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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.
High-frequency QPOs in GRO J1655-40
Bursa, Michal
2005 - English
We determine angular momentum from QPOs. Určujeme moment hybnosti pomocí studia QPO.
Keywords:
quasiperiodic oscillations
Available at various institutes of the ASCR
High-frequency QPOs in GRO J1655-40
We determine angular momentum from QPOs.
Určujeme moment hybnosti pomocí studia QPO.
Center for Earth Dynamics Research (CEDR) - results of five years of activity
Kostelecký, J.; Vondrák, Jan; Zeman, A.; Kalvoda, J.; Schenk, Vladimír
2005 - English
Five years of activities of the Center of Earth Dynamics Research is described. Jsou popsány aktivity Výzkumného centra dynamiky Země za posledních pět let.
Keywords:
geodynamics; geodesy
Available at various institutes of the ASCR
Center for Earth Dynamics Research (CEDR) - results of five years of activity
Five years of activities of the Center of Earth Dynamics Research is described.
Jsou popsány aktivity Výzkumného centra dynamiky Země za posledních pět let.
The relativistic shift of spectral lines from black-hole accretion discs
Pecháček, T.; Dovčiak, Michal; Karas, Vladimír
2005 - English
We study gravitational redshift of spectral lines. Studujeme gravitační posuv spektrálních čar.
Keywords:
accretion
Available at various institutes of the ASCR
The relativistic shift of spectral lines from black-hole accretion discs
We study gravitational redshift of spectral lines.
Studujeme gravitační posuv spektrálních čar.
Polarization of radiation from AGN accretion discs
Dovčiak, Michal; Karas, Vladimír; Matt, G.; Martocchia, A.
2005 - English
The effects of strong gravity on polarization are studied. Studujeme vliv silné gravitace na polarizaci záření.
Keywords:
polarization
Available at various institutes of the ASCR
Polarization of radiation from AGN accretion discs
The effects of strong gravity on polarization are studied.
Studujeme vliv silné gravitace na polarizaci záření.
Kinetic model of quasiperiodic oscillations of gaseous rings
Hadrava, Petr
2005 - English
In context of 3:2 resonant quasiperiodic oscillations, a method of "1+1/2 -dimensional" non-ideal gas dynamics is used to model axisymmetric oscillations of an orbiting ring. It is shown that the characteristic frequencies of the oscillations are influenced by the degree of freedom in the inner shear of the ring and by the rate of relaxation. Metoda "1+1/2 -dimensionalní" dynamiky neideálního plynu je užita k modelování orbitujícího disku v souvislosti s kvasiperiodickými oscilacemi v rezonanci 3:2. Je ukázáno, že charakteristické frekvence oscilací jsou ovlivněny vnitřním stupněm volnosti odpovídajícím smyku v prstenci a také mírou relaxace.
Keywords:
accretion disks; quasiperiodic oscillations
Available at various institutes of the ASCR
Kinetic model of quasiperiodic oscillations of gaseous rings
In context of 3:2 resonant quasiperiodic oscillations, a method of "1+1/2 -dimensional" non-ideal gas dynamics is used to model axisymmetric oscillations of an orbiting ring. It is shown that the ...
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