References of "Hutsemekers, Damien"
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See detailSpectropolarimetry of the iron low ionization broad absorption line quasar Q 0059-2735
Lamy, H.; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (2000), 356(Letters), 9-12

We present optical (ultraviolet rest-frame) spectropolarimetric observations of the rare iron low ionization broad absorption line (BAL) QSO Q 0059-2735. The continuum polarization increases to the blue ... [more ▼]

We present optical (ultraviolet rest-frame) spectropolarimetric observations of the rare iron low ionization broad absorption line (BAL) QSO Q 0059-2735. The continuum polarization increases to the blue with a regular rotation of the polarization position angle, suggesting that at least two mechanisms are at the origin of the polarization. There is also some evidence for dilution by a ion {Fe}{ii} pseudo-continuum in emission. In the broad absorption lines, the polarization strongly rises, with the largest values ever reported. On the contrary, the ion {Fe}{ii} blends in absorption are not more polarized than the continuum, while they are clearly visible in the polarized flux. These different polarization properties of ion {Fe}{ii} absorption lines suggest a different origin and/or geometry. The observed properties of Q 0059-2735 are consistent with a hybrid QSO / starburst model. Based on observations collected at the European Southern Observatory, La Silla, Chile [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 detailOptical Polarization of 47 QSOs (Lamy+, 2000)
Lamy, H.; Hutsemekers, Damien ULg

Textual, factual or bibliographical database (2000)

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. (2 data files).

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See detailErratum : A procedure for deriving accurate linear polarimetric measurements
Lamy, H.; Hutsemekers, Damien ULg

in The Messenger (1999), 97

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See detailThe orientation within the Galaxy and the Large Magellanic Cloud of nebulae ejected by massive stars
Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1999), 344

The orientation of nebulae ejected by massive stars (Luminous Blue Variables, WR stars, SN1987A) is investigated with respect to the structure of the galaxy to which they belong. In the Galaxy, we find ... [more ▼]

The orientation of nebulae ejected by massive stars (Luminous Blue Variables, WR stars, SN1987A) is investigated with respect to the structure of the galaxy to which they belong. In the Galaxy, we find that the projected long axes of the nebulae most often align with the galactic plane, and then also with the galactic magnetic field. This alignment is statistically significant. In addition, a few nebulae are apparently oriented perpendicular to the galactic plane. In the Large Magellanic Cloud, the nebular axes are found to closely follow the spiral magnetic field. With different inclinations, the Galaxy and the Large Magellanic Cloud probably offer complementary views of the same phenomenon. Although the sample studied thus far is small and the statistics limited, these results suggest that the orientation of massive star ejecta depends on galactic magnetic fields. Since the nebular axes are apparently correlated to the symmetry axes of the stars themselves, and since, in the early evolutionary stages, alignments of accretion disk axes with the interstellar magnetic field have been reported, it is argued that the observed alignment effect results from the star formation process. Based in part on observations collected at the European Southern Observatory (ESO, La Silla) [less ▲]

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See detailPolarimetry and Spectropolarimetry of a Sample of Broad Absorption Line Quasars
Lamy, H.; Hutsemekers, Damien ULg

in Structure and Kinematics of Quasar Broad Line Regions. ASPC 175 (1999)

Optical polarimetric and spectropolarimetric observations of a sample of broad absorption line QSOs were recently carried out with the 3.6m telescope and EFOSC1 in La Silla, Chile. Some preliminary ... [more ▼]

Optical polarimetric and spectropolarimetric observations of a sample of broad absorption line QSOs were recently carried out with the 3.6m telescope and EFOSC1 in La Silla, Chile. Some preliminary results are presented here with emphasis on interesting correlations between polarization and other quantities characterizing the optical spectra of the objects. [less ▲]

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See detailA procedure for deriving accurate linear polarimetric measurements.
Lamy, H.; Hutsemekers, Damien ULg

in The Messenger (1999), 96

The authors present here a procedure written within the ESO MIDAS reduction package with the aim of deriving semi-automatically linear polarisation data from CCD images obtained with beam-splitters such ... [more ▼]

The authors present here a procedure written within the ESO MIDAS reduction package with the aim of deriving semi-automatically linear polarisation data from CCD images obtained with beam-splitters such as those available at the ESO 3.6-m telescope equipped with EFOSC2 or at the VLT equipped with FORS1. The method is adequate for point-like objects and was used for measuring quasar polarisation. [less ▲]

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See detailPolarization properties of a sample of broad absorption line and gravitationally lensed quasars
Hutsemekers, Damien ULg; Lamy, H.; Remy, M.

in Astronomy and Astrophysics (1998), 340

New broad-band linear polarization measurements have been obtained for a sample of 42 optically selected QSOs including 29 broad absorption line (BAL) QSOs. The polarization properties of different sub ... [more ▼]

New broad-band linear polarization measurements have been obtained for a sample of 42 optically selected QSOs including 29 broad absorption line (BAL) QSOs. The polarization properties of different sub-classes have been compared, and possible correlations with various spectral indices searched for. The main results of our study are: (1) Nearly all highly polarized QSOs of our sample belong to the sub-class of BAL QSOs with low-ionization absorption features (LIBAL QSOs). (2) The range of polarization is significantly larger for LIBAL QSOs than for high-ionization (HI) BAL QSOs and non-BAL QSOs. (3) There is some indication that HIBAL QSOs as a class may be more polarized than non-BAL QSOs and therefore intermediate between LIBAL and non-BAL QSOs, but the statistics are not compelling from the sample surveyed thus far. (4) For LIBAL QSOs, the continuum polarization appears significantly correlated with the line profile detachment index, in the sense that LIBAL QSOs with P Cygni-type profiles are more polarized. No correlation was found with the strength of the low- or the high-ionization absorption features, nor with the strength or the width of the emission lines. These results are consistent with a scenario in which LIBAL QSOs constitute a different class of radio-quiet QSOs with more absorbing material and more dust. Higher maximum polarization can therefore be reached, while the actually measured polarization depends on the geometry and orientation of the system as do the line profiles. The observed correlation is interpreted within the framework of recent ``wind-from-disk'' models. Tables~2 and 3 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}\fnmsep\thanks{Based on observations collected at the European Southern Observatory (ESO, La Silla) [less ▲]

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See detailQuasar polarization (Hutsemekers+ 1998)
Hutsemekers, Damien ULg; Lamy, H.; Remy, Marc

Textual, factual or bibliographical database (1998)

Table 2 contains optical (V) polarimetric measurements for 42 optically selected QSOs including 29 broad absorption line QSOs. Table 3 contains a series of spectral indices characterizing the broad ... [more ▼]

Table 2 contains optical (V) polarimetric measurements for 42 optically selected QSOs including 29 broad absorption line QSOs. Table 3 contains a series of spectral indices characterizing the broad absorption line QSOs. (2 data files). [less ▲]

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See detailEvidence for very large-scale coherent orientations of quasar polarization vectors
Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1998), 332

On the basis of a new sample of quasar optical polarization measurements, we have found that, in a region of the sky, the quasar polarization vectors are not randomly oriented as naturally expected, but ... [more ▼]

On the basis of a new sample of quasar optical polarization measurements, we have found that, in a region of the sky, the quasar polarization vectors are not randomly oriented as naturally expected, but appear concentrated around one preferential direction. In order to verify this surprising although preliminary result, we have compiled a large sample of quasar polarization measurements from the literature. With quite severe criteria to eliminate at best the contamination by our Galaxy, a sample of 170 quasars with good quality polarization measurements has been defined. Maps in redshift slices reveal a few regions where the polarization vectors are apparently aligned. To handle the problem more quantitatively, non-parametric 3D statistical tests were designed, as well as a method for visualizing spatially the results. The significance is evaluated through Monte-Carlo simulations. Applied to our sample of 170 polarized quasars, two different statistical tests provide evidence, with significance levels of 0.005 and 0.015 respectively, that the optical polarization vectors of quasars are not randomly distributed over the sky but are coherently oriented on very large spatial scales. This orientation effect appears spatially delimited in the 3D Universe, mainly occuring in a few groups of 10-20 objects. The polarization vectors of objects located along the same line of sight but at different redshifts do not appear accordingly aligned. Essentially for this reason, instrumental bias and contamination by interstellar polarization in our Galaxy are unlikely to be responsible for the observed effect. The very large scale at which this local orientation effect is observed indicates the presence of correlations in objects or fields on spatial scales ~ 1000 h(-1) Mpc at redshifts z =~ 1-2, suggesting an effect of cosmological importance. Several possible and testable interpretations are discussed. Tables~2 and 3 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 detailProduction and kinematics of sodium atoms in the coma of comet Hale-Bopp
Arpigny, Claude ULg; Rauer, H.; Manfroid, Jean ULg et al

in Astronomy and Astrophysics (1998), 334(Letters), 53-56

High-resolution spectra of sodium D line emission in comet Hale-Bopp (C/1995 O1) were obtained at the Observatoire de Haute-Provence, France, on 25-27 March and on 15-17 April, 1997. The observations have ... [more ▼]

High-resolution spectra of sodium D line emission in comet Hale-Bopp (C/1995 O1) were obtained at the Observatoire de Haute-Provence, France, on 25-27 March and on 15-17 April, 1997. The observations have been used to measure the velocity of sodium atoms in the coma within 2 10(5) km from the nucleus. A comparison between the March and April data provides an illustration of the influence of the heliocentric radial velocity on the strength of the fluorescence (Swings effect), and on the velocity of Na atoms achieved by solar radiation pressure acceleration. Evidence for the presence of a distributed source in the coma is found from the relatively high tailward velocities on the sunward side of the coma, in addition to the sunward extent of sodium emission up to 1.4 10(5) km in April. Based on observations secured at OHP (France) [less ▲]

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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 detailQuasar polarization (Hutsemekers 1998)
Hutsemekers, Damien ULg

Textual, factual or bibliographical database (1997)

The table contains optical polarization data for a sample of 170 moderate to high-redshift quasars (1 data file).

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See detailOn the Production and Kinematics of Sodium Atoms in the Head of Comet Hale-Bopp
Rauer, H.; Arpigny, Claude ULg; Hutsemekers, Damien ULg et al

in Bulletin of the American Astronomical Society (1997, July 01), 29

The interpretation of the presence and extent of the atomic sodium observed in comet Hale-Bopp raises a number of questions related to the production, motion, and lifetime of these Na atoms under the ... [more ▼]

The interpretation of the presence and extent of the atomic sodium observed in comet Hale-Bopp raises a number of questions related to the production, motion, and lifetime of these Na atoms under the action of the solar radiation near 1 AU. Here we report on data which pertain to the study of sodium in the head of the comet, yielding information on the Na emission in the coma out to ~ 0.15 x 10(6) km on the sunward side, to ~ 0.2 x 10(6) km tailwards. The observations were carried out at the Observatoire de Haute-Provence, with the 1.93 m telescope and the ELODIE spectrometer, which is fed by a pair of optical fibers with 2-arcsec apertures separated by 1.8 arcmin. In particular, spectra were obtained on 15-17 April, 1997, near the discovery date of the sodium tail at the La Palma Observatory. These spectra (resolution ~ 7 km/s) were used to determine Na D line profiles, as well as the relative intensities of the emissions corresponding to the two positions observed simultaneously. The main outcome of our first analysis concerns the profiles recorded some distance away from the optical centre, which all show velocity shifts and asymmetric line broadening in the direction of anti-sunward velocities. Some evidence is found to suggest the existence of an extended or multi-source production of sodium atoms, at least in the coma. Another series of spectra secured just before perihelion, 25-27 March, was analysed in the same way as the April spectra. Comparison between the two sets of data provides a nice illustration of the marked influence of the heliocentric radial velocity, not only upon the strength of the fluorescence ("Swings effect"), but also upon the motion of the emitting atoms, which are accelerated by the radiation pressure to widely different degrees as their excitation wavelengths fall at different places within the Fraunhofer Na D line profiles. [less ▲]

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See detailSub-arcsecond imaging and spectroscopy of the radio-loud highly polarized quasar PKS 1610-771.
Courbin, F.; Hutsemekers, Damien ULg; Meylan, G. et al

in Astronomy and Astrophysics (1997), 317

We report on imaging and spectroscopic observations of the radio-loud, highly polarized quasar PKS 1610-771 (z=1.71). Our long-slit spectroscopy of the companion 4.55" NW of the quasar confirms the ... [more ▼]

We report on imaging and spectroscopic observations of the radio-loud, highly polarized quasar PKS 1610-771 (z=1.71). Our long-slit spectroscopy of the companion 4.55" NW of the quasar confirms the stellar nature of this object, so ruling out the previously suspected gravitationally lensed nature of this system. PKS 1610-771 looks fuzzy on our sub-arcsecond R and I images and appears located in a rich environment of faint galaxies. Possible magnification, without image splitting of the quasar itself, by some of these maybe foreground galaxies cannot be excluded. The continuum fuzz (made of the closest two objects, viz. A and D) is elongated in a direction orthogonal to the E vector of the optical polarization, as in high-redshift radio-galaxies. The spectrum of PKS 1610-771 appears strongly curved, in a convex way, with a maximum of intensity at ~7,600Å (2,800AÅ rest frame), possibly indicating a strong ultraviolet absorption by dust. [less ▲]

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See detailDust in LBV-type Nebulae
Hutsemekers, Damien ULg

in Luminous Blue Variables: Massive Stars in Transition. ASPC 120 (1997)

Some systematic properties of dust in LBV-type nebulae are reviewed on the basis of the far-infrared thermal emission measured by the IRAS satellite, and the scattering of visible stellar light.

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See detailPKS 1610-771: a highly reddened quasar?
Courbin, F.; Hutsemekers, Damien ULg; Meylan, G. et al

in The Messenger (1996), 85

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See detailWR22: the most massive Wolf-Rayet star ever weighed.
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Gosset, Eric ULg et al

in Astronomy and Astrophysics (1996), 306

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the ... [more ▼]

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the orbit, formerly determined on the basis of photographic spectra. The high signal-to-noise ratio of our data also allows the detection of some weak absorption lines which, for the first time, can definitely be attributed to the companion. A study of their radial velocities gives a mass ratio of m_WR_/m_O_=2.78 leading to a minimum mass of 72M[SUB]sun[/SUB]_ for the WN7 star. The companion can be classified as a "late O" (O6.5-O8.5) star with a luminosity ratio of the system q=L_WR_^y^/L_O_^y^ at 5500A of about 8. The exceptionally high mass of the WN7 star and its high hydrogen mass-fraction suggest that WR22 is at the beginning of its Wolf-Rayet evolution. As a matter of fact, with such a high mass, WR22 most probably is still a hydrogen burning object. Therefore, the WN7 component is much closer to a main sequence O star with a "Wolf-Rayet clothing" than to the other members of the Wolf-Rayet family, which are rather highly evolved He-burning descendants of massive progenitors. [less ▲]

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See detailThe Clover Leaf Quasar H1413+117: New Photometric Light Curves
Remy, M.; Gosset, Eric ULg; Hutsemekers, Damien ULg et al

in Kochanek, C. S.; Hewitt, Jacqueline N (Eds.) Astrophysical applications of gravitational lensing: proceedings of the 173rd Symposium of the International Astronomical Union (1996)

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See detailSpectropolarimetry of WR66
Lamy, H.; Hutsemekers, Damien ULg; Rauw, Grégor ULg

in Wolf-Rayet stars in the framework of stellar evolution ; 33rd Liege International Astrophysical Coll (1996)

We have carried out spectropolarimetric observations of the Wolf-Rayet star WR66 (WN8) with EFOSC1 mounted on the ESO 3.6m telescope of La Silla. The results indicate a polarization level of about 5 to 6 ... [more ▼]

We have carried out spectropolarimetric observations of the Wolf-Rayet star WR66 (WN8) with EFOSC1 mounted on the ESO 3.6m telescope of La Silla. The results indicate a polarization level of about 5 to 6 % in the continuum which is most probably due to interstellar polarization. [less ▲]

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