References of "Hutsemekers, Damien"
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See detailA dusty nebula around the luminous blue variable candidate HD 168625
Hutsemekers, Damien ULg; van Drom, E.; Gosset, Eric ULg et al

in Astronomy and Astrophysics (1994), 290

On the basis of narrow-band visible and near-infrared imagery as well as high-resolution spectroscopy, we report the discovery of a new LBV-type nebula around the B supergiant HD 168625. We find that it ... [more ▼]

On the basis of narrow-band visible and near-infrared imagery as well as high-resolution spectroscopy, we report the discovery of a new LBV-type nebula around the B supergiant HD 168625. We find that it essentially consists of a dusty expanding shell from which seems to emerge a bipolar emission nebula, the whole embedded in a reflection nebulosity. The inner shell is stratified: the continuum emission arises beyond the ionized gas, and is possibly due to scattering of stellar light by large dust grains or to non-equilibrium dust emission. The unexpected presence of unidentified infrared emission bands (UIRs) in the spectrum of this object is also discussed. We finally report the non-detection of a comparable nebula around the nearby LBV HD 168607. [less ▲]

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See detailThe use of gravitational microlensing to scan the structure of BAL QSOs
Hutsemekers, Damien ULg; Surdej, Jean ULg; van Drom, E.

in Astrophysics & Space Science (1994), 216

Approximately 10% of the quasi-stellar objects (QSOs) show broad absorption lines (BAL) in their spectra which, if interpreted in terms of Doppler velocities, reveal the presence of high velocity gas ... [more ▼]

Approximately 10% of the quasi-stellar objects (QSOs) show broad absorption lines (BAL) in their spectra which, if interpreted in terms of Doppler velocities, reveal the presence of high velocity gas outflows. One of these BAL QSOs is known to be gravitationally lensed. It therefore constitutes a good candidate to search for microlensing effects, i.e., the selective amplification of different line forming regions. Considering current models for the BAL region, we have investigated the effects of moving microlenses on the line profiles, and we conclude that these effects strongly depend on the adopted model. A regular spectroscopic monitoring of lensed BAL QSOs would therefore be highly valuable to distinguish between the various models proposed so far to interpret the origin of broad absorption lines. [less ▲]

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See detailEvidence for violent ejection of nebulae from massive stars
Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1994), 281(Letters), 81-84

We report the results of a systematic search for nebulae around Luminous Blue Variable LBVs) and the discovery of a strong correlation between the mass of the nebulae and the luminosity of the central ... [more ▼]

We report the results of a systematic search for nebulae around Luminous Blue Variable LBVs) and the discovery of a strong correlation between the mass of the nebulae and the luminosity of the central stars. This correlation holds for both the dust and ionized gas masses of the nebulae. The existence of a 'nebular mass-stellar luminosity' relation and the fact that not all LBVs are presently associated with a nebula give evidence against a continuous mass-loss mechanism for the formation of these nebulae. Further, the good agreement found between the observed relation and predictions by Maeder (1989), suggests that all these nebulae may be due to a violent ejection of matter caused by an instability of structural origin. [less ▲]

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See detailSelective gravitational microlensing and line profile variations in the BAL quasar H 1413+117
Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1993), 280

In order to interpret the spectral differences observed between the four images of the gravitationally lensed broad absorption line (BAL) quasar H 1413+117, we have investigated the effect on the line ... [more ▼]

In order to interpret the spectral differences observed between the four images of the gravitationally lensed broad absorption line (BAL) quasar H 1413+117, we have investigated the effect on the line profiles of the selective magnification of individual BAL clouds by gravitational microlenses. Since microlenses magnify both the selected cloud and the whole BAL region, this effect is only differential, and general constraints on its capability to produce spectral variations have been derived. Considering simple but realistic models for the microlenses, we find that the selective magnification of a relatively large optically thick BAL cloud can be at the origin of the spectral differences reported between the components of H 1413+117. However, a very precise configuration is needed: the magnified cloud must be at the border of the BAL region which must itself partially lie in a region of strong de-magnification. The fine tuning of the parameters mecessary to reproduce the observations either seriously questions this kind of interpretation or puts strong constraints on the lensing models. Another interpretation of the observed line profile differences in terms of effects due to microlensing is also briefly discussed. [less ▲]

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See detailFormation of P Cygni Line Profiles in Relativistically Expanding Atmospheres. II. The Effect of the Continuum Frequency Shape and Limb Darkening of the Core
Hutsemekers, Damien ULg

in Astrophysical Journal (1993), 417

Abstract image available at: http://adsabs.harvard.edu/abs/1993ApJ...417...97H

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See detailGravitational lensing statistics based on a large sample of highly luminous quasars
Surdej, Jean ULg; Claeskens, Jean-François ULg; Crampton, D. et al

in Astronomical Journal (The) (1993), 105

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported. The objects were directly imaged, either from the ground under optimal seeing conditions, or ... [more ▼]

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported. The objects were directly imaged, either from the ground under optimal seeing conditions, or using the HST. We have derived values for the effectiveness parameter F of galaxies, modeled by means of singular isothermal spheres, to produce macrolensed images of distant quasars, and upper limits on the density parameter Omega(L) of compact objects with masses between 10 exp 10 and 10 exp 12 solar masses. Adopting H(0)= 50 km/s/Mpc, Omega(0)= 1, and Lambda = 0, we find that at the 99.7 percent confidence level, F is between 0.005 and 0.478 and that Omega(L) is less than 0.02. A critical discussion of these results is presented. Finally, comparing the efficiencies of ground-based and space instruments used to search for gravitational lens systems among highly luminous quasars, we conclude that for the near future, ground-based direct imaging characterized by a good dynamical range still constitutes the best observational strategy. [less ▲]

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See detailErratum - Q:1208+1011 - the Most Distant Multiply Imaged Quasar or a Binary
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in Astronomy and Astrophysics (1993), 272

In the title of this Letter, the word "multiply" was accidentally omitted. The correct title is shown above.

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See detailGalaxies statistics around highly luminous quasars: the ESO Sample
van Drom, E.; Surdej, Jean ULg; Magain, Pierre ULg et al

in Surdej, Jean; Fraipont-Caro, Denise; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in the Universe" (1993)

We present observational evidence on the correlation between the positions of Highly Luminous Quasars and those of galaxies for a sample of 136 objects, observed under good seeing conditions.

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See detailCan micro-lensing effects help to distinguish between the models for the BAL region of QSOs?
Hutsemekers, Damien ULg; Surdej, Jean ULg; van Drom, E.

in Surdej, Jean; Fraipont-Caro, D.; Gosset, Eric (Eds.) et al Liege International Astrophysical Colloquia, Gravitational Lenses in the Universe (1993)

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See detailThe relative photometric lightcurve of UM673 A&B
Daulie, G.; Hainaut, O.; Hutsemekers, Damien ULg et al

in Surdej, Jean; Fraipont-Caro, Denise; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in (1993)

From 1987 to 1993, we have carried out at ESO a photometric monitoring of the gravitationally lensed quasar UM673. The main result is that the two lensed images of UM673 did not show any significant ... [more ▼]

From 1987 to 1993, we have carried out at ESO a photometric monitoring of the gravitationally lensed quasar UM673. The main result is that the two lensed images of UM673 did not show any significant relative variation during more than five years. [less ▲]

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See detailThe cloverleaf quasar H1413+117: a preliminary light curve
Arnould, P.; Remy, M.; Gosset, Eric ULg et al

in Surdej, Jean; Fraipont-Caro, Denise; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in the Universe" (1993)

The cloverleaf quasar H1413+117 was discovered to be a gravitational lens system in 1988. Since then, it has been photometrically monitored essentially as part of the ESO key-program Gravitational lensing ... [more ▼]

The cloverleaf quasar H1413+117 was discovered to be a gravitational lens system in 1988. Since then, it has been photometrically monitored essentially as part of the ESO key-program Gravitational lensing: we present here a first preliminary lightcurve for its four individual images. [less ▲]

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See detailSearch for gravitational lenses in a large sample of highly luminous quasars and statistical determination of cosmological parameters
Claeskens, Jean-François ULg; Crampton, D.; Filippenko, A. V. et al

in Surdej, Jean; Fraipont-Caro, D.; Gosset, Eric (Eds.) et al The proceedings of the 31st Liège International Astrophysical Colloquium "Gravitational lenses in the Universe" (1993)

Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported.

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See detailESO key programme, gravitational lensing: quasars and radio galaxies; a status report
Surdej, Jean ULg; Angonin, M. C.; Arnaud, J. et al

in Distribution of Matter in the Universe (1992, December 01)

The scientific background and objectives of our ESO Key Programme are first recalled. A brief account of our research activities (observing runs at ESO and elsewhere, meetings, etc.) is then given ... [more ▼]

The scientific background and objectives of our ESO Key Programme are first recalled. A brief account of our research activities (observing runs at ESO and elsewhere, meetings, etc.) is then given. Preliminary scientific results are presented concerning 1) our observational database for highly luminous quasars and distant powerful radiogalaxies; 2) speckle observations of highly luminous quasars; 3) the photometric monitoring and 4) detailed studies of several known gravitational lenses; 5) optical observations of 3C and 4C radio galaxies and 6) of the well known Einstein ring MG 1131+0456. [less ▲]

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See detailThe new gravitational lens candidate Q 1208+1011 and the importance of high quality data.
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in The Messenger (1992), 67

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See detailQ 1208 + 1011 - The most distant imaged quasar, or a binary?
Magain, Pierre ULg; Surdej, Jean ULg; Vanderriest, C. et al

in Astronomy and Astrophysics (1992), 253(Letters), 13-16

The paper reports the discovery of a new gravitational lens candidate: the high redshift (z = 3.803) and highly luminous (V = 17.5, M[SUB]V[/SUB] = -30.3) quasar Q 1208 + 1011. As derived from the ... [more ▼]

The paper reports the discovery of a new gravitational lens candidate: the high redshift (z = 3.803) and highly luminous (V = 17.5, M[SUB]V[/SUB] = -30.3) quasar Q 1208 + 1011. As derived from the analysis of direct CCD frames taken with the ESO/MPI 2.2 m telescope, this multiple quasar consists of two pointlike images, separated by 0.45 arcsec and characterized by a brightness ratio of 3.5, in red light. Existing spectroscopic data support the gravitational lens interpretation for this system but cannot exclude the hypothesis of a binary quasar. In the former case, the spectrum suggests that, if the metallic absorption line system reported by Steidel (1990) at a redshift z = 2.9157 is associated with the deflector, the mass of the lens should be of the order of M = 7.8 x 10 exp 11 solar masses. Evaluation of a recent HST PC frame obtained for Q 1208 + 1011 within the snapshot survey for gravitational lenses confirms the above results. [less ▲]

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See detailSearch for gravitational lensing in a sample of highly luminous quasars
Magain, Pierre ULg; Hutsemekers, Damien ULg; Surdej, Jean ULg et al

in Kayser, R.; Schramm, T.; Nieser, L. (Eds.) Proceedings of the Hamburg conference on ’Gravitational Lenses’, Lecture Notes in Physics 406 (1992)

The status of the ESO survey for gravitational lensing among highly luminous quasars (HLQs) is briefly reviewed. The statistics of lensing, both concerning the multiple images and the associations of ... [more ▼]

The status of the ESO survey for gravitational lensing among highly luminous quasars (HLQs) is briefly reviewed. The statistics of lensing, both concerning the multiple images and the associations of galaxies with quasars, are examined. We find a significant overdensity of galaxies very close to the line-of-sight to the HLQs. We also report the discovery of a new multiply lensed quasar candidate. [less ▲]

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See detailGravitational lensing statistics based on a large sample of highly luminous quasars observed with ground-based telescopes and HST
Surdej, Jean ULg; Claeskens, Jean-François ULg; Crampton, D. et al

in Benvenuti, Piero; Schreier, Ethan J (Eds.) Proceedings of a ST-ECF/STScI Workshop "Science with the Hubble Space Telescope" (1992)

We present here some recent results on gravitational lensing statistics as applied to a sample of 470 highly luminous quasars.

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See detailOptical observations of gravitational lenses
Surdej, Jean ULg; Claeskens, Jean-François ULg; Hutsemekers, Damien ULg et al

in Kayser, Rainer; Schramm, Thomas; Nieser, Lars (Eds.) Proceedings of the Hamburg conference on ’Gravitational Lenses’, Lecture Notes in Physics 406 (1992)

We report here on some of the major developments achieved on optical observations of gravitational lenses since the last conference devoted to 'Gravitational Lensing'.

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See detailDeformation of P Cygni line profiles by gravitational microlensing effects
Hutsemekers, Damien ULg; Surdej, Jean ULg; Vandrom, E.

in Kayser, R.; Schramm, T.; Nieser, L. (Eds.) Gravitational Lenses, Lecture Notes in Physics, volume 406 (1992)

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See detailUnusual solar halos over La Silla
Hutsemekers, Damien ULg

in The Messenger (1991), 66

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