No (136)
Number of found documents:
136
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On existence of halo orbits in Kerr–Newman spacetimes
Kovář, J.; Stuchlík, Z.; Karas, Vladimír
2007 - English
We discuss existence of halo orbits in Kerr–Newman spacetimes. Diskutujme existenci haló orbit v Kerrových-Newmanových prostoročasech.
Keywords:
black holes
Available at various institutes of the ASCR
On existence of halo orbits in Kerr–Newman spacetimes
We discuss existence of halo orbits in Kerr–Newman spacetimes.
Diskutujme existenci haló orbit v Kerrových-Newmanových prostoročasech.
Variation of the primary and reprocessed radiation in the flare-spot model
Dovčiak, Michal; Karas, Vladimír; Matt, G.; Goosmann, René
2007 - English
We study variation of the primary and reprocessed radiation in the flare-spot model. Studujeme změny primárního a reprocesovaného záření v modelu záblesků a skvrn.
Keywords:
black holes
Available at various institutes of the ASCR
Variation of the primary and reprocessed radiation in the flare-spot model
We study variation of the primary and reprocessed radiation in the flare-spot model.
Studujeme změny primárního a reprocesovaného záření v modelu záblesků a skvrn.
Modeling an accretion disc stochastical variability
Pecháček, Tomáš; Karas, Vladimír
2007 - English
We model an accretion disc stochastical variability. V této práci modelujeme stochastickou proměnnost akrečních disků.
Keywords:
black holes
Available at various institutes of the ASCR
Modeling an accretion disc stochastical variability
We model an accretion disc stochastical variability.
V této práci modelujeme stochastickou proměnnost akrečních disků.
The timescale of encircling light
Bursa, Michal; Abramowicz, M. A.; Karas, Vladimír; Kluzniak, W.; Schwarzenberg-Czerny, A.
2007 - English
We study the timescale of encircling light. Studujeme časové škály pojící se ke kruhovému pohybu světla.
Keywords:
black holes
Available at various institutes of the ASCR
The timescale of encircling light
We study the timescale of encircling light.
Studujeme časové škály pojící se ke kruhovému pohybu světla.
On mutual relation of kHz QPOs
Török, G.; Bursa, Michal; Horák, Jiří; Stuchlík, Z.; Bakala, P.
2007 - English
We further investigate the issue of kHz QPO frequency ratios in neutron star low mass X-ray binaries. In this note we report on recent analysis of occurrences and properties of kHz QPOs in the source 4U1636-53. Assuming that kHz QPOs occur in pairs whose frequencies are linearly correlated, we find a prominent frequency range that separates upper and lower QPO observations. Na základě analýzy dat QPO frekvencí zdroje 4U1636-53 a pěti dalších zdrojů ukazujeme, že páry QPO jsou detekovány zejména v okolí přechodových bodů, kde se mění některé vlastnosti QPO, zejména amplituda a koherence QPO.
Keywords:
X-rays; binaries stars; accretion disks
Available at various institutes of the ASCR
On mutual relation of kHz QPOs
We further investigate the issue of kHz QPO frequency ratios in neutron star low mass X-ray binaries. In this note we report on recent analysis of occurrences and properties of kHz QPOs in the source ...
Disk instability as an energy source for quasi-periodic oscillations
Horák, Jiří
2007 - English
We discuss a scenario, in which the energy for quasi-periodic oscillations comes from instabilities of the accretion disk. We demonstrate this mechanism on the interaction among stable and unstable modes of oscillations in slender accretion tori. In our model, the unstable non-axisymmetric corotation modes are nonlinearly coupled to stable acoustic modes of torus oscillations. The increasing energy of corotation modes is advected to the acoustic modes by the means of parametric instability. The stable modes may reach substantial amplitudes even if they are damped according to the linear theory. Energie pro kvazi-periodické oscilace může pocházet z nestabilit akrečního disku. Jako příklad je diskutována interakce mezi stabilními a nestabilními mody malého akrečního torusu. V našem případě je nestabilní neaxiálně symetrický korotující mod svázán nelineární vazbou se dvěma stabilními akustickými mody. Rostoucí energie korotujícího modu je předávána akusticým modum pomocí parametrické nestability. Stabilní mody mohou dosáhnout značných amplitud i když jsou podle lineární teorie tlumeny.
Keywords:
black hole physics; accretin discs; instabilities
Available at various institutes of the ASCR
Disk instability as an energy source for quasi-periodic oscillations
We discuss a scenario, in which the energy for quasi-periodic oscillations comes from instabilities of the accretion disk. We demonstrate this mechanism on the interaction among stable and unstable ...
Optical spectroscopy of Cyg X-1
Hadrava, Petr
2007 - English
The star HDE 226868 known as an optical counterpart of the black hole candidate Cyg X-1 has been observed in H_alpha region using spectrograph at Ondrejov 2-m telescope. The orbital parameters are determined from HeI-line by means of the author's method of Fourier disentangling. Preliminary results are also presented of disentangling the H_alpha-line into a P-Cyg profile of the (optical) primary and an emission profile of the circumstellar matter (and a telluric component). Hvězda HDE 226868, známá jako optický protějšek objektu Cyg X-1 s předpokládanou černou dírou, byla pozorována v oblasti H_alfa spektrografem ondřejovského 2-m dalekohledu. Orbitální parametry jsou určeny z čáry HeI pomocí autorovy metody fourierovského disentanglingu. V práci jsou předloženy také předběžné výsledky disentanglingu čáry H_alfa na P-Cyg profil optického primáru a na emisní profil okolohvězdné hmoty (a na telurickou složku).
Keywords:
Cyg X-1
Available at various institutes of the ASCR
Optical spectroscopy of Cyg X-1
The star HDE 226868 known as an optical counterpart of the black hole candidate Cyg X-1 has been observed in H_alpha region using spectrograph at Ondrejov 2-m telescope. The orbital parameters are ...
Modulation of high-frequency QPOs
Bursa, Michal
2007 - English
We study strong-gravity effects on modulation of radiation emerging from accreting compact objects as a possible mechanism for flux modulation in QPOs. Zkoumáme vlivy silné gravitace na modulaci záření z akrečních disků jako možný zdroj mechanismus modulace kvaziperiodických oscilací.
Keywords:
black hole physics; gravitation; X-rays
Available at various institutes of the ASCR
Modulation of high-frequency QPOs
We study strong-gravity effects on modulation of radiation emerging from accreting compact objects as a possible mechanism for flux modulation in QPOs....
Asymmetries of Spectral Lines in Solar Flares
Prosecký, Tomáš
2006 - English
This contribusion deals with line profile asymmetries in solar flares. Basic knowledge of asymmetries and review of possible explanations and recent works is presented. Week of doctoral students 2006. Proceedings of contributed papers. Praha : Matfyzpress, 2006. Part III - Physics, p. 27-32. Praha, 06.06.2006-9.06.2006
Keywords:
solar flares; spectrum; line profile asymmetry
Available at various institutes of the ASCR
Asymmetries of Spectral Lines in Solar Flares
This contribusion deals with line profile asymmetries in solar flares. Basic knowledge of asymmetries and review of possible explanations and recent works is presented....
A manifestation of the Kozai mechanism in the galactic nuclei
Šubr, L.; Karas, Vladimír
2005 - English
Kozai mechanism is studied in galactic nuclei. Studujeme vliv Kozaiova mechanismu na jádra galaxií.
Keywords:
galaxies
Available at various institutes of the ASCR
A manifestation of the Kozai mechanism in the galactic nuclei
Kozai mechanism is studied in galactic nuclei.
Studujeme vliv Kozaiova mechanismu na jádra galaxií.
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