# Ergoregion instability of exotic compact objects: Electromagnetic and gravitational perturbations and the role of absorption

@article{Maggio2019ErgoregionIO, title={Ergoregion instability of exotic compact objects: Electromagnetic and gravitational perturbations and the role of absorption}, author={Elisa Maggio and Vitor Cardoso and Sam R. Dolan and Paolo Pani}, journal={Physical Review D}, year={2019} }

Spinning horizonless compact objects may be unstable against an ``ergoregion instability.'' We investigate this mechanism for electromagnetic perturbations of ultracompact Kerr-like objects with a reflecting surface, extending previous (numerical and analytical) work limited to the scalar case. We derive an analytical result for the frequency and the instability timescale of unstable modes which is valid at small frequencies. We argue that our analysis can be directly extended to gravitational…

## 53 Citations

### Ergoregion instability and echoes for braneworld black holes: Scalar, electromagnetic, and gravitational perturbations

- Physics
- 2020

In the context of higher dimensional braneworld scenario, we have argued that the occurrence of horizonless exotic compact objects, as an alternative to classical black holes, are more natural. These…

### Exotic compact objects interacting with fundamental fields

- Physics
- 2018

Gravitational-wave astronomy offers a novel testing ground for fundamental physics, namely by unfolding new prospects of success in probing the nature of gravity. Current and near-future…

### Superradiant instability of charged scalar fields in higher-dimensional Reissner-Nordström-de Sitter black holes

- PhysicsPhysical Review D
- 2019

Black holes possess trapping regions which lead to intriguing dynamical effects. By properly scattering test fields off a black hole, one can extract energy from it, leading to the growth of the…

### Impact of multiple modes on the black-hole superradiant instability

- PhysicsPhysical Review D
- 2019

Ultralight bosonic fields in the mass range $\sim (10^{-20}-10^{-11})\,{\rm eV}$ can trigger a superradiant instability that extracts energy and angular momentum from an astrophysical black hole with…

### Spicing up the recipe for echoes from exotic compact objects: Orbital differences and corrections in rotating backgrounds

- PhysicsPhysical Review D
- 2020

Recently it has been argued that near-horizon modifications of the standard (classical) black hole spacetime could lead to observable alterations of the gravitational waveform generated by a binary…

### Electromagnetic tests of horizonless rotating black hole mimickers

- Physics
- 2020

The interest in the implications that astrophysical observations have for the understanding of the structure of black holes has grown since the first detection of gravitational waves. Many arguments…

### Black-hole microstate spectroscopy: Ringdown, quasinormal modes, and echoes

- PhysicsPhysical Review D
- 2021

Deep conceptual problems associated with classical black holes can be addressed in string theory by the “fuzzball” paradigm, which provides a microscopic description of a black hole in terms of a…

### Quantum black hole seismology. I. Echoes, ergospheres, and spectra

- Physics
- 2020

Searches for gravitational wave echoes in the aftermath of mergers and/or formation of astrophysical black holes have recently opened a novel and surprising window into the quantum nature of their…

### Lower limit on the entropy of black holes as inferred from gravitational wave observations

- PhysicsPhysical Review D
- 2019

Black hole (BH) thermodynamics was established by Bekenstein and Hawking, who made abstract theoretical arguments about the second law of thermodynamics and quantum theory in curved spacetime…

### Tidal heating as a discriminator for horizons in extreme mass ratio inspirals

- PhysicsPhysical Review D
- 2020

The defining feature of a classical black hole is being a perfect absorber. Any evidence showing otherwise would indicate a departure from the standard black-hole picture. Energy and angular momentum…

## References

SHOWING 1-10 OF 137 REFERENCES

### Exotic Compact Objects and How to Quench their Ergoregion Instability

- Physics, Geology
- 2017

Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some…

### Ergoregion instability of ultracompact astrophysical objects

- Physics
- 2008

Most of the properties of black holes can be mimicked by horizonless compact objects such as gravastars and boson stars. We show that these ultracompact objects develop a strong ergoregion…

### On the ergoregion instability

- PhysicsProceedings of the Royal Society of London. A. Mathematical and Physical Sciences
- 1978

Rotating, ultra-compact stars in general relativity can have an ergo-region, in which all trajectories are dragged in the direction of the star’s rotation. The existence of the ergoregion leads to a…

### Light rings as observational evidence for event horizons: Long-lived modes, ergoregions and nonlinear instabilities of ultracompact objects

- Physics
- 2014

Ultracompact objects are self-gravitating systems with a light ring. It was recently suggested that fluctuations in the background of these objects are extremely long-lived and might turn unstable at…

### The stochastic gravitational-wave background in the absence of horizons

- PhysicsClassical and Quantum Gravity
- 2018

Gravitational-wave astronomy has the potential to explore one of the deepest and most puzzling aspects of Einstein’s theory: the existence of black holes. A plethora of ultracompact, horizonless…

### Gravitational instabilities of superspinars

- Physics
- 2010

Superspinars are ultracompact objects whose mass M and angular momentum J violate the Kerr bound (cJ/GM^2>1). Recent studies analyzed the observable consequences of gravitational lensing and…

### Gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale

- Physics
- 2016

Gravitational waves from binary coalescences provide one of the cleanest signatures of the nature of compact objects. It has been recently argued that the postmerger ringdown waveform of exotic…

### Gravitational wave signatures of the absence of an event horizon: Nonradial oscillations of a thin-shell gravastar

- Physics
- 2009

Gravitational waves from compact objects provide information about their structure, probing deep into strong-gravity regions. Here we illustrate how the presence or absence of an event horizon can…

### Ultra-spinning exotic compact objects supporting static massless scalar field configurations

- Physics
- 2017

### Testing strong-field gravity with tidal Love numbers

- Physics
- 2017

The tidal Love numbers (TLNs) encode the deformability of a self-gravitating object immersed in a tidal environment and depend significantly both on the object's internal structure and on the…