Struktur und Entwicklung kompakter Radioquellen     

G. M. Richter 《Astronomische Nachrichten》1976,297(1):5-21

A model is suggested which accounts for (i) the observed shape and angular variation of compact radio sources (especially the apparent superrelativistic velocities and the absence of contracting sources), (ii) the flux variation associated with the angular variation, and (iii) all the known cases of apparent occurence of surface brightness exceeding the theoretical upper limit provided by the inverse COMPTON effect, preserving the usual premises: cosmological origin of the redshift and incoherent synchrotron radiation of electrons. The model consists of a plasma ring expanding with moderate relativistic velocity. It provides two possibilities for estimating the distance of the sources by radio data: from the time dependence of the angular expansion and from the angular diameter and the shape of flux variation. In the context of cosmology this distances are „angular distances”︁ and therefore, if the redshift is also known, the HUBBLE constant or the acceleration parameter q₀ may be obtained. The second method is applied to BL Lac yielding approximately 6 Mpc. So the underlying galaxy would be a dwarf system of M ≈︂–13. The active nucleus of M ≈︂ – 16 is rather below the normal quasars. This seems very satisfactory in view of the short time scale of variations in BL Lac compared to the quasars.  相似文献   

Suspected OB stars near the andromeda nebula     

G. A. Richter 《Astronomische Nachrichten》1976,297(6):269-273

An investigation of suspected OB stars on plates of the Schmidt telescope of Karl Schwarzschild Observatory Tautenburg gave the following results: I. There exists a sharp boundary of the M 31 disk. For distances larger than R = 30 kpc from the centre no OB stars of the Andromeda galaxy could be found. 2. The isolated OB stars in the outer regions of M 31 fit into the spiral structure. 3. The suspected OB stars outside M 31 (R>30 kpc) in all probability belong to our own galaxy. It is to be expected that they partly are blue horizontal branch stars of extreme population II, partly white dwarfs rather far left of the black body line in the two colour diagram.  相似文献   

Kukarkin-Parenago relationship,period gap,and cause of dwarf nova outbursts     

G.A. Richter  H.-J. Bruer 《Astronomische Nachrichten》1989,310(6):413-418

It is shown that it can be useful to incorporate the orbital period P as an additional parameter into the Kukarkin-Parenago relationship. Then it turns out that the relationship splits into two, one holding for objects above and the other for objects below the well-known and much-discussed period gap between 2.2 and 2.8 hours A = -2.03 + 2.26 log C + 8.80 log P for P > 2.2 h A = 2.07 + 2.46 log C - 3.68 log P for P > 2.8 h (A amplitude (mag), C cycle length (d), P orbital period (h)). Future theories of the dwarf nova phenomenon and the origin of the period gap will have to deal with this.  相似文献   

Selection,statistics and photometry of compact galaxies with different instrumental equipment. Part III. Selection and statistics with objective prism plates     

N. Richter 《Astronomische Nachrichten》1981,302(1):29-30

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A new strong emission line quasar with a redshift z = 0.189     

H. Lorenz  G. A. Richter  V. L. Afanasjev  V. A. Lipovetsky 《Astronomische Nachrichten》1979,300(2):81-83

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The neighbourhoods of the nearest hickson groups     

J. Vennik  G. M. Richter  G. Longo 《Astronomische Nachrichten》1993,314(6):393-397

The comparison of the spatial distribution of galaxies in the surroundings of the nearest compact and loose groups of galaxies confirms that compact groups are very likely to be part of looser groups and shows that loose groups associated to compact groups tend to have higher spatial density than normal ones.  相似文献   

Photometry of groups of galaxies. I     

G. M. Richter  J. Vennik  W. Struve 《Astronomische Nachrichten》1985,306(3):107-116

Photometric data (magnitudes, radii, profiles) for galaxies in the field of 7 nearby groups of galaxies are measured by photographic surface photometry. Most of them are dwarf galaxies.  相似文献   

On the Real Number of Objects in the Tautenburg Catalogues of Blue Objects Suspected as Quasistellar (QSO)     

N. Richter 《Astronomische Nachrichten》1978,299(6):325-330

The results of the U, B, V photometries of W. BRONKALLA and N. RICHTER near the north galactic pole are discussed. In these photometries which have been carried out on the same Tautenburg Schmidt plates the share of blue objects suspected as quasistellar (QSO) has been determined by total photometry of all starlike objects in selected partly overlapping test fields. The results of both photometries agree very well. The position of the blue objects of the Tautenburg catalogues and BRONKALLA's photometry in the two-colour diagram is compared with the two-colour diagram of QSO's published by C. BARBIERI and M. CAPPACIOLI . In both cases 65 per cent of the objects are placed on the right-hand side and 35 per cent on the left-hand side (region of white dwarfs) of the black-body line. Therefore, it is no longer admissible to qualify in a photometric statistics of blue objects all those objects as white dwarfs which are situated on the left-hand side of the black-body line in the two-colour plot. This result is confirmed by the discussion of the number-magnitude relation of these objects. Clustering of blue objects and their connection with clusters of galaxies are discussed. Using results from A. SANDAGE and E. M. BURBIDGE and our own results one can conclude that more than 60 per cent of Tautenburg blue objects must be QSO's. For further spectroscopic and proper motion investigations it is proposed to prefer the objects placed on the left-hand side of the black-body line in order to obtain the real share of white dwarfs in this group of objects suspected to be quasistellar.  相似文献   

The knotty structure of the HII dwarf galaxy F348     

P. Rafanelli  S. Roi  A. Tegon  H. Schulz  S. Di Serego-Alighieri  S. Komossa  G. Richter  J. Vennik 《Astronomische Nachrichten》1997,318(6):319-327

[OIII] images and blue spectra of the emission-line dwarf galaxy F348 are presented. In [OIII] light, the object contains two knots about 9” NE of the nucleus and one large extended knot 11” to the SW. The nuclear region is hundred times less luminous in emission-line light than the knots. Despite the presence of line intensity ratios [OIII]λ5007/Hβ > 3 the prior classification as a Seyfert-2 object cannot be upheld. This clinches an earlier suggestion by Veron-Cetty & Veron (1986). In particular, we show that the line spectra can be modeled with photoionization models employing stellar input continua. Also, the line luminosities of the extranuclear knots are typical for giant HII regions. There is neither evidence for tidal tails nor for high velocity differences between the knots. In addition, the linear arrangement of the knots does not support interaction. It rather suggests self-propagating star formation In this picture, the faintness of the nuclear region can be understood by an edge-on view. In addition, the nuclear starburst appears to be fading in contrast to the young extranuclear star formation regions. Within the scheme of Melnick (1987), F348 has to be classified as a multiple-system HII galaxy.  相似文献   

S.A. KAPLAN and V. N. TSYIOVICH: Plaema Astrophysics. Pergamon Press,Oxford, New York,Toronto, Sidney,Braunschweig, 1973. XIII + 302 Seiten. Preis £ 9.50     

G.M. Richter 《Astronomische Nachrichten》1975,296(4):194-194

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