Astronomický ústav

Astronomický ústav Nalezeno 248 záznamů.  začátekpředchozí41 - 50dalšíkonec  přejít na záznam: Hledání trvalo 0.00 vteřin. 
Variace geoidu detekované z družicové mise GRACE
Kostelecký, J. ; Bezděk, Aleš ; Klokočník, Jaroslav
Časově proměnné gravitační pole, získané z pozorování mise GRACE od roku 2002, je v tomto příspěvku založené na transformaci měsíčních gravitačních polích na výšku geoidu. Ukážeme gravitační změny působené globálním hydrologickým cyklem a hydrologií na pevninách.
Infrared-excess Source DSO/G2 Near the Galactic Center: Theory vs. Observations
Zajaček, M. ; Eckart, A. ; Peissker, F. ; Karssen, G. ; Karas, Vladimír
Based on the monitoring of the Dusty S-cluster Object (DSO/G2) during its closest approach to the Galactic Center supermassive black hole in 2014 and 2015 with ESO VLT/SINFONI, we further explore the model of a young, accreting star to explain observed spectral and morphological features. The stellar scenario is supported by our ndings, i.e., ionized-hydrogen emission from the DSO that remains spatially compact before and after the peribothron passage. The detection of DSO/G2 object as a compact single-peak emission-line source is not consistent with the original hypothesis of a core-less cloud that is necessarily tidally stretched, hence producing a double-peak emission line prole around the pericentre passage. This strengthens the evidence that the DSO/G2 source is a dust-enshrouded young star that appears to be in an accretion phase. The infall of material from the circumstellar disc onto the stellar surface can contribute signicantly to the emission of Br line as well as the observed large line width of the order of 10 angstrom.
Twin peak quasi-periodic oscillations as signature of oscillating cusp torus
Török, G. ; Goluchová, K. ; Horák, Jiří ; Šrámková, E. ; Urbanec, M. ; Urbancová, G. ; Pecháček, Tomáš ; Bakala, P.
The authors propose a new model of twin-peak quasi-periodic oscillations.This model considers an oscillating torus with cusp that changes location of its centre around radii very close to innermost stable circular orbit.
Confronting models of twin peak quasi-periodic oscillations: Mass and spin estimates fixed by neutron star equation of state
Török, G. ; Goluchová, K. ; Urbanec, M. ; Šrámková, E. ; Adámek, K. ; Urbancová, G. ; Pecháček, Tomáš ; Bakala, P. ; Stuchlík, Z. ; Horák, Jiří ; Juryšek, J.
In the work authors compare simplified calculations that assume Kerr background geometry to the detailed calculations considering NS oblateness influence in Hartle-Thorne spacetimes.
Equilibria of charged dust tori in a dipole magnetic field: hydrodynamic approach
Slaný, P. ; Kovář, J. ; Stuchlík, Z. ; Karas, Vladimír
The authors present Newtonian model of non-conductive charge perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields, focusing on stationary, axisymmetric toroidal structures.
Effects of environmental drag onto a fast-moving magnetic compact star near a supermassive black hole
Karas, Vladimír ; Šubr, L. ; Kunneriath, Devaky ; Zajaček, Michal
The authors discuss whether a strong magnetic field of a neutron star can significantly enhance the drag effect by increasing the effective cross-sectional area for the mutual interaction.
Tidal disruption events from a nuclear star cluster as possible origin of transient relativistic spectral lines near SMBH
Karas, Vladimír ; Dovčiak, Michal ; Kunneriath, Devaky ; Yu, W. ; Zhang, W.
The authors discuss a possibility that a tidal disruption event near a dormant supermassive black hole can give rise to spectral features of iron in 6-7keV X-ray signal.
Triggered oscillations and destruction of magnetized relativistic tori in 2D
Hamerský, Jaroslav ; Karas, Vladimír
The toroidal magnetic field plays a more important role in the early phases of the accretion process until the perturbed configuration finds a new equilibrium or disappears because of the runaway instability. We showed that additional perturbations in the vertical direction can lead to relativistic outflows if the perturbations are strong enough so that the mass could get far from the equatorial plane.
Compton scattering in strong gravity
Bursa, Michal ; Adámek, K.
The authors present new numerical code for radiation transport in strong gravity regime that includes arbitrary emission and absorption mechanisms and also electron scattering.
Simulating Compton scattering using Monte Carlo method: COSMOC library
Adámek, K. ; Bursa, Michal
The authors present properties and functionality of the COSMOC library designed to exploit basic features of Compton scattering process and its computational modelling.

Astronomický ústav : Nalezeno 248 záznamů.   začátekpředchozí41 - 50dalšíkonec  přejít na záznam:
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