Author name code: vandessel ADS astronomy entries on 2022-09-14 author:Van Dessel, Edwin L.J. ------------------------------------------------------------------------ Title: Mesures d'Étoiles doubles visuelles obtenues - l'observatoire de nice en 1968 (lunette de 50 cm) et avec la lunette Équatoriale de 45 cm de l'observatoire royal de belgique de 1969 - 1974 Title: Mesures d'Étoiles doubles visuelles obtenues - l'observatoire de nice en 1968 (lunette de 50 cm) et avec la lunette Équatoriale de 45 cm de l'observatoire royal de belgique de 1969 - 1974 Title: Measurements of visual double stars collected with the 50-cm refractor of the observatoire denice in1968 and with the45-cm refractor of theobservatoire royal de belgique from 1969 to 1974. Authors: Lampens, P.; Van Dessel, E.; Rabtach, S.; Durand, P. Bibcode: 2011O&T....79...17L Altcode: We present in an electronic form the measurements of the relative positions of 129 visual double and multiple systems performed by Dr E. Van Dessel during the years 1968-1974. In the summer of 1968, 64 measurements of 38 different systems were collected at the Observatoire de Nice. From 1969 till 1974, 295 measurements of 91 systems were collected at the Observatoire royal de Belgique. The original booklet of the observations was put at our disposal for this task performed by one of us (S.R.). In addition, we also present the residuals in the sense (Observed-Calculated) based on the orbits listed in the Sixth Catalog of Orbits of Visual Double Stars (Hartkopf and Mason, 2012).

2 Title: Division i / Commission 8 / Working Group Astrographic Catalogue and Carte du Ciel Plates Authors: Bucciarelli, Beatrice; Fresnau, Alain; Abad, Carlos; Argyle, Robert W.; Biggs, James; Brosch, Noah; Coyne, George V.; Davoust, Emmanuael; De Cuyper, Jean-Pierre M.; van Dessel, Edwin L.; Ducourant, Christine; Fierro, Ivan H. Bustos; Geffert, Michael; Glushkova, Elena V.; Irwin, Michael J.; Jones, Dayton L.; Lumme, Kari A.; Muiños, J. L.; Odenkirchen, Michael; Orellana, Rosa B.; Pauwels, Thierry; Rafferty, Theodore J.; Sanchez, M.; Sanner, Jörg; Tsvetkov, Milcho K.; Vaughan, Alan E. Bibcode: 2007IAUTB..26...95B Altcode: Various experiments have definitely demonstrated that one-micron accuracy (0.″06) on the definition of stellar images on CdC plates cannot be claimed, as it was speculated back in 1999. More realistically, a 2-3 micron accuracy is achievable, getting worse toward the survey magnitude limit, with an average magnitude error of 0.3. The level of astrometric accuracy corresponds to a 0.″2 - 0.″3 error in position at Epoch 1900, which, once used as first Epoch for proper motion determination in combination with modern epoch observations, can produce errors at the level of 2-5 mas/yr, thereby allowing to detect stellar motions larger than 0.″01/yr, which at a distance of 500 pc from the Sun correspond to ~25-60 km/s tangential velocity. Therefore, the AC/CdC heritage collection can be regarded as a highly valuable first-epoch material, e.g., for the realization of a Tycho-2 extension to fainter magnitudes (~15 photographic), especially in selected areas where radial velocity data are available, for the exploration of stellar kinematics beyond our solar neighborhood. Title: VizieR Online Data Catalog: Photometric standards around gravitational lenses (Nakos+ 2003) Authors: Nakos, T.; Ofek, E. O.; Boumis, P.; Cuypers, J.; Sinachopoulos, D.; van Dessel, E.; Gal-Yam, A.; Papamastorakis, J. Bibcode: 2003yCat..34021157N Altcode: We present a catalog of secondary photometric standard stars in the neighborhood of 14 gravitationally lensed quasars. These stars were verified to be non variable using long-term monitoring.

The instrumental magnitudes of the new standard stars have been transformed to the Johnson-Cousins BV(RI)c photometric system. For ten gravitational lenses (GLs) we also provide the BV(RI)c mean magnitudes of the integrated flux of all the lens components, for the epochs of the photometric calibration.

(3 data files). Title: A catalog of secondary photometric standard stars around gravitational lenses Authors: Nakos, Th.; Ofek, E. O.; Boumis, P.; Cuypers, J.; Sinachopoulos, D.; van Dessel, E.; Gal-Yam, A.; Papamastorakis, J. Bibcode: 2003A&A...402.1157N Altcode: We present a catalog of secondary photometric standard stars in the neighborhood of 14 gravitationally lensed quasars. These stars were verified to be non variable using long-term monitoring. The instrumental magnitudes of the new standard stars have been transformed to the Johnson-Cousins BV(RI)c photometric system. For ten gravitational lenses (GLs) we also provide the BV(RI)c mean magnitudes of the integrated flux of all the lens components, for the epochs of the photometric calibration.

Based on observations made with a) the 1.0 m telescope at Wise Observatory, Israel, b) the 1.3 m telescope at Skinakas Observatory, Crete, Greece, and c) the 1.9 m SAAO telescope, Sutherland Observatory, South Africa.

Tables \ref{info}-\ref{colors-gls} and Fig. \ref{findingchart} are only available in electronic form at http://www.edpsciences.org Title: Digital Access to Aero- and Astrophotographic Archives Authors: de Cuyper, J. -P.; van Dessel, E.; Pauwels, T.; Vanommeslaeghe, J.; Prils, H.; de Decker, G.; Pierre, O.; Lavreau, J.; Fernandez, M.; Tran, T.; Sterken, C.; David, M.; Schots, M.; Daelemans, G. Bibcode: 2003ASPC..295...93D Altcode: 2003adass..12...93D The aim of this test-bed project, initiated and financed by the Belgian Federal Services for Scientific, Technical and Cultural Affairs (SSTC Project I2/AE/103), is to acquire within the coming 4 years, the necessary know-how, hardware and software in order (i) to preserve the historic and the scientific information contained in aero- and astrophotographic archives, both on glass plates and on film; (ii) to provide a user-friendly intranet and internet access to the catalogue and the (meta)data; (iii) to make the photographic information exploitable again for scientific applications, by means of a high resolution digitisation technique. Title: Photometric Variability of the Gravitational Lens 0142-100 (UM 673) Authors: Sinachopoulos, D.; Nakos, Th.; Boumis, P.; van Dessel, E.; Burger, M.; Rodríguez-Gil, P. Bibcode: 2001AJ....122.1692S Altcode: 2001astro.ph..7312S We present the results of a photometric CCD monitoring of the gravitational lens system UM 673 that took place from 1995 to 2000. In total, the doubly imaged quasar (QSO) was observed in the R band during 29 photometric nights, using optical telescopes with dimensions in the range 0.6-1.3 m. We detected a significant variability in the total light of the UM 673 system, that is, in the light of the two QSO images plus the lensing galaxy. With respect to the magnitude of the gravitational lens system at its discovery, in 1986, UM 673 was 0.3 mag brighter. Furthermore, our 1996 December measurements show that between 1995 November and 1997 October the system became even brighter, reaching a magnitude difference of 0.5 mag with respect to its discovery value. We also present R magnitudes and V-R colors of seven field stars situated in the vicinity of the lens, based on a 3.5 month monitoring during the year 2000. Based on observations made with (1) the 60 cm Bochum and the ESO 90 cm Dutch telescopes, at La Silla, Chile, (2) the 1.2 m telescope at Kryonerion Observatory, Greece, (3) the 1.3 m telescope at Skinakas Observatory, Crete, Greece, and (4) the European Space Agency OGS telescope operated on the island of Tenerife by the Instituto de Astrofísica de Canarias in the Spanish Observatorio del Teide of the Instituto de Astrofísica de Canarias. Title: Photometric Variability of the gravitational lens UM 673 Authors: Sinachopoulos, D.; Nakos, T.; Boumis, P.; van Dessel, E.; Burger, M.; Rodriguez-Gil, P. Bibcode: 2001hell.confE.133S Altcode: No abstract at ADS Title: Photometric Variability of UM 673 Authors: Sinachopoulos, D.; Nakos, T.; van Dessel, E.; Burger, M. Bibcode: 2001ASPC..237..101S Altcode: 2001glrp.conf..101S No abstract at ADS Title: Surveys with the 4-m International Liquid Mirror Telescope Authors: Poels, J.; Moreau, O.; Manfroid, J.; Surdej, J.; Borra, E.; Claeskens, J. F.; Jean, C.; Montfort, F.; Swings, J. P.; Vangeyte, B.; van Dessel, E.; Nakos, Th. Bibcode: 2001misk.conf..598P Altcode: The working principle of liquid mirror telescopes (LMTs) is first reminded as well as their advantages and disadvantages over classical telescopes. For several obvious reasons (access to regions near the south galactic pole, galactic center, good image quality, ...), a best site location for such a LMT is somewhere in the Atacama desert. At latitudes near -22 - -29 degree, a deep (B = 24 mag.) LMT survey will approximately cover 90 square degrees at high galactic latitude, specially useful for gravitational lensing studies, for the identification of various classes of interesting extragalactic objects (cf. clusters, supernovae, etc. at high redshift) and subsequent follow-up observations with 8m-class telescopes. A short description of the handling of data products is also presented. Title: The Uccle Direct Astronomical Plate Archive Centre UDAPAC---A New International Facility for Inherited Observations Authors: de Cuyper, J. -P.; Elst, E.; Hensberge, H.; Lampens, P.; Pauwels, T.; van Dessel, E.; Brosch, N.; Hudec, R.; Kroll, P.; Tsvetkov, M. Bibcode: 2001ASPC..238..125D Altcode: 2001adass..10..125D An international facility to store, catalogue and digitise photographic plates is under development at the Royal Observatory of Belgium in Uccle-Brussels. The creation of such a facility requires a well-organized effort and substantial resources. However, the cost is not exorbitantly high if one takes advantage of the new generation of commercial, photogrammetric, flatbed scanners, which use the latest CCD technology. These scanners are relatively inexpensive, very fast, and comparable to dedicated scanners like PDS instruments in geometric and radiometric precision. Title: The 4-m International Liquid Mirror Telescope Project (ILMT) Authors: Poels, J.; Borra, E.; Claeskens, J. F.; Jean, C.; Manfroid, J.; Montfort, F.; Moreau, O.; Nakos, Th.; Surdej, J.; Swings, J. P.; van Dessel, E.; Vangeyte, B. Bibcode: 2001ASPC..238...97P Altcode: 2001adass..10...97P The working principle of liquid mirror telescopes (LMTs) is first reviewed along with their advantages and disadvantages over classical telescopes. For several reasons (access to regions near the south galactic pole, galactic center, good image quality, etc.), an excellent site for such an LMT is the Atacama desert. A deep (B~24 mag) LMT survey at latitudes near -22deg -- -29deg will cover ~90 square degrees at high galactic latitude and be especially useful for gravitational lensing studies, for the identification of various classes of interesting extragalactic objects (cf. clusters, supernovae, etc. at high redshift) and for subsequent follow-up observations with 8 m-class telescopes. A short description of the handling of data products is also presented. Title: UBV absolute CCD photometry and differential astrometry of a sample of visual double stars with A-type primaries Authors: Shatsky, N.; Sinachopoulos, D.; Prado, P.; van Dessel, E. Bibcode: 1999A&AS..139...69S Altcode: We present V magnitudes, (B-V) and (U-B) colours of the components of 111 visual double stars and their relative position measurements rho and theta . The primaries are of spectral class A; the angular separation is in the 2farcs5 -8arcsec range. The observations were made at the 61-cm reflector of University of Toronto Southern Observatory, Chile. The obtained photometric results are of a moderate quality for absolute values (0.04() m (mag) in V and about 0.02() m in the (B-V) and (U-B) colour indices) and more precise in Delta V and Delta (U-B), Delta (B-V) (0.023() m and 0.015() m, respectively). We find that about 60% of secondaries are also of spectral type A; 56% of pairs have Delta (B-V) less than 0.1() m. The two-colour diagram reveals significant offset of objects from the curve of unreddened Main Sequence stars. A comprehensive survey of stars in the close vicinity to the objects is also presented. The final astrometric accuracy of ~ 0farcs01 in rho and 0fdg1 in theta provides additional measurements for study of relative motion of the components. Based on observations made at University of Toronto Southern Observatory, Las Campanas, Chile. Tables \arabic{tabptm}--\arabic{tabast} are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: CCD photometry and astrometry for visual double and multiple stars of the HIPPARCOS catalogue. I. Presentation of the large scale project Authors: Oblak, E.; Lampens, P.; Cuypers, J.; Halbwachs, J. L.; Martín, E.; Seggewiss, W.; Sinachopoulos, D.; van Dessel, E. L.; Chareton, M.; Duval, D. Bibcode: 1999A&A...346..523O Altcode: 1999astro.ph..4266O A description is given of the activities of an international working group created with the aim of obtaining both photometric and astrometric observations of visual double and multiple stars with angular separations in the range of one to fifteen arcseconds, that formed part of the HIPPARCOS Input Catalogue. The scientific aims and realisations of this European network are given. About 50 observational missions have been carried out in both hemispheres according to a pre-defined protocol. We describe the general and specifically designed methods used for the reduction of large amounts of CCD observations of double stars and give an outline of the results already presented and soon to be expected. Based on observations made at La Silla (ESO, Chile - Key Programme 7-009-49 K), Observatoire de Haute-Provence (OHP), Calar Alto (CLA), La Palma (LPL) and Jungfraujoch (JFJ) Observatories} Title: VizieR Online Data Catalog: UBV Astrometry and Photometry of doubles (Shatsky+, 1999) Authors: Shatsky, N.; Sinachopoulos, D.; Prado, P.; van Dessel, E. Bibcode: 1999yCat..41390069S Altcode: UBV CCD absolute photometry and differential astrometry of 111 southern visual binaries are presented. Observations have been performed at Las Campanas Observatory (Chile) in 1991-92 at 61-cm telescope. The separation range is 2.5-8arcsec. The mean epoch of the measurements is 1992.0. The photometry (table 1) was calibrated by one night of standard star observations. The positional parameters (table 3) are given in the reference system J2000 and calibrated using Hipparcos and CDS data. An additional table 2 provides the notes on observational circumstances. (3 data files). Title: CCD astrometry and instrumental Delta V photometry of visual double stars. V. Differential measurements of pairs with angular separations 1arcsec to 4arcsec Authors: Sinachopoulos, D.; Dapergolas, A.; van Dessel, E.; Kontizas, E. Bibcode: 1999A&AS..136..525S Altcode: We present angular separations, position angles and Delta V instrumental magnitude differences of 83 visual double stars with angular separations around two arcseconds. Our observations were made by means of a CCD detector attached to the Kryonerion 1.2 m telescope. 12 of them are common proper motion stars and their components should therefore be stars of common origin. Based on observations made at Kryonerion Observatory, Greece. Table 2 only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html} Title: VizieR Online Data Catalog: DeltaV photometry of visual double stars (Sinachopoulos+, 1999) Authors: Sinachopoulos, D.; Dapergolas, A.; van Dessel, E.; Kontizas, E. Bibcode: 1999yCat..41360525S Altcode: We present angular separations, position angles and ΔV instrumental magnitude differences of 83 visual double stars with angular separations around two arcseconds. Our observations were made by means of a CCD detector attached to the Kryonerion 1.2m telescope. 12 of them are common proper motion stars and their components should therefore be stars of common origin. (1 data file). Title: CCD astrometry and UBV photometry of visual binaries. II. Visual double stars with mainly G - type primaries and relatively small angular separation Authors: Sinachopoulos, D.; van Dessel, E. Bibcode: 1998A&AS..130..299S Altcode: Differences Delta V of magnitude and Delta (B-V) and Delta (U-B) colours, as well as separations and position angles of 42 relatively close double stars are presented. The selection criteria of our sample are: the relatively small separation (between 2.5 and 5 arcseconds), magnitude difference under 1.25 mag, and mainly G-type primaries. The CCD observations, performed at the 90 cm Dutch telescope at ESO, were made using the Bessel U, B and V filters; the astrometry was done in the V filter only. From the analysis of the photometric data we conclude that 16 binaries in our sample have components with practically the same T_eff, since they have almost the same colours; one binary has components with identical characteristics. We also note the good internal accuracy of the astrometric CCD measurements. Based on observations made at ESO La Silla, Chile. Title: A list of Hipparcos very wide visual double stars for the astrometric calibration of imaging with CCDs Authors: Sinachopoulos, Dimitrios; van Dessel, Edwin; Geffert, Michael Bibcode: 1998AcHA....3..195S Altcode: We have selected from the Hipparcos catalogue (ESA 1997) a list of 307 very wide visual double stars, which can be used for performing an accurate astrometric calibration of CCD detectors mounted on telescopes. Angular separations are between 10 and 100 arcsec, mainly around 20 arc seconds and less than 35 arc seconds. Our list can be obtained from the Internet at the address http://midas.oma.be/www_root/serverdoc/www/ccdlas.html or it can be obtained from the authors directly. All information in our list was extracted, or computed from the Hipparcos catalogue. The format is simple containing one line per visual double star. (RA, Dec) coordinates of the component with the smallest RA value are given first. This component is obviously not always the primary. The epoch of the coordinates is the Hipparcos one: 1995.25. The following columns give V magnitudes and (B-V) colours of both components, their angular separation, and Hipparcos identifiers (HIC numbers). For the information that will enable you to compute the current value of the angular separation of each wide visual double star used for calibration, you have to search in the main Hipparcos catalogue. Each component of the double stars in our list has a separate entry in this catalogue. According to Sinachopoulos and van Dessel (1998), the Hipparcos catalogue contains some erroneous entries for wide visual double stars components as well. For this reason, it is advised to use at least three double stars of the list each time you calibrate your detector. All double stars in our list have been introduced to the Hipparcos mission by Brosche and Sinachopoulos (1988, 1989). In case you get problems or doubts on the correctness of the Hipparcos results for a particular double star, you can use information of these two publications for an additional control. Title: EIT Observations of the Extreme Ultraviolet Sun Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner, G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.; Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R. Bibcode: 1997SoPh..175..571M Altcode: The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. Title: EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection Authors: Dere, K. P.; Brueckner, G. E.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Kreplin, R. W.; Michels, D. J.; Moses, J. D.; Moulton, N. E.; Socker, D. G.; St. Cyr, O. C.; Delaboudinière, J. P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Chauvineau, J. P.; Marioge, J. P.; Defise, J. M.; Jamar, C.; Rochus, P.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert, W.; Clette, F.; Cugnon, P.; Van Dessel, E. L.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M. Bibcode: 1997SoPh..175..601D Altcode: We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200-400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. Title: UBV absolute CCD photometry and differential astrometry of close visual double stars, with G-type primaries Authors: Nakos, T.; Sinachopoulos, D.; van Dessel, E. Bibcode: 1997A&AS..124..353N Altcode: We present V magnitudes, (B-V) and (U-B) colours of close visual double star components, and their differences as well as separations and position angles of 40 visual double stars. The common properties of the members of this sample are the small angular separation rho, which is less than 7'', and the common spectral type of the primaries, which are of G-type. The observations made with the Bessel U, B and V filters, while the astrometry was performed in the V filter only. For the observations, the CCD camera attached to the Cassegrain focus of the 90 cm Dutch telescope, at La Silla, Chile, had been used. From the analysis of the data we concluded that from the sample of the fourty double stars observed seven proved to be physical pairs, while the rest must have common origin components. Based on observations made at ESO La Silla, Chile. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: Imaging the solar corona in the EUV Authors: Delaboudiniere, J. -P.; Stern, R. A.; Maucherat, A.; Portier-Fozzani, F.; Neupert, W. M.; Gurman, J. B.; Catura, R. C.; Lemen, J. R.; Shing, L.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Michels, D. J.; Moses, J. D.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Clette, F.; Cugnon, P.; van Dessel, E. L. Bibcode: 1997AdSpR..20.2231D Altcode: The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 A˚ images the chromosphere and the base of the transition region at a temperature of 5 - 8 x 10^4 K; the Fe IX-X filter at 171 A˚ images the corona at a temperature of ~ 1.3 x 10^6 K; the Fe XII filter at 195 A˚ images the quiet corona outside coronal holes at a temperature of ~ 1.6 x 10^6 K; and the Fe XV filter at 284 A˚ images active regions with a temperature of ~ 2.0 x 10^6 K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection. Title: First Results from EIT Authors: Clette, F.; Delaboudiniere, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. -F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise, J. -M.; Jamar, C.; Rochus, P.; Chauvineau, J. -P.; Marioge, J. -P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Maucherat, A.; Cugnon, P.; van Dessel, E. L. Bibcode: 1997ASPC..118..268C Altcode: 1997fasp.conf..268C The Extreme-UV Imaging telescope has already produced more than 15000 wide-field images of the corona and transition region, on the disk and up to 1.5R_⊙ above the limb, with a pixel size of 2.6\arcsec. By using four different emission lines, it provides the global temperature distribution in the quiet corona, in the range 0.5 to 3*E(6) K. Its excellent sensitivity and wide dynamic range allow unprecedented views of low emission features, even inside coronal holes. Those so-called ``quiet'' regions actually display a wide range of dynamical phenomena, in particular at small spatial scales and at time scales going down to only a few seconds, as revealed by all EIT time sequences of full- or partial-field images. The initial results presented here demonstrate the importance of this wide-field imaging experiment for a good coordination between SOHO and ground-based solar telescopes, as well as for science planning. Title: UBV photometry of wide visual double stars. V. Double stars with mainly K- and M- type primaries. Authors: Sinachopoulos, D.; van Dessel, E. L. Bibcode: 1996A&AS..119..483S Altcode: We present UBV photometric observations of 55 wide visual double stars with K- and M- type primaries. Our observations have been compared and combined with information available in the literature. At least 58% of them are optical pairs. Title: VizieR Online Data Catalog: CCD UBV photometry of close visual doubles (Nakos+ 1997) Authors: Nakos, T.; Sinachopoulos, D.; van Dessel, E. Bibcode: 1996yCat..41240353N Altcode: We present V magnitudes, (B-V) and (U-B) colours of close visual double star components, and their differences as well as separations and position angles of 40 visual double stars. The common properties of the members of this sample are the small angular separation ρ, which is less than 7", and the common spectral type of the primaries, which are of G-type. The observations made with the Bessel U, B and V filters, while the astrometry was performed in the V filter only. For the observations, the CCD camera attached to the Cassegrain focus of the 90 cm Dutch telescope, at La Silla, Chile, had been used. From the analysis of the data we concluded that from the sample of the fourty double stars observed seven proved to be physical pairs, while the rest must have common origin components. (3 data files). Title: VizieR Online Data Catalog: UBV photometry of double stars. (Sinachopoulos+ 1996) Authors: Sinachopoulos, D.; van Dessel, E. L. Bibcode: 1996yCat..41190483S Altcode: We present UBV photometric observations of 55 wide visual double stars with K- and M- type primaries. Our observations have been compared and combined with information available in the literature. At least 58% of them are optical pairs. (2 data files). Title: VizieR Online Data Catalog: VRI photometry of wide double stars (Sinachopoulos+ 1995) Authors: Sinachopoulos, D.; Cuypers, J.; Lampens, P.; Oblak, E.; van Dessel, E. L. Bibcode: 1996yCat..41120291S Altcode: We are presenting VRI photometry of 93 wide visual double stars having late B- or A- type primaries, taken from the Annex of Double and Multiple Stars of the HIPPARCOS Input Catalogue. Spectral types have been estimated for most of the primaries and for the majority of the secondaries. 40% of them probably have common origin components, for which we calculated photometric parallaxes and some orbital values estimates. (4 data files). Title: Old and new on A0535+26 / HDE 245770. Authors: Burger, M.; van Dessel, E. L.; Giovannelli, F.; Sabau-Graziati, L.; Bartolini, C.; Guarnieri, A.; Piccioni, A. Bibcode: 1996MmSAI..67..365B Altcode: No abstract at ADS Title: Photometric Monitoring Of The Lensed QSO 0957+561 Authors: Sinachopoulos, D.; Burger, M.; van Dessel, E.; Geffert, M.; Thibor, M.; Colin, J.; Ducourant, Ch. Bibcode: 1996IAUS..173...53S Altcode: No abstract at ADS Title: EIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission Authors: Delaboudinière, J. -P.; Artzner, G. E.; Brunaud, J.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Moses, J. D.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Maucherat, A.; Clette, F.; Cugnon, P.; Van Dessel, E. L. Bibcode: 1995SoPh..162..291D Altcode: The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 å), Fe XII (195 å), Fe XV (284 å), and He II (304 å) to provide sensitive temperature diagnostics in the range from 6 × 104 K to 3 × 106 K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes. Title: VRI photometry of wide double stars with A- type primaries. Authors: Sinachopoulos, D.; Cuypers, J.; Lampens, P.; Oblak, E.; van Dessel, E. L. Bibcode: 1995A&AS..112..291S Altcode: We are presenting VRI photometry of 93 wide visual double stars having late B- or A- type primaries, taken from the Annex of Double and Multiple Stars of the HIPPARCOS Input Catalogue. Spectral types have been estimated for most of the primaries and for the majority of the secondaries. 40% of them probably have common origin components, for which we calculated photometric parallaxes and some orbital values estimates. Title: CCD astrometry and instrumental {DELTA}V photometry of wide visual double stars. IV. Differential measurements of northern pairs. Authors: Nakos, T.; Sinachopoulos, D.; van Dessel, E. Bibcode: 1995A&AS..112..453N Altcode: We present relative positions and instrumental visual magnitude differences ({DELTA}V) of 101 northern wide double star components. The mean accuracy of the magnitude differences is 0.01 magnitudes, of the angular separation 0.04 arcseconds, and of position angle 0.13 degrees. Most of the programme pairs are targets of the HIPPARCOS mission and they have been often observed during the last 150 years. Title: CCD astrometry and instrumental (Delta)V photometry of wide visual double stars. III. Differential measurements of often observed southern pairs. Authors: van Dessel, E.; Sinachopoulos, D. Bibcode: 1993A&AS..100..517V Altcode: We present accurate relative positions and instrumental visual (Bessel V) magnitude differences of southern wide star components. The mean accuracy of the angular separation is 0.02 arcsecs, which corresponds to 1.5 micron on the CCD chip, and of magnitude difference 0.007 mag/exposure. The program pairs are targets of the HIPPARCOS mission and they have been observed at least four times in the last 150 yrs. Title: A photometric study of wide visual double stars. IV. UVBY photometry of wide visual double stars with G-type primaries. Authors: Sinachopoulos, D.; van Dessel, E. Bibcode: 1993A&AS...98...17S Altcode: We performed uvby aperture photometry of wide visual double stars with G-type primaries. The minimum angular separation of the components is 10 arcsecs and mainly less than 20 arcsecs. As both components have often similar photometric and astrophysical parameters, we infer that most of these double stars have components of common origin. Title: Photometry of Close Visual Binaries Authors: Oblak, E.; Argue, A. N.; Brosche, P.; Cuypers, J.; Dommanget, J.; Duquennoy, A.; Froeschle, M.; Grenon, M.; Halbwachs, J. L.; Jasniewicz, C.; Lampens, P.; Martin, F.; Mermilliod, J. C.; Mignard, F.; Sinachopoulos, D.; Seggewiss, W.; van Dessel, E. Bibcode: 1993ppsp.conf..139O Altcode: 1993IAUCo.136P.139O No abstract at ADS Title: The use of Expert Systems in astronomical data handling. Authors: Sinachopoulos, D.; Sinachopoulos, A.; van Dessel, E. Bibcode: 1993ESOC...47..209S Altcode: 1993daan.work..209S Numerical instabilities are a common problem in least square fitting of mathematical functions to observational data. Procedures corresponding to the expert systems method can then be very helpful. Expert Systems are computer programs offerring problem solving methods based on facts and rules which formalize the knowledge on special topics. The idea behind such expert system programs is that the users, the "experts", know the possible limit values of the variables to be determined by the least square fitting. Title: Solar corona synoptic observations from SOHO with an Extreme Ultraviolet Imaging Telescope. Authors: Delaboudinière, J. P.; Gabriel, A. H.; Artzner, G. E.; Dere, K.; Howard, R.; Michels, D.; Catura, R.; Lemen, J.; Stern, R.; Gurman, J.; Neupert, W.; Cugnon, P.; Koeckelenbergh, A.; van Dessel, E. L.; Jamar, C.; Maucherat, A. Bibcode: 1992ESASP.348...21D Altcode: 1992cscl.work...21D The major scientific objective of the EUV Imaging Telescope (EIT) is to study the evolution of coronal structure over a wide range of spatial and temporal scales and temperatures. A second strategic objective is to provide full disk synoptic maps of the global corona to aid in unifying SOHO (Solar and Heliospheric Observatory)/Cluster investigations. EIT will also provide images to support the planning of detailed spectroscopic investigations by the CDS (Coronal Diagnostic Spectrometer) and SUMER spectrometers in SOHO. EIT observations will be made in four narrow spectral bands, centered at 171 A (Fe 9), 195 A(Fe 12), 284 A (Fe 15), and 304 A (He 2) representing restricted temperature domains within a wide temperature range from 40,000 to 3,000,000 K. The results will be images of the solar atmosphere from the upper chromosphere and transition region to the active region corona. These maps, made at appropriate time intervals, will be used to study the fine structures in the solar corona and to relate their dynamic properties to the underlying chromosphere and photosphere. Dynamic events in the inner corona will be related to white light transients in the outer corona, and observations of the internal structure of coronal holes will be used to investigate origins of the solar wind. Title: CCD and conventional photometry of components of visual binaries. Authors: Oblak, E.; Argue, A. N.; Brosche, P.; Cuypers, J.; Dommanget, J.; Duquennoy, A.; Froeschlé, M.; Grenon, M.; Halbwachs, J. L.; Jasniewicz, G.; Lampens, P.; Martin, E.; Mermilliod, J. C.; Mignard, F.; Sinachopoulos, D.; Seggewiss, W.; van Dessel, E. Bibcode: 1992Msngr..69...14O Altcode: No abstract at ADS Title: An Impression from Programmes Performed at ESO about the Interest of European Astronomers in Visual Double and Multiple Star Research Authors: van Dessel, E. L. Bibcode: 1992ASPC...32..259V Altcode: 1992IAUCo.135..259V; 1992cadm.conf..259V No abstract at ADS Title: The European Network of Laboratories: Visual Double Stars Authors: Oblak, E.; Argue, A. N.; Brosche, P.; Cuypers, J.; Dommanget, J.; Duquennoy, A.; Froeschle, M.; Grenon, M.; Haibwachs, J. -L.; Jasniewicz, G.; Lampens, P.; Mermilliod, J. C.; Mignard, F.; Sinachopoulos, D.; Seggewiss, W.; van Dessel, E. Bibcode: 1992ASPC...32..454O Altcode: 1992IAUCo.135..454O; 1992cadm.conf..454O No abstract at ADS Title: Stromgren Photometry of Wide Visual Double Stars with G-type Primaries, Most of Which Have Common Origin Components Authors: Sinachopoulos, D.; van Dessel, E. Bibcode: 1992ASPC...32..355S Altcode: 1992IAUCo.135..355S; 1992cadm.conf..355S No abstract at ADS Title: UBV CCD Photometry and Astrometry of "Close" Visual Double Stars Authors: van Dessel, E.; Sinachopoulos, D.; Prado, P. Bibcode: 1992ASPC...32..362V Altcode: 1992cadm.conf..362V; 1992IAUCo.135..362V No abstract at ADS Title: High precision radial velocity determinations for the study of the internal kinematical and dynamical structure and evolution of young stellar groups. Authors: Hensberge, H.; van Dessel, E. L.; Burger, M.; de Zeeuw, P. T.; Lub, J.; Lepoole, R. S.; Verschueren, W.; David, M.; Theuns, T.; De Loore, C.; de Geus, E. J.; Mathieu, R. D.; Blaauw, A. Bibcode: 1990Msngr..61...20H Altcode: No abstract at ADS Title: Multifrequency behaviour of the X-ray/Be system A 0535 + 26/HDE 245770 at the perioastron passage in March/April 1989 Authors: Giovannelli, F.; Persi, P.; de Martino, D.; Bartolini, C.; Guarnieri, A.; Piccioni, A.; Teoderani, M.; Burger, M.; van Dessel, E. L.; Kurt, V. G.; Sheffer, E. K.; Waters, L. B.; Gonzalez Martinez-Pais, I.; Gnedin, Y. N.; Larionov, V. M.; Shakovskaya, N. I.; Dapergolas, A.; Kontizas, E. Bibcode: 1990ESASP.310..379G Altcode: 1990eaia.conf..379G No abstract at ADS Title: Fourteen Years of Multifrequency Coordinated Observations of the X-Ray / BE System A:0535+26 / HDE245770 Authors: Giovannelli, F.; Bartolini, C.; Guarnieri, A.; Piccioni, A.; Burger, M.; van Dessel, E. L.; Kurt, V. G.; Sheffer, E. K.; de Martino, D.; Waters, R.; Martinez-Pais, I. Gonzalez; Gnedin, Yu. N.; Larionov, V. M.; Shakovskaya, N. I. Bibcode: 1990Ap&SS.169..139G Altcode: Within the framework of a very long multifrequency campaign of coordinated, and very often simultaneous, observations of the transient X-ray/Be system A 0535+26/HDE 245770, we present a summary of this large collection of data taken with IUE and ASTRON satellites as well as with many ground-based telescopes in optical and IR regions. In this paper we emphasize the study of the physics and dynamics of the mass transfer at periastron and subsequent X-ray flaring, which is a typical problem of the X-ray/Be binary system class. Title: Extreme ultraviolet imaging telescope on board the Solar Heliospheric Observatory Authors: Delaboudiniere, Jean-Pierre; Gabriel, Alan H.; Artzner, Guy E.; Millier, F.; Michels, Donald J.; Dere, Kenneth P.; Howard, Russell A.; Kreplin, Robert W.; Catura, Richard C.; Stern, Robert A.; Lemen, James R.; Neupert, Werner M.; Gurman, Joseph B.; Cugnon, P.; Koeckelenbergh, A.; van Dessel, E. L.; Jamar, Claude A.; Maucherat, Andre J.; Chauvineau, Jean-Pierre; Marioge, Jean-Paul Bibcode: 1989SPIE.1160..518D Altcode: 1989xeoa.conf..518D The design of the multibandpass Extreme-Ultraviolet Imaging Telescope designed for 1996 launch on board the Solar Heliospheric Observatory is described. The telescope will observe simultaneously distinct temperature ranges in the solar corona, defined by well chosen emission lines. Images in four narrow bandpasses at wavelengths ranging from 17 to 31 nm will be obtained using normal-incidence multilayered optics deposited on quadrants of a Ritchey-Chretien telescope. Results are presented on the performances measured on a 2/3 scale mock-up. The bandpasses could be adjusted to better than 1 percent in wavelength. Title: A 0535+26/HD 245770 - A typical Be/X-ray transient system : coordinated multiwavelength twelve years monitor. Authors: Giovannelli, F.; Burger, M.; van Dessel, E. L.; Bartolini, C.; Guarnieri, A.; Piccioni, A.; Kurt, V. G.; Sheffer, E. K. Bibcode: 1988ESASP.281a.141G Altcode: 1988uvai....1..141G; 1988IUE88...1..141G The transient X-ray binary system A 0535+26/HDE 245770 was monitored at different wavelengths since its discovery as X-ray emitter. These coordinated observations reveal correlations in the variability of the optical and X-ray emissions. During activity periods of the system, UV discrete absorption components in Si IV and C IV resonance lines whose velocities vary between -300 and -600 km/sec were detected. The study of the narrow absorption components at the expected activity epochs (periastron passages of the neutron star) simultaneously with X-ray, optical, and IR observations is essential for a better knowledge of the wind structure of the Be star and its interaction with the neutron star. The physics and dynamics of mass transfer at periastron and subsequent X-ray flaring, are emphasized. Title: Wide components in double and multiple stars Authors: Dommanget, J.; van Dessel, E. L.; Kopal, Zdenek Bibcode: 1988Ap&SS.142.....D Altcode: 1988IAUCo..97.....D Papers are presented on the concept of star multiplicity, the photometric cataloging of visual and multiple stellar systems, the cataloging of ephemerides and apparent orbits for visual binaries, and a search for wide pairs among nearby stars. Also considered are distant companions in double and multiple stars, the kinematics of trapezium-type systems, the classification of multiple systems in the general field, and photoelectric observations of CPM stars in the BVRI system. Other topics include the frequency of wide binaries among the southern barium stars, statistical studies on wide pairs, theoretical models for wide binary evolution, and evidence of mass loss in visual binary stars. Title: Wide components in double and multiple stars. Proceedings of the 97thColloquium of the International Astronomical Union, held in Brussels,Belgium, 8 - 13 June 1987. Authors: Dommanget, J.; van Dessel, E. L.; Kopal, Z.; Melchior, P. Bibcode: 1988wcdm.book.....D Altcode: No abstract at ADS Title: The Be/X-RAY System HDE 245770/A0535+26 in an Active Phase Authors: Bartolini, C.; Burger, M.; van Dessel, E. L.; Giovannelli, F.; Guarnieri, A.; De Loore, C.; Piccioni, A. Bibcode: 1987pbes.coll..309B Altcode: 1987IAUCo..92..309B The authors report on the sudden appearance and disappearance of (mainly) Fe II emission lines in the Be/X-ray system HDE 245770/A0535+26, about 24 days before an X-ray outburst was observed. Title: X-Ray Ultraviolet and Optical Monitoring of the X-Ray / BE Transient System A:0535+26 / HDE245770 Authors: Giovannelli, F.; van Dessel, E. L.; Burger, M.; De Loore, C.; Bartolini, C.; Guarnieri, A.; Piccioni, A.; Golynskaya, I. M.; Kurt, V. G.; Mizyakina, T. A.; Shafer, E. Y.; Shamolin, V. M.; Sheffer, E. K.; Smirnoff, A. S. Bibcode: 1986ESASP.263..459G Altcode: 1986NIA86......459G; 1986niia.conf..459G The X-ray/Be transient system A 0535+26/HDE 245770 was monitored in X-ray, UV, and optical wavelengths to study the lighting of X-ray outbursts. The X-ray observations were carried out with ASTRON satellite on April 19, 1985 and March 17, 1986, dates of expected X-ray outbursts as predicted by the 111 day orbital periodicity. The measured fluxes are 6.5 mCrab and less than 5 mCrab in April 1985 and March 1986, respectively. The IUE observations were performed on January 29, and on March 13 and 15, 1986, predicted periods of quiescence and a bit earlier than an outburst, respectively. Optical spectroscopic observations were performed too. The absence of two X-ray expected outbursts implies either an inaccuracy of 111 day period or a temporary turning-off of the source. Title: The transient X-ray source A 0535+26: coordinated observations in X-ray, UV, optical and IR regions. Authors: Giovannelli, F.; Ferrari Toniolo, M.; Persi, P.; Golinskaya, I. M.; Golynskaya, I. M.; Kurt, V. G.; Mizyakina, T. A.; Shafer, E. Yu.; Shamolin, V. M.; Smirnoff, A. S.; Smirnov, A. S.; Sheffer, E. K.; Zaytzeva, G. V.; Zajtseva, G. V.; van Dessel, E. L.; van Diest, H.; Hensberge, H.; Burger, M.; De Loore, C.; Bartolini, C.; Guarnieri, A.; Lolli, M.; Piccioni, A.; Gnedin, Yu. N.; Khozov, G. V.; Larionov, V. M.; Shakovskaya, N. I.; Shakhovskaya, N. I. Bibcode: 1985xra..conf..205G Altcode: 1984xra..conf..205G Multispectral coordinated observations of the Be/X-ray binary HDE 245770/A 0535+26 are briefly presented and discussed. A strong X-ray event was revealed and the period of the X-ray pulsar measured during a quiescent phase. Title: Multispectral analysis in the UV, optical and IR of HDE 245770 = A 0535+26. Authors: De Loore, C.; Giovannelli, F.; van Dessel, E. L.; Bartolini, C.; Burger, M.; Ferrari-Toniolo, M.; Giangrande, A.; Guarnieri, A.; Hellings, P.; Hensberge, H.; Persi, P.; Piccioni, A.; van Diest, H. Bibcode: 1984A&A...141..279D Altcode: The characteristics of the Be/X-ray binary system HDE 245770/A0535+26 are examined from UV, visual, IR and X-ray data. A sequence of observations in the optical preceding an X-ray outburst is interpreted as the ejection of a shell by the Be primary. An evolutionary scenario is presented that produces a system like HDE 245770. An effective temperature of 26000±2000K is derived for the Be star. The mass loss rate through stellar wind from the primary is determined. The Be star is not filling its Roche lobe and there is no accretion disk around the compact companion. The system configuration can be simulated with an evolution code allowing for the simultaneous evolution of two components - a 20 M_sun; primary and a 15 M_sun; secondary - producing Be/X-ray binaries of this kind, with systems like φ Per as progenitor. Title: Coordinated X-ray, ultraviolet, optical, and infrared observations ofthe transient source A0535+26. Authors: Giovannelli, F.; Ferrari-Toniolo, M.; Persi, P.; Bartolini, C.; Guarnieri, A.; Piccioni, A.; van Dessel, E. L.; Burger, M.; de Loore, C.; Bisnovatyi-Kogan, G. S.; Bisnovatyj-Kogan, G. S.; Golynskaya, I. M.; Kurt, V. G.; Mizyakina, T. A.; Shafer, E. Yu.; Shamolin, V. M.; Sheffer, E. K.; Smirnoff, A. S.; Smirnov, A. S. Bibcode: 1984ESASP.218..439G Altcode: 1984iue..conf..439G Data of A 0535+26/HDE 245770 from IR, optical, UV and X wavelengths before and after one of the strongest X-ray outbursts, expected on the basis of the 111-day periodicity of this source and detected by the ASTRON satellite on February 1, 1984 are presented. The IUE observations performed on Nov 10, 1983 and Jan 23, 1984 are entirely compatible with earlier measurements. Optical spectra taken immediately before the X-ray outburst show H gamma in absorption and H alpha in weakened emission. In September and in January 1984 before the X-ray outburst the star presents diminished IR excess. Mass loss is discussed. Title: New orbital elements for the visual binary IDS 14527 S 2715 = ADS 9453. Authors: van Dessel, E. Bibcode: 1983BAORB...9..254V Altcode: No abstract at ADS Title: New orbital elements for the visual binary IDS 14527 S 2715 = ADS 9453. Authors: van Dessel, E. Bibcode: 1983BuAst...9..254V Altcode: No abstract at ADS Title: The observation of radial velocities of visual binaries Authors: van Dessel, E.; Dommanget, J. Bibcode: 1982BICDS..23..106V Altcode: No abstract at ADS Title: Ultraviolet, optical, and infrared observations of HDE 245770/A 0535+26. Authors: Giovannelli, F.; De Loore, C.; Bartolini, C.; Burger, M.; Ferrari-Toniolo, M.; Giangrande, A.; Guarnieri, A.; Persi, P.; Piccioni, A.; van Dessel, E. L. Bibcode: 1982ESASP.176..233G Altcode: 1982iue..conf..233G; 1982IUE3r......233G Observations of the Be X-ray source A 0535 + 26 are described. The features of the source changed notably between Feb. and Oct. 1981: the magnitude of the optical companion decreased by 0.2 M in less than one year, in passbands U, B. and V. The infrared magnitude decreased by 0.6 M in the K band and the ultraviolet flux is nearly invariable. The variations in different wavelength regions are probably due to changes in the circumstellar envelope. November 1981 high resolution IUE spectra clearly show C IV and Si IV lines with P Cygni profiles. February and October 1980 profiles did not show this characteristic (due to intrinsic variability of the source and/or a consequence of the smaller S/N ratio of the spectra). From the Si IV and C IV P Cygni profiles, a mass loss rate of 6 X 10 to the minus 9th to 10 to the minus 8th power M/yr is estimated. From the infrared excess, a mass loss rate of 6 x 10 to the minus 6th power M/yr is obtained. Radio observations at 18 cm give an upper limit of 36 mJy from A 0535+26. Title: Be components in X-ray binaries Authors: De Loore, C.; Burger, M.; Mouchet, M.; van Dessel, E. L. Bibcode: 1982IAUS...98..347D Altcode: The parameters of Be X-ray binaries, the most important spectral lines of three such sources, and the evolutionary tracks and positions of Be components are discussed. It is found necessary to study the variability of the entire spectral range, from X-rays to IR, in order to determine whether Be X-ray sources are binaries. Although an optical orbit has not yet been derived for any of the sources in question, two arguments are adduced on behalf of their binary character: the fact that the X-ray pulsation is the signature of a rotating compact object, and the determination that several classical Be stars are binaries. Such systems could be precursors for Be X-ray systems. Title: Mass Determination of Massive X-Ray Binaries Authors: De Loore, C.; Mouchet, M.; van Dessel, E. L.; Burger, M. Bibcode: 1982Msngr..27...14D Altcode: Massive X-ray binaries consist of anormal component of spectral type 0 or B which is transferring matter to a compact companion, generally a neutron star, with possibly one exception, Cyg X-1, where the compact component could be a black hole. These compact stars have enormous magnetic fields (of the order of 1012 gauss), and extremely large gravities; accreted matter will be accelerated to velocities of half the light velocity, and guided by the field lines to restricted areas near the magnetic poles, the hot spots. These regions acquire in this way temperatures of the order of 107 K, and X-rays are generated. The X-rays are transported outwards as beams, and since the compact objects rotate rapidly, X-rays are observed as pulse-shaped beams. Title: Ultraviolet observations of the Be star and X-ray binary 4U 1145-61 (=HD 102567 = HEN 715) obtained with the IUE. Authors: De Loore, C.; Burger, M.; Hensberge, H.; van Dessel, E. L. Bibcode: 1981A&A...104..150D Altcode: Two high resolution spectrograms in the range of 1150-2050 A were obtained by the IUE satellite, and from the spectrograms line lists of the stellar and interstellar absorption were compiled. The most important ions were found to be He (+); one, two and three times ionized C and Si; two and three times ionized O, three times ionized Mn; and two, three and four times ionized N. Eight interstellar molecular bands of (C-12)(O-16) of the fourth positive system were found, although the (C-13(O-16) bands were not detected. Due to uncertainties and the observed ionization fractions in other early-type stars, it is concluded that the mass loss rate of HD 102567 is between 10 to the -9th and 10 to the -10th solar mass/yr, with a most probable value of 3 x 10 to the -10th solar mass/yr. Title: IUE and optical observations of V861 Sco. Authors: Howarth, I. D.; Wilson, R.; Carter, B. S.; Menzies, J. W.; Roberts, G.; Whitelock, P. A.; van Dessel, E. L.; De Loore, C.; Sanford, M. C. W.; Burger, M. Bibcode: 1981A&A....93..219H Altcode: We present the first results of high dispersion (Δλ ≃ 0.2 Å) IUE spectra of the possible X-ray binary V 861 Sco (HD 152667) taken at several orbital phases. Contemporary optical spectroscopy, uvbyβ and infrared photometry are also reported.

The UV spectrum is quite normal for the spectral type (B0Ia), with P Cygni profiles on a number of lines. Several of these lines show sharp multiple absorption components. The high ionisation interstellar species are not significantly enhanced by possible Xray emission. There are no large phase dependent variations in the UV spectra available; the optical spectra show significant changes, particularly at Hα, which is seen in absorption and emission at different times.

Our photometry confirms earlier results in general. The IR data do not support an earlier suggestion of a non-stellar secondary; indeed, our data lend no support to the hypothesis of a compact companion. The mass loss rate is found to be 1 10-5 Msun yr-1. Title: Data Inferred from Visual Binaries Authors: van Dessel, E. L.; Dommanget, J. Bibcode: 1980IrAJ...14..226V Altcode: A star can be identified as a binary by observing the separation between the components or their common proper motion, or by taking micrometer measurements. Orbital parameters are known through interferometry and statistical material on binaries provides evidence for theories on star formation. Different populations of binaries exist that vary in their orbital period, indicating that different formation processes are at work. Where the assumed Jeans mass nearly equals the total mass of the system, a single nucleus will be surrounded by matter organizing itself into one or more companions or into planets. Examination of the mass ratio of binary systems is biased toward detection of equal mass systems, but additional data may correct this. A discontinuity appears to exist between stellar/stellar and stellar/planetary mass ratios, but this must be regarded with much caution because of the increasing difficulty of observing the variability of radial velocity. Title: Simultaneous ultraviolet, optical and X-ray observations of the X-raysource Vel X-1 (HD 77581). Authors: Dupree, A. K.; Gursky, H.; Black, J. H.; Davis, R. J.; Hartmann, L.; Matilsky, T.; Raymond, J. C.; Hammerschlag-Hensberge, G.; van den Heuvel, E. P. J.; Burger, M.; Lamers, H. J. G. L. M.; Vanden Bout, P. A.; Morton, D. C.; De Loore, C.; van Dessel, E. L.; Menzies, J. W.; Whitelock, P. A.; Watson, M.; Sanford, P. W.; Pollard, G. S. G. Bibcode: 1980ApJ...238..969D Altcode: UV spectra (obtained by the IUE) of HD 77581, associated with the binary X-ray source Vela X-1, show a spectrum typical of an early B-type supergiant. However, the P Cygni profiles of strong resonance lines show substantial variations with orbital phase. These variations can be ascribed to the changing ionization state in the stellar wind caused by the X-ray emitting companion. X-ray and spectroscopic and photometric optical observations, simultaneous with the IUE observations, indicate behavior consistent with previous epochs. Title: IUE observations of the Be stars HD 102567 (4U 1145-61), X Per and GAM Cas. Authors: Hammerschlag-Hensberge, G.; van den Heuvel, E. P. J.; Lamers, H. J. G. L. M.; Burger, M.; de Loore, C.; Glencross, W.; Howarth, I.; Willis, A. J.; Wilson, R.; Menzies, J.; Whitelock, P. A.; van Dessel, E. L.; Sanford, P. Bibcode: 1980A&A....85..119H Altcode: The first analysis of ultraviolet spectroscopic observation obtained with the IUE satellite of the Be stars HD 102567, X Per, and Gamma Cas, which all are associated with X-ray sources, is presented. The ultraviolet data for HD 102567 (4U 1145-61) consist of low-resolution spectra covering the wavelength range 1150-3200 A. The ultraviolet fluxes are consistent with a reddening of the source of E(B-V)=0.45 magnitude. For this source a complementary program of visible photometry and spectroscopy and X-ray photometry was carried out. During the IUE observations the source 4U 1145-61 was not detectable in X-rays while the spectroscopic observations show dramatic intensity variations of the lower Balmer lines. For the bright Be stars Gamma Cas and X Per high-resolution (0.2 A) ultraviolet spectra covering the wavelength range 1150-3200 A have been obtained. The asymmetric profiles of resonance lines which are present in the spectra of both Gamma Cas and X Per indicate mass loss rates of 7 x 10 to the -9th and 10 to the -8th solar masses/yr, respectively. Title: Simultaneous observations of V861 Sco. Authors: De Loore, C.; Burger, M.; Howarth, I. D.; Wilson, R.; Carter, B. S.; Menzies, J. W.; Roberts, G.; Whitelock, P. A.; van Dessel, E. L.; Sandford, M. C. W. Bibcode: 1980ESASP.157..237D Altcode: 1980IUE2n......237D; 1980iue..conf..237D High dispersion spectra of V861 Sco (HD 152667) taken with International Ultraviolet Explorer at several orbital phases are presented, as well as simultaneous optical spectroscopy, and UVBY and infrared photometry. The UV spectrum is normal for a BOIa supergiant; a number of lines show P Cygni profiles with, in several cases, sharp multiple absorption components. No large phase dependent variations in the UV are detectable. The optical spectra reveal significant changes at H, He I 6678 and especially at H which is seen in emission and in absorption at different times. The velocity variability is strongly correlated with the outward velocity in the sense that velocities further out in the wind show more variability. The infrared photometry does not support the idea of a compact secondary. An evolutionary scenario, starting from a ZAMS-system of 80 solar masses + 10 solar masses is developed leading to an actual system of a 34 solar masses (BOI a) primary with a 10 solar mass (B2V) companion. The primary which just ignited helium in the core is nearly filling its Roche lobe, and will start soon (or has just started) a case B of mass transfer. The mass loss rate is estimated from the UV at 1.5 x 10 to the minus 6th power solar masses/year, and from theoretical considerations of the system parameters at 2.5 x 10 to the minus 6th power solar masses/year infrared excess points to 0.00005 solar masses/year. Title: Ultraviolet, visible, infrared and X-ray observations of SCO X-1. Authors: Willis, A. J.; Wilson, R.; vanden Bout, P.; Sanner, F.; Black, J.; Davis, R. J.; Dupree, A. K.; Gursky, H.; Hartmann, L.; Raymond, J.; Matilsky, T.; Burger, M.; De Loore, C.; van Dessel, E. L.; Whitelock, P.; Menzies, J.; Meikle, W. P. S.; Joseph, R. D.; Sanford, P.; Pollard, G.; Sandford, M. C. W. Bibcode: 1980ApJ...237..596W Altcode: The first UV spectroscopic observations of the X-ray source Scorpius X-1, obtained with the IUE satellite, are presented. The UV data consist of low-resolution spectra in the 1150-3200 A wavelength range, and show emission lines arising in Si II and IV; C III and IV; N III, IV, and V; O IV and V, and He II. Also discussed are observations using visible photometry and spectroscopy, and infrared and X-ray photometry. Significant changes between the strengths of the emission lines with phase are observed when the source changes its UV and optical brightness. Significant variations are also observed in the UV continuum brightness of Sco X-1 which approximately match those observed simultaneously in the visible B band. The color excess of Sco X-1 is found to be 0.35 plus or minus 0.05, and the UV continuum energy distribution is shown to be well fitted by a bremsstrahlung distribution. Title: Photometric observations of X Persei made in January - February 1979 with the one meter-telescope at Gornergrat. Authors: van Dessel, E. L. Bibcode: 1980BAORB...9..159V Altcode: No abstract at ADS Title: De IUE röntgenveertiendaagse. Authors: Burger, M.; van Dessel, E. L.; De Loore, C.; Willis, A. J. Bibcode: 1980Zenit...7..218B Altcode: No abstract at ADS Title: Het eerste jaar van IUE. Authors: Willis, A. J.; De Loore, C.; van Dessel, E. L.; Burger, M. Bibcode: 1980Zenit...7..138W Altcode: No abstract at ADS Title: Observations of X Persei in the U B2 V1 Colours of the Geneva System Authors: van Dessel, E. L.; Burger, M.; de Loore, C.; Packet, W.; Vanbeveren, D. Bibcode: 1979IBVS.1679....1V Altcode: No abstract at ADS Title: Radial Velocities of Visual Binaries Authors: van Dessel, E. L. Bibcode: 1979Msngr..18....1V Altcode: In addition to the initial chemical composition, the mass of a star is a fundamental parameter; it determines the life of the star from its birth, through its long or short period of luminous glory and to its inevitable end as a compact object. And yet, few stars have actually had their mass accurately measured. The programme that has recently been undertaken by Dr. Edwin van Dessel of the Royal Observatory in Brussels, Belgium, is therefore of particular importance. By obtaining precise measurements of radial velocities of stars in double or multiple systems, Dr. van Dessel expects soon to add new, welldetermined stellar masses to the present, all to short list. Title: Non-conservative evolution of massive close binaries including stellar wind mass loss. Authors: Vanbeveren, D.; de Grève, J. P.; van Dessel, E. L.; de Loore, C. Bibcode: 1979A&A....73...19V Altcode: No abstract at ADS Title: Conservative and non-conservative evolutionary computations in connection with Wolf-Rayet binaries. Authors: Vanbeveren, D.; De Greve, J. P.; De Loore, C.; van Dessel, E. L. Bibcode: 1979IAUS...83..483V Altcode: No abstract at ADS Title: The influence of stellar wind mass loss on the evolution of massive close binaries Authors: Vanbeveren, D.; De Greve, J. P.; De Loore, C.; van Dessel, E. L. Bibcode: 1979IAUS...83..409V Altcode: No abstract at ADS Title: IUE ultraviolet and complementary visible and X-ray observations of SCO X-1 Authors: Willis, A. J.; Wilson, R.; vanden Bout, P.; Sanner, F.; Black, J.; Davis, R. J.; Dupree, A. K.; Gursky, H.; Hartmann, L.; Matilsky, T.; Burger, M.; De Loore, C.; van Dessel, E. L.; Whitelock, P.; Menzies, J.; Sanford, P.; Pollard, G.; Sandford, M. C. W. Bibcode: 1979IUE1.symp..291W Altcode: IUE observations providing the first ultraviolet spectroscopic data of the X-ray source Sco X-1 are presented and discussed. The IUE data were obtained in the low resolution mode and cover the wavelength range 1150-3200 A. Data were obtained at many different phases and cycles in the binary period of the system of 0d.8. The short wavelength IUE spectra are dominated by numerous emission lines in Si II, IV, C III, IV, N III, IV, V, O IV, V and He II. The variations in the strengths of these lines both as a function of binary phase and brightness level of the source is discussed as well as those observed in the visible spectra of the source. The observed line strength variations can be explained in terms of a varying level of ionization with varying ionising X-ray radiation emitted from the compact object. Title: Radial velocities of visual binaries with an orbit derived from astrometric observations. II Authors: van Dessel, E. Bibcode: 1979MRASB..41....1V Altcode: 1979STIA...8021990V The list of visual binaries compiled by van Dessel (1977), for which an orbit had been computed from astrometric observations and which are believed to be capable of yielding useful radial velocity determinations in the near future, is updated and extended. Three kinds of systems are included in the updated list: (1) binaries of which at least one component has been shown to be spectroscopically double (triple and multiple systems); (2) binaries that are suspected of containing a third component because of the large scatter in radial velocity values; and (3) binaries for which the semiamplitude of the relative radial velocity variation is greater than 15 km/sec, according to the computed orbital elements. Title: Orbit of the visual binary ADS 3588 = IDS 04546 S 1632. Authors: van Dessel, E. Bibcode: 1978BAORB...9...44V Altcode: No abstract at ADS Title: The Evolution of Massive Close Binaries, VI: Final Considerations for the Conservative Case Authors: De Greve, J. P.; De Loore, C.; van Dessel, E. L. Bibcode: 1978Ap&SS..53..105D Altcode: The results of evolutionary computations for massive binary systems (initial masses of the primary ≳10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found. Title: Occultations d'étoiles par la lune, observées à l'équatorial de 45 cm de 1974 à 1977. Authors: Dommanget, J.; van Dessel, E. Bibcode: 1978BAORB...9...32D Altcode: No abstract at ADS Title: Spectroscopic observers please help! Authors: van Dessel, E. L. Bibcode: 1977Obs....97..203V Altcode: No abstract at ADS Title: Radial velocities of visual binaries with an orbit derived from astrometric observations. Authors: van Dessel, E. Bibcode: 1977tras.conf..151V Altcode: No abstract at ADS Title: Orbital elements and removal of the nodal ambiguity for the visual binary ADS 7390 = ω Leo Authors: van Dessel, E. L. Bibcode: 1976A&AS...26..415V Altcode: Orbital elements and ephemeris of the binary ADS 7390. The ascending node is identified on the basis of high resolution spectra. Key words: visual binaries - orbit - radial velocities Title: Radial velocities of the visual binary 70 Ophiuchi. Authors: Batten, A. H.; van Dessel, E. L. Bibcode: 1976PDAO...14..345B Altcode: No abstract at ADS Title: Dubbelsterren (2) - (4). Meervoudige sterren eerder regel dan uitzondering. Authors: van Dessel, E. L. Bibcode: 1976Zenit...3...20V Altcode: No abstract at ADS Title: Observation photographique de l'éclipse de Soleil du 29 avril 1976 à l'équatorial Cooke-Zeiss. Authors: Dommanget, J.; van Dessel, E.; Nys, O. Bibcode: 1976BAORB...8..325D Altcode: No abstract at ADS Title: Line Intensities in the Photosphere-Chromosphere Transition Region. IV: Cr I and Metallic Ion Lines Authors: van Dessel, E. L. Bibcode: 1975SoPh...44...13V Altcode: Eclipse observations of total line intensities (Cr I: two groups of lines; Ti II, Fe II and Cr II: two lines each) are interpreted in terms of departures from LTE. The same method as described in Paper III (van Dessel, 1974) is used. The HSRA model is used to compute the LTE populations. A distribution of NLTE-coefficients is obtained for each group of lines. The lines discussed in the present paper are seen to remain in emission down to some 1000 km inside the limb. As a consequence, interpretation is less simple than for the Fe I lines (Paper III); population and excitation temperatures are found to be rather divergent from Holweger's temperature, which was used for a first approximation. Title: Dubbelsterren (1). Indeling gebaseerd op waarnemingsmethoden. Authors: van Dessel, E. L. Bibcode: 1975Zenit...2..419V Altcode: No abstract at ADS Title: Line Intensities in the Photosphere-Chromosphere Transition Region. III: Empirical NLTE Analysis of FeI Lines Authors: van Dessel, E. L. Bibcode: 1974SoPh...38..351V Altcode: We analyse Fe I lines observed during the 1961 eclipse at Brač, Yugoslavia (see paper II: van Dessel et al., 1973), using a computer program for the calculation of theoretical line intensities, which was described in Paper I (van Dessel, 1970). A few minor modifications to the physical input are discussed in Section 2. NLTE-coefficients, affecting the line absorption coefficient and the source function, are introduced and discussed in Section 3. Starting from coefficients derived from the combination Tel (HSRA) + Tex (Holweger), suitable distributions with height of the NLTE-coefficients are determined for the most striking cases among the observed lines. Only little deviation from the populations derived from Holweger's temperature distribution is needed to explain the observed line behaviour. Title: Occultations d'étoiles par la lune, observées à l'équatorial de 45 cm en 1972 et 1973. Authors: Dommanget, J.; van Dessel, E. Bibcode: 1974BAORB...8..141D Altcode: No abstract at ADS Title: Line-Intensities in the Photosphere-Chromosphere Transition Region. II: Observational Material from the 1961 Eclipse at Brač Authors: Van Dessel, E. L.; Houtgast, J.; Koelbloed, D. Bibcode: 1973SoPh...33..375V Altcode: We present results from eclipse spectra in the wavelength region 4588-4682 Å, taken during the eclipse of February 15, 1961 at Brač, Yugoslavia. Absolute line intensities have been determined in the photosphere-chromosphere transition region. The method of reduction is discussed in Section 2 and the observed variation of the total intensity as a function of the height is shown for a number of lines in Figures 5-8. The results for the Fe I lines are compared with computations (as described in Paper I: van Dessel, 1970) for various solar model atmospheres (Section 4). The model, which combines Holweger's (1967) temperature distribution for the excitation temperature with the HSRA model (Gingerich et al., 1971) for the electron temperature, yields a better agreement than all pure LTE-models. Title: New orbit and mass of the visual binary and magnetic Ap star ADS 7334 = HR 3724. Authors: van Dessel, E. L. Bibcode: 1972A&A....21..155V Altcode: Summary. Calculation of the orbital elements, physical characteristics and ephemeris of the visual binary ADS 7334. A previous orbit of this star, computed by Finsen (1968), is shown to be unsatisfactory. The present orbit is in better agreement with spectroscopic observations by van den Heuvel (1971) and leads to plausible masses. Resumee'. Calcul des e'le'ments orbitaux, des elements physiques et de l'e'phe'me'nde du couple ADS 7334. On montre qu'une orbite antefleure, calculee par Finsen (1968) pour cette etoile, ne donne pas satisfaction. L'orbite actuelle est en meilleur accord avec les observations spectroscopiques de van den Heuvel (1971) et conduit a' des masses plausibles. Key words: orbital elements - visual binary - peculiar A stars - magnetic stars Title: Occultations d'étoiles par la lune observées à l'équatorial de 45 cm, en 1969, 1970 et 1071. Authors: Dommanget, J.; van Dessel, E. Bibcode: 1972BAORB...8...42D Altcode: No abstract at ADS Title: Passage de Mercure sur le disque solaire le 9 mai 1970. Observations photographiques à l'équatorial Cooke-Zeiss. Authors: Dommanget, J.; van Dessel, E.; Nys, O. Bibcode: 1971BAORB...7..188D Altcode: No abstract at ADS Title: A Comparison of Computed and Observed Line Profiles and Flash Intensities in the Photosphere-Chromosphere Transition Region Authors: Van Dessel, E. L. J. Bibcode: 1970SoPh...15..322V Altcode: This paper mainly deals with the development of a method for the interpretation of eclipse observations in the extreme limb - lower chromosphere transition region. We compute line profiles emitted by a column of 1 cm2 cross section along the line of sight and, by integration, profiles and total (flash) intensities from a slice of 1 cm width beyond the Moon's edge, at various heights with respect to the solar limb. The solar models used are mentioned in Section 1; method and approximations are described in Section 2. Calculations have been made for some FeI lines with various equivalent widths (Table I); the results are discussed in Section 3. It appears that the method enables one to distinguish between the various models. Particularly line intensities just inside the limb are very important. Title: Preliminary orbit of the visual binary ADS 9975 = A 1642 = JDS 2417. Authors: Dommanget, J.; van Dessel, E. L. Bibcode: 1970A&A.....6..423D Altcode: Calculation of the orbital elements and physical characteristics of the visual binary ADS 9975, adopting a change of quadrant for the observations later than 1950. This assumption is based on the possible variability of one of the components. Calcul des e'ments orbitaux et des 6ments physiques du couple ADS 9975, dans l' d'un changement de quadrant intervenu aux environs de 1950. Cette est sur une variabilit6 d'6datpossible de l'une des composantes. Key words: orbital elements - visual binary