Messenger No. 41 (September 1985)
Comet Halley observed at La Silla.
West, R. M.
While Periodic Comet Halley rapidly approaches the Sun, preparations are being made in many places to observe this distinguished celestial visitor. During most of the months of June and July 1985, Halley was "behind" the Sun and could not be observed. From about July 15, attempts to obtain images of Halley were made in various places, and it now appears that the first confirmed sighting was made at the European Southern Observatory on July 19.
The ESA PCD (Photon Counting Detector) at the 2.2 m telescope.
di Serego Alighieri, S.; D'Odorico, S.; Dekker, H.; Delabre, B.; Huster, G.; Sinclaire, P.; Perryman, M. A. C.; Adriaens, M.; Macchetto, F.
AA(The Space Telescope European Coordinating Facility, European Southern Observatory) AB(European Southern Observatory M. A. C. Perryman, M. Adriaens, ESTEC, Noordwljk) AC(European Southern Observatory M. A. C. Perryman, M. Adriaens, ESTEC, Noordwljk) AD(European Southern Observatory M. A. C. Perryman, M. Adriaens, ESTEC, Noordwljk) AE(European Southern Observatory M. A. C. Perryman, M. Adriaens, ESTEC, Noordwljk) AF(European Southern Observatory M. A. C. Perryman, M. Adriaens, ESTEC, Noordwljk) AG(ESTEC, Noordwljk) AH(ESTEC, Noordwljk) AI(Space Telescope Science Institute, Baltimore)
The ESA PCD (Photon Counting Detector) (di Serego Alighieri et al., 1985 a) was developed at ESTEC as a scientific model for the Faint Object Camera (FOG) of the Hubble Space Telescope (HST). It has been used at various telescopes (Asiago 1.8 m, ESO 3.6 m and 2.2 m, CFHT 3.6 m) providing us with data whose properties are very similar to those expected for FOC data (di Serego Alighieri et al., 1984 and 1985 b). Since last April the PCD is offered to ESO visiting astronomers at the 2.2 m telescope within the terms of an ESAIESO agreement, where ESA provides the detector and its computer system, the documentation and support during the first few times the instrument is operated at the telescope; ESO provides the interfaces for long slit spectroscopy and direct imaging, operational support, telescope time and data reduction software.
di Serego Alighieri, S., Perryman, M.A. C., Macchetto, F., 1984,
Astrophys. J. 285, 567.
di Serego Alighieri, S., Perryman, M.A.C., Macchetto. F., 1985a,
Astron. Astrophys. 149, 179.
di Serego Alighieri, S., Perryman, M.A.C., Macchetto, F., 1985b,
ESA Bull. 42, 17.
Tentative Time-table of Council Sessions and Committee Meetings in 1985
An ESO/OHP Workshop on 'The Optimization of the Use of CCD Detectors in Astronomy'
Geometric rectification of PCD and ST-FOC data with MIDAS.
Baade, D.; Ponz, D.; di Serego Alighieri, S.
AA(The Space Telescape European Coordinating Facility, European Southern Observatory) AB(European Southern Observatory) AC(The Space Telescape European Coordinating Facility, European Southern Observatory,Affiliated to the Astrophysics Division. Space Science Department,European Space Agency,On leave from Osservatorio Astronomico, Padova)
It is now about six months since ESA's Photon Counting Detector (PCD), the ground-based counterpart to the FaintObject Camera (FOG) to be flown with the Hubble Space Telescope, was put into operation at la Silla and made available to Visiting Astronomers. There it proved to be very reliable and, also thanks to good weather conditions, was very productive. By now, quite a few readers of the Messenger will be busy analysing their own PCD observations.
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di Serego Alighieri, S., Perryman, M.A. C., Macchelto, F.: 1985,
Asuon.Asuophys. 149, 179.
Variations of the high resolution H-alpha-line profiles of the very young stars - HR 5999 and HD 163296
The, P. S.; Tjin A Djie, H. R. E.; Catala, C.; Praderie, F.; Felenbok, P.
AA(Sterrekundig Instituut, Amsterdam, Netherlands), AB(Sterrekundig Instituut, Amsterdam, Netherlands), AC(Paris, Observatoire, Meudon, France), AD(Paris, Observatoire, Meudon, France), AE(Paris, Observatoire, Meudon, France)
Results are reported of a campaign of simultaneous observations of the H-alpha lines of HR 5999 and HD 163296 in a study of the stellar wind shapes of very young stars. The H-alpha lines were observed with EXOSAT instrumentation and a ground-based spectrograph equipped with a Reticon. Long-term variations in HD 163296 included the disappearance of significant blue absorption features and the lack of a nebulosity. The profile was classified with the type I or II P Cygni profile with variations which could have come, it is suggested, from a spherically expanding thin shell, a uniform atmosphere experiencing differential inner and outer rotations, a chromosphere surrounded by a cool, decelerating wind, or a cool, expanding envelope surrounding a hot region containing high velocity turbulence.
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Irish Astronomical Journal, in press.
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The photometric capabilities of the IDS (Image Dissector Scanner) system.
Wampler, E. J.
In the early days of the IDS development crude tests of the system indicated that its response was approximately linear with intensity (McNall, Robinson and Wampler, Pub. A. S. P. 82,488,1970; C. M. GaskeIl; J.A. Baldwin, private communication). In the March 1985 issue of the Messenger (No. 39, p. 15) M. Rosa pointed out that the response of the lOS system depended on the intensity of the input light source.
Rotational velocity of F-type stars.
Noci, G.; Ortolani, S.; Pomilia, A.
AA(Istituto di Astronomia, Universita di Firenze) AB(Osservatorio Astronomico di Asiago) AC(Istituto di Astronomia, Universita di Firenze)
The rotation is a general property of celestial objects, which is probably generated by the vorticity of the interstellar matter. Obviously, stars forming from turbulent vortices conserve some of the initial angular momentum, depending on the early formation history. It is weil known that there is a well-determined trend of the rotational velocity of main sequence and giant stars with the spectral type. This is shown by the continuous and dashed curves of Figure 1, which are from the paper of Bernacca and Perinotto (A A, 33, 443, 1974). Earlytype stars have high rotational velocities, while late-type stars are slow rotators. There is a sharp drop in the velocities from F0 to F5, particularly for main sequence stars: stars later than F5 have all very little angular momentum. This has been attributed to the presence of planets around late-type stars, which would contain most of the angular momentum of the system, as it happens in the case of the solar system. The angular momentum is probably transferred during the T Tauri pre-main-sequence phase. Another possibility suggested for the rotation velocity drop is the loss of angular momentum caused by stellar winds, which should occur for stars having convective layers close to the surface, i. e. late-type stars.
Visiting Astronomers (October 1, 1985 - April 1, 1986)
List of ESO Preprints (June - August 1985)
Globular clusters in NGC 3109: probes for the study of galaxy evolution.
Geyer, E. H.; Hoffmann, M.
AA(Observatorium Hoher List der Universitäts-Sternwarte Bonn) AB(Astronomisches Institut der Universit
Any observer at La Silla who is not working in a telescope control room or watching a movie during a stormy night has the opportunity to see one of the most splendid wonders in the sky without any telescope: Omega Centauri, seemingly a patchy star, but in fact the brightest globular cluster of our Galaxy. Such massive subsystems of a galaxy, each with a content of up to a million stars are quite frequent in the universe. We know many thousands of them, most of them around the giant elliptical galaxies of the Virgo cluster of galaxies.
The 2nd ESO/CERN Symposium on 'Cosmology, Astronomy and Fundamental Physics'
Chromospheric modelling in late-type dwarfs. II - CES observations of active and quiescent stars
Foing, B. H.; Beckman, J.; Crivellari, L.; Galleguillos, D.
AA(European Southern Observatory, Garching, West Germany), AB(Consejo Superior de Investigaciones Cientificas, Instituto de Astrofisica de Canarias, La Laguna, Spain), AC(Osservatorio Astronomico, Trieste, Italy), AD(La Serena, Universidad, Chile; Max-Planck-Institut fuer Radioastronomie, Bonn, West Germany)
The characteristics of the chromospheres of late-type dwarf stars were studied using the CoudeEchelle Spectrograph (CES) at ESO and the IUE. The study focused on the h and k Mg II lines of F and G dwarfs. The stability of the IUE spectra permitted calculations of averaged absorption features and the subtraction of the Mg II lines to leave intrinsic chromospheric and photospheric line characteristics. Stras with Mg emission cores are very similar in their chromospheres, while stars with Ca II cores vary greatly and exhibit more intense emissions. The higher activity has been linked to magnetic forces which produce spicules with diameters in the range of 1000 km. CES spectra on the Ca II core H lines in Epsilon Eri and Alpha Cen B, active and passive stars, respectively, show a 40 percent lower intensity in the quiescnet star than in the active star, which has an asymmetric core emission and a sharp central absorption with Ca IR triplet lines. The emission features in the active stars are similar to those of the active regions, photospheric spots, chromospheric plages and coronal structures observed in the sun.
The Increasing Importance of Statistical Methods in Astronomy
Heck, A.; Murtagh, F.; Ponz, D.
AA(Observatoire Astronomique, Strasbourg, France) AB(The Space Telescope European Coordinating Facility, European Southern Observatory) AC(European Southern Observatory)
In the past, astronomers did everything individually, from the conception of a project to the collection of data and their analysis. As the instrumentation became more complex, teams had to be set up and they progressively included people (astronomers or otherwise) specialized in technology. Today it is practically impossible to run a project at the forefront of astronomical research without the help of these technologists.
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01 IUE low-dispersion stellar spectra, in preparation.
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News on ESO Instrumentation
El Comenta Halley observado desda La Silla