates for compact astrophysical objects. [ABSTRACT FROM AUTHOR]
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  Data: &lt;i&gt;Copyright of European Physical Journal C -- Particles &amp; Fields is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder&#39;s express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.&lt;/i&gt; (Copyright applies to all Abstracts.)
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      – SubjectFull: Mathematical singularities
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      – SubjectFull: Ray tracing algorithms
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      – TitleFull: Shadows of naked singularity in Brans–Dicke gravity.
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            NameFull: Puttasiddappa, Prajwal Hassan
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              M: 09
              Text: Sep2025
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