Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
Articles 1 - 2 of 2
Full-Text Articles in Physical Sciences and Mathematics
Ergoregion Instability Of Black Hole Mimickers, Paolo Pani, Vitor Cardoso, Mariano Cadoni, Marco Cavaglia
Ergoregion Instability Of Black Hole Mimickers, Paolo Pani, Vitor Cardoso, Mariano Cadoni, Marco Cavaglia
Physics Faculty Research & Creative Works
Ultra-compact, horizonless objects such as gravastars, boson stars, wormholes and superspinars can mimick most of the properties of black holes. Here we show that these "black hole mimickers" will most likely develop a strong ergoregion instability when rapidly spinning. Instability timescales range between ∼ 10-5s and ∼ weeks depending on the object, its mass and its angular momentum. For a wide range of parameters the instability is truly effective. This provides a strong indication that astrophysical ultra-compact objects with large rotation are black holes.
Initial Measurements Of Black Hole Spin In Gx 339-4 From Suzaku Spectroscopy, J. M. Miller, C. S. Reynolds, A. C. Fabian, E. M. Cackett, G. Miniutti, J. Raymond, D. Steeghs, R. Reis, J. Homan
Initial Measurements Of Black Hole Spin In Gx 339-4 From Suzaku Spectroscopy, J. M. Miller, C. S. Reynolds, A. C. Fabian, E. M. Cackett, G. Miniutti, J. Raymond, D. Steeghs, R. Reis, J. Homan
Physics and Astronomy Faculty Research Publications
We report on a deep Suzaku observation of the stellar-mass black hole GX 339-4 in outburst. A clear, strong, relativistically shaped iron emission line from the inner accretion disk is observed. The broadband disk reflection spectrum revealed is one of the most sensitive yet obtained from an accreting black hole. We fit the Suzaku spectra with a physically motivated disk reflection model, blurred by a new relativistic line function in which the black hole spin parameter is a variable. This procedure yielded a black hole spin parameter of a=0.89+/-0.04. Joint modeling of these Suzaku spectra and prior XMM-Newton spectra obtained …