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2. Contemporary problems of relativistic celestial mechanics and astrometry

Creator:
Brumberg, V. A.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astronomical measurements, relativistic celestial mechanics, and relativistic astrometry
Language:
Czech
Description:
The general theory of relativity (GRT) should be considered at present as a necessary framework for the construction of accurate dynamical ephemerides (relativistic celestial mechanics) and In the discussion of high-precision observations (relativistic astrometry). The main achievements of recent years and the most promising investigations are related to experimental foundation of the theory of gravitation, gravltational radiation treated as the subject of celestial mechanics, mathematical correctness and physical meaning of the equatlons of motion, astronomical reference systems, time scales, astronomical units of measurements, reduction of astronomical observations.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

4. On the instability time scale of the outflow associated with the HH 7-11 chain

Creator:
Silvestro, G., Busso, M., Persi, P., Robberto, M., and Scaltriti, F.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astronomical measurements, instability time scale, and HH 7-11 system
Language:
Czech
Description:
We investigate the conditions for development of Kelvin-Helmoltz instabilities along a collimated wind flow from a low-mass star surrounded by a dense circumstellar disk, which could give rise to condensations with the characteristics of the chain of HH knots in the HH 7-11 system. The flow, using the observational parameters of the source, turns out to be clearly unstable. We give a simple estimate of the instability time scale, which turns out to be in good agreement with the characteristic time of development for outflows from low-mass young stellar objects.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

5. Physical conditions in chromospheric flares

Creator:
Švestka, Zdeněk
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astronomical measurements, chromospheric flares, and physical conditions
Language:
Czech
Description:
Using the observations of line-profiles in flare spectra published by Ellison, Mustel, Severny, and Suemoto, we investigate the physical conditions in chromospheric flares. We find in agreement with Mustel and Severny that flares are optically thick in all few lines of the Balmer series, and that lines higher than Hα line is broadened by the radiation damping, and the lines higher than Hβ by the Stark effect. On the contrary, we differ from the Soviet writers in the conclusion that the state of excitation al least in the surface layers of a flare, is rather close to the state of thermal equilibrium. Comparing the theoretical course of intensity at the Hα line with Ellison´s observation, we find systematic deviations, which may be explained by an influence of the Lα back-radiation of flares on the upper photospheric level. The central absorption in the Hα line is due to a self reversal of the line due to a decrease of temperature towards the surface of the flare. In large chromospheric flares kinetic temperature is 9000°-10000° inside a flare, and decreases to about 6000° on its surface. Excitation temperature is about 8000° inside a flare and close to 6000° on its surface. Electron temperature is probably close to 10000°. The number of free electrons may be estimated at 6 . 10^12 cm^-3. The radial optical thickness in the center of the Hα line may be as high as 10^4 in the largest flares. In large flares normally observed the optical thickness is equal to 2 . 10^3 - 6 . 10^3. The lowest limit of the optical thickness is given by the thickness of bright flocculi, shich does not much exceed the value of 10; nevertheless in all the phenomena which are usually classified as flares the optical thickness is probably higher than 200.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

6. Sur une nouvelle construction de microphotomètre de l'Observatoire de Praha

Creator:
Link, František
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, astronomical measurements, and microphotometer
Language:
Czech
Description:
Description d'un microphotomètre destiné aux besoins astronomiques. L'appareil travaille avec deux cellules à couche d'arrêt au sélénium (Tungsram S 44) par compensation optique à l'aide d'un coin neutre. Il en résulte l'indépendence de l'intensité de la source qui est une lampe de 100 W alimentée sur le secteur. On donne in théorie de l'instrument ainsi que le résultat des essaies pratiques.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

7. Tafeln zur Berechnung der galaktischen Bewegungskomponenten der Sterne

Creator:
Link, František and Oort, J. H.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astronomical measurements, components of stellar motion, and parallaxes
Language:
Czech
Description:
Le calcul des tables facilitant le calcul des composantes galactiques des vitesses d'étoilles a été recommandé en 1935 par J. H. Oort [2]. Nos tables permettent d'atteindre ce but directement à partir des éléments équatoriaux du mouvement c'est a dire le mouvement propre en ascension droite μα en déclinaison μδ la vitesse radiale V et la paralaxe π. Le calcul se fait à l'aide des formules (1) du texte précédent où les coefficients a1, a2 ...c3 se trouvent dans nos tables. Il-y-a à remarquer que les nombres en italiques sont negatifs et que tous les nombres sont exprimés en 0,001 comme unité. Les tables auxiliaires complètent les tables principales. and J. H. Oort je autorem předmluvy
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public