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12. Accretion disks in soft potential wells

Creator:
Duschl, Wolfgang J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics and accretion
Language:
Czech
Description:
The softer a potential is, the closer the corresponding Keplerian rotation is to a rigid rotation law. Because of the small radial coupling in such a situation the radial mass flow due to viscosity in an α-accretion disk is very inefficient. Here a model is presented in which the mass of an accretion disk in a soft potential well changes this potential in a sense that an efficient mass flow in radial direction becomes possible, thus making the formation of a centra! mass condensation possib!e. This mechanism is of interest in the context of galactic central regions since it is capable of explaining the existence of centra! masses such as observed in the cores of norma! galaxies; it might aiso be of relevance for the explanation of the activity in AGNs.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

13. Are cometary dust Mars loss rates deduced from optical emissions reliable?

Creator:
Crifo, J. F.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, Comet Halley, and cometary dust
Language:
Czech
Description:
We present additional evidence in support of our prevlous work (Crifo, 1987 bc) in which, from theoretical fits to Comet Halley near -to far- infrared emissions, based on the in-situ flyby probes data, we estimated that the comet was losing half or more of its mass under the form of large (> 1 gram) grains of small (0.3 g cm-^3) density. We confirm that the comet dust-to-gas mass loss rate ratio lies somewhere between the values 0.80 and 18.6, with a best estimate at 3.46. We discuss this result in the context of the general agreement that comets loose less than half of their total mass loss in dust, and this dominantly at very smáli grain sizes. We trace this agreement back to overconfidence placed in a model size distribution which inherently excludes substantial mass loss in large grains without appropriate experimental justification.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

14. Atlas of the wavelength dependence of UV extinction in the galaxy: a presentation

Creator:
Aiello, S., Barsella, B., Chlewicki, G., Mayo Greenberg, J., Patriarchi, P., and Perinotto, M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, galaxy, and UV extinction
Language:
Czech
Description:
A short description is given of the Atlas of UV extinction which will be published on Astronomy and Astrophysics Suppl. Series. The Atlas presents a collection of 115 extinction curves derived fron low dispersion IUE spectra retrieved from VILSPA Data Bank.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

15. Binary evolution

Creator:
de Loore, C.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics and binary evolution
Language:
Czech
Description:
Consideration of mass transfer and mass loss processes allows the explanation of the existence of well determined groups of binaries, such as Algols, cataclysmic variables, massive and low masa X ray binaries. The characteristics of these groups are briefly outlined, and evolutionary scenarios are discussed. The importance of detailed observations for advances in evolutionary computations are stressed. It isargued that, although the linka between the mentionned groups of binaries and their progenitors is rather well known, the situation is completely different if the detailed evolutionary history for a given system is required.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

16. Český materiálový výzkum v kosmu

Creator:
Barta, sen., Čestmír and Barta, jun., Čestmír
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrofyzika, materiálový výzkum v kosmu, astrophysics, and cosmic materials space research
Language:
Czech
Description:
Článek podává komplexní informaci o vědecko-technické motivaci, předmětu a cílech oboru materiálového výzkumu v kosmu. Vhodným způsobem využité vlastnosti dlouhodobé mikrogravitace vedou k zajímavým rozdílům v procesu přenosu tepla a hmoty, a to zejména při nukleaci, krystalizaci a vzniku skelného stavu. To otevírá možnosti hlubšího poznání přípravy materiálů odlišného složení a struktury a tedy i změněných fyzikálních vlastností. Získané zkušenosti lze využít i při zlepšování technologie výroby dosavadních technicky využívaných materiálů. Především jde o slitiny skla, kompozity a monokrystaly dielektrických, polovodičových a konstrukčních materiálů. Zajímavou oblast představují i koloidy. V České republice má materiálový výzkum v kosmu již čtyřiadvacetiletou tradici a autoři tohoto článku se jím zabývají od samého počátku. Podávají proto kompetentní informaci o historii i současnosti tohoto oboru u nás, tj. o výsledcích, jakých bylo zatím dosaženo i o aktuálních tématech a perspektivách. Dosažené výsledky a základní údaje dokládá řada obrázků a tabulek. Případný zájemce má možnost si informace o českém materiálovém výzkumu v kosmu doplnit ze seznamu vybraných publikací autorů k danému tématu., Čestmír Barta, sen., Čestmír Barta, jun., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

18. Continuum intensity and magnetic flux of solar fluxtubes

Creator:
del Toro Iniesta, J. C., Semel, M., Collados, M., and Sánchez Almeida, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, magnetic flux, and solar fluxtubes
Language:
Czech
Description:
The continuum contrast between fluxtubes and their quiet background, and the magnetic řlux carried by these magnetic elements, have been determined at different points of a solar facula, In the frame of a two-component model from spectropolarimetric observations of 1^11 spatial resolution. Local spatial variations of these two parameters have been obtained.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

19. Den s Astropisem a Kopalova přednáška 2017

Creator:
Kopecký, Vladimír
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
Česká astronomická společnost, astronomie, astrofyzika, popularizace vědy, astronomy, astrophysics, popularization of science, časopis Astropis, Astropis magazine, přednášky, lectures, 6, and 53
Language:
Czech
Description:
25. listopadu 2017 se konal již 15. přednáškový den s časopisem Astropis. Na akci pro širokou veřejnost vystoupilo v průběhu dne pět přednášejících z oborů blízkých astronomii či astrofyzice a Česká astronomická společnost zde tradičně udělila svoji cenu - Kopalovu přednášku., Vladimír Kopecký Jr., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

20. Density profiles of star clusters in the magellanic clouds

Creator:
Kontizas, M., Metaxa, M., Chrysovergis, M., and Kontizas, E.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
astrophysics, star clusters, and magellanic clouds
Language:
Czech
Description:
The observed dynamical parameters of the Magellanic Clouds (MCs) clusters are derived by means of star counts. There are many rich globular, young disk clusters in the MCs with no counterparts in our galaxy. The old clusters were found statistically less extended with systematically smaller total masses than those of the galactic globulars. So it is worth emphasizing that clusters of all ages (from stellar evolution point of view) are detected in the MCs with very large total number of stars and structural parameters characterising the old halo galactic globulars. The radial density profiles of these stellar systems were used for deriving information on their dynamical stage. Some of the clusters indicate mass segregation of post core collapse profiles, giving evidence for a two body relaxation mechanism. Nevertheless some very young clusters show well relaxed profiles with evolutionary ages too short for a two body relaxation mechanism, so that the shape of their profiles is due to their initial relaxation. A number of clusters were found with an unexpected distortion in the outer areas of their density profiles at systematically constant distances to their centres. It is probable that an halo is formed around these clusters giving evidence that the morphology of the MCs may favorite the occurence of such effects.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public