References of "Hutsemekers, Damien"
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See detailFurther observations of the light echoes from SN 1987 A
Detal, Alain ULg; Surdej, Jean ULg; Hutsemekers, Damien ULg et al

in Astronomy and Astrophysics (1990), 229

Further direct observations of the light echoes from SN 1987 A were obtained on November 12 1988 with the 3.6-m telescope and EFOSC at ESO. In agreement with predictions made from earlier observations ... [more ▼]

Further direct observations of the light echoes from SN 1987 A were obtained on November 12 1988 with the 3.6-m telescope and EFOSC at ESO. In agreement with predictions made from earlier observations, the radii of the two light rings are measured to be 43.3 and 72.5 arcsec. However, a noticeable diaplacement of the center of the outer ring by 2.6 arcsec to the NE from the SN position is also reported. Application of the model of planar-like sheets of material located between the SN and the observer leads to improved results. [less ▲]

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See detailThe supergiant Bep star CD - 42 11721 deg and its surrounding nebula
Hutsemekers, Damien ULg; van Drom, E.

in Astronomy and Astrophysics (1990), 238

New spectroscopic and direct imagery observations of the supergiant Bep star CD - 42 11721 deg and its surrounding nebula are reported. The spectrum of the star essentially consists of Balmer and Fe II ... [more ▼]

New spectroscopic and direct imagery observations of the supergiant Bep star CD - 42 11721 deg and its surrounding nebula are reported. The spectrum of the star essentially consists of Balmer and Fe II emission lines, He I emission lines are also observed, confirming the presence of spectral variations on long timescales. The clumpy arc-shaped structure of the nebula as well as the presence of motions relative to the central star highly suggest that it has been influenced by a variable mass-loss. The nebula shows both the reflection and emission characteristics. Its spectrum displays the red forbidden N II and S II lines while no oxygen forbidden lines can be detected. Its tempting to interpret this situation by a N/O overabundance which may indicate the presence of processed material in the nebula and thus confirm the evolved nature of the star. [less ▲]

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See detailA search for gravitational lensing among highly luminous quasars - Observational strategy and survey
Swings, Jean-Pierre ULg; Magain, Pierre ULg; Remy, M. et al

in Soucail, G.; Mellier, Y.; Fort, B. (Eds.) Gravitational Lensing (1990)

The observational techniques employed to search for gravitational lensing effects in highly luminous quasars (HLQs) are given, along with results of the observations. The program, begun in 1986, considers ... [more ▼]

The observational techniques employed to search for gravitational lensing effects in highly luminous quasars (HLQs) are given, along with results of the observations. The program, begun in 1986, considers the visible and dark matter distributions at different scales in the universe to determine which extragalactic objects are gravitationally lensed. The Hubble parameter and galaxy masses are determined from the observations, and observations of microlensing effects provide data on HLQ size and structures. The redshifts are found to be between 1 and 3.6, with apparent visual magnitudes 16-18.5 and absolute visual magnitudes between -29 and -30.6. About one quarter of the images exhibit either multiple components, elongated structures, jetlike features, or faint nearby galaxies. The double quasar UM 673 and its 'overlying' lens galaxy is given as a prime example of an HLQ that is gravitationally lensed. It is theorized many more HLQs are gravitationally lensed, and specific future observations are recommended. [less ▲]

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See detailRevisited mass-loss rates for a sample of central stars of planetary nebulae
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Astronomy and Astrophysics (1989), 219

Using improved relations for the first order moment of a P Cygni line profile, mass-loss rates have been rederived for a sample of seventeen central stars of planetary nebulae observed with IUE in the low ... [more ▼]

Using improved relations for the first order moment of a P Cygni line profile, mass-loss rates have been rederived for a sample of seventeen central stars of planetary nebulae observed with IUE in the low resolution mode. The average value of the mass-loss rates lies between 10 to the -7th and 10 to the -8th solar masses/yr. It is confirmed that the mass-loss rates of central stars of planetary nebulae cannot be simply extrapolated from the 'mass-loss rate-luminosity' relation existing for Population I OB stars. [less ▲]

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See detailA new and improved camera for the 1.5m B&C spectrograph
Jarvis, B.; Hutsemekers, Damien ULg

in The Messenger (1989), 56

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See detailProfiles of a Key Programme: Gravitational Lensing
Surdej, Jean ULg; Arnaud, J.; Borgeest, U. et al

in The Messenger (1989), 55

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs ... [more ▼]

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs) at the European 80uthern Observatory, at least three distinct groups (including more than half of the above authors) were already involved in the study of "gravitational lensing" effects (see box on pages 10-11). Observations were being performed with the help of various telescopes on La 8illa as weil as at other observatories (VLA, CFHT, Palomar, Kitt Peak, etc.). [less ▲]

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See detailRevisited Mass-Loss Rates of Planetary Nebula Nuclei Observed with IUE
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Torres-Peimbert, Silvia (Ed.) Planetary Nebulae, 131st. Symposium of the International Astronomical Union (1989)

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See detailStudy of AG Carinae. I - The 1977 spectrum of the star
Hutsemekers, Damien ULg; Kohoutek, L.

in Astronomy and Astrophysics. Supplement Series (1988), 73

Spectroscopic observations of the variable P Cygni-like star AG Car have been obtained in February 1977. At this epoch, the star was in a relative minimum phase (V = 7.6) observed during a long and ... [more ▼]

Spectroscopic observations of the variable P Cygni-like star AG Car have been obtained in February 1977. At this epoch, the star was in a relative minimum phase (V = 7.6) observed during a long and comparatively quiet period of intermediate brightness. The spectrum displays prominent P Cygni lines of He I, Si III, N II and Fe III. The corresponding equivalent spectral type is B2-3 Ib. The presence of an outward accelerated envelope with a multiple shell structure is confirmed. The observation of broad [Fe II] emission lines, in contrast with the absence of permitted ones, implies the presence of a low density shell expanding at about 200 km/s. [less ▲]

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See detailNew arguments supporting the intrinsic origin of BAL QSOs - Formation of the complex Ly-alpha+NV line profile
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Bianchi, L.; Gilmozzi, R. (Eds.) Proceedings of the Second Torino Workshop "Mass Outflows from Stars and Galactic Nuclei" (1988)

A study is presented to further elucidate the question of whether or not all quasars are affected by the BAL phenomenon. The possibility that observed BAL profiles are formed in spherically symmetric ... [more ▼]

A study is presented to further elucidate the question of whether or not all quasars are affected by the BAL phenomenon. The possibility that observed BAL profiles are formed in spherically symmetric expanding atmospheres is investigated. [less ▲]

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See detailImproved first order moment method for determination of mass-loss rates
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Bianchi, L.; Gilmozzi, R. (Eds.) Mass outflows from stars and galactic nuclei; Proceedings of the Second Torino Workshop (1988)

The first order moment of P Cygni line profiles has been computed for the case of doublets and subordinate line transitions. This improved method can be used for deriving more accurate mass-loss rates of ... [more ▼]

The first order moment of P Cygni line profiles has been computed for the case of doublets and subordinate line transitions. This improved method can be used for deriving more accurate mass-loss rates of planetary nebula nuclei, broad absorption line quasars, etc. [less ▲]

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See detailPhotoelectric scans of comet Halley.
Sterken, C.; Manfroid, Jean ULg; Hutsemekers, Damien ULg et al

in Diversity and Similarity of Comets (1987, September 01)

The authors compare radial photometric scans of comet Halley obtained in April 1986 at the European Southern Observatory, La Silla, Chile, with theoretical profiles derived from Haser's model.

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See detailRevisited mass-loss rates for the nuclei of the planetary nebulae NGC 6210, NGC 6826 and NGC 6543 - The first order moment W1 of subordinate line profiles
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Astronomy and Astrophysics (1987), 173

The authors present the results of numerical calculations for the first order moment W[SUB]1[/SUB] of subordinate P Cygni line profiles as a function of the parameter W[SUB]1[/SUB][SUP]0[/SUP]alphaM>n[SUB ... [more ▼]

The authors present the results of numerical calculations for the first order moment W[SUB]1[/SUB] of subordinate P Cygni line profiles as a function of the parameter W[SUB]1[/SUB][SUP]0[/SUP]alphaM>n[SUB]g[/SUB]<[SUB]s[/SUB], where Mrepresents the mass-loss rate of the central star and >n[SUB]g[/SUB]<[SUB]s[/SUB] the average fractional abundance of the relevant ion across the region of the envelope where the subordinate line profile is formed. The calculations clearly show that for unsaturated P Cygni line profiles the relation W[SUB]1[/SUB]alphaM>n[SUB]g[/SUB]<[SUB]s[/SUB] holds irrespective of the type of the opacity and/or velocity distributions. For currently observed P Cygni line profiles, the misuse of this relation can lead to an underestimate of the mass-loss rates by more than one order of magnitude. This is illustrated for the case of 3 selected central stars of planetary nebulae (NGC 6210, NGC 6826 and NGC 6543) for which mass-loss rates have been revisited. [less ▲]

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See detailOn the interpretation of the CH cometary spectrum
Arpigny, Claude ULg; Zeippen, C. J.; Klutz, M. et al

in Diversity and Similarity of Comets (1987)

A procedure to compute cometary spectra taking into account radiative processes and collisional effects is described. The populations of the rotational levels are determined by solving the statistical ... [more ▼]

A procedure to compute cometary spectra taking into account radiative processes and collisional effects is described. The populations of the rotational levels are determined by solving the statistical equilibrium equations at a certain number of locations within the coma (which can be modelled with n(R), T(R), v(R) laws) and the emerging intensity is then evaluated by integrating the emissions along the line of sight. Such a program was applied to the CH radical. The importance of collisions in exciting the lower rotational levels of CH is confirmed. [less ▲]

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See detailGeometry of the mass-outflows around broad absorption line QSOs and formation of the complex Ly-alpha + N V line profile
Surdej, Jean ULg; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1987), 177

The possibility that the observed broad absorption line (BAL) profiles are formed in spherically symmetric atmospheres is investigated, and it is found that BAL and non-BAL QSOs form two distinct classes ... [more ▼]

The possibility that the observed broad absorption line (BAL) profiles are formed in spherically symmetric atmospheres is investigated, and it is found that BAL and non-BAL QSOs form two distinct classes of quasars. It is shown that the small residual intensity and large equivalent width noted for some absorption troughs may be reproduced by the resonance scattering of line photons across spherically symmetric BAL regions. N V emission strength is found to be higher in the spectrum of BAL QSOs than in that of non-BAL QSOs. Good agreement between theory and the observed attenuation of the Ly-alpha emission line, the observed enhancement of the N V emission strength, and the possible presence of a shoulderlike feature in the red wing of the N V emission profile is obtained. [less ▲]

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See detailLong-slit pre and postperihelion spectrography of Comet P/Halley
Arpigny, Claude ULg; Dossin, F.; Zucconi, J. M. et al

in ESLAB Symposium on the Exploration of Halley's Comet (1986, December 01)

A series of about forty long-slit spectra of Halley's comet has been secured in the optical wavelength region, using different instruments, at resolution ranging from 0.05 to 1.6 nm. The interval of ... [more ▼]

A series of about forty long-slit spectra of Halley's comet has been secured in the optical wavelength region, using different instruments, at resolution ranging from 0.05 to 1.6 nm. The interval of heliocentric distance r covered by these observations is 1.7 to 0.9 a.u. before perihelion, while r = 0.95 a.u. after perihelion. The main characteristics of the pre-perihelion spectra are described. In particular, some emissions due to the OH[SUP]+[/SUP] (0,1) and CH[SUP]+[/SUP](1,0) bands have been detected for the first time. [less ▲]

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See detailDetermination of mass-loss rates of planetary nebulae nuclei using the first order moment of P Cygni line profiles.
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Comptes rendus sur les Journées de Strasbourg, 8ème réunion - Les Nébuleuses Planétaires (1986)

The authors conclude that the mass-loss rates of planetary nebulae nuclei derived by Cerruti-Sola, Perinotto (1985) have been systematically underestimated by one or nearly two orders of magnitude.

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See detailRadial velocities along the light curve of the peculiar emission-line star GG Carinae
Gosset, Eric ULg; Hutsemekers, Damien ULg; Swings, Jean-Pierre ULg et al

in Astronomy and Astrophysics (1985), 153

Measurements of the radial velocities of several emission and absorption lines in a large series of high dispersion spectra of the peculiar emission-line object GG Carinae are combined with the ... [more ▼]

Measurements of the radial velocities of several emission and absorption lines in a large series of high dispersion spectra of the peculiar emission-line object GG Carinae are combined with the photometric data described by Gosset et al. (1984) in an attempt to derive constraints on a qualitative physical model of this peculiar, and most probably binary, object. Previously unreported spectral features are the double absorption components of the Balmer lines and the He I absorption lines appearing around phase phi = 0.45 of the 31.02 day period deduced from the radial velocity curve. [less ▲]

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See detailThe structure and spectral characteristics of the low-excitation planetary nebula HD 316248
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Astronomy and Astrophysics (1985), 153

Analysis of two medium dispersion (39 Å/mm) optical spectra of the compact planetary nebula HD 316248 is reported here. When compared with observations collected in 1968 - 70, the authors' data obtained ... [more ▼]

Analysis of two medium dispersion (39 Å/mm) optical spectra of the compact planetary nebula HD 316248 is reported here. When compared with observations collected in 1968 - 70, the authors' data obtained in 1978 reveal a net increase of the [O III] lambdalambda4959, 5007 line intensities. Furthermore, despite showing unusual emission lines due to [Ti III], the low-excitation spectrum of HD 316248 presents striking similarities with that of a typical H II region. Direct plates taken through broad-band and interference filters at the prime focus of the ESO 3.6 m telescope clearly show that HD 316248 is an elongated (d â 4arcsec.4) and diffuse object as seen in the light of Halpha. [less ▲]

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See detailCPD - 59 deg 2857 - A new red variable star
Gosset, Eric ULg; Hutsemekers, Damien ULg; Surdej, Jean ULg

in Publications of the Astronomical Society of the Pacific [=PASP] (1985), 97

Two (C3 and C4) of the four comparison stars monitored during the photometric study of the peculiar emission-line star GG Car (Gosset et al., 1984) have been found to be variable. Available photometric ... [more ▼]

Two (C3 and C4) of the four comparison stars monitored during the photometric study of the peculiar emission-line star GG Car (Gosset et al., 1984) have been found to be variable. Available photometric and spectroscopic data allow us to identify C4 with CPD - 59 deg 2857 and classify it as a late-type giant (M3-4 III) belonging to the red variable stars of the semiregular or irregular type. [less ▲]

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