Verfahren zur Abgleichautomatisierung von Irisblendenpohotometern (Mitteilung der Universitäts-Sternwarte zu Jena Nr. 121)

Following a critical review of automatical output techniques of equality-information in iris-type photometers put into practice previously, in this paper new possibilities are discussed. One of these methods which is based on digital-techniques and is easy to realize resolves differences between the intensities of the comparison and measuring beam of less then 10⁻³.     

On the Widths of Dust Layers in Galaxies (Mitteilungen der Universitätssternwarte Jena Nr. 156)

From prints of the Palomar Observatory Sky Survey the widths of the equatorial dust layers of a sample of 39 galaxies seen on edge are obtained to be in the range 500 ≤ D ≤ 1600 pc. The width of a dust layer seems to be correlated with the luminosity of the galaxy. The dust lanes of field galaxies are obviously broader than those of the members of the Virgo cluster. This result may be interpreted as a dust deficiency caused by stripping of interstellar matter resulting from galactic collisions and interaction of the galaxies with the intracluster medium.     

On Measuring the Dynamical Age of Clusters of Galaxies (Mitteilungen der Universitätssternwarte zu Jena Nr. 139) Universitätssternwarte and Zentralinstitut für Astrophysik der Akademie der Wissenschaften der DDR With 4 Figures

The method for measuring the dynamical age of n-body systems proposed by S. von HOERNER (1976) is applied to clusters of galaxies. The modulus of evolution W characterizing quantitatively the dynamical state of the cluster was determined for several objects. It turns out that the Virgo cluster is one of the dynamically youngest clusters.     

Über eine lichtelektrische Nachführung als Hauptelement einer automatisierten Teleskopsteuerung (Mitteilung der Universitäts-Sternwarte zu Jena Nr. 131)

An autoguider based on the time-method is described. It is characterized by using one multiplier only, taking into account the szintillation, compensating if necessary the backlash of the gearing, and using digital techniques. Therefore, it is possible to use for the guider the special electronics described or a control computer. The accuracy of the setting is about ±0″.1.     

Beobachtungsmöglichkeiten zur Linschen Dichtewellentheorie (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 130)

After summarizing the most important effects predicted by the density-wave theory the possibilities of observing these effects are discussed. The observation of structural effects in our own Galaxy is very difficult, mainly because of the inaccurate distances available. Only rough structures can be obtained. That is also true for observations near such points, in which the line of sight is tangential to the spiral arms. Observations of kinematical effects in our own Galaxy and of structural effects (kinematical ones are not discussed) in extragalactic spiral systems should yield some useful results.     

Automatisierung astronomischer Beobachtungs- und Auswertemeßtechnik mit Hilfe eines Kleinrechners im Dialogbetrieb (Mitteilung der Universitäts-Sternwarte zu Jena Nr. 142)

For the optional online control of three devices of measurement (photoncounting stellar photometer, microdensitometer, and iris diaphragm photometer) by a mini control computer an interpreting programming language was modified. It is possible now to control the devices by conversational processing as well as by programming, to sample and evaluate the measuring values, and to optimize the parameters of the process if it is wanted.     

Mass loss from very young massive stars (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 172)

A very important property of very young and massive stars (BN objects) is their intensive mass loss. We describe the main methods to derive the mass loss rates. Available observations are used to characterize the ionized stellar winds and the CO flows. The results are confronted with theories describing the anisotropic mass loss.     

On the properties of very young massive infrared sources (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 169)

The data compiled for 34 very young massive compact infrared source (Becklin-Neugebauer objects) in a separately published catalogue serve as the basis for an investigation of their general properties. First, the correlations of the strength of the ice and silicate bands at 3.1 μm and 10 μm, resp., with each other and with other parameters of the sources are investigated. In accordance with theoretical expectations the strengths of both bands are not well correlated with each other. The ratio τ₁₀/τ₃ of their optical depths veries from 0.85 to 8 (and possibly up to 22). That implies for the number densities of the grains that (naked) silicate grains always are considerably more abundant than ice grains (grains with ice mantles). It follows from the discussion of the relationships between τ₁₀, the temperature parameter of the sources, and their luminosity that relations between τ₁₀ and temperature and possibly between τ₁₀ and the luminosity exist. Stellar wind models for the ionized region around the embedded star are favoured after the analysis of the intensities of the hydrogen infrred emission lines and the radio continuum. The limited observational data do not yet allow a decision on a correlation between the silicate band depth and energy content and/or the velocity of the bipolar outflow detected in a number of sources. The BN objects are clearly more frequently associated with H₂O masers than OH masers. The linear separations of the infrared peaks from the masers are compatible with models where the H₂O masers are situated near the edges the gas-dust shells of the BN objects.     

A Catalogue of Extremely Young,Massive and Compact Infrared Objects (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 165)

Starting from the Becklin-Neugebauer Object in Orion as a prototype, a class of compact infrared sources thought to be young massive stars surrounded by optically thick dust shells is identified by means of a wide range of their observable features. A catalogue of 34 such objects is compiled, providing comprehensive information such as infrared and radio spectra, maser sources, and outflow phenomena.     

The Interstellar 2200 Å Band: A Catalogue of Equivalent Widths (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 151)

Using the data of the Ultraviolet Bright-Star Spectrophotometric Catalogue, the equivalent width of the interstellar absorption band at 2200 Å is derived for 422 stars. A preliminary statistical analysis confirms the good correlation between the equivalent width of the 2200 Å band and the colour excess. The wavelength position of the band centre seems to vary to a small extent.     

X-ray emission – an ageing effect of galaxy clusters (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 145)

Die Röntgenleuchtkraft L_X und -temperatur T_X von Galaxienhaufen wurden zu dem dynamischen Entwicklungsparameter W in Beziehung gesetzt, den VON HOERNER (1976) eingeführt hat. Offensichtlich ist Röntgenstrahlung eine Alterserscheinung der Galaxienhaufen.     

New red variable stars in two fields in Cepheus and Cygnus (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 143)

The detection of 15 probably long period variables is announced. The observed range of light changes in the r system are given.     

A Model of the 10 Micrometer Silicate Feature in the Spectra of BN-like IR-Point Sources (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 150)

A model representing the profile of the silicate absorption band at 9.8 μm in the spectra of BECKLIN -NEUGEBAUER objects has been developed, solving the equation of radiative transfer. The model based on the condition of radiative equilibrium, on an analytical temperature distribution and on the assumption of constant density in the circumstellar shell allows the evaluation of the optical depth in the band's centre and the investigation of the effect of the temperature variation at the inner boundary of the envelope. The optical depth in the band's centre ist calculated for the BN point source.     

Rechnergesteuerte schnelle Photometrie am Beispiel der Bedeckung von 57 Orionis durch den Mond. I. (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 154)

For high speed photometric observations the photoelectric system was modified. The supplement of the interpreting programming language permits measurements down to 1 ms integration time with an overall measuring time of at least 4 s. The application in the case of lunar occultations is described and an outlook of the data reduction treatment is given.     

Rechnergesteuerte schnelle Photometrie am Beispiel der Bedeckung von 57 Orionis durch den Mond. II. (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 155)

The needed formulae for the reduction of lunar occulations are presented and used for the treatment of the occultation data of 57 Orionis. A computing method for the determination of the object profile is given and the influence of noise is discussed. The results for the spectroscopic binary 57 Orionis cannot be explained by the parameters published.     

The Fragmentation of Asteroids – A Synopsis of Analytical Methods (Mitteilungen der Universitäts-Sternwarte Jena Nr. 119)

Basing on the author's work a review of the possibilities as well as the limits of treating the problem of the collisional history of the asteroids by analytical methods is given. Using empirical data on rock fragmentation and general principles like symmetry and mass conservation the distribution function of the fragments arising from a single collision is analytically formulated. The size distribution of asteroids adjusting when crushing collisions have taken place a sufficiently long time can be obtained as the solution of an integrodifferential equation with partial derivatives (equation of fragmentation). Quasi-stationary solutions of the equation of fragmentation are discussed for particular cases. The problem of the steady state is reduced to the solution of a transcendental equation. The results obtained show that analytical methods already offer a good theoretical understanding of the observed size distribution of the asteroids. They should be, therefore, a useful basis of carrying out numerical calculations.     

The interstellar 2200 Å band: A second catalogue of equivalent widths and preliminary statistical analysis (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 162)

A second catalogue of equivalent widths of the interstellar 2200 Å band is presented. It is based on spectrophotometric data obtained with the TD-1 satellite and supplements a catalogue already published (paper I). Both catalogues list a total of 779 stars. The reliability of the derived parameters is analysed. There is a satisfying agreement with spectrophotometric data obtained with the OAO-2 satellite. The relationship between the equivalent width of the 2200-Å band and and the colour excess is discussed, making use of additional data for more strongly reddened stars obtained with OAO-2 and IUE.     

Suppositions for the Comparison of Infrared Spectra from Terrestrial Silicates with Interstellar Spectra and the Selection of Suitable Silicates (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 149)

The influence of potassium bromide on the bands near 10 μm, 18 μm and 33 μm was calculated for any silicate. The wavelength shift, the deepening, and the broadening of the bands were calculated for different band's depths of each band. The results were applied on the investigation of an extensive catalogue of silicate spectra, which were got on the basis of the KBr pressing technique too. So it was possible to picle out those silicates from the variety of silicates, which are probable candidates for the interstellar silicate component.     

The luminosity function of nearby galaxies (mitteilungen der universitätssternwarte zu jena nr. 147)

Using the catalogue of galaxies within 10 Mpc by Kraan-Korteweg and Tammann (1979) the local luminosity function of galaxies is derived. Possibly there exists a large population of faint elliptical systems being an important constituent in the Universe. From this luminosity function the local mass density Q = 5.1 · 10^-31 g cm^-3 = 0.11 Q_c was obtained.