ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 107 (1984), S. 1-9 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Equations connecting the transmission and reflection functions of a finite medium to the reflection function of a semi-infinite one are used to get the albedos in the slowing-down region. The transport equation is solved by the modified Eddington method using Fermi's backward-forward scattering model, modulated to allow for different orders of backward-forward and isotropic scattering. Numerical results for the energy albedos are obtained and compared.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To explain the scattering of sunlight observed from theF-corona and from the zodiac, the scattering particles must have radii of order 15 μm, and must have an imaginary component of the refractive index that requires the presence of from 5 to 10% of free carbon. The particles, therefore, have a composition very like the material of C 1 carbonaceous chondrites and like extraterrestrial particles which have been recovered from the high atmosphere. Such particles absorb sunlight, the absorbed solar energy being reradiated in the infrared with a close approximation to black-body emission, even as far into the infrared as 100 μm, a deduction in good agreement with recently published observations from the IRAS satellite. The IRAS observations at high ecliptic latitudes require similar particles to be present in large quantity in the interstellar medium, ∼106 solar masses or more of them. The presence of such a quantity of material with properties very like the material of the C 1 carbonaceous chondrites is a remarkable outcome of the IRAS observations and is likely to have profound implications in many directions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 107 (1984), S. 255-270 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this work a model has been proposed to explain how the nucleus of a Galaxy can accumulate mass and becomes supermassive — ultimately giving way to gravitational instability leading to an explosion in the nucleus. The process may be repeated many times during the life-span of a Galaxy. The mass shed by the evolved stars populating the central region of the Galaxy can be attracted toward the nuclear core by gravitational pull. Since the incident gas possesses rotational velocity, the centrifugal repulsion of the gas may balance the gravitational pull of the nucleus; thus infall of mass into the nucleus will ordinarily be inhibited. But dissipative agents — such as the prevailing magnetic field and the viscosity of gas — may be sufficient to destroy the rotational velocity of the incident gas and keep the accretion process efficient. The correlation between rotational velocity of gas and its distance from the centre of the Galaxy has been deduced. The radial equation of motion has been solved and the time-scale during which the nucleus accumulates mass sufficient for explosion, has been estimated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Moderately accurate oscillator strengths are obtained by application of systematic corrections to Warner's-log(gf) for the once ionized elements of the iron group. Corrections are derived by comparison of Warner's values with those of Kurucz-Peytremann (Scii, Tiii,Vii, Crii, Mnii, Coii, and Niii) and Kurucz (Feii).K−P andK derived log(gf) by semi-empirical methods for many transitions using scaled Thomas-Fermi-Dirac potentials for the atoms of the elements from B to Ni. Although their individual values may be seriously in error, it has been shown that their mean scales are acceptable, being affected at most by rather small errors. It is known, for example, that when interacting terms are not properly accounted for in the semi-empirical method, very small values are derived for log(gf); these were dropped away in calculating mean corrections as they exhibited gross deviations. The relations loggf(KP)−loggf(W) vs λ, loggf(W), andE u (energy of the upper level) have been investigated, and constant corrections, or weak dependences are found. Using Warner's corrected log(gf) for these elements, we have shown in a rather qualitative way that abundances consistent with the values accepted at present are found in the solar photosphere.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We solved the equation of radiative transfer in spherically-symmetric shells with arbitrary internal sources. We integrated the equation of transfer on the discrete grid of angle and radius given by [μj−1, μj] [ri−1, ri]. The size in the angle coordinates is determined by the roots of a quadrature formula where as the size in the radial coordinate is determined by the non-negativity of the reflection and transmission operators. We considered two cases of variation of the Planck function. (1) Constant throughout the medium and (2) varying as 1/r 2. We find that in the inner shells, the radiation directed toward the centre of the sphere is more than that directed away from the centre of the sphere. In the outer shells the converse is true.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 107 (1984), S. 167-176 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A period-luminosity-colour relation is derived from the data of 29 galactic Cepheids with known distances collected from the literature, and is then compared with the simpler period-luminosity relation. The insignificant reduction in the dispersion seems to argue against the introduction of the colour term. It is, however, demonstrated that this evidence may be fictitious and due to the use of Cepheids, whose membership in a star aggregate is still doubtful. The exclusion of these stars leads to a PLC relation which shows a significantly smaller dispersion than that given by the corresponding PL relation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the preceding paper by Vengeret al. (1984) the results of observations of neutral gas in the vicinity of some galacticHii regions were considered; and it was demonstrated that 17 of the regions observed are surrounded by expandingHi envelopes. This paper describes a model of interaction between theHii regions and the surrounding interstellar medium constructed on the basis of the said results. It is assumed that the main dynamic factor in the envelope formation mechanism is the total stellar wind from the stars which ionze theHii regions. The employment of the observations of the line at λ=21 cm, of the radio continuum and IR dust continuum made it possible to determine the differential mass spectra of the stars exciting theHii zones and calculate some characteristics of the stellar population. The mass spectrum index of the objects considered turned out to be much higher than that for the mass spectra of background stars and scattered clusters of stars.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, screened reaction rates and mean lifetimes are studied for the reactions H 1 1 (Pβ + v)H 2 1 and He 2 3 (He3 2H)He 2 4 in the light of recent work on screening effects. We have interpreted that the dimensionless parameter Γ can remain constant only when the core starts forming and departs from the hydrostatic equilibrium. It is seen that a Main-Sequence star develops its helium core in a very short time after the hydrostatic equilibrium phase. The stellar longevity depends entirely on the reaction H1 (Pβ + v)H2 at the densities ϱX A=102 g cm−3 and 103 g cm−3. Again, the reaction He3(He3 2H)He4 plays a vital role at ϱX A=102 g cm−3 to retain a star for some million years in its Main-Sequence stage.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results are reported from investigations of neutral hydrogen in the vicinity of a number ofHii regions. The observations were performed on a RATAN-600 radio-telescope with angular and velocity resolutions of 2′×130′ and 6.3 km s−1, respectively. It is demonstrated that the distribution of the neutral gas in the vicinity of 17Hii regions is similar to that of the expanding envelopes. Dimensions and expansion velocities of the envelopes are determined and their masses and kinetic energies estimated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 107 (1984), S. 347-356 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The contact binary XY Boo is observed photoelectrically, and variations of the orbital period and the light curves are indicated. NewBV light curves and those of Binnendijk (1971) and Winkler (1977) are analysed by used of the light curve synthesis method. Combining the derived photometric elements with the spectroscopic elements of McLean and Hilditch (1983), we obtain values of the masses and the radii of the components of the system.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...