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How well is the vacuum Kerr geometry a good description of the dark, compact objects in our universe? Precision measurements of accreting matter in the deep infrared and gravitational-wave measurements of coalescing objects are finally providing answers to this question. Here, we study the possibility of resonant excitation of the modes of the central object -- taken to be very compact but horizonless -- during an extreme-mass-ratio inspiral. We show that for very compact objects resonances are indeed excited. However, the impact of such excitation on the phase of the gravitational-wave signal is negligible, since resonances are crossed very quickly during inspiral.
We study here the precession of the spin of a test gyroscope attached to a stationary observer in the Kerr spacetime, specifically, to distinguish naked singularity (NS) from black hole (BH). It was shown recently that for gyros attached to static ob
During the early phase of in-spiral of a binary system, the tidal heating of a compact object due to its companion plays a significant role in the determination of the orbital evolution of the binary. The phenomenon depends crucially on the `hairs, a
Gravitational waves from coalescing binary black holes encode the evolution of their spins prior to merger. In the post-Newtonian regime and on the precession timescale, this evolution has one of three morphologies, with the spins either librating ar
We show that photon spheres of supermassive black holes generate high-frequency stochastic gravitational waves through the photon-graviton conversion. Remarkably, the frequency is universally determined as $m_esqrt{m_e /m_p} simeq 10^{20} text{Hz}$ i
Black-holes in asymptotically flat space-times have negative specific heat --- they get hotter as they loose energy. A clear statistical mechanical understanding of this has remained a challenge. In this work, we address this issue using fluid-gravit