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Wave excitation at Lindblad resonances using the method of multiple scales
Horák, Jiří
In this note, the method of multiple scales is adopted to the problem of excitation of non–axisymmetric acoustic waves in vertically integrated disk by tidal gravitational fields. We derive a formula describing a waveform of exited wave that is uniformly valid in a whole disk as long as only a single Lindblad resonance is present. Our formalism is subsequently applied to two classical problems: trapped p–mode oscillations in relativistic accretion disks and the excitation of waves in infinite disk.
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Analysis and Suppression of Noise in Astronomical Video
Švihlík, J. ; Fliegel, K. ; Koten, Pavel ; Jerhotova, E. ; Vítek, S. ; Páta, P.
This paper is devoted to noise suppression in systems for double station observation of meteors, nowadays known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis based on acquisition of testing video sequences at different lighting conditions and their statistical evaluation were described in our previous paper The measurement showed that the type of noise generated by the system is signal-independent in a certain illumination range. The noise and image models in the wavelet domain are based on the Generalized Laplacian Model (GLM) and it is the most convenient to estimate the model parameters using the moment method. Furthermore, the noise component may be modeled by the GLM also in the space domain. Overall, we verified that the GLM allows for modeling various types of probability density functions. In the final section of this paper, the performance of the proposed advanced de noising algorithm is verified on the real data, which were acquired in the Astronomical Institute.
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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.
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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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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.
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