Is the Gravitational-Wave Ringdown a Probe of the Event Horizon?

Cardoso, Vítor; Franzin, Edgardo; Pani, Paolo

doi:10.1103/physrevlett.116.171101

Cited by 681 publications

(565 citation statements)

References 52 publications

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“…However, Cardoso et al [40] also realized that the later portion of the ringdown of highly compact ECOs contains a train of decaying echo pulses (note that similar observations have been made before; see for example [44][45][46]). The time delay between the echoes is related to the ECO compactness while the decay and shape of each pulse encodes the reflective properties of the ECO.…”

Section: Introductionmentioning

confidence: 88%

“…In this appendix, we computeRðωÞ for a wormhole [40] describing two Schwarzschild spacetimes of mass M identified with a thin shell of exotic stress-energy at an areal radius r 0 corresponding to a tortoise coordinate location of x 0 . Note that the value ofR depends on our phase convention, and we use that of Eq.…”

Section: Appendix C: Wormhole Reflectivitymentioning

confidence: 99%

“…Standard tests of the nature of the final merged object call for the black hole's resonant frequencies [31][32][33], known as quasinormal mode (QNM) frequencies, to be extracted from the ringdown portion of the waveform and compared to theoretical calculations [34][35][36][37][38][39]. Working in the test particle limit, Cardoso et al [40] pointed out that in the case of highly compact wormholes, the ringdown of the final ECO is initially nearly identical to that of a BH despite the fact that QNM spectrum is radically changed [41][42][43]. A naive application of the QNM based tests would be fooled by a highly compact ECO.…”

Section: Introductionmentioning

confidence: 99%

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A recipe for echoes from exotic compact objects

et al. 2017

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Gravitational wave astronomy provides an unprecedented opportunity to test the nature of black holes and search for exotic, compact alternatives. Recent studies have shown that exotic compact objects (ECOs) can ring down in a manner similar to black holes, but can also produce a sequence of distinct pulses resembling the initial ringdown. These "echoes" would provide definite evidence for the existence of ECOs. In this work we study the generation of these echoes in a generic, parametrized model for the ECO, using Green's functions. We show how to reprocess radiation in the near-horizon region of a Schwarzschild black hole into the asymptotic radiation from the corresponding source in an ECO spacetime. Our methods allow us to understand the connection between distinct echoes and ringing at the resonant frequencies of the compact object. We find that the quasinormal mode ringing in the black hole spacetime plays a central role in determining the shape of the first few echoes. We use this observation to develop a simple template for echo waveforms. This template preforms well over a variety of ECO parameters, and with improvements may prove useful in the analysis of gravitational waves.

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Section: Introductionmentioning

confidence: 88%

Section: Appendix C: Wormhole Reflectivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A recipe for echoes from exotic compact objects

et al. 2017

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“…The cooperative efforts coming from both "classical", electromagnetic observational astrophysics and the new gravitational wave astrophysics will substantially contribute to our future picture of supermassive black holes. However, Cardoso et al (2016) point out that very compact objects with a light ring will display similar ringdown signals as black holes, implying that universal ringdown waveforms indicate the presence of light rings, rather than that of horizons. Hence, it is only that high precision measurements of the late-time ringdown signals may allow us to rule out exotic alternatives to black holes.…”

Section: (Anti)realism and Underdeterminationmentioning

confidence: 99%

“…It was reported that at a distance of about 410 Mpc in the system GW 150914 two very compact objects of about 36 M ⊙ and 29 M ⊙ merged. These objects were probably black holes; however, exotic alternatives still need to be ruled out (see sections 5 and 3.1, Cardoso et al (2016), as well as a comment in The LIGO Scientific Collaboration and The Virgo Collaboration (2016)). For most of the alternative theories, predictions for the specific shape of the ringing signal still need to be performed, although at a higher frequency, these measurements validate the method proposed to search for supermassive binary black holes and support the possibility of detection gravitational wave ringing from such systems.…”

Section: Gravitational Wave Signals From Inspiraling Objectsmentioning

confidence: 99%

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

Eckart

Hüttemann²,

Kiefer³

et al. 2017

Found Phys

123

105

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The compact and, with 4.3±0.3×106 M ⊙ , very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity. The strongest evidence for this is provided by measurements of stellar orbits, variable X-ray emission, and strongly variable polarized near-infrared emission from the location of the radio source Sagittarius A* (SgrA*) in the middle of the central stellar cluster. Simultaneous near-infrared and X-ray observations of SgrA* have revealed insights into the emission mechanisms responsible for the powerful near-infrared and X-ray flares from within a few tens to one hundred Schwarzschild radii of such a putative SMBH at the center of the Milky Way. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target of the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) observations currently being prepared. These observations in combination with the infrared interferometry experiment GRAVITY at the Very Large Telescope Interferometer (VLTI) and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. The large body of evidence continues to discriminate the identification of SgrA* as a SMBH from alternative possibilities. It is, however, unclear when the ever mounting evidence for SgrA* being associated with a SMBH will suffice as a convincing proof. Additional compelling evidence may come from future gravitational wave observatories. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about "(Anti)Realism and Underdetermination", as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts.

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The basic physics of the binary black hole merger GW150914

Abbott¹,

Abbott²,

Abbott³

et al. 2016

Annalen der Physik

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The first direct gravitational-wave detection was made by the Advanced Laser Interferometer Gravitational Wave Observatory on September 14, 2015. The GW150914 signal was strong enough to be apparent, without using any waveform model, in the filtered detector strain data. Here, features of the signal visible in the data are analyzed using concepts from Newtonian physics and general relativity, accessible to anyone with a general physics background. The simple analysis presented here is consistent with the fully general-relativistic analyses published elsewhere, in showing that the signal was produced by the inspiral and subsequent merger of two black holes. The black holes were each of approximately 35 Mʘ, still orbited each other as close as ∼350 km apart and subsequently merged to form a single black hole. Similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the Earth, and the energy that they radiated in gravitational waves

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Is the Gravitational-Wave Ringdown a Probe of the Event Horizon?

Cited by 681 publications

References 52 publications

A recipe for echoes from exotic compact objects

A recipe for echoes from exotic compact objects

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

The basic physics of the binary black hole merger GW150914

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