|
|
Astrofyzikální procesy v blízkosti kompaktních objektů
Sochora, Vjačeslav ; Karas, Vladimír (advisor) ; Schee, Jan (referee) ; Semerák, Oldřich (referee)
Title: Astrophysical processes near compact objects: studying extremal en- ergy shifts from accretion rings Author: Vjačeslav Sochora Department: Academy of Sciences of the Czech Republic, Astronomical In- stitute Supervisor: doc. RNDr. Vladimír Karas, DrSc.; Academy of Sciences of the Czech Republic, Astronomical Institute Abstract: The X-ray emission from inner regions of an accretion disk around black holes provides wealth of information about matter in extreme con- ditions. A spectral profile of radiation from a narrow circular ring has a characteristic double-horn profile. Red and blue peaks of the profile are close to the extremal values of the energy shift. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. We dis- cuss if the radial structure of the disk emission could be reconstructed using extremal energy shifts of the individual rings. For this purpose, we simulate artificial data from a bright active galactic nucleus and show that the re- quired sensitivity and energy resolution can be reached with the proposed LOFT mission. Keywords: black hole physics, accretion disks, galactic nuclei
|
|
|
Accretion discs in the context of tidal disruption of stars in nuclei of galaxies
Štolc, Marcel ; Karas, Vladimír (advisor) ; Schee, Jan (referee)
Stars can be stretched and ripped apart by the super-massive black hole at the core of a galaxy. The remnant gaseous trail gradually circularizes in a ring of mass that spreads by the viscous forces into an accretion disc. In this thesis we have studied the spectral line profle time evolution of radiation refected by the accretion disc located around a super-massive black hole. We assume the central body to be a slowly rotating or non-rotating super-massive black hole with no charge, in the frst approximation represented by the Schwarzschild solution. In a sense of Shakura-Sunyaev standard accretion disc model with the kinematic viscosity parameter α ≈ 1 we allow the accretion disc evolution to be guided by the angular momentum transfer equation with the initial mass ring located at the tidal radius being the product of tidal disruption of a star passing by a super-massive black hole. During the simulations we keep varying the mass of the central body while we keep the mass and the radius of the star constant (M = 1M⊙ and R = 1R⊙), i.e. taking into account the solar-type stars only. We defer the prospects of the full analysis involving spin (and charge) of the central body for the future study as it will be necessary to use the equations for the redshift factor and the accretion disc evolution...
|
|
|
Accretion discs in the context of tidal disruption of stars in nuclei of galaxies
Štolc, Marcel ; Karas, Vladimír (advisor) ; Schee, Jan (referee)
Stars can be stretched and ripped apart by the super-massive black hole at the core of a galaxy. The remnant gaseous trail gradually circularizes in a ring of mass that spreads by the viscous forces into an accretion disc. In this thesis we have studied the spectral line profle time evolution of radiation refected by the accretion disc located around a super-massive black hole. We assume the central body to be a slowly rotating or non-rotating super-massive black hole with no charge, in the frst approximation represented by the Schwarzschild solution. In a sense of Shakura-Sunyaev standard accretion disc model with the kinematic viscosity parameter α ≈ 1 we allow the accretion disc evolution to be guided by the angular momentum transfer equation with the initial mass ring located at the tidal radius being the product of tidal disruption of a star passing by a super-massive black hole. During the simulations we keep varying the mass of the central body while we keep the mass and the radius of the star constant (M = 1M⊙ and R = 1R⊙), i.e. taking into account the solar-type stars only. We defer the prospects of the full analysis involving spin (and charge) of the central body for the future study as it will be necessary to use the equations for the redshift factor and the accretion disc evolution...
|
|
|
Astrofyzikální procesy v blízkosti kompaktních objektů
Sochora, Vjačeslav ; Karas, Vladimír (advisor) ; Schee, Jan (referee) ; Semerák, Oldřich (referee)
Title: Astrophysical processes near compact objects: studying extremal en- ergy shifts from accretion rings Author: Vjačeslav Sochora Department: Academy of Sciences of the Czech Republic, Astronomical In- stitute Supervisor: doc. RNDr. Vladimír Karas, DrSc.; Academy of Sciences of the Czech Republic, Astronomical Institute Abstract: The X-ray emission from inner regions of an accretion disk around black holes provides wealth of information about matter in extreme con- ditions. A spectral profile of radiation from a narrow circular ring has a characteristic double-horn profile. Red and blue peaks of the profile are close to the extremal values of the energy shift. We describe a useful approach to calculate the extremal energy shifts in the regime of strong gravity. We dis- cuss if the radial structure of the disk emission could be reconstructed using extremal energy shifts of the individual rings. For this purpose, we simulate artificial data from a bright active galactic nucleus and show that the re- quired sensitivity and energy resolution can be reached with the proposed LOFT mission. Keywords: black hole physics, accretion disks, galactic nuclei
|
|
|
Vliv silného gravitačního pole kompaktních objektů na jejich záření
Sochora, Vjačeslav ; Karas, Vladimír (advisor) ; Schee, Jan (referee)
In the present work we describe different cosmic systems that contain the compact objects (neutron stars or black holes). The accretion of the matter on the compact object is a main source of the radiation and that is why we consider several models of accretion. The energy of emitted radiation is different from the observed energy due to the gravitational redshift and the Doppler shift. We are interested in the minimum and maximum values of this change of emitted radiation. We show how to calculate these extremes in Kerr metric by the help of the elliptic integrals assuming that the emission radius, the angular momentum of black hole, and the inclination angle of the observer are given.
|
guest ::
