ADS BibCode:
1981Msngr..23....1V
Author(s)/Affiliation(s):
van Paradijs, J.
AA(Astronomical Institute, University of Amsterdam)
Abstract:
The majority of the bright galactic X-ray sources are mass-exchanging binary stars in which anormal companion star is transferring matter to its compact companion, in most cases a neutron star. A neutron star is an extremely dense concentration of matter: a mass equal to that of the sun (diameter 1.4 million km) is concentrated in a sphere with a diameter of only about 20 km. The gravitational force near such a star is very strong, and, upon falling on the neutron star surface, the infalling matter reaches a velocity of about half that of light. The kinetic energy of this matter is transformed into heat (the temperature reaches values in excess of 10 million degrees) and radiated in the form of X-rays.

ADS BibCode:
1981Msngr..23....3.
Author(s)/Affiliation(s):
ESO
AA(ESO)

ADS BibCode:
1981Msngr..23....5L
Author(s)/Affiliation(s):
Lamy, P.; Koutchmy, S.
AA(Laboratoire d'Astronomie Spatiale du CNRS, Marseille) AB(Institut d'Astrophysique du CNRS, Paris)
Abstract:
The lack of suitable two-dimensional detectors has been a major problem for infrared imaging in astronomy, and most results so far have been obtained by scanning the object with a single detector (e. g., Terrile and Westphal,lcarus, 30, 730, 1977). The relative merit of both techniques was thoroughly investigated by Hall (Applied Optics, 10, 838, 1971) who concluded that, below about 2.5 ~lm, camera tubes should be preferred to scanners. Besides, sufticiently long times required by the scanning technique are not always available for some astronomical applications. These considerations led us to acquire a standard television camera equipped with an infrared vidicon tube N156 manufactured by Hamamatsu Co. (Japan).

ADS BibCode:
1981Msngr..23....6.
Author(s)/Affiliation(s):
ESO
AA(ESO)

ADS BibCode:
1981Msngr..23....7O
Author(s)/Affiliation(s):
Ott, H. A.
AA(Astronomisches Institut der Universität Münster)
Abstract:
Cireumstellar speetral lines, espeeially those whieh direetly indieate the flow of stellar material, like P Cygni lines have been observed sinee the beginning of our eent~ry. The peeuliar eharaeter of P Cygni itself was eonspieuous on Harvard objeetive prism plates al ready in 1890. Though until today the number of these obviously mass-Ioosing stars grew steadily, espeeially sinee the beginning of UV astronomy, we do not know very mueh about the physieal meehanisms whieh are basieally responsible for the loss of stellar material. Regarding the hot stars, models are favoured in whieh the photospherie radiation pressure, espeeially in the UV, or meehanisms in stellar eoronae are supposed to be the driving motors of stellar winds (see e.g. J. P. Cassinelli et al., Publications of theAstronomical Societyofthe Pacific, 90, 496,1978), while for the eold end of the speetral sequenee, aeoustie phenomena, generated in the outer stellar eonveetion zones, seem to aeeeierate the outflowing masses. The medium speetral types Fand G appear to show the least tendeney towards mass loss. Or is it possible that the laek of suitable theories in this temperature range is at least partially responsible for the laek of systematie observations? Whether these stars are indeed more resistant to mass loss is one of the questions of our programme.

ADS BibCode:
1981Msngr..23....9.
Author(s)/Affiliation(s):
ESO
AA(ESO)

ADS BibCode:
1981Msngr..23...11B
Author(s)/Affiliation(s):
Bergvall, N.
AA(Astronomiska Observatoriet, Uppsala, Sweden)
Abstract:
One of the most fundamental issues of modern astronomy is the question of the origin and early evolution of galaxies. The deeper we penetrate into the past history of the universe, the more important these questions seem to be. In particular, we may ask why the galaxies show up in so many different shapes and if the morphology of a galaxy may be substantially altered during the evolution of the universe. In this context, the galaxies which have a peculiar, i. e. non-Hubble, morphology, have attracted special attention. Among these objects, we find the interacting galaxies, which constitute approximately 5% of all galaxies.

ADS BibCode:
1981Msngr..23R..14.
Author(s)/Affiliation(s):
ESO
AA(ESO)
Abstract:
126. A.C. Danks and M. Dennefeld: Near-infrared Spectroscopy of Comet Bradfield (1979L). Astronomical Journal. December 1980.

ADS BibCode:
1981Msngr..23Q..14.
Author(s)/Affiliation(s):
ESO
AA(ESO)
Abstract:
The European Southern Observatory is organizing an international conference on the subject "SCIENTIFIC IMPORTANCE OF HIGH ANGULAR RESOLUTION AT INFRARED AND OPTICAL WAVELENGTHS", to be held in the ESO building at Garching bei München during the period of 24-27 March 1981. The purpose of this conference is to discuss, on the one hand, the systems in use or under construction and possible future developments to achieve high angular resolution and, on the other hand, to discuss the areas of astrophysics which, in the next decades, will most benefit from observations at high angular resolution.

ADS BibCode:
1981Msngr..23...15C
Author(s)/Affiliation(s):
Courtes, G.; Sivan, J. P.; Boulesteix, J.; Petit, H.
AA(Laboratoire d'Astronomie Spatiale, CNRS, Marseille) AB(Laboratoire d'Astronomie Spatiale, CNRS, Marseille) AC(Observatoire de Marseille) AD(Observatoire de Marseille)
Abstract:
With few exceptions, the ionized hydrogen regions in a galaxy are extended sources emitting only a few lines of very faint intensity. The use of a narrow interference filter (to select one of the most intense lines) in combination with a focal reducer design (to increase the illumination of thefocal plane) at the focus of a large telescope is the best way to obtain deep photographs of the ionized hydrogen features in nearby galaxies (Courtes, G.: 1973, Vistas in Astronomy 14, 81). lt should be noted that in this optical arrangement, the filter is not set in the small f-number beam of the focal reducer, but in the lower aperture beam of the telescope, thus making possible the use of very selective interference filters (wh ich accept a very narrow angular field). This method has been extensively used for several years by Courtes and his co-workers at the 1.93 m telescope of Haute-Provence Observatory, at the Palomar 200 inch telescope, and, more recently, at the 3.6 m telescope of ESO.

ADS BibCode:
1981Msngr..23...15.
Author(s)/Affiliation(s):
ESO
AA(ESO)

ADS BibCode:
1981Msngr..23...18K
Author(s)/Affiliation(s):
Kappelmann, N.; Mauder, H.
AA(Astronomisches Institut der Universität Tübingen) AB(Astronomisches Institut der Universität Tübingen)
Abstract:
During a photographic survey of the Chamaeleon T association in 1971/72, evidence was found by Mauder and Sosna (Information Bulletin on Variable Stars, 1049, 1975) for quasi-cyclic light and colour variations of three variable stars, members of this nearby group of young stars. They were classified by Hoffmeister (Veröff. Sonneberg 6, 1, 1963) as T Tauri stars because of their light variations, and this type was confirmed with objective prism spectra by Henize and Mendoza (Astrophysical Journal, 180, 115, 1973).

ADS BibCode:
1981Msngr..23...19B
Author(s)/Affiliation(s):
Bergeron, J.
AA(Institut d'Astrophysique, Paris)
Abstract:
Very extended nebulosities of high excitation have been discovered around a few active galaxies. For the two radio galaxies 3C120 and PKS 2158-380 they extend over dimensions of at least one arcminute (or about 50 kpc) and can be studied in the optical with a reasonable spatial resolution. These observations give information on the interaction between the active nucleus and its surrounding and on the nature of the gaseous envelope.

ADS BibCode:
1981Msngr..23...21H
Author(s)/Affiliation(s):
Hayli, A.; Bertola, F.; Capaccioli, M.
AA(Observatoire de Lyon, France) AB(Istituto di Astronomia, Padova, Italy) AC(Istituto di Astronomia, Padova, Italy)
Abstract:
Two epochs have to be recognized in the study of elliptical galaxies. Prior to 1975 it was believed that a globally correct description of the structural and dynamical properties of these objects had been achieved. It was thought that these galaxies were weil understood, not only because their morphology appeared to be simple and they were considered to contain only one stellar population, but also, paradoxically, because of the lack of observational data. Then the observation of the first rotation curve called the validity of the currently admitted ideas in question.

ADS BibCode:
1981Msngr..23...25T
Author(s)/Affiliation(s):
The, P. S.; Tjin-A-Djie, H. R. E.
AA(Astronomical Institute, University of Amsterdam) AB(Astronomical Institute, University of Amsterdam)
Abstract:
The star HR 5999 is embedded in a dusty gaseous nebulosity and is surrounded by more than 10 faint T Tauri stars. From these facts and from studies so far made of the physical properties of HR 5999, we strongly believe that it is a very young pre-main-sequence object; it varies irregularly due most probably to changes in the properties of dust grains embedded in its circumstellar gas shell.

ADS BibCode:
1981Msngr..23...27.
Author(s)/Affiliation(s):
ESO
AA(ESO)
Abstract:
En principio, los grandes telescopios, como el de 3.6 m de la ESO, tienen una resolucion angular mejor que 0.1 segundo de arco, vale decir, que detalles asi de pequenos pueden ser vistos; pero comunmente este no es el caso. Las mejores fotografias tomadas con grandes telescopios pocas veces muestran detalles mas pequenos que 1 segundo de arco (un segundo de arco es la separacion angular de dos puntos separados por un milimetro a una distancia de 200 metros); esto se debe a la presencia de la atmosfera que es turbulenta, y esta turbulencia produce una imagen borrosa dei objeto.

ADS BibCode:
1981Msngr..23...27V
Author(s)/Affiliation(s):
Veron, P.
AA(ESO)
Abstract:
Dr. Andre B. Muller from ESO recently described (The Messenger No. 19, p. 29, 1979) a new system allowing an easy and efficient monitoring of galaxies for the detection of supernovae. Using this system, H.E. Schuster discovered a supernova in NGC 1255 on December 30,1980 (lAU Circular No. 3559, 1981). At the time of discovery its magnitude was 17. This was the first supernova found on La Silla.

ADS BibCode:
1981Msngr..23...27T
Author(s)/Affiliation(s):
Tarenghi, M.
AA(ESO)
Abstract:
With the aim of encouraging European cooperation and coordination in the use of the Space Telescope within some fields of research, ESO and ESA have arranged aseries of workshops on the use of the Space Telescope and coordinated ground-baserJ observations. The second of these workshops, entitled "Optlcal Jets in Galaxies", took place in the auditorium of the new ESO Headquarters in Garching on February 18-19, 1~81.