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Showing papers by "European Southern Observatory published in 1983"


Journal ArticleDOI
TL;DR: In this paper, the radial velocity curves, in spite of their small amplitudes, are weil defined and do not show any peculiarities, and the accuracy of observations seems to be sufficient for determining both the moments of particular phases and the amplitudes.
Abstract: The radial velocity curves, in spite of their small amplitudes, are weil defined and do not show any peculiarities. The accuracy of observations seems to be sufficient for determining both the moments of particular phases and the amplitudes (about 3 km/s for v Cen and 6 km/s for (3 Cen). Points denote velocities actually observed, the broken line is a sinusoid fitted by eye to the observations. Both objects are bright, so the exposure times were typically 2-3 min.

585 citations


BookDOI
01 Jan 1983
TL;DR: The proceedings from the International Astronomical Union Symposium No. 101 on supernova remnants were published in this article, containing a complete report on the effects of X-ray information on the ideas about supernova restorations.
Abstract: This book contains the proceedings from the International Astronomical Union Symposium No. 101 on supernova remnants. The proceedings contain a complete report on the effects of X-ray information on the ideas about supernova remnants. Also included are reviews of radio, optical, and theoretical results. The volume contains transcriptions of some of the discussions that followed the papers given at the symposium.

252 citations


Journal ArticleDOI
TL;DR: It is suggested that virtually all the X-ray sources in the Einstein Observatory's Medium Sensitivity Survey flux range can be identified with objects visible on the POSS, on the basis of the complete identification of all sources north of -25 deg declination.
Abstract: It is suggested that virtually all the X-ray sources in the Einstein Observatory's Medium Sensitivity Survey flux range can be identified with objects visible on the POSS, on the basis of the complete identification of all sources north of -25 deg declination. There is no evidence for a significant population of 'blank field' X-ray sources at this flux level, and therefore no evidence for any new X-ray source class with very high L(x)/L(v). Most of the quasars detected in the present survey are spectroscopically similar to optical or radio-selected quasars. About 25 percent of the quasar sample, however, had reddish colors, and permitted lines dominated by a narrow-line component. These objects form a second sequence of active galactic nuclei, distinct in their optical properties from the broad line objects.

54 citations





Journal ArticleDOI
TL;DR: In this paper, the results from the Einstein deep X-ray survey in Pavo, with correlated optical and radio observations of a complete sample of candidate identifications, are presented.
Abstract: Results are presented from the Einstein deep X-ray survey in Pavo, with correlated optical and radio observations of a complete sample of candidate identifications. There are 16 X-ray sources detected with positional accuracy better than 10 arcsec, of which five are identified, with a further seven (and a maximum nine) probable identifications. Of the identified sources, four are QSOs with J-magnitude about 20 (one is an inverted spectrum radio source) and one is associated with extended emission from a pair or cluster of galaxies. Of the probable identifications, one is a galaxy and the rest are a subset of a yellow stellar object population which may also be QSOs. Identifications with QSOs and QSO candidates with J less than 24 account for 60-80 percent of the detected sources.

27 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied the characteristics of families of periodic orbits in Hamiltonian systems of two degrees of freedom and found infinite gaps and bubbles along the characteristics. But they also found infinite pitchfork period doubling bifurcations and in all cases the Feigenbaum ratio is consistent with the universal value δ = 8.72.

26 citations



Journal ArticleDOI
TL;DR: It seems that there are no infinite sequences of period-doubling bifurcations, except in systems reducible to 2 degrees of freedom.
Abstract: Two mechanisms terminate the sequences of period doubling bifurcations in Hamiltonian systems of 3 degrees of freedom:a) complex instability andb) inverse bifurcations. It seems that there are no infinite sequences of period-doubling bifurcations, except in systems reducible to 2 degrees of freedom.

14 citations


Journal ArticleDOI
TL;DR: In this article, the cosmological evolution and the X-ray luminosity function of selected active galactic nuclei (AGNs) are derived and discussed using a single power law over a limited range of absolute luminosities.
Abstract: The cosmological evolution and the X-ray luminosity function of X-ray selected active galactic nuclei (AGNs) are derived and discussed. The sample used consists of 31 AGNs extracted from a fully identified sample of X-ray sources from the Einstein Observatory Medium Sensitivity Survey and is therefore exclusively defined by its X-ray properties. The distribution in space is found to be strongly nonuniform. The amount of cosmological evolution required by the X-ray data is derived in the framework of pure luminosity evolution and is found to be smaller than the amount determined from optically selected samples. The X-ray luminosity function is derived. It can be satisfactorily represented by a single power law only over a limited range of absolute luminosities. Evidence that the luminosity function flattens at low luminosity or steepens at high luminosity, or both, is presented and discussed.

Book ChapterDOI
01 Jan 1983
TL;DR: In this paper, an increasing tempo of detailed optical and UV spectroscopy of SNR leading to comparisons with prevailing models of radiative shocks was reported. But the results were limited.
Abstract: Over the past decade there has been an increasing tempo of detailed optical and UV spectroscopy of SNR leading to comparisons with prevailing models of radiative shocks.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the various families of periodic orbits in a dynamical system representing a plane rotating bar galaxy, and the evolution of the various types of orbits is described, as the Jacobi constanth and the bar amplitude increase.
Abstract: We study the various families of periodic orbits in a dynamical system representing a plane rotating barred galaxy. One can have a general view of the main resonant types of orbits by considering the axisymmetric background. The introduction of a bar perturbation produces infinite gaps along the central familyx1 (the family of circular orbits in the axisymmetric case). It produces also higher order bifurcations, unstable regions along the familyx1, and long period orbits aroundL4 andL5. The evolution of the various types of orbits is described, as the Jacobi constanth, and the bar amplitude, increase. Of special importance are the infinities of period doubling pitchfork bifurcations. The genealogy of the long and short period orbits is described in detail. There are infinite gaps along the long period orbits producing an infinity of families. All of them bifurcate from the short period family. The rules followed by these families are described. Also an infinity of higher order bridges join the short and long period families. The analogies with the restricted three body problem are stressed.

Book ChapterDOI
01 Jan 1983
TL;DR: In the recent past supernova remnants (SNR) have been identified in external galaxies as far as 5 Mpc as mentioned in this paper, where the numbers of SNR confirmed by optical spectroscopy are given in parenthesis.
Abstract: In the recent past supernova remnants (SNR) have been identified in external galaxies as far as 5 Mpc These galaxies are: M 33(12), M 31(12), NGC 6822(1), IC 1613(1), NGC 2403(2), NGC 300 (2), NGC 4449(1), where the numbers of SNR confirmed by optical spectroscopy are given in parenthesis. Data for objects in the Magellanic Clouds are discussed extensively elsewhere in this volume.

Journal ArticleDOI
TL;DR: In this paper, a brief discussion of the systematic effects of selection bias on the extragalactic distance scale is given, and it is concluded that type I supernovae, calibrated through brightest M supergiants, yield presently the most reliable determination of the large-scale value of the Hubble constant, i.e., 50 + or - 7 km/s Mpc.
Abstract: A brief discussion of the systematic effects of selection bias on the extragalactic distance scale is given. Distance indicators with intrinsic scatter yield only upper limits to Ho, unless the true intrinsic scatter is either small or well determined. Several distance indicators (luminosity index, diameters, globular clusters, 21 cm line widths) are discussed. It is concluded that type I supernovae, calibrated through brightest M supergiants, yield presently the most reliable determination of the large-scale value of the Hubble constant, i.e., 50 + or - 7 km/s Mpc.

Book ChapterDOI
01 Jan 1983
TL;DR: In this article, surface photometry, velocity measurements in the bar and a dynamical model were used to complement the existing data with surface photometric, velocity measurement and a dynamic model.
Abstract: NGC 5383 has often been used as a prototype of SB(s)b type galaxies, particulary in studies of gas flow. We have therefore set out to complement the existing data with surface photometry, velocity measurements in the bar and a dynamical model.

Journal Article
TL;DR: In this article, the periode de rotation synodique is computed in 3 h 44 m 51s6±7s4 for the UBV and Geneve system.
Abstract: Observations photoelectriques dans les systemes UBV et de Geneve entre le 6 octobre et le 7 novembre 1980. Analyse de la courbe de lumiere comportant des maxima et minima distincts. La periode de rotation synodique est de 3 h 44 m 51s6±7s4

Book ChapterDOI
01 Jan 1983
TL;DR: In this article, optical velocity field mapping of G292.0+1.8 was carried out using the IPCS with the 3.6 m ESO telescop_e at La Silla.
Abstract: Optical velocity field mapping of G292.0+1.8 in the [0III] λ5007 A line has been carried out using the IPCS with the 3.6 m ESO telescop_e at La Silla. Our data are not consistent with the suggestion that the [0III] emitting material in the western portion of this remnant is concentrated in an expanding ring. The existing data on G292.0+1.8 suggests that only the brightest portion of a thick shell of ejecta with high velocity spurs is observed. The expansion centroid, size, velocity and age of this SNR are derived.


Journal ArticleDOI
TL;DR: In this paper, the authors examined X-ray observations of the Horologium supercluster and found that the density structure of its emitting gas, determined in a model-independent way, is remarkably featureless, being consistent with a nearly isothermal polytrope out to approximately 2 Mpc from the cluster center.
Abstract: X-ray observations of the Horologium supercluster are examined. Results show that the optically Coma-like cluster CA 0340-538 has a smooth X-ray structure which also resembles that of Coma. The density structure of its X-ray emitting gas, determined in a model-independent way, is found to be remarkably featureless, being consistent with a nearly isothermal polytrope out to approximately 2 Mpc from the cluster center. The total mass of the gas is determined to exceed 10% of the cluster virial mass and may contribute a substantial fraction of the cluster binding mass. Although CA 0329-527 is found to be an X-ray double cluster, its structure appears to be confused. CA 0325-539 is found to show no substantial X-ray emission. An upper limit of 1.3 x 10 to the 44th erg/s is determined for any diffuse 2-10 keV emission from the Horologium supercluster.


Journal Article
TL;DR: In this article, the color gradients between the galaxy centers and a 50 kpc radius are found, which are interpreted as the result of ongoing star formation which is fueled by the accreted cluster gas.
Abstract: Carefully calibrated B, V, and B-V radial surface brightness profiles of 7 cD galaxies which are known to be centered on extended X-ray sources are presented. Pronounced color gradients between the galaxy centers and a 50 kpc radius are found. All observed cD galaxies have blue haloes. The global color profile properties of the observed galaxies are described. No systematic trend in the ellipticity parameters between B and V images is found, suggesting a similar kinematic origin for the stars that dominate both bands. No isophotal twisting greater than 10 deg is observed, but the eccentricity of the isophotes increases with increasing radii. It is argued that gas accretion from the cluster reservoir onto cD galaxies by means of radiative cooling is a very general phenomenon. The optical observations reported here are interpreted in terms of this process. The color gradients are interpreted as the result of ongoing star formation which is fueled by the accreted cluster gas.



Journal ArticleDOI
TL;DR: In this article, the observations CCD revelent la presence of un objet tres rouge et legerement etendu (2,5×1,3 sec arc 2 ) which se superpose a l'image de la spirale, a 1,5 sec arc du centroide radio.
Abstract: La radiosource PKS 0400-181 a une structure classique a double lobe et renforcement de brillance au bord, semblable a celle de Cyg A. Aucun cœur radio n'a ete detecte, mais le centroide radio est situe a 2,8 sec arc du centre d'une galaxie spirale de 16eme magnitude. Les observations CCD revelent la presence d'un objet tres rouge et legerement etendu (2,5×1,3 sec arc 2 ) qui se superpose a l'image de la spirale, a 1,5 sec arc du centroide radio. Les proprietes de l'objet rouge et de la radiosource sont compatibles avec une radiogalaxie puissante de decalage spectral voisin de 0,5; la spirale est probablement un objet du fond qui se trouve par hasard sur la ligne de visee

Journal ArticleDOI
12 May 1983-Nature
TL;DR: Close QSO pairs can be used to test the cosmological interpretation of QSO redshifts by using associated absorption to distinguish which QSO of a pair is in front of the other.
Abstract: Close QSO pairs can be used to test the cosmological interpretation of QSO redshifts If (some of) the narrow absorption lines in QSO spectra arise in intervening matter, and if QSOs are surrounded by gaseous haloes or located in regions of high matter density (for example, clusters of galaxies), one may expect to find absorption in the spectrum of one QSO at the redshift of a foreground QSO which happens to be located nearby on the plane of the sky (‘associated absorption’) According to the cosmological interpretation, the foreground QSO should have the lower redshift If, on the other hand, QSO redshifts are unrelated to their distances, one would expect to find as many cases in which the foreground QSO has the higher redshift of the two; or if the absorption lines are not even due to intervening matter, there should be no coincidences of absorption and emission redshifts beyond random expectation Thus, by using associated absorption to distinguish which QSO of a pair is in front of the other, we have a simple and straightforward test of the cosmological interpretation

Journal ArticleDOI
TL;DR: In this article, UAV observations of the short-period eclipsing binary BV Eri are reported and analyzed, showing a light curve distortion, making an analysis difficult, and the secondary fills its critical Roche lobe.
Abstract: UBV observations of the short-period eclipsing binary BV Eri are reported and analyzed. The radial velocity curve is given. The system shows a light curve distortion, making an analysis difficult. The secondary fills its critical Roche lobe. The system seems to be in an interesting evolutionary.

Book ChapterDOI
01 Jan 1983
TL;DR: The radio galaxy PKS 0521-36 contains a variety of physical features that make it an object worth studying in some detail as discussed by the authors, but at the present time it is not clear how all of these various features relate to one another and whether they can be unified.
Abstract: The radio galaxy PKS 0521-36 contains a variety of physical features that makes it an object worth studying in some detail. At the present time it is not clear how all of these various features relate to one another and whether they can be unified. It is worthwhile listing them all in the hope that this might provide insight into the evolution of such an object.

Journal Article
TL;DR: In this article, a test field No 358 of the ESO/Uppsala catalog has been used for parameter extraction for the Fornax cluster, where the data for the 70 galaxies in this test field yield results which are of general interest, such as estimates of total magnitude from a combination of major and minor diameters that yields angular size.
Abstract: Under a restriction for minimum angular diameter of not less than 1 arcmin, corresponding to the 15th magnitude and allowing morphological classification of structure, 16,000 galaxies have been brought together in the single volume of the ESO/Uppsala catalog (1982) Attention is given to the automatic parameter extraction methods employed, and detailed information is presented for preliminary results on test field No 358, which covers the Fornax cluster The data for the 70 galaxies in this test field yield results which are of general interest, such as estimates of total magnitude from a combination of major and minor diameters that yields angular size

Book ChapterDOI
01 Jan 1983
TL;DR: In this article, it has been known for several decades that about 15% of elliptical galaxies contain ionized gas and very little data is available in the literature on the properties of this gas such as spatial distribution, velocity field, and abundances.
Abstract: It has been known for several decades that about 15% of elliptical galaxies contain ionized gas yet very little data is available in the literature on the properties of this gas such as spatial distribution, velocity field, and abundances. The properties of this gas are related to current problems about elliptical galaxies: (1) origin of the gas (stellar mass loss vs. accretion from a nearby gas-rich galaxy or an intergalactic cloud) ; (2) structure of the galaxy itself, because the locus of the stationary orbits of the gas depends on whether the galaxy is prolate or oblate and on whether the galaxy is rotating or not; (3) the relationship between the presence of gas in elliptical galaxies and their radio properties.