Where are all the gravastars? Limits upon the gravastar model from accreting black holes

Broderick, Avery E.; Narayan, Ramesh

doi:10.1088/0264-9381/24/3/009

Cited by 107 publications

(114 citation statements)

References 20 publications

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“…It has been proposed as an alternative to black holes first by Mazur and Mottola (2001). Broderick and Narayan (2007) discuss the grava-star model for SgrA* but conclude that present day astronomical observations rule out modifications of GR of the kind described by Chapline (2003) on all scales larger than the Planck length.…”

Section: Grava-starsmentioning

confidence: 84%

“…One observational consequence of the analysis presented by Broderick and Narayan (2007) is that (in particular) in the case of SgrA*, a grava-star will not have had sufficient opportunity to cool if the accretion is continuous. However, if mass accretion is predominantly done through stellar capture events during a rather transient rapid accretion, this would allow us SgrA* to cool over timescales between captures of the order of 10 4 years.…”

Section: Grava-starsmentioning

confidence: 99%

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

Eckart

Hüttemann²,

Kiefer³

et al. 2017

Found Phys

122

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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Section: Grava-starsmentioning

confidence: 84%

Section: Grava-starsmentioning

confidence: 99%

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

Eckart

Hüttemann²,

Kiefer³

et al. 2017

Found Phys

122

105

View full text Add to dashboard Cite

show abstract

“…Unfortunately, when attempting to move beyond qualitative statements of this type, specific predictions are frustratingly model-dependent, but there is some "wriggle room" for interesting new physics. On a cautionary note, we should point out that several authors have looked at the question of what observational signals for black hole mimics might look like [36,37]. Critically, once you add rotation, the ergosurface is probably more important than the "would-be horizon".…”

Section: Pos(bhs Gr and Strings)010mentioning

confidence: 98%

Small, dark, and heavy: But is it a black hole?

Visser

Barceló²,

Liberati³

et al. 2009

Proceedings of Black Holes in General Relativity and String Theory — PoS(BHs, GR and Strings)

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“…Several examples of this strategy have been considered in the past. For instance, would-be black holes within Rosen's bimetric theory of gravity [8], or, more recently, some "gravstar" models [9].…”

Section: Introductionmentioning

confidence: 99%

Wormholes as black hole foils

2007

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We study to what extent wormholes can mimic the observational features of black holes. It is surprisingly found that many features that could be thought of as "characteristic" of a black hole (endowed with an event horizon) can be closely mimicked by a globally static wormhole, having no event horizon. This is the case for: the apparently irreversible accretion of matter down a hole, no-hair properties, quasinormal-mode ringing, and even the dissipative properties of black hole horizons, such as a finite surface resistivity equal to 377 Ohms. The only way to distinguish the two geometries on an observationally reasonable time scale would be through the detection of Hawking's radiation, which is, however, too weak to be of practical relevance for astrophysical black holes. We point out the existence of an interesting spectrum of quantum microstates trapped in the throat of a wormhole which could be relevant for storing the information "lost" during a gravitational collapse.

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Where are all the gravastars? Limits upon the gravastar model from accreting black holes

Cited by 107 publications

References 20 publications

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

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

Small, dark, and heavy: But is it a black hole?

Wormholes as black hole foils

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