Abstract
Ultracompact objects with light rings (LRs) but without an event horizon could mimic black holes (BHs) in their strong gravity phenomenology. But are such objects dynamically viable? Stationary and axisymmetric ultracompact objects that can form from smooth, quasi-Minkowski initial data must have at least one stable LR, which has been argued to trigger a spacetime instability; but its development and fate have been unknown. Using fully nonlinear numerical evolutions of ultracompact bosonic stars free of any other known instabilities and introducing a novel adiabatic effective potential technique, we confirm the LRs triggered instability, identifying two possible fates: migration to nonultracompact configurations or collapse to BHs. In concrete examples we show that typical migration (collapse) timescales are not larger than light-crossing times, unless the stable LR potential well is very shallow. Our results show that the LR instability is effective in destroying horizonless ultracompact objects that could be plausible BH imitators.
- Received 12 August 2022
- Accepted 6 December 2022
DOI:https://doi.org/10.1103/PhysRevLett.130.061401
© 2023 American Physical Society
Physics Subject Headings (PhySH)
synopsis
Don’t Be Sold on Black Hole Imitators
Published 7 February 2023
The results of new simulations negate the argument that some objects thought to be black holes are instead hypothetical exotic systems called bosonic stars.
See more in Physics