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See detailSimulations of observations with the Optical Monitor of the X-ray Multi-Mirror Satellite
Royer, P.; Manfroid, Jean ULg; Gosset, Eric ULg et al

in Astronomy and Astrophysics. Supplement Series (2000), 145

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric ... [more ▼]

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric system and its colour transformations towards the standard U BV system. Second, we establish a set of procedures to determine the temperature and the amount of interstellar absorption affecting the observed stars. Last, we address the possibility of isolating quasars in multidimensional colour diagrams based on the XMM-OM filter set. [less ▲]

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See detailOptical polarization of 47 quasi-stellar objects: The data
Lamy, H.; Hutsemekers, Damien ULg

in Astronomy and Astrophysics. Supplement Series (2000), 142

New broad-band linear polarization measurements are presented for a sample of 47 QSOs which includes 27 broad absorption line QSOs and 2 gravitational lens candidates. Tables 3 and 4 are also available in ... [more ▼]

New broad-band linear polarization measurements are presented for a sample of 47 QSOs which includes 27 broad absorption line QSOs and 2 gravitational lens candidates. Tables 3 and 4 are also 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 Based on observations collected at the European Southern Observatory (ESO, La Silla). [less ▲]

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See detailA dedicated photometric system for the classification of Wolf-Rayet stars
Royer, P.; Vreux, Jean-Marie ULg; Manfroid, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1998), 130

We present here tests of a five-filter photometric system aimed at WR classification. In addition to the well-known easy separation between the WN and WC spectral types, these tests indicate interesting ... [more ▼]

We present here tests of a five-filter photometric system aimed at WR classification. In addition to the well-known easy separation between the WN and WC spectral types, these tests indicate interesting potentialities in the discrimination of subgroups among the WN and the WC which look well related to the classical subtypes. The proposed combinations of filters (or derived ones) bear enough discriminating power to satisfy some evolutionary studies in crowded fields where spectroscopic follow-up is not possible. Based on observations collected at the European Southern Observatory, La Silla, Chile. [less ▲]

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See detailThe observed periods of Ap and Bp stars
Catalano, F. A.; Renson, Pierre ULg

in Astronomy and Astrophysics. Supplement Series (1998), 127

A catalogue of all the periods up to now proposed for the variations of CP2, CP3, and CP4 stars is presented. The main identifiers (HD and HR), the proper name, the variable-star name, and the spectral ... [more ▼]

A catalogue of all the periods up to now proposed for the variations of CP2, CP3, and CP4 stars is presented. The main identifiers (HD and HR), the proper name, the variable-star name, and the spectral type and peculiarity are given for each star as far as the coordinates at 2000.0 and the visual magnitude. The nature of the observed variations (light, spectrum, magnetic field, etc.) is presented in a codified way. The catalogue is arranged in three tables: the bulk of the data, i.e. those referring to CP2, CP3, and CP4 stars, are given in Table 1, while the data concerning He-strong stars are given in Table 2 and those for eclipsing or ellipsoidal variables are collected in Table 3. Notes are also provided at the end of each table, mainly about duplicities. The catalogue contains data on 364 CP stars and is updated to 1996, October 31. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. [less ▲]

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See detailVariations of Ap stars in the Geneva system
Manfroid, Jean ULg; Burnet, M.; Renson, Pierre ULg

in Astronomy and Astrophysics. Supplement Series (1998), 127

The photometric behaviour of 21 Ap stars has been analyzed from observations obtained in the Geneva system. Variability has been detected for 9 Ap stars, as well as for a star which initially was a ... [more ▼]

The photometric behaviour of 21 Ap stars has been analyzed from observations obtained in the Geneva system. Variability has been detected for 9 Ap stars, as well as for a star which initially was a comparison star. Preliminary values for the periods are presented as well as an analytical description of the light curves. based on observations made at the Swiss telescope of the European Southern Observatory, La Silla, Chile. Complete Table 4 is available in electronic form at the CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html and full figures are accessible on the on-line version of the paper. [less ▲]

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See detailRadiative transition probabilities for forbidden lines in singly ionized cobalt (Co II)
Quinet, Pascal ULg

in Astronomy and Astrophysics. Supplement Series (1998), 129

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See detailESO & NOT photometric monitoring of the Cloverleaf quasar
Ostensen, R.; Remy, M.; Lindblad, P. O. et al

in Astronomy and Astrophysics. Supplement Series (1997), 126

The Cloverleaf quasar, H1413+117, has been photometrically monitored at ESO (La Silla, Chile) and with the NOT (La Palma, Spain) during the period 1987--1994. All good quality CCD frames have been ... [more ▼]

The Cloverleaf quasar, H1413+117, has been photometrically monitored at ESO (La Silla, Chile) and with the NOT (La Palma, Spain) during the period 1987--1994. All good quality CCD frames have been successfully analysed using two independent methods (i.e. an automatic image decomposition technique and an interactive CLEAN algorithm). The photometric results from the two methods are found to be very similar, and they show that the four lensed QSO images vary significantly in brightness (by up to 0.45 mag), nearly in parallel. The lightcurve of the $D$ component presents some slight departures from the general trend which are very likely caused by micro-lensing effects. Upper limits, at the 99% confidence level, of 150 days on the absolute value for the time delays between the photometric lightcurves of this quadruply imaged variable QSO, are derived. This is unfortunately too large to constrain the lens model but there is little doubt that a better sampling of the lightcurves should allow to accurately derive these time delays. Pending a direct detection of the lensing galaxy (position and redshift), this system thus constitutes another good candidate for a direct and independent determination of the Hubble parameter. Based on observations collected at the European Southern Observatory (La Silla, Chile) and with the Nordic Optical Telescope (La Palma, Spain). Table 1. Logbook for the ESO and NOT observations together with photometric results for the Cloverleaf quasar. This long table can be accessed on the WWW at the URL address: http://vela.astro.ulg.ac.be/grav_lens/glp_homepage.html} [less ▲]

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See detailThe mean magnetic field modulus of AP stars
Mathys, G.; Hubrig, S.; Landstreet, J. D. et al

in Astronomy and Astrophysics. Supplement Series (1997), 123

We present new measurements of the mean magnetic field modulus of a sample of Ap stars with spectral lines resolved into magnetically split components. We report the discovery of 16 new stars having this ... [more ▼]

We present new measurements of the mean magnetic field modulus of a sample of Ap stars with spectral lines resolved into magnetically split components. We report the discovery of 16 new stars having this property. This brings the total number of such stars known to 42. We have performed more than 750 measurements of the mean field modulus of 40 of these 42 stars, between May 1988 and August 1995. The best of them have an estimated accuracy of 25 - 30 G. The availability of such a large number of measurements allows us to discuss for the first time the distribution of the field modulus intensities. A most intriguing result is the apparent existence of a sharp cutoff at the low end of this distribution, since no star with a field modulus (averaged over the rotation period) smaller than 2.8 kG has been found in this study. For more than one third of the studied stars, enough field determinations well distributed throughout the stellar rotation cycle have been achieved to allow us to characterize at least to some extent the variations of the field modulus. These variations are often significantly anharmonic, and it is not unusual for their extrema not to coincide in phase with the extrema of the longitudinal field (for the few stars for which enough data exist about the latter). This, together with considerations on the distribution of the relative amplitude of variation of the studied stars, supports the recently emerging evidence for markedly non-dipolar geometry and fine structure of the magnetic fields of most Ap stars. New or improved determinations of the rotation periods of 9 Ap stars have been achieved from the analysis of the variations of their mean magnetic field modulus. Tentative values of the period have been derived for 5 additional stars, and lower limits have been established for 10 stars. The shortest definite rotation period of an Ap star with magnetically resolved lines is 3.4 deg, while those stars that rotate slowest appear to have periods in excess of 70 or 75 years. As a result of this study, the number of known Ap stars with rotation periods longer than 30 days is almost doubled. We briefly rediscuss the slow-rotation tail of the period distribution of Ap stars. This study also yielded the discovery of radial velocity variations in 8 stars. There seems to be a deficiency of binaries with short orbital periods among Ap stars with magnetically resolved lines. Based on observations collected at the European Southern Observatory (La Silla, Chile; ESO programmes Nos. 43.7-004, 44.7-012, 49.7-030, 50.7-067, 51.7-041, 52.7-063, 53.7-028, 54.E-0416, and 55.E-0751), at the Observatoire de Haute-Provence (Saint-Michel-l'Observatoire, France), at Kitt Peak National Observatory, and at the Canada-France-Hawaii Telescope. Tables 2, 3, and 4 are also 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. [less ▲]

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See detailFourth supplement to the catalogue of observed periods of Ap stars
Catalano, F. A.; Renson, Pierre ULg

in Astronomy and Astrophysics. Supplement Series (1997), 121

New data on the periods of Ap stars with references are presented (Table 1). 21 further stars are introduced for which a periodic variability has recently been discovered or for which it was known before ... [more ▼]

New data on the periods of Ap stars with references are presented (Table 1). 21 further stars are introduced for which a periodic variability has recently been discovered or for which it was known before but it was not reported in previous issues of this catalogue. For many stars also present in previous issues of the catalogue new determinations of the periods are given. Recently attributed variable star names are also quoted. Table 1, notes to this Table and related references are only available in LaTEX form at the CDS via anonymous ftp 130.79.128.5 (filename: DS1178.tex). [less ▲]

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See detailSurveys of ultraviolet-excess quasar candidates in large fields
Gosset, Eric ULg; Moreau, O.; Surdej, Jean ULg et al

in Astronomy and Astrophysics. Supplement Series (1997), 123

We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet ... [more ▼]

We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates were selected on the basis of their $U$ image being too bright. The spectroscopic identification of the primary candidates led to the discovery of 59 bona fide quasars (out of which 6 were previously known). The Palomar Schmidt plate was digitised using the MAMA measuring machine and the outcoming data reduced using ad hoc procedures. A photometric calibration allowed us to derive values for the limiting magnitudes and for the U-B index selection threshold of the survey. A catalogue containing 60 quasars is presented with accurate positions, magnitudes and additional information such as redshifts. We studied the spatial distribution of the objects and detected, for the quasars of our sample, a significant deviation from randomness in the form of a propensity to cluster in pairs on the celestial sphere with a typical scale of about 10 arcmin. We also formally detected a tendency towards a 3-D clustering, but this result is induced by a single pair of quasars. A forthcoming paper will deal with a similar work performed in a field around NGC 520; the latter field is located directly to the North of the present one and slightly overlaps it. Based on observations acquired at the Mount Palomar and Las Campanas Observatories as well as at the European Southern Observatory. Also based on Schmidt-plate digitisations performed with the MAMA measuring machine of C.A.I. (I.N.S.U., Paris). [less ▲]

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See detailInfrared aperture photometry at ESO (1983-1994) and its future use.
van der Bliek, N. S.; Manfroid, Jean ULg; Bouchet, P.

in Astronomy and Astrophysics. Supplement Series (1996), 119

We describe the infrared (IR) photometric system for the single channel photometers at ESO, which have been used from 1983 until 1994. In addition to the broadband near infrared (NIR, 1-5μm) photometric ... [more ▼]

We describe the infrared (IR) photometric system for the single channel photometers at ESO, which have been used from 1983 until 1994. In addition to the broadband near infrared (NIR, 1-5μm) photometric system presented in 1991 by Bouchet et al. and Bersanelli et al., we describe a narrow-band NIR photometric system and a mid infrared (MIR, 7-20μm) photometric system. We also extend the set of NIR standard stars by Bouchet et al. towards fainter objects (K=~9). The photometric data of the standard stars in these systems were extracted from the complete IR photometric data archive of ESO, covering 10 years. The zeropoints of the NIR photometry are set by assuming that HR 3314 has a V-magnitude of 3.89, and that V-K=-0.05, J-K=-0.01, H-K=-0.01, K-L'=0.00, K-M=0.00. The zeropoints of the MIR photometry are set by assuming that the colours ofβ Hyi (HR 0098) and α CenA (HR 5459) are equal to the colours of the Sun. We adopt the absolute calibration of Megessier (1995A&A...296..771M) for the NIR and we argue that this calibration can be extrapolated to 20μm, using the MIR calibrations by Rieke et al. (1985AJ.....90..900R) and Cohen et al. (1992AJ....104.1650C). The definition of the zeropoints is consistent with the absolute calibration. We obtained accurate (Ï =~0.02mag.) NIR photometry of about 240 standard stars and MIR photometry of about 40 standard stars (Ï =~0.04mag). Comparison of our NIR photometric system with other well established systems shows that there are some small colour dependencies and zeropoint offsets which are always smaller than about 0.02mag. except for the L' band. [less ▲]

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See detailA method to optimize intermediate-passband photometric systems.
Royer, P.; Manfroid, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1996), 119

A method is proposed to optimize the definition of existing photometric filters in order to minimize passband-matching problems. It is argued that the "improved" systems should generally yield better ... [more ▼]

A method is proposed to optimize the definition of existing photometric filters in order to minimize passband-matching problems. It is argued that the "improved" systems should generally yield better astrophysical parameters than the original ones. Although of a general scope, the method is checked on intermediate-passband filters of the Stroemgren system. [less ▲]

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See detailOn CCD standard stars and flat-field calibration.
Manfroid, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1996), 118

Numerical simulations of a CCD flat-fielding calibration procedure on stellar fields have been performed in the monochromatic case. The relations between the photometric conditions, the observational ... [more ▼]

Numerical simulations of a CCD flat-fielding calibration procedure on stellar fields have been performed in the monochromatic case. The relations between the photometric conditions, the observational procedure and the calibration accuracy are explored. This analysis shows how and why one must establish high-quality standard sequences in clusters or moderately crowded fields. The advantages of a long-term management of the reduction procedures is stressed. [less ▲]

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See detailTransition probabilities for forbidden lines of Fe III
Quinet, Pascal ULg

in Astronomy and Astrophysics. Supplement Series (1996), 116

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See detailAtomic data from the IRON Project. XIX. Radiative transition probabilities for forbidden lines in Fe II
Quinet, Pascal ULg; Le Dourneuf, M; Zeippen, C J

in Astronomy and Astrophysics. Supplement Series (1996), 120

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See detailTransition probabilities for [Ni I] and [Ni II] lines
Quinet, Pascal ULg; Le Dourneuf, M

in Astronomy and Astrophysics. Supplement Series (1996), 119

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See detailStellar calibration of CCD flat fielding.
Manfroid, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1995), 113

The role of star observations is advocated in the photometric calibration of the low spatial-frequency non-uniformities of CCD detectors.

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See detailLong-term photometry of variables at ESO. IV. The fourth data catalogue (1992-1994).
Sterken, C.; Manfroid, Jean ULg; Beele, D. et al

in Astronomy and Astrophysics. Supplement Series (1995), 113

In this paper we present the fourth catalogue of photometric data in the Stroemgren system obtained during the period June 18, 1992-August 23, 1994 in the framework of the Long-Term Photometry of ... [more ▼]

In this paper we present the fourth catalogue of photometric data in the Stroemgren system obtained during the period June 18, 1992-August 23, 1994 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. The catalogue is available in computer readable form at the Centre de Donnees de Strasbourg via anonymous ftp 130.79.128.5. [less ▲]

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See detailLong-term photometry of variables at ESO. III. The third data catalogue (1990-1992).
Manfroid, Jean ULg; Sterken, C.; Cunow, B. et al

in Astronomy and Astrophysics. Supplement Series (1995), 109

In this paper we present the third catalogue of photometric data in the Stroemgren system obtained during the period October 1990-January 1992 in the framework of the Long-Term Photometry of Variables ... [more ▼]

In this paper we present the third catalogue of photometric data in the Stroemgren system obtained during the period October 1990-January 1992 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. The catalogue is available in computer readable form at the Centre de Donnees de Strasbourg. [less ▲]

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