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Evidence for the Black Hole Event Horizon
, 2002
"... Abstract. Roughly a dozen Xray binaries are presently known in which the compact accreting primary stars are too massive to be neutron stars. These primaries are identified as black holes, though there is as yet no definite proof that any of the candidate black holes actually possesses an event hor ..."
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Abstract. Roughly a dozen Xray binaries are presently known in which the compact accreting primary stars are too massive to be neutron stars. These primaries are identified as black holes, though there is as yet no definite proof that any of the candidate black holes actually possesses an event horizon. We discuss how Type I Xray bursts may be used to verify the presence of the event horizon in these objects. Type I bursts are caused by thermonuclear explosions when gas accretes onto a compact star. The bursts are commonly seen in many neutron star Xray binaries, but they have never been seen in any black hole Xray binary. Our model calculations indicate that black hole candidates ought to burst frequently if they have surfaces. Based on this, we argue that the lack of bursts constitutes strong evidence for the presence of event horizons in these objects.
1 Black holes
, 2002
"... Abstract. This paper is concerned with several notquantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole spacetimes. Part of the material has a review character, but some new results or proposals are also presented. We revie ..."
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Abstract. This paper is concerned with several notquantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole spacetimes. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usual one for gravity, and leads to the one associated with the Unruh metric in the case of Euler equations. We review the global conditions which have been used in the Scribased definition of a black hole and point out the deficiencies of the Scri approach. Various results on the structure of horizons and apparent horizons are presented, and a new proof of semiconvexity of horizons based on a variational principle is given. Recent results on the classification of stationary singularityfree vacuum solutions are reviewed. Two new frameworks for discussing black holes are proposed: a “naive approach”, based on coordinate systems, and a “quasilocal approach”, based on timelike boundaries satisfying a null convexity condition. Some properties of the resulting black holes are established, including an area theorem, topology theorems, and an approximation theorem for the location of the horizon. 1.1