Number of found documents: 214
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Study of Cataclysmic Variables with the Satellites LOFT and Gaia
Hudec, René; Šimon, Vojtěch
2015 - English
The goal of this paper is to discuss the capabilities of ESA satellite missions Gaia (already in space) and LOFT\n(considered for the ESA M4 slot) for investigation of cataclysmic variables (CVs). Both Gaia and LOFT\ncan contribute to study of CVs and related objects. Spectrophotometry and low dispersion spectroscopy are the most important for CV analyses with the observations of Gaia. We present the possible strategies for investigation of CVs in the sampled photometric\nand spectroscopic data provided by Gaia. E.g. statistical properties of the long-term activity of various types of CVs can be determined from them. LOFTcan be a promising satellite to provide a sensitive X-ray monitor which will enable to investigate the little studied long-term activity of various types of CVs (especially the magnetic ones) in the X-ray band. Keywords: catalysmic variables; dwarf novae -; intermediate polar Available at various institutes of the ASCR
Study of Cataclysmic Variables with the Satellites LOFT and Gaia

The goal of this paper is to discuss the capabilities of ESA satellite missions Gaia (already in space) and LOFT\n(considered for the ESA M4 slot) for investigation of cataclysmic variables (CVs). ...

Hudec, René; Šimon, Vojtěch
Astronomický ústav, 2015

Activity of the Polar AM Her (RX J1816.2+4952): A Short Review
Šimon, Vojtěch; Henden, A.
2015 - English
We show that AM Her displays the transitions between the high and low states with an intermittently existing dominant\ncycle with length between 400 and 800 days. Moreover, these transitions accumulate in clusters, which produces an\nadditional long cycle after smoothing; a single isolated short episode of the low state does not suggest a break of this cycle. The seasons of existence of the cycle can be controlled by the lifetime of the active regions (e.g. prominences, spots) on the donor. In some high-state episodes, a higher luminosity of the bremsstrahlung emission is not accompanied by a higher optical (cyclotron+stream) emission. Part of the bremsstrahlung emission can be buried in some episodes. Changes of\nthe structure of the accretion region(s) are necessary to explain the variations of the optical and X-ray activity in the\nhigh-state episodes of AM Her. Keywords: catalysmic variables; polars; emission mechanism Available at various institutes of the ASCR
Activity of the Polar AM Her (RX J1816.2+4952): A Short Review

We show that AM Her displays the transitions between the high and low states with an intermittently existing dominant\ncycle with length between 400 and 800 days. Moreover, these transitions ...

Šimon, Vojtěch; Henden, A.
Astronomický ústav, 2015

Infrared-excess Source DSO/G2 Near the Galactic Center: Theory vs. Observations
Zajaček, M.; Eckart, A.; Peissker, F.; Karssen, G.; Karas, Vladimír
2015 - English
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. Keywords: galactic centre Fulltext is available at external website.
Infrared-excess Source DSO/G2 Near the Galactic Center: Theory vs. Observations

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 ...

Zajaček, M.; Eckart, A.; Peissker, F.; Karssen, G.; Karas, Vladimír
Astronomický ústav, 2015

GLORIA and Study of Cataclysmic Variables
Šimon, Vojtěch; Hudec, René
2015 - English
We report here on the ongoing EU FP7 Project GLORIA (GLObal Robotic-telescopes Intelligent Array) with emphasis on possibility of investigation of cataclysmic variables by users. GLORIA will enable the rst free and open-access network of robotic telescopes in the world. We show several examples of the not often used topics (but suitable for GLORIA) for the studies of activity of cataclysmic variables, e.g. search for outbursts in intermediate polars and the uctuations of/nbrightness in their quiescence, and investigation of the optical counterparts of supersoft X-ray sources. Keywords: catalysmic variables; spectroscopy; low-dispersion spectra Available at various institutes of the ASCR
GLORIA and Study of Cataclysmic Variables

We report here on the ongoing EU FP7 Project GLORIA (GLObal Robotic-telescopes Intelligent Array) with emphasis on possibility of investigation of cataclysmic variables by users. GLORIA will enable ...

Šimon, Vojtěch; Hudec, René
Astronomický ústav, 2015

Equilibria of charged dust tori in a dipole magnetic field: hydrodynamic approach
Slaný, P.; Kovář, J.; Stuchlík, Z.; Karas, Vladimír
2014 - English
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. Keywords: dust tori; electric charge; magnetic field Available at various institutes of the ASCR
Equilibria of charged dust tori in a dipole magnetic field: hydrodynamic approach

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 ...

Slaný, P.; Kovář, J.; Stuchlík, Z.; Karas, Vladimír
Astronomický ústav, 2014

Polarization vector transport in Kerr geometry
Bursa, Michal; Horák, Jiří; Karssen, G.
2014 - English
In this paper the authors proved a set of practical formulae that are helpful in calculating the orientation of polarization vectors that are parallel transported from a region of strong gravitational field of a Kerr black hole to a distant observer. Keywords: polarization; black hole; electromagnetic radiation Available at various institutes of the ASCR
Polarization vector transport in Kerr geometry

In this paper the authors proved a set of practical formulae that are helpful in calculating the orientation of polarization vectors that are parallel transported from a region of strong gravitational ...

Bursa, Michal; Horák, Jiří; Karssen, G.
Astronomický ústav, 2014

An Introduction to relativistic magnetohydrodynamics. II. Case of stationary electro-vacuum fields around black holes
Karas, Vladimír
2014 - English
The lecture on electrodynamical effects near black holes. The author summarize the basic equations of relativistic electrodynamics in terms of spin-coefficien formalism. Keywords: black holes; electromagnetic fields; relativity Available at various institutes of the ASCR
An Introduction to relativistic magnetohydrodynamics. II. Case of stationary electro-vacuum fields around black holes

The lecture on electrodynamical effects near black holes. The author summarize the basic equations of relativistic electrodynamics in terms of spin-coefficien formalism.

Karas, Vladimír
Astronomický ústav, 2014

Simulating Compton scattering using Monte Carlo method: COSMOC library
Adámek, K.; Bursa, Michal
2014 - English
The authors present properties and functionality of the COSMOC library designed to exploit basic features of Compton scattering process and its computational modelling. Keywords: Monte Carlo; Compton scattering; C++ Available at various institutes of the ASCR
Simulating Compton scattering using Monte Carlo method: COSMOC library

The authors present properties and functionality of the COSMOC library designed to exploit basic features of Compton scattering process and its computational modelling.

Adámek, K.; Bursa, Michal
Astronomický ústav, 2014

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.
2014 - English
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. Keywords: accretion discs; black hole physics Available at various institutes of the ASCR
Tidal disruption events from a nuclear star cluster as possible origin of transient relativistic spectral lines near SMBH

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.

Karas, Vladimír; Dovčiak, Michal; Kunneriath, Devaky; Yu, W.; Zhang, W.
Astronomický ústav, 2014

Modified Newtonian potentials for particles and fluids in permanent rotation around black holes
Karas, Vladimír; Abramowicz, M. A.
2014 - English
Modified Newtonian potentials have been proposed for the description of relativistic effects acting on particles and fluids in permanent orbital motion around black holes. Keywords: accretion discs; black hole physics Available at various institutes of the ASCR
Modified Newtonian potentials for particles and fluids in permanent rotation around black holes

Modified Newtonian potentials have been proposed for the description of relativistic effects acting on particles and fluids in permanent orbital motion around black holes.

Karas, Vladimír; Abramowicz, M. A.
Astronomický ústav, 2014

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