Found 16 talks width keyword black holes
AbstractTwo-dimensional stellar kinematics obtained with the integral-field spectrograph SAURON allow the classification of early-type galaxies into 'slow' and 'fast' rotators, different from their morphological classification into ellipticals and lenticulars. Most fast rotators, including lenticular as well as many elliptical galaxies, are consistent with oblate axisymmetric disk-like systems. On the other hand, the slow-rotator ellipticals show clear deviations from axisymmetry, which can be modeled with our extension of Schwarzschild's orbit superposition method to triaxial geometry. Besides galaxies, I show that Schwarzschild's method can also be used to model in detail globular clusters such as ω Cen and M15. The recovered internal orbital structure of ω Cen reveals besides a signature of tidal interaction, also a central stellar disk, supporting its origin as the nucleus of a stripped dwarf galaxy. The formally best-fit Schwarzschild model for M15 includes an intermediate-mass black hole, but we cannot exclude a model in which dark remnants make up the dark mass in the collapsed core.
AbstractFor most persistent low mass X-ray binaries (LMXBs) and transients in outbursts the optical emission is dominated by reprocessing of the X-rays in the outer accretion disk. This has severely hampered any dynamical studies and thereby our knowledge of their system parameters. A new avenue opened thanks to the discovery of narrow high-excitation emission components arising from the irradiated companion star. These lines are most prominent in the Bowen region (a blend of N III and C III lines between 4630 and 4650 Å). In this talk I will discuss this new technique, give an overview of the main results of our survey on the optically brightest LMXBs, and discuss the implications for their system parameters. Furthermore, I will point out the main limitations of this technique and how they might be overcome.
There is a "Warped side" of our universe, consisting of objects and phenomena that are made solely or largely from warped spacetime. Examples are black holes, singularities (inside black holes and in the big bang), and cosmic strings. Numerical-relativity simulations are revolutionizing our understanding of what could exist on our universe's Warped Side; and gravitational-wave observations (LIGO, VIRGO, LISA, ...) will reveal what phenomena actually do exist on the Warped Side, and how they behave.
AbstractExact solutions of the Einstein-Maxwell equations in the Kerr-Schild formalism are discussed. We show that black hole horizon is unstable with respect to electromagnetic excitations. Contrary to smooth harmonic functions used in perturbative solutions, the exact solutions for electromagnetic excitations on the Kerr background have the form of singular twistor-beams which have very strong back reaction to metric and break the black-hole horizon, forming in it holes which allow radiation to escape interior of black-hole. As a result, under action of the external electromagnetic field the horizon may be covered by a set of fluctuating micro-holes, which corresponds to a semi-classical mechanism of Hawking radiation.
AbstractThe 3.8m optical and infrared telescope, which is Japan's first segmented mirror telescope, is now being constructed using the world's first super high precision, high speed grinding technology and the world's first truss structure drive system. This is the joint project between Kyoto University, Nagoya University, National Astronomical Observatory, and Nano-Optonics Energy (private company) with the budget of the Nnao-Optonics Energy and Dr Hiroshi Fujiwara (CEO of the Nano-Optonics Energy). The telescope will be completed in 2012 and installed in Okayama, and will become the biggest optical and infrared telescope in east Asia. The technologies for making this telescope such as (1) grinding technology, (2) segmented mirror, and (3) truss structure drive system are also basic technologies for the future extremely large telescope such as the 30m telescope. The scientific objective of the telescope is the search for the transient objects (gamma ray bursts, black hole binaries, stellar flares) and the extra solar planets. How this project has emerged and developed will be discussed in detail, including also the discussion about the possible future international collaboration.
AbstractThe coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil of the system and its ejection from the galaxy core. We have carried out N-body simulations of the motion of a M=3.7 M⊙ MBH remnant in the “Via Lactea I” Milky Way-sized halo. The hole receives a kick velocity of Vkick = 80, 120, 200, 300, and 400 km/s at redshift 1.5, and its orbit is followed for over 1 Gyr within a “live” host halo, subject only to gravity and dynamical friction against the dark matter background. We show that, owing to asphericities in the dark matter potential, the orbit of the MBH is highly non-radial, resulting in a significantly increased decay timescale compared to a spherical halo. The simulations are used to construct a semi-analytic model of the motion of the MBH in a time-varying triaxial Navarro-Frenk-White dark matter halo plus a spherical stellar bulge, where the dynamical friction force is calculated directly from the velocity dispersion tensor. Such a model should offer a realistic picture of the dynamics of kicked MBHs in situations where gas drag, friction by disk stars, and the flattening of the central cusp by the returning hole are all negligible effects. We find that, in a Milky Way-sized galaxy, a recoiling hole carrying a gaseous disk of initial mass ~2 MBH may shine as a quasar for a substantial fraction of its “wandering” phase. The long decay timescales of recoiling MBHs predicted by this study may thus be favorable to the detection of off-nuclear quasar activity.
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- Astronomical dating of ancient societies in the 2nd millennium BCEDr. Rita GautschyWednesday March 4, 2020 - 10:30 (Aula)
- The impossible Local Group of galaxiesDr. Pavel KroupaTuesday March 17, 2020 - 12:30 (Aula)