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See detailWater, hydrogen cyanide, and dust production from the distant comet 29P/Scwassmann-Wachmann 1
Bockelee-Morvan, D.; Biver, N.; Opitom, Cyrielle ULg et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

Comet 29P/Schwassmann-Wachmann is a periodic comet, also classified as a Centaur, orbiting on a nearly circular orbit at 6 au from the Sun. It is well known for its permanent activity driven by CO ... [more ▼]

Comet 29P/Schwassmann-Wachmann is a periodic comet, also classified as a Centaur, orbiting on a nearly circular orbit at 6 au from the Sun. It is well known for its permanent activity driven by CO outgassing, and its episodic outbursts. Comet 29P was observed in 2010--2011 with the Herschel space observatory. Observations of water and ammonia were performed with the Heterodyne Instrument for the Far-Infrared (HIFI). One set of measurements was obtained two days after a major outburst (16 Apr. 2010). Images of the dust coma at 70 and 160 μ m were obtained using the Photodetector Array Camera and Spectrometer (PACS). To support these observations, observations of CO and HCN were undertaken at the 30-m telescope of the Institut de radioastronomie millimétrique (IRAM). We present an overview of this set of observations. H_2O and CO are detected. We also obtain the first detection of HCN in this distant comet. Relative abundances are similar to those measured in the coma of comet C/1995 O1 (Hale-Bopp) when at r_h = 6 au from the Sun, but strongly differ from coma compositions at r_h = 1 au. The line profiles show evidence that both H_2O, HCN are released from long-lived icy grains. Detailed modeling of water production from icy-grain suggests continuous release of icy grains from the nucleus. The thermal emission from the nucleus is detected in the PACS 70 μ m images. The thermal emission from dust grains is analyzed with a thermal model of dust emission, which takes into account the dust size distribution. Both the size index and the dust production rate are measured. [less ▲]

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See detailMicrolensing of the broad-line region in the quadruply imaged quasar HE0435-1223
Braibant, Lorraine ULg; Hutsemekers, Damien ULg; Sluse, Dominique ULg et al

in Astronomy and Astrophysics (2014), 565

Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223 acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope, we have detected a clear microlensing effect in ... [more ▼]

Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223 acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope, we have detected a clear microlensing effect in images A and D. While microlensing affects the blue and red wings of the Hα line profile in image D very differently, it de-magnifies the line core in image A. The combination of these different effects sets constraints on the line-emitting region; these constraints suggest that a rotating ring is at the origin of the Hα line. Visible spectra obtained in 2004 and 2012 indicate that the MgII line profile is microlensed in the same way as the Hα line. Our results therefore favour flattened geometries for the low-ionization line-emitting region, for example, a Keplerian disk. Biconical models cannot be ruled out but require more fine-tuning. Flux ratios between the different images are also derived and confirm flux anomalies with respect to estimates from lens models with smooth mass distributions. Based on observations made with the ESO-VLT, Paranal, Chile; Proposal 084.B-0013 (PI: Rix).Tables 2, 3 and Appendix A are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201423633/olm">http://www.aanda.org</A> [less ▲]

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See detailMeasurements of the 14N/15N isotopic ratio in comets's ammonia
Rousselot, P.; Pirali, O.; Jehin, Emmanuel ULg et al

Conference (2014, May)

La détermination des rapports isotopiques de l'azote dans les différents objets du système solaire est importante pour une bonne compréhension de leur origine. Les mesures du rapport 14N/15N faites jusqu ... [more ▼]

La détermination des rapports isotopiques de l'azote dans les différents objets du système solaire est importante pour une bonne compréhension de leur origine. Les mesures du rapport 14N/15N faites jusqu'à présent ont montré une grande dispersion des valeurs (de 50 à 441), tous les objets du système solaire excepté Jupiter apparaissant enrichis en 15N comparés à la nébuleuse protosolaire. Différentes explications ont été proposées pour expliquer les valeurs observées, qui sont complexes à interpréter car dues non seulement au réservoir d'origine de l'azote d'où provient l'objet étudié mais également à des mécanismes de fractionnement isotopique. Le cas des comètes, dans ce contexte, est intéressant, car leur composition est supposée relativement proche de celle de la nébuleuse protosolaire et la seule valeur disponible jusqu'à l'année dernière, avait été calculée à partir de la molécule HCN et du radical CN (issu du HCN). Ce rapport était d'environ 150, bien en dessous de la valeur mesurée dans l'atmosphère terrestre (272). Les comètes contiennent beaucoup d'azote sous forme de NH3, photodissocié en NH2 dont les raies sont nombreuses dans le spectre visible. Il était donc possible de mesurer le rapport 14N/15N dans l'ammoniac pour vérifier l'influence possible de phénomènes de fractionnement isotopique entre le HCN et le NH3, ceci à condition de connaître avec précision les longueurs d'onde des raies de 15NH2. Pour déterminer ces longueurs d'onde, nous avons mesuré le spectre d'émission de la transition Ã2A1~X2B1 de 14NH2 et 15NH2 dans la gamme spectrale 5700 Å – 6000 Å sur la ligne AILES du synchrotron SOLEIL, avec un spectromètre par transformée de Fourier. L'analyse de ces spectres a permis, au final, la détection du 15NH2 dans les spectres cométaires et la première détermination du rapport 14N/15N dans l'ammoniac des comètes. [less ▲]

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See detailThe XMM-Newton view of the yellow hypergiant IRC+10420 and its surroundings
De Becker, Michaël ULg; Hutsemekers, Damien ULg; Gosset, Eric ULg

in New Astronomy (2014), 29

Among evolved massive stars likely in transition to the Wolf-Rayet phase, IRC +10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by ... [more ▼]

Among evolved massive stars likely in transition to the Wolf-Rayet phase, IRC +10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by quite high mass loss episodes. Even though IRC+10420 benefited of many observations in several wavelength domains, it has never been a target for an X-ray observatory. We report here on the very first dedicated observation of IRC+10420 in X-rays, using the XMM-Newton satellite. Even though the target is not detected, we derive X-ray flux upper limits of the order of 1–3 ×10−14 erg cm−2 s−1 (between 0.3 and 10.0 keV), and we discuss the case of IRC+10420 in the framework of emission models likely to be adequate for such an object. Using the Optical/UV Monitor on board XMM-Newton, we present the very first upper limits of the flux density of IRC +10420 in the UV domain (between 1800 and 2250 Å and between 2050 and 2450 Å). Finally, we also report on the detection in this field of 10 X-ray and 7 UV point sources, and we briefly discuss their properties and potential counterparts at longer wavelengths. [less ▲]

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

Poster (2014, April)

C/2012 F6 (Lemmon) is a long period comet discovered by the Mount Lemmon Survey on 2012 March 23 at 5 AU from the sun. C/2012 F6 (Lemmon) reached perihelion on March 23, 2013 at 0.73 AU from the sun. In ... [more ▼]

C/2012 F6 (Lemmon) is a long period comet discovered by the Mount Lemmon Survey on 2012 March 23 at 5 AU from the sun. C/2012 F6 (Lemmon) reached perihelion on March 23, 2013 at 0.73 AU from the sun. In December 2012 the comet was unexpectedly bright, allowing us to make an extensive monitoring during several months with both broadband and narrowband filters to follow the evolution of the comet chemical composition. The monitoring was made with TRAPPIST robotic telescope installed at La Silla observatory [1]. TRAPPIST is a 60-cm telescope dedicated to the study of exoplanets and small bodies in the solar system. The telescope is equipped with a 2Kx2K FLI Proline CCD camera very sensitive in the blue and the red. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins B, V, Rc, and Ic filters. We observed the comet from December 11, 2012 to March 4, 2013 (pre-perihelion) and from April 29, 2013 to June 11, 2013 (post-perihelion). At least 2 or 3 observing runs per week were programmed during this period. We collected 1358 images on 52 nights. In January and February the comet visibility allowed us to make several long runs and to detect the comet rotational variability. From the comet images in narrowband filters we studied the gaseous coma chemical composition and activity by deriving OH, NH, CN, C2 and C3 production rates using a classical Haser model [3]. The production and properties of the dust component were studied through the observation of C/2012 F6 (Lemmon) with narrowband continuum filters at 344.2 nm (UC), 444.9 nm (BC), 525.7 nm (GC) and 713.0 nm (RC). We used A(θ)fρ [4] parameter as a proxy for the dust production. [less ▲]

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See detailLarge-scale alignments of quasar polarization vectors. Observational evidence and possible implications for cosmology and fundamental physics
Hutsemekers, Damien ULg

Scientific conference (2014, March 05)

Based on a sample of 355 quasars with significant optical linear polarization and using various statistical methods, we show that quasar polarization vectors are not randomly oriented over the sky with a ... [more ▼]

Based on a sample of 355 quasars with significant optical linear polarization and using various statistical methods, we show that quasar polarization vectors are not randomly oriented over the sky with a probability often in excess of 99.9%. The polarization vectors appear coherently aligned over huge regions of the sky (~1 Gpc), located at both low (z ~0.5) and high (z ~1.5) redshifts and characterized by different preferred directions of the polarization. These characteristics make the alignment effect difficult to explain in terms of contamination by instrumental or interstellar polarization in our Galaxy. We notice that the region of the sky where the alignments are prominent is not far from preferred directions tentatively identified in the Cosmic Microwave Background. Polarization alignments may thus reveal structures at scales beyond the homogeneity scale of concordance cosmology. Several interpretations are discussed. In particular, we show that the dichroism and birefringence predicted by photon pseudo-scalar oscillation along the line of sight cannot reproduce the observed properties of the alignments. Besides, accurate measurements of quasar circular polarization allow us to strongly constrain the parameter space of axion-like particles. [less ▲]

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See detailToward a Unique Nitrogen Isotopic Ratio in Cometary Ices
Rousselot, Philippe; Pirali, Olivier; Jehin, Emmanuel ULg et al

in Astrophysical Journal Letters (2014), 780

Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in ... [more ▼]

Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in comets due to the [SUP]15[/SUP]NH[SUB]2[/SUB] radical produced by the photodissociation of [SUP]15[/SUP]NH[SUB]3[/SUB]. Analysis of our data has permitted us to measure the [SUP]14[/SUP]N/[SUP]15[/SUP]N isotopic ratio in comets for a molecule carrying the amine (-NH) functional group. This ratio, within the error, appears similar to that measured in comets in the HCN molecule and the CN radical, and lower than the protosolar value, suggesting that N[SUB]2[/SUB] and NH[SUB]3[/SUB] result from the separation of nitrogen into two distinct reservoirs in the solar nebula. This ratio also appears similar to that measured in Titan's atmospheric N[SUB]2[/SUB], supporting the hypothesis that, if the latter is representative of its primordial value in NH[SUB]3[/SUB], these bodies were assembled from building blocks sharing a common formation location. [less ▲]

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See detailHerschel observations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun
de Val-Borro, M; Bockelée-Morvan, D; Jehin, Emmanuel ULg et al

in Astronomy and Astrophysics (2014), 564

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See detailNonthermal O(1S) and O(1D) populations in cometary atmospheres
Hubert, Benoît ULg; Bisikalo, D.V.; Shematovich, V.I. et al

Conference (2013, December)

Recent developments in the field of cometary science have motivated many studies dealing with the nucleus composition and mineralogy, and also with the photochemistry of the coma. In particular, ground ... [more ▼]

Recent developments in the field of cometary science have motivated many studies dealing with the nucleus composition and mineralogy, and also with the photochemistry of the coma. In particular, ground based observations have shown that the visible oxygen emissions at 557.7 and 630 nm, both belonging to the Rosetta-VIRTIS-M passband, present different line profiles, pointing to specific photochemical processes. In this work, we present a Monte Carlo simulation of the O(1D) and O(1S) photochemistry including photodissociation of H2O, CO2 and CO, quenching, collisional thermalization and radiative decay. The model solves Boltzmann's integro differential equation including sources and sinks, as well as a prescribed expansion velocity of the coma. The energy distribution functions (EDF's) of O(1S) and O(1D) are computed at cometocentric distances ranging between 10 and 5000 km. We find that the EDF's of both O(1D) and O(1S) are strongly nonthermal, up to a degree that sharply varies with cometocentric distance, as thermalization is less efficient when the density of the dominant species is reduced. It follows that the Doppler profile of the visible radiations emitted by both species is non-gaussian in a frame of reference moving with the expanding coma. The nonthermal volume emission rate is then integrated along a set of chosen line of sights, accounting for the explicit Doppler profiles derived from the EDF's as well as the expansion motion, and the Doppler profile of the full coma is computed. It appears that most of the line width is due to the expansion motion, although the detailed line shape remains sensitive to the nonthermal nature of the EDF's. Our computation can then be compared with the line profiles observed from the ground with the UVES spectrograph mounted on the ESO-VLT. [less ▲]

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See detailStudy of the Forbidden Oxygen Lines in Comets at Different Heliocentric and Nucleocentric Distances
Decock, Alice ULg; Rousselot, P.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2013, October 01), 45

Oxygen is an important element in the chemistry of the solar system objects given its abundance and its presence in many molecules including H2O 80% of cometary ices). The analysis of oxygen atoms in ... [more ▼]

Oxygen is an important element in the chemistry of the solar system objects given its abundance and its presence in many molecules including H2O 80% of cometary ices). The analysis of oxygen atoms in comets can provide information not only on the comets themselves but also on the solar system. These atoms have been analyzed using the 3 forbidden oxygen lines [OI] observed in emission in the optical region at 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the red lines) (Swings, 1962). Our analysis is based on a sample of 12 comets of various origins. The observing material is made of 53 high signal-to-noise spectra obtained with the high-resolution UVES spectrograph at the ESO VLT from 2002 to 2012 (Manfroid et al, 2009). After noticing that the green line is blended with one C2 line, we built synthetic spectra of C2 for each observing circumstances and we subtracted its contribution to the cometary spectra in order to ensure the decontamination of the 5577 Å line. Then, we measured the intensity of the 3 [OI] lines at different heliocentric distances. By comparing the green to red lines ratio (G/R) with the Bhardwaj & Raghuram (2012) effective excitation rates, we found that H2O is the main parent molecule when the comet is observed at 1 au. When the comet is located beyond 2.5 au from the Sun, CO2 also contributes to the production of oxygen. Studying forbidden oxygen lines could be a new way to estimate the abundances of CO2 in comets, a very difficult task from the ground (Decock et al. 2013). In order to estimate the effect of the quenching on our results, we analyzed the evolution of the G/R ratio at different nucleocentric distances. For nearby comets, we divided the extended 2D spectrum into several zones in order to analyze the oxygen lines as close as possible to the nucleus (down to ~10 km for the closest comets). Their analysis will allow us to study the link of the oxygen lines with the nucleocentric distance. We found a clear variation of the G/R ratio close to the comet nucleus that is in agreement with a contribution from CO2 as predicted by Raghuram & Bhardwaj (2013). [less ▲]

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See detailA Search For 15NH2 Emission Lines In Comets
Rousselot, Philippe; Pirali, O.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2013, October 01), 45

The determination of nitrogen isotopic ratios in solar system objects is important for a good understanding of their origin. The measurements of [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio done so far in ... [more ▼]

The determination of nitrogen isotopic ratios in solar system objects is important for a good understanding of their origin. The measurements of [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio done so far in various solar system objects and molecules have revealed a great diversity (from 50 to 441), all of them, except Jupiter, being enriched in [SUB]15[/SUB]N compared to the protosolar nebula. Different explanations have been proposed to explain this enrichement. One of them suggests that these differences reflect the different interstellar N reservoirs from which N-bearing molecules are originating (Hily-Blant et al., 2013). These authors, from observations of H[SUB]13[/SUB]CN and HC[SUB]15[/SUB]N in two prestellar cores, suggest that the molecules carrying the nitrile- (-CN) functional group would be more enriched in [SUB]15[/SUB]N than the molecules carrying the amine (-NH) functional group. Comets are interesting targets to test this theory because they contain both HCN and NH[SUP]3[/SUP] molecules. So far the [SUB]14[/SUB]N/[SUB]15[/SUB]N ratio has only been measured in CN (Arpigny et al., 2003; Manfroid et al., 2009) and HCN (Bockelée-Morvan et al., 2005, 2008) in comets, leading for both species to [SUB]14[/SUB]N/[SUB]15[/SUB]N ≈ 150. Our work aimed at measuring the [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio in NH[SUP]2[/SUP], which comes from NH[SUP]3[/SUP]. We have determined accurately the wavelengths of [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines with the AILES beamline spectrometer at synchrotron SOLEIL by Fourier transform spectroscopy. The analysis of this spectrum has permitted to extract the [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines wavelengths and to search for [SUB]15[/SUB]NH[SUP]2[/SUP] cometary emission lines. Thanks to a collection of spectra of 12 different comets obtained from 2002 to 2011 with the UVES spectrometer at the VLT ESO 8-m telescope (Manfroid et al., 2009), it has been possible to search for [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines with a high sensitivity. We will present the results obtained from these data. Arpigny et al., Science, 301, 1522-1525, 2003 Bockelée-Morvan et al., in Comets II, ed. M. C. Festou, H. U. Keller, & H. A. Weaver (Tucson: Univ. Arizona Press), 391-423, 2005 Bockelée-Morvan et al., ApJ, 679, L49-L52, 2008 Hily-Blant et al., Icarus 223, 582-590, 2013 Manfroid et al., A&A, 503, 613-624, 2009 [less ▲]

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See detailHerschel observations of nebulae ejected by massive evolved stars
Vamvatira-Nakou, Chloi ULg; Hutsemekers, Damien ULg; Royer, P. et al

Poster (2013, October)

We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of nebulae associated to massive evolved stars. The study of these nebulae is crucial to understand the evolution of ... [more ▼]

We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of nebulae associated to massive evolved stars. The study of these nebulae is crucial to understand the evolution of these stars as it can reveal the mass-loss history. The infrared images along with available data at other wavelengths give a complete view of their morphology. The dust modeling provides the dust parameters, such as the temperature, the mass and the composition of dust. The spectroscopic analysis provides the gas C,N,O abundances and mass. Based on these observations, the evolutionary status of the star at the time of the nebula ejection can be constrained. We present here selected results of an ongoing exhaustive study of nebulae around low- and high-luminosity LBVs (AG Car, HR Car, WRAY 15-751, G79.29+0.46, HD168625), WN stars (NGC6888, M1-67, He3-519) and Of stars (NGC6164/5). [less ▲]

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See detailComet dust profiles from PACS images obtained in the framework of the HSSO project
Opitom, Cyrielle ULg; Bockelée-Morvan, D.; Hutsemekers, Damien ULg et al

Poster (2013, October)

In the framework of the HssO project the Herschel PACS instrument acquired images of 7 comets between June 2010 and February 2013. Three of these comets have been imaged at several heliocentric distances ... [more ▼]

In the framework of the HssO project the Herschel PACS instrument acquired images of 7 comets between June 2010 and February 2013. Three of these comets have been imaged at several heliocentric distances allowing us to follow up the evolution of the dust coma . Radial profiles have been derived for each image. We measured flux densities at 70, 110 and 160 μm in order to determine the comet dust production rate. In some cases, after deconvolution by the instrumental PSF, we might have detected the nucleus signal in the central pixels. [less ▲]

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See detailAstrospheres of young and old stars
Cox, N.; Decin, L.; Marle, A.J. et al

Poster (2013, October)

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See detailYellow Hypergiant /Luminous Blue Variable
Cox, N. L. J.; Hutsemekers, Damien ULg; Vamvatira-Nakou, Chloi ULg

Poster (2013, October)

Hen3-1379 is a yellow hypergiant (YHG) with evidence for episodic non-quiescent mass-loss over in last 400-1000 years in this post-red supergiant (RSG) phase of its evolution. The observational evidence ... [more ▼]

Hen3-1379 is a yellow hypergiant (YHG) with evidence for episodic non-quiescent mass-loss over in last 400-1000 years in this post-red supergiant (RSG) phase of its evolution. The observational evidence suggests that though similar to the low-luminosity LBV Wray15-751, it has not yet moved to the hotter phase and is thus pre-LBV. This confirms the scenario of significant mass-loss during the RSG phase. [less ▲]

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See detailTRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope)
Jehin, Emmanuel ULg; Gillon, Michaël ULg; Opitom, Cyrielle ULg et al

in EPSC Abstract 2013 (2013, September 13), 8

TRAPPIST is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of ... [more ▼]

TRAPPIST is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) 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 hardware and the goals of the project and give an overview of the comet production rates monitoring after three years of operations. [less ▲]

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

Poster (2013, September 12)

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in EPSC Abstract 2013 (2013, September 12), 8

Comet C/2012 F6 is a long-period comet that reached perihelion on March 23, 2012. The unexpected brightness of this comet since December 2012 allowed us to obtain narrowband photometry and to study its ... [more ▼]

Comet C/2012 F6 is a long-period comet that reached perihelion on March 23, 2012. The unexpected brightness of this comet since December 2012 allowed us to obtain narrowband photometry and to study its chemical composition as well as its rotation. [less ▲]

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See detailStudy of the forbidden oxygen lines in comets at different heliocentric and nucleocentric distances
Decock, Alice ULg; Jehin, Emmanuel ULg; Rousselot, Philippe et al

in EPSC Abstract 2013 (2013, September 12), 8

Oxygen is an important element in the chemistry of the Solar System objects given its abundance and its presence in many molecules including H2O, which constitutes 80% of cometary ices. The analysis of ... [more ▼]

Oxygen is an important element in the chemistry of the Solar System objects given its abundance and its presence in many molecules including H2O, which constitutes 80% of cometary ices. The analysis of oxygen atoms in comets can provide information not only on the comets themselves but also on our Solar System. These atoms have been analyzed using the three forbidden oxygen lines [OI] observed in emission in the optical region at 5577 Å (the green line), 6300 Å and 6364 Å (the red lines) [1]. These lines are difficult to analyze because their detection requires high spectral and spatial resolutions. The oxygen analysis is interesting because it allows the determination of its parent molecules. [less ▲]

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