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TOPIC: Black Holes


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SDSS J0927+2943
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A mammoth black hole has been discovered fleeing its host galaxy at high speed, according to a controversial new study. The galactic eviction may be the result of a violent merger between two black holes.

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RE: Black Holes
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A colossal black hole has been spotted exiting its home galaxy, kicked out after a huge cosmic merger took place.
The event, seen for the first time, was announced today.

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Light echo of a high-energy flash from a black hole first observed in detail
A light echo occurs when interstellar gas is heated by radiation and reacts by emission of light. An international team led by Stefanie Komossa from the Max Planck Institute for extraterrestrial Physics in Garching, Germany, has observed the light echo of an enormous X-ray flare, which was almost certainly produced when a single star was disrupted by a supermassive black hole. For the first time, the light echo of such a rare and highly dramatic event could be observed in great detail. The light echo not only revealed the stellar disruption process, but it also provides a powerful new method for mapping galactic nuclei (Astrophysical Journal Letters, Mai 2008).

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Three-black-hole collisions
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Title: Close encounters of three black holes
Authors: Manuela Campanelli, Carlos O. Lousto, Yosef Zlochower
(Version v2)

We present the first fully relativistic longterm numerical evolutions of three equal-mass black holes in a system consisting of a third black hole in a close orbit about a black-hole binary. We find that these close-three-black-hole systems have very different merger dynamics from black-hole binaries. In particular, we see complex trajectories, a redistribution of energy that can impart substantial kicks to one of the holes, distinctive waveforms, and suppression of the emitted gravitational radiation. We evolve two such configurations and find very different behaviors. In one configuration the binary is quickly disrupted and the individual holes follow complicated trajectories and merge with the third hole in rapid succession, while in the other, the binary completes a half-orbit before the initial merger of one of the members with the third black hole, and the resulting two-black-hole system forms a highly elliptical, well separated binary that shows no significant inspiral for (at least) the first t~1000M of evolution.

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The same team of astrophysicists that cracked the computer code simulating two black holes crashing and merging together has now, for the first time, caused a three-black-hole collision.
Manuela Campanelli, Carlos Lousto and Yosef Zlochowerscientists in Rochester Institute of Technologys Centre for Computational Relativity and Gravitationsimulated triplet black holes to test their breakthrough method that, in 2005, merged two of these large mass objects on a supercomputer following Einsteins theory of general relativity.
The new simulation of multiple black holes evolving, orbiting and eventually colliding confirmed a robust computer code free of limitations. The May issue of Physical Review D will publish the teams latest findings in the article Close Encounters of Three Black Holes, revealing the distinct gravitational signature three black holes might produce. The story will run under the Rapid Communications section.

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How does one weigh a supermassive black hole that is anywhere between a million and a billion times the mass of the Sun? The answer could be as easy as taking a snapshot of its surrounding galaxy.
A team of astronomers has concluded that the larger the black hole at the centre of a spiral galaxy, the tighter the galaxy's arms wrap around itself. If correct, the simple relationship would give researchers an easy way to learn about black holes up to 8 billion light years away thousands of times farther than most black hole masses can be resolved today.
Marc Seigar of the University of Arkansas in Little Rock, US, and colleagues studied 37 spiral galaxies, including the Milky Way and our neighbour, Andromeda.
Those with the smallest black holes had their arms outstretched at angles of as much as 43° (scroll down for image), while those with the biggest black holes hugged themselves much more tightly, with as few as 7° separating the galaxies' arms from their cores.

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Title: Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morpholohy. I. Method Outline
Authors: Marc S. Seigar

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Title: The fuzzball proposal for black holes
Authors: Kostas Skenderis, Marika Taylor

The fuzzball proposal states that associated with a black hole of entropy S there are exp S horizon-free non-singular solutions that asymptotically look like the black hole but generically differ from the black hole up to the horizon scale. These solutions, the fuzzballs, are considered to be the black hole microstates while the original black hole represents the average description of the system. The purpose of this report is to review current evidence for the fuzzball proposal, emphasizing the use of AdS/CFT methods in developing and testing the proposal. In particular, we discuss the status of the proposal for 2 and 3 charge black holes in the D1-D5 system, presenting new derivations and streamlining the discussion of their properties. Results to date support the fuzzball proposal but further progress is likely to require going beyond the supergravity approximation and sharpening the definition of a "stringy fuzzball". We outline how the fuzzball proposal could resolve longstanding issues in black hole physics, such as Hawking radiation and information loss. Our emphasis throughout is on connecting different developments and identifying open problems and directions for future research.

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Title: New theoretical approaches to black holes
Authors: Eric Gourgoulhon (LUTH, Meudon), Jose Luis Jaramillo (IAA, Granada)
(Version v2)

Quite recently, some new mathematical approaches to black holes have appeared in the literature. They do not rely on the classical concept of event horizon -- which is very global, but on the local concept of hypersurfaces foliated by trapped surfaces. After a brief introduction to these new horizons, we focus on a viscous fluid analogy that can be developed to describe their dynamics, in a fashion similar to the membrane paradigm introduced for event horizons in the seventies, but with a significant change of sign of the bulk viscosity.

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