https://doi.org/10.1140/epjc/s10052-024-13053-5
Regular Article - Theoretical Physics
Upper bound on the radius of the innermost photonsphere in the regular compact star spacetime
1
School of Physics and Physical Engineering, Qufu Normal University, 273165, Qufu, Shandong, China
2
School of Mathematical Sciences, Qufu Normal University, 273165, Qufu, Shandong, China
Received:
20
May
2024
Accepted:
25
June
2024
Published online:
11
July
2024
We study properties of the innermost photonsphere in the regular compact star background. We take the traceless energy–momentum tensor and dominant energy conditions. In the regular compact star background, we analytically obtain an upper bound on the radius of the innermost photonsphere as 
where 
is the radius of the innermost photonsphere and M is the total ADM mass of the asymptotically flat compact star spacetime.
© The Author(s) 2024
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