Messenger No. 26 (December 1981)
Information on Vinchucas and Chagas disease.
AA(Director of the Department of Microbiology and Parasitology of the University of Chile)
Following a significant increase in the number of vinchucas observed at La Silla during the last summer, the Director-General of ESO asked Prof. Hugo Schenone, Director of the Department of Microbiology and Parasitology of the University of Chile to pay a visit to La Silla to investigate the situation. The following gives a summary of the resulting report.
Star formation in Bok globules
AA(Copenhagen University Observatory)
Among the many dark clouds seen projected against the luminous band of the Milky Way are a number of smalI, isolated compact clouds, which often exhibit a large degree of regularity. These objects are today known as Bok globules, after the Dutch-American astronomer Bart Bok, who more than 30 years aga singled out the globules as a group of special interest among the dark clouds. Bok globules usually have angular sizes of from a few arcminutes to about 20 arcminutes, with real sizes of typically 0.15 to 0.8 parsecs. It is generally not so easy to estimate the distance, and thus the dimensions, of a given globule. Most known globules are closer than 500 pc, since they normally are found by their obscuring effects, and more distant globules become less conspicuous because of foreground stars. A nearby, compact Bok globule is indeed a spectacular sight; when William Herschel for the first time saw a globule in his telescape, he exclaimed: ' Mein Gott, da ist ein Loch im Himmel.'
ESO User's Manual
X-ray surveys with the Einstein Observatory
Two different types of survey with the imaging instruments included in the Einstein Observatory are yielding results of particular interest in extragalactic astronomy and cosmology. The first is known as a "deep field" survey, and we will describe here the results for an observed region in Pavo. The second type is the "medium sensitivity survey" which attempts to identify a complete sampie of faint X-ray sources (energy 10-11.5to 10-13 ergs cm-2 S-1 in the 0.3-3.5 keV soft X-ray band) detected in the fields of previously known or studied X-ray sources. At present, the "medium sensitivity survey" is still being worked on and results are very preliminary.
List of Preprints Published at ESO Scientific Group
169. E. A. Valentijn and R. Giovanelli: 21 cm Une Observations 01 cD Galaxies. Astronomy and Astrophysics. September 1981.
The 'continuous' central stars of planetary nebulae - are their spectra really continuous?
Kudritzki, R. P.; Simon, K. P.; Méndez, R. H.
AA(Institut für Theoretische Physik und Sternwarte der Universität Kiel) AB(Institut für Theoretische Physik und Sternwarte der Universität Kiel) AC(Instituto de Astronomia y Fisica del Espacio, Buenos Aires)
Twenty-five per cent of all central stars 01 planetary nebulae which have been studied spectroscopically are classified as "continuous", which means that they do not show any sign of stellar absorption or emission lines, at least in the visible part of the spectrum. The existence of this kind of spectrum poses an interesting problem: The effective temperatures of the "continuous" objects can be estimated from the emission line spectrum of the surrounding nebula my means of the wellknown "Zanstra method". As it turns out, the temperatures are mainly between 50,000 K and 100,000 K. On the other hand, non-LTE model atmosphere calculations lor very hot stars (as carried out in Kiel) show that even at 100,000 Kthere should be easily detectable H or He lines for any reasonable surface gravity, unless the atmosphere is essentially free of these elements. But even if we admit the absence of hydrogen and helium, we can estimate that strong lines 01 carbon (or nitrogen or oxygen) should be observable in this case.
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Variability of the continuum and the emission lines in the Seyfert galaxy Arakelian 120.
Fricke, K. J.; Kollatschny, W.
AA(Universitäts-Sternwarte Göttingen) AB(Universitäts-Sternwarte Göttingen)
The brightness variability of Seyfert galaxies and quasars is one of the most direct pieces of evidence for the intrinsic smallness of the optical continuum source in these objects. If the power of a source varies with a time scale l: by a significant amount it must originate fram a region which cannot have a size much larger than c . l: acrass where c is the velocity of light; l: is observed to be typically of the order of months for such sources but may be much less. Not only the continuum strength but also the emission lines may vary in strength and shapes. This phenomenon is interesting with regard to the structure and kinematics of the line-emitting region as weil as to the radiation mechanism within the continuum source.
Observations of the giant bubbles in the Large Magellanic Cloud.
Georgelin, Y.; Georgelin, Y.; Laval, A.; Monnet, G.; Rosado, M.
AA(Observatoire de Marseille) AB(Observatoire de Marseille) AC(Observatoire de Marseille) AD(Observatoire de Lyon) AE(Instituto de Astronomfa (Mexico))
Deep monochromatic photographs through narrow-band interterence filters on nearby spiral galaxies reveal large numbers (50-100) of circular shaped H 1I regions, with usually weak or absent central emission. They are called by various names; ares, loops, rings, shells, etc...., and are clearly the two-dimensional projections of more or less spherical bubbles of ionized gas. This is by no means a new phenomenon: Hubble (1925, Astrophysical Journal 62, 409) had already described three "ring nebulae" in the spiral of the Local Group NGC 6822. But it is the advent of large narrow-band interference filters that had made possible the detection of tens of bubbles in the galaxies in our vicinity. A number of surveys have recently been published, including one by Sivan (1974, Astronomy and Astrophysics Suppl. 16, 163) of our Galaxy with a 1-m telescope and one of M 33 with the Soviet 6-m telescope (Courtes et al., 1981, The Messenger No. 23).
Announcement - Second ESO Infrared Workshop
Organizing Committee: R. van Ouinen (Groningen), M. Grewing (Tübingen), A. Moorwood (ESO, Chairman), P. Salinari (Florence), F. Sibille (Lyon). This Workshop is being organized with the aims 01 reviewing the status and performance 01 the many inlrared groundbased lacilities and instruments which have come into operation since the last ESO Inlrared Workshop in Sweden in 1978 and to promote discussion on three topics 01 interest lor the luture:
Large-scale structure of the universe.
AA(University of Oklahoma)
One of the major tasks of astronomy is to find how matter is arranged and distributed in our Universe. On the largest scale it has usually been assumed by cosmologists and by the majority of astronomers that matter is spread uniformly throughout the Universe. This picture is changing and astronomers are recognizing, by focussing more and more on the study of the distribution of visible matter, that the distribution of galaxies is very clumpy on a small scale (pairs and groups) as weil as on a much larger scale (superclusters or filamentary structures). It is not clear, in fact, whether any isolated structure exists.
The discovery of a new SU UMa star.
For the observing run in NovemberlDecember 1980 at La Silla, R. Schoembs and myself had astriet observing schedule long before travelling to Chile in order to make best use of the allotted instruments. A usual behaviour common to all astronomers, I think. But a lucky chance made us change our plans in some details on the spot: We discovered a new member of the SU UMa subgroup of dwarf novae. It's my aim to tell some of the exciting circumstances of that discovery and to report some results of the measurements of the new SU UMa object TU Men.
The Uranus occultation of August 15, 1980.
Bouchet, P.; Perrier, C.; Brahic, A.; Lecacheux, J.; Sicardy, B.
AA(ESO) AB(ESO) AC(Observataire de Paris) AD(Observataire de Paris) AE(Observataire de Paris)
One of the very exciting discoveries in astronomy and planetary sciences in recent times is the detection of aseries of narrow rings around Uranus. During more than three centuries, the rings of Saturn have had a special fascination and symbolism and an enormous amount of iiterature has been devoted to studies of their nature, properties and origin. The discovery of Uranus' rings, and two years later of Jupiter's rings has not only renewed interest but also raised a number of new cosmogonical questions.
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No. 60, G. Hunt ed)., Cambridge University Press.
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(1978) Astron. J., 83(8), 980.
Elliot, J. L., French, R. G., Fragei, J. A., Elias, J. H., Mink, D. and Liller,
W: (1980), Center for Astrophysics, Preprint series No. 1407.
Elliot, J. L. (1981) in Uranus and the outer planets (lAU/RAS Colloquium
No. 60 (G. Hunt, ed.), Cambridge University Press.
Goldreich, P. and Tremaine, S. (1978), Icarus, 34,227.
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Henon, M. (1981), Nature, to be published.
Klemola, A. R. and Marsden, B. G. (1977), Astron. J., 82,849.
Lecacheux, J. (1980) (Journees Scienlifiques de la S.F.S.A.), le
Journal des Astronomes Franr;ais, November 1980.
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RCW 58: a remarkable H II region around a WN 8 star.
Lortet, M. C.; Testor, G.
AA(Observatoire de Meudon, and L. Deharveng, Observatoire de Marseille) AB(Observatoire de Meudon, and L. Deharveng, Observatoire de Marseille)
In the course of a programme of detailed study of galactic ring nebulae around Wolf-Rayet stars, we obtained an Ha photograph, Ha interferograms and Boiler and Chivens spectrograms of the H 11 region RCW 58 (Rodgers et al. 1960). The Ha photograph is reproduced in Figure 1. The overall shape, as was known previously (Smith, 1968), is a ring centered on the WN 8 star HO 96548. However, the nebula is remarkable for its clumpiness, the presence of large scale curls to the south, and above all the existence of radial features never observed for any other H II region.
Chu, Y. H.: 1980, Bull. Amer. Astron. Soe. 12,842, and preprint.
Chu, Y. H.: 1981, Submilted toAp. J.
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et R. N. Thomas).
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Spaee Sei. Rev., 28,227.
Installation and first results of the Coudé Echelle Spectrometer.
The Couda Echelle Spectrometer was installed in the 3.6-m telescope building in November and Oecember 1980. Oespite several unexpected difficulties-like the necessity of the replacement of the granite table supporting the monochromator, which arrived broken into three pieces, and the astonishing discovery that the wall paint of the couda room was slightly fluorescent-the instrument was assembled and pretested. Unfortunately, and because of lack of time, the final adjustment and first improvement of the software in the light of the first practical observations could not be done during this period. It is only in May 1981 that the first test observations were done with the active collaboration of E. Maurice and P. E. Nissen.
New large interference filters for the 3.6-m triplet.
Enard, D.; Tarenghi, M.
The triplet adaptor (see The Messenger No. 16, page 26 for a description by M. Ziebell) was put into operation in November 1979 and since then it has been used regularly both with large 240 x 240-mm plates and with the 40-mm McMullan electronographic camera (The Messenger No. 19, p. 33).
Discovery of a very fast optical activity in the X-ray source GX 339-4.
Motch, C.; Ilovaisky, S. A.; Chevalier, C.
AA(ESO) AB(Observatoire de Meudon, France) AC(Observatoire de Meudon, France)
Most galactic X-ray sources are compact objects (white dwarfs, neutron stars and maybe black holes) in binary systems. Matter coming from anormal companion star is driven onto the surface of the compact object where the release of gravitational energy powers the X-ray emission. The energy emitted at X-ray wavelengths ranges from 1035 to 1038 erg/s and a mass transfer rate of typically 10-11 to 10-8 M0 /year is enough to explain the X-ray luminosity. In most of the cases an accretion disk is formed around the compact object due to the angular momentum carried by the matter escaping the companion star. Recent investigations have shown that the accretion disks can be very large and that the heating of theirsurface by the X-rays emitted by the central source can make them very luminous.
Informacion sobre vinchucas y la enfermedad de Chagas
Sonia (1967 - 1981).
During a thundery evening, on May 13, 1967, a litlle female with fiery eyes and an independent character was born on La Silla. She was called Sonia. It was said that she was very pretty.