Magnetic Black Holes: from Thomson Dipoles to the Penrose Process and Cosmic Censorship

We consider accretion of charged test matter by rotating, magnetic black holes and discuss a number of aspects in which the interaction of the angular momentum contained in the electromagnetic field and the spin of the hole plays a fundamental role. First, we argue that such a black hole tends to lose its angular momentum by accreting charges while remaining globally neutral. Then, we show that accretion can happen in a superradiant manner via an enhanced Penrose process. In particular, we find that the regions from which energy and angular momentum can be extracted contain the axis of rotation and, in some cases, consist of floating bubbles disconnected from the black hole itself. Finally, we address the question of whether extremal dyonic rotating black holes can be overcharged or overspun via accretion of arbitrary matter, and prove that this can not happen if the null-energy condition holds. We conclude by discussing some future research directions.Comment: 12+5 pages, 4 figures, one mathematica packag

Kerr-fully Diving into the Abyss: Analytic Solutions to Plunging Geodesics in Kerr

We present closed-form solutions for plunging geodesics in the extended Kerr spacetime using Boyer-Lindquist coordinates. Our solutions directly solve for the dynamics of generic timelike plunges, we also specialise to the case of test particles plunging from a precessing innermost stable circular orbit (ISSO). We find these solutions in the form of elementary and Jacobi elliptic functions parameterized by Mino time. In particular, we demonstrate that solutions for the ISSO case can be determined almost entirely in terms of elementary functions, depending only on the spin parameter of the black hole and the radius of the ISSO. This extends recent work on the case of equatorial plunges from the innermost stable circular orbit. Furthermore, we introduce a new equation that characterizes the radial inflow from the ISSO to the horizon, taking into account the inclination. For ease of application, our results have been implemented in the KerrGeodesics package in the Black Hole Perturbation Toolkit.Comment: 22 pages, 7 Figure

Waveform Modelling for the Laser Interferometer Space Antenna

International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome

Waveform Modelling for the Laser Interferometer Space Antenna

International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome