摘要:

AbstractThis study reports on the results of the application of an adaptive filtering technique to the two‐dimensional photometric mapping of galaxies. For this test we used the elliptical galaxy NGC 3379, which is a luminosity standard. Our plate material (B‐band), obtained with the Tautenburg Schmidt telescope, was digitized with the Babelsberg microdensitometer and with the ESO PDS. The 2‐D scans were reduced according to the Babelsberg Image Processing Systems, whose key feature is an adaptive filter called ‘H‐Transform’. By comparing our results (E‐Wlight profile and isophotal parameters) to the most recent studies of NGC 3379 (DE VAUCOULEURS and CAPACCIOLI 1979, and NIETO and VIDAL 1984), we found no systematic errors in the photometric calibration and in the reduction procedure, with typical mean residuals from the other studies not larger than ±0.05B‐mag up to a threshold of 1% of the night sky level on each plate. We also re‐confirmed the geometrical properties of the galaxy. The new filtering technique proved quite efficient in reducing the noise, with negligible effects on the photometric and geometric characteristics of the

ISSN:0004-6337    

DOI:10.1002/asna.2113090202

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA photographic photometry inBandVwas performed for the cD cluster of galaxies A 1795 which is located near the north galactic pole. Our catalogue contains 721 galaxies in a field of 1.6 ° around the cluster center

ISSN:0004-6337    

DOI:10.1002/asna.2113090203

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractSpectroscopic investigations of this dwarf nova of Z Camelopardalis type were performed during quiescence and eruption. Although over the period of spectroscopic observations the cycle‐length was only 8d.2 at times, no systematic differences to results on objects of larger cycle‐lengths could be establis

ISSN:0004-6337    

DOI:10.1002/asna.2113090204

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractAn examination of the published observational data concerning the light curves of magnetic CP stars has shown that only one star — HD 56022 — shows a light curve with a very long phase interval of light constancy. Only for this type of variability it is imaginable that the equatorial symmetry of the surface brightness distribution could be excluded. However, the analysis of the light curve of HD 56022 in the colouruof the Strömgren system has indicated that the possibly equatorial position of the small bright spot is not in contradiction to this observed curve.From the analysis inuthe maximum amplitude of a light curve at another wavelength, where the curve is in counterphase to the light curve inu, can be predicted. The amplitude of such a light curve must be much smaller than 0.1 mag. From unpublished observations of HD 56022 by the satellites TD‐1 A and ANS we have determined the amplitude at $LD = 155 nm, where the light curve is in counterphase to that inu, to be 0.2 mag.The consequences from the contradiction between the model and the observations in UV are dis

ISSN:0004-6337    

DOI:10.1002/asna.2113090205

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113090206

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe collapse, bounce, shock wave and expansion of the envelope of a rotating star have been analysed in the adiabatic approximation using the particle‐in‐cell method.The bounce takes place first in the equatorial plane and a shock wave arises there which shortly afterwards crosses the surface of the star. In the envelope, and to a less extent in the remainder of the star, there is a fast and lasting meridional motion the direction of which changes. As a consequence of the fast meridional motion in the envelope, mass and angular momentum are transported towards the axis of rotation. If the initial star rotates fast enough this will cause a secondary radial expansion in the polar region and a mass ejection. These motions reduce the strong anisotropy caused originally by the equatorial expansion. Strong whirls may arise along the axis of rotation. In the remainder of the star the meridional motion becomes supersonic. The temperature in the envelope depends to a high degree on the choice of the equation of state. Massloss is proportional to the energy initially added. The final loss of angular momentum and of energy is quite large, both losses being about

ISSN:0004-6337    

DOI:10.1002/asna.2113090207

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe test function for the method proposed by DUMONT, MORGULEFF, RUTILY, and TERZAN (1978) is investigated analytically and numerically for some examples with constant and variable periods. The properties of the test function of the DMRT method are discussed in comparison with that of the leastsquare method.

ISSN:0004-6337    

DOI:10.1002/asna.2113090208

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2113090212

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractWe reanalyse positions and motion of the striae in the dust tails of the bright comets Mrkos 1957 V and West 1976 VI. Two theories are compared to the data: the high speed particle ejection theory of NOTNI (1964) and the two‐step kinematical sequence proposed by SEKANINA and FARRELL (1980) in their particle fragmentation theory. The final decision is in favour of the two step sequence, though the real situation may be a mixtum compositum of both. The parent clouds (first step) are found to have low lateral velocity dispersion and higher than expected acceleration. The question how these clouds originate remains unsolved. It is suggested that they comprise particles which left the coma into a tailward region of high magnetic field and plasma density. Another possibility, additionally accounting for the sometimes apparent duplicity, is an origin out of an optically thick coma at angles orthogonal to the radius vecto

ISSN:0004-6337    

DOI:10.1002/asna.2113090210

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe internal dynamics of an illuminated dust cloud of finite optical thickness is investigated. The dependence of the radiation pressure on the optical depth makes the individual particles oscillate, in one dimension, around the accelerated centre of gravity of the cloud. The cloud moves as an entity, irrespectively of the velocity dispersion of the particles and their efficiency for radiation pressure. If the optical depth does not change, i.e. if the cloud does not expand laterally, its lifetime is unlimited. A contraction caused by energy dissipation in mechanical collissions between the dust particles is expected.The range of particle sizes which can be transported by such a “coherent cloud” is estimated, as well as the acceleration of the whole cloud. The structure of the cloud in real space and in velocity space is investigated. A comparison with the “striae” observed in the dust tails of great comets shows that theparentclouds of these striae may have been of the kind con

ISSN:0004-6337    

DOI:10.1002/asna.2113090211

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY