Astronomický ústav

Nejnovější přírůstky:
2016-03-22
13:55
Modified Newtonian potentials for particles and fluids in permanent rotation around black holes
Karas, Vladimír ; Abramowicz, M. A.
Modified Newtonian potentials have been proposed for the description of relativistic effects acting on particles and fluids in permanent orbital motion around black holes.

Úplný záznam
2016-03-22
13:55
Polarization vector transport in Kerr geometry
Bursa, Michal ; Horák, Jiří ; Karssen, G.
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.

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2016-02-08
14:39
An XSPEC model to explore spectral features from black-hle sources. II. The relativistic iron line in the lamp-post geometry
Dovčiak, Michal ; Svoboda, Jiří ; Goosmann, R. W. ; Karas, Vladimír ; Matt, G. ; Sochora, Vjačeslav
In the paper authors compare the two radial profiles of the line emission - the broken power-law dependence and illumination in the lamp-post scenario.

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2016-01-25
14:41
Study of Cataclysmic Variables with the Satellites LOFT and Gaia
Hudec, René ; Šimon, Vojtěch
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.

Úplný záznam
2016-01-25
14:41
Activity of the Polar AM Her (RX J1816.2+4952): A Short Review
Šimon, Vojtěch ; Henden, A.
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.

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2016-01-25
14:41
GLORIA and Study of Cataclysmic Variables
Šimon, Vojtěch ; Hudec, René
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.

Úplný záznam
2016-01-25
14:41
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.

Úplný záznam
2016-01-25
14:41
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.

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2015-12-04
15:53
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.

Úplný záznam
2015-12-04
15:53
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.

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