References of "Hutsemekers, Damien"
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See detailMicrolensing of the broad line region in 17 lensed quasars
Sluse, D.; Hutsemekers, Damien ULg; Courbin, F. et al

in Astronomy and Astrophysics (2012), 544

When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting ... [more ▼]

When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting region. Chromatic changes are expected to be observed in the continuum while the emission lines should be deformed as a function of the size, geometry and kinematics of the regions from which they originate. Microlensing of the emission lines has been reported only in a handful of systems so far. In this paper we search for microlensing deformations of the optical spectra of pairs of images in 17 lensed quasars with bolometric luminosities between 10[SUP]44.7 - 47.4[/SUP] erg/s and black hole masses 10[SUP]7.6 - 9.8[/SUP] M[SUB]&sun;[/SUB]. This sample is composed of 13 pairs of previously unpublished spectra and four pairs of spectra from literature. Our analysis is based on a simple spectral decomposition technique which allows us to isolate the microlensed fraction of the flux independently of a detailed modeling of the quasar emission lines. Using this technique, we detect microlensing of the continuum in 85% of the systems. Among them, 80% show microlensing of the broad emission lines. Focusing on the most common emission lines in our spectra (C III] and Mg II) we detect microlensing of either the blue or the red wing, or of both wings with the same amplitude. This observation implies that the broad line region is not in general spherically symmetric. In addition, the frequent detection of microlensing of the blue and red wings independently but not simultaneously with a different amplitude, does not support existing microlensing simulations of a biconical outflow. Our analysis also provides the intrinsic flux ratio between the lensed images and the magnitude of the microlensing affecting the continuum. These two quantities are particularly relevant for the determination of the fraction of matter in clumpy form in galaxies and for the detection of dark matter substructures via the identification of flux ratio anomalies. Based on observations made with the ESO-VLT Unit Telescope # 2 Kueyen (Cerro Paranal, Chile; Proposals 074.A-0563, 075.A-0377, 077.A-0155, PI: G. Meylan).Figure 1 and the new spectra presented in this paper are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A62">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A62</A> and via the German virtual observatory <A href="http://dc.g-vo.org/mlqso/q/web/form">http://dc.g-vo.org/mlqso/q/web/form</A>Appendices are available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailNew polarimetric constraints on axion-like particles
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Journal of Cosmology and Astroparticle Physics [= JCAP] (2012), 1207

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical ... [more ▼]

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical circular polarisation and from the distribution of linear polarisations of quasars. As an outlook, this technique can be improved by the observation of objects located behind clusters of galaxies, using upcoming space-borne X-ray polarimeters. [less ▲]

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See detailSpectra of 13 lensed quasars (Sluse+, 2012)
Sluse, D.; Hutsemekers, Damien ULg; Courbin, F. et al

Textual, factual or bibliographical database (2012)

Extracted flux calibrated spectra of 13 lensed quasars following the methodology described in Sect. 2.1. of the oaoer. The data were obtained with the FORS spectrograph at VLT in multi-object spectroscopy ... [more ▼]

Extracted flux calibrated spectra of 13 lensed quasars following the methodology described in Sect. 2.1. of the oaoer. The data were obtained with the FORS spectrograph at VLT in multi-object spectroscopy mode. The typical wavelength coverage is from 4200 to 8200Å. The data concern the following objects: HE0047-1756 (HE0047), Q0142-100 (Q0142), SDSSJ0246-0825 (SDSS0246), HE0435-1223 (HE0435), SDSSJ0806+2006 (SDSS0806), FBQ0951+2635 (FBQ0951), BRI0952-0115 (BRI0952), SDSSJ1138+0314 (J1138), J1226-0006 (J1226), SDSSJ1335+0118 (J1335), Q1355-2257 (Q1355), WFI2033-4723 (WFI2033), and HE2149-2745 (HE2149). For each object, we provide the 1D flux calibrated spectrum of the 2 individual images in the slit. In addition, we also provide the 2D reduced spectrum and corresponding 1σ error frame (corresponding files are named "objectname[SUB]data" and "objectname[/SUB]err"), and the 2D processed spectra associated to the deconvolution, as shown in Fig.1 of the paper. These processed 2D spectra are the deconvolved frame ("[SUB]dec"), the extended component of the flux emission ("[/SUB]ext") and the residual frame in σ units ("_res") corresponding to panel (b), (c) and (d) of Fig.1. A pdf file file similar to Fig.1 is also provided for each object. (4 data files). [less ▲]

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See detailEjecta around evolved massive stars observed with Herschel
Vamvatira-Nakou, Chloi ULg; Hutsemekers, Damien ULg; Royer, P. et al

Conference (2012, March)

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See detailThe first X-ray survey of Galactic Luminous Blue Variables
Nazé, Yaël ULg; Rauw, Grégor ULg; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (2012), 538

Aims: The X-ray emission of massive stars has been studied when these objects are in their main-sequence phase, as well as in their Wolf-Rayet phase. However, the X-ray properties of the transitional ... [more ▼]

Aims: The X-ray emission of massive stars has been studied when these objects are in their main-sequence phase, as well as in their Wolf-Rayet phase. However, the X-ray properties of the transitional Luminous Blue Variable (LBV) phase remain unknown. Methods: Using a dedicated but limited XMM survey as well as archival XMM and Chandra observations, we performed the first X-ray survey of LBVs: about half of the known LBVs or candidate LBVs are studied. Results: Apart from the well known X-ray sources eta Car and Cyg OB2 #12, four additional LBVs are detected in this survey, though some doubt remains on the association with the X-ray source for two of these. For the other LBVs, upper limits on the flux were derived, down to $\log[L_{\rm X}/L_{\rm BOL}]-9.4$ for PCyg. This variety in the strength of the X-ray emission is discussed, with particular emphasis on the potential influence of binarity. [less ▲]

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See detailNew constraints on very light pseudoscalars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Zioutas, K. (Ed.) 7th Patras Workshop on Axions, WIMPs and WISPs (2012, January 01)

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on ... [more ▼]

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on these particles using polarisation and, in particular, the polarisation differences observed between different quasar classes. [less ▲]

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See detailProbing the inner structure of distant AGNs with gravitational lensing
Sluse, D.; Hutsemekers, Damien ULg; Courbin, F. et al

in Proceedings of Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation. Proceedings of Science, PoS (Seyfert 2012) 057 (2012)

Microlensing is a powerful technique which can be used to study the continuum and the broad line emitting regions in distant AGNs. After a brief description of the methods and required data, we present ... [more ▼]

Microlensing is a powerful technique which can be used to study the continuum and the broad line emitting regions in distant AGNs. After a brief description of the methods and required data, we present recent applications of this technique. We show that microlensing allows one to measure the temperature profile of the accretion disc, estimate the size and study the geometry of the region emitting the broad emission lines. [less ▲]

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See detailThe C2-hydrocarbon link in cometary comae
Weiler, M.; Bockelée-Morvan, D.; Hutsemekers, Damien ULg et al

in EPSC Abstract 2012 (2012)

Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the ... [more ▼]

Comet 8P/Tuttle was the target of an ESO multiwavelength observing campaign in 2008. Observations of the spatial distribution of C2 and C3 were obtained, as well as simultaneous direct detections of the C2 parent species C2H2 and C2H6. We combine these observations to investigate the origin of cometary C2. The observed C2 column densities are inconsistent with a production of C2 from C2H2, C2H6, and C3. Based on a photochemical model, we quantitatively discuss the influence of further potential C2 parent species. The assumption of C4H2 as an additional C2 parent species in comet 8P/Tuttle provides the best explanation for the observed C2 column densities. [less ▲]

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See detailA Search For 15NH2 Lines In Comet C/2002 T7 (LINEAR)
Rousselot, Philippe; Pirali, O.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2012), 44

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an ... [more ▼]

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an interesting tracer, because of its variability among various solar system bodies. So far it has only been measured in bright comets through optical observations of the CN radical (Arpigny et al., 2003; Manfroid et al., 2009) and millimeter observations of HCN (Bockelée-Morvan et al., 2005, 2008). The measurements give for both species the same non-terrestrial isotopic composition ([SUP]14[/SUP]N/[SUP]15[/SUP]N≈150 in comets versus 272 in the Earth atmosphere), but HCN and CN are minor species. In order to get a determination of this ratio in another molecule we have searched for [SUP]15[/SUP]NH[SUB]2[/SUB] lines in a high-resolution and high signal-to-noise ratio spectrum of comet C/2002 T7 (LINEAR) obtained with the UVES spectrometer at the VLT ESO 8-m telescope (Hutsemékers et al., 2008). This work is based on a new laboratory experiment conducted with the AILES beamline spectrometer at synchrotron SOLEIL to determine the [SUP]15[/SUP]NH[SUB]2[/SUB] wavelengths by Fourier transform spectroscopy. We will present the first results obtained from these data, which have allowed to search for the first time [SUP]15[/SUP]NH[SUB]2[/SUB] emission lines in a comet. References: Arpigny et al., 2003, Science, 301, 1522 Bockelée-Morvan et al.,2005, in Comets II, ed. M. C. Festou, H. U. Keller, & H. A. Weaver (Tucson: Univ. Arizona Press), 391 Bockelée-Morvan et al., 2008, ApJ, 679, L49 Hutsemékers et al., 2008, A&A 490, L31 Manfroid et al., 2009, A&A 503, 613 [less ▲]

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See detailFifty Years of Quasars. Quasars Classes and Their Relationships
D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W. et al

in D'Onofrio, M. (Ed.) Fifty Years of Quasars: From Early Observations and Ideas to Future Research (2012)

Most of the questions in this chapter deal with sources that do not show the "classical" broad emission-line spectrum that characterizes the majority of known AGNs at high and low redshift. If that ... [more ▼]

Most of the questions in this chapter deal with sources that do not show the "classical" broad emission-line spectrum that characterizes the majority of known AGNs at high and low redshift. If that majority represents a "parent population" of AGNs, is the apparent absence of broad lines a result of obscuration, orientation, or different physical conditions? Can all of the subclasses be unified under the AGN umbrella? With the unification scheme set in place and assumed to be fundamentally correct, there are at least four overarching questions: do all type-2 AGNs possess an obscured broad-line region? Or how can we distinguishing type-2 AGNs without a broad-line region if they exist? Where is the low end of quasar activity? The least luminous AGNs are the so-called low-ionization nuclear emission-line regions (LINERs), but it is legitimate to ask if they are all true AGNs. [less ▲]

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See detailFifty Years of Quasars. From Observations to Physical Parameters
D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W. et al

in D'Onofrio, M. (Ed.) Fifty Years of Quasars: From Early Observations and Ideas to Future Research (2012)

Observational measures of AGNs allow us to directly infer some basic physical properties of quasars including (1) physical conditions and chemical abundances in the broad-line emitting gas as well as (2 ... [more ▼]

Observational measures of AGNs allow us to directly infer some basic physical properties of quasars including (1) physical conditions and chemical abundances in the broad-line emitting gas as well as (2) radius of the line-emitting region, (3) black hole mass, (4) and Eddington ratio. In this chapter, we seek information on how these quantities are measured. One of the surprises of recent times, that would have shocked the discoverers in the 1960s are the large BH masses and high chemical abundances inferred for even some of the highest redshift quasars known. [less ▲]

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See detailLarge-Scale Alignments of Quasar Polarization Vectors: Evidence at Cosmological Scales for Very Light Pseudoscalar Particles Mixing with Photons ?
Hutsemekers, Damien ULg; Payez, Alexandre ULg; Cabanac, R et al

in Bastien, Pierre (Ed.) Astronomical Polarimetry 2008: Science from Small to Large Telescopes. ASPC 449 (2011, November 01)

Based on a sample of 355 quasars with significant optical polarization, we found that quasar polarization vectors are not randomly oriented over the sky as naturally expected. The probability that the ... [more ▼]

Based on a sample of 355 quasars with significant optical polarization, we found that quasar polarization vectors are not randomly oriented over the sky as naturally expected. The probability that the observed distribution of polarization angles is due to chance is lower than 0.1%. The polarization vectors of the light from quasars are aligned although the sources span huge regions of the sky (˜ 1 Gpc). Groups of quasars located along similar lines of sight but at different redshifts (typically z ≍ 0.5 and z ≍ 1.5) are characterized by different preferred directions of polarization. These characteristics make the observed alignment effect difficult to explain in terms of a local contamination by interstellar polarization in our Galaxy. Interpreted in terms of a cosmological-size effect, we show that the dichroism and birefringence predicted by a mixing between photons and very light pseudoscalar particles within a magnetic field can qualitatively reproduce the observations. We find that circular polarization measurements could help constrain this mechanism. [less ▲]

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See detailNew Insights into the Quasar Type 1/Type 2 Dichotomy from Correlations between Quasar Host Orientation and Polarization
Borguet, Benoît ULg; Hutsemekers, Damien ULg; Letawe, Géraldine ULg et al

in Bastien, Pierre (Ed.) Astronomical Polarimetry 2008: Science from Small to Large Telescopes. ASPC 449 (2011, November 01)

We investigate correlations between the direction of the optical linear polarization and the orientation of the host galaxy/extended emission for type 1 and type 2 radio-loud and radio-quiet quasars. We ... [more ▼]

We investigate correlations between the direction of the optical linear polarization and the orientation of the host galaxy/extended emission for type 1 and type 2 radio-loud and radio-quiet quasars. We have used high resolution Hubble Space Telescope data and a deconvolution process to obtain a good determination of the host galaxy/extended emission (EE) position angle. With these new measurements and a compilation of data from the literature, we find a significant correlation, different for type 1 and type 2 objects, between the linear polarization position angle and the orientation of the EE, suggesting scattering by an extended UV/blue region in both types of objects. Our observations support the extension of the Unification Model to the higher luminosity AGNs like the quasars, assuming a two component scattering model. [less ▲]

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See detailCan axionlike particles explain the alignments of the polarizations of light from quasars?
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Physical Review. D : Particles and Fields (2011), 84

The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation ... [more ▼]

The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation. We introduce a more general wave-packet formalism and show that, although decoherence effects between waves of different frequencies can reduce significantly the amount of circular polarisation, the axion-like particle hypothesis is disfavoured given the bandwidth with which part of the observations were performed. Finally, we show that a more sophisticated model of extragalactic fields does not lead to an alignment of polarisations. [less ▲]

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See detailTRAPPIST: TRAnsiting Planets and PlanetesImals Small Telescope
Jehin, Emmanuel ULg; Gillon, Michaël ULg; Queloz, D. et al

in The Messenger (2011), 145

TRAPPIST is a 60-cm robotic telescope that was installed in April 2010 at the ESO La Silla Observatory. The project is led by the Astrophysics and Image Processing group (AIP) at the Department of ... [more ▼]

TRAPPIST is a 60-cm robotic telescope that was installed in April 2010 at the ESO La Silla Observatory. The project is led by the Astrophysics and Image Processing group (AIP) at the Department of Astrophysics, Geophysics and Oceanography (AGO) of the University of Liège, in close collaboration with the Geneva Observatory, and has been funded by the Belgian Fund for Scientific Research (F.R.S.-FNRS) and the Swiss National Science Foundation (SNF). It is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. We describe here the goals of the project and the hardware and present some results obtained during the first six months of operation. [less ▲]

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See detailEPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
Meech, K. J.; A'Hearn, M. F.; Adams, J. A. et al

in Astrophysical Journal (2011), 734(Letters), 11-9

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible ... [more ▼]

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO[SUB]2[/SUB]-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. [less ▲]

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See detailZooming into the broad line region of the gravitationally lensed quasar Q2237+0305 = the Einstein Cross: III. Determination of the size and structure of the CIV and CIII] emitting regions using microlensing
Sluse, D.; Schmidt, R.; Courbin, F. et al

in Astronomy and Astrophysics (2011), 528

Aims: We aim to use microlensing taking place in the lensed quasar Q2237+0305 to study the structure of the broad line region and measure the size of the region emitting the CIV and CIII] lines. Methods ... [more ▼]

Aims: We aim to use microlensing taking place in the lensed quasar Q2237+0305 to study the structure of the broad line region and measure the size of the region emitting the CIV and CIII] lines. Methods: Based on 39 spectrophotometric monitoring data points obtained between Oct. 2004 and Dec. 2007, we derive lightcurves for the CIV and CIII] emission lines. We use three different techniques to analyse the microlensing signal. Different components of the lines (narrow, broad and very broad) are identified and studied. We build a library of simulated microlensing lightcurves which reproduce the signal observed in the continuum and in the lines provided only the source size is changed. A Bayesian analysis scheme is then developed to derive the size of the various components of the BLR. Results: 1. The half-light radius of the region emitting the CIV line is found to be R_CIV ~ 66^{+110}_{-46} lt-days = 0.06^{+0.09}_{-0.04} pc = 1.7^{+2.8}_{-1.1} 10^17 cm (at 68.3% CI). Similar values are obtained for CIII]. Relative sizes of the V-band continuum and of the carbon line emitting regions are also derived with median values of R(line)/R(cont) in the range [4,29], depending of the FWHM of the line component. 2. The size of the CIV emitting region agrees with the Radius-Luminosity relationship derived from reverberation mapping. Using the virial theorem we derive the mass of the black hole in Q2237+0305 to be M_BH ~ 10^{8.3+/-0.3} M_sun. 3. We find that the CIV and CIII] lines are produced in at least 2 spatially distinct regions, the most compact one giving rise to the broadest component of the line. The broad and narrow line profiles are slightly different for CIV and CIII]. 4. Our analysis suggests a different structure of the CIV and FeII+III emitting regions, with the latter being produced in the inner part of the BLR or in a less extended emitting region than CIV. [less ▲]

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See detailOrtho-to-para Abundance Ratio (OPR) of Ammonia in 15 Comets: OPRs of Ammonia Versus 14N/15N Ratios in CN
Shinnaka, Yoshiharu; Kawakita, Hideyo; Kobayashi, Hitomi et al

in Astrophysical Journal (2011), 729

The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one of the primordial characteristics of cometary ices. We present OPRs of ammonia (NH[SUB]3[/SUB]) in 15 comets based on ... [more ▼]

The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one of the primordial characteristics of cometary ices. We present OPRs of ammonia (NH[SUB]3[/SUB]) in 15 comets based on optical high-dispersion spectroscopic observations of NH[SUB]2[/SUB], which is a photodissociation product of ammonia in the gaseous coma. The observations were mainly carried out with the VLT/UVES. The OPR of ammonia is estimated from the OPR of NH[SUB]2[/SUB] based on the observations of the NH[SUB]2[/SUB] (0, 9, 0) vibronic band. The absorption lines by the telluric atmosphere are corrected and the cometary C[SUB]2[/SUB] emission lines blended with NH[SUB]2[/SUB] lines are removed in our analysis. The ammonia OPRs show a cluster between 1.1 and 1.2 (this corresponds to a nuclear spin temperature of ~30 K) for all comets in our sample except for 73P/Schwassmann-Wachmann 3 (73P/SW3). Comet 73P/SW3 (both B- and C-fragments) shows the OPR of ammonia consistent with nuclear spin statistical weight ratio (1.0) that indicates a high-temperature limit as nuclear spin temperature. We compared the ammonia OPRs with other properties ([SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN, D/H ratios of water, and mixing ratios of volatiles). Comet 73P/SW3 is clearly different from the other comets in the plot of ammonia OPRs versus [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN. The ammonia OPRs of 1.0 and lower [SUP]15[/SUP]N-fractionation of CN in comet 73P/SW3 imply that icy materials in this comet formed under warmer conditions than other comets. Comets may be classified into two groups in the plot of ammonia OPRs against [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN. [less ▲]

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