Publications of Jean Manfroid
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See detailAbel inversion method for cometary atmospheres.
Hubert, Benoît ULiege; Opitom, Cyrielle ULiege; Hutsemekers, Damien ULiege et al

in Geophysical Research Abstracts (2016, April 01), 18

Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight joining the observing instrument and the gas of the coma. This integration is ... [more ▼]

Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight joining the observing instrument and the gas of the coma. This integration is the so-called Abel transform of the local emission rate. We develop a method specifically adapted to the inversion of the Abel transform of cometary emissions, that retrieves the radial profile of the emission rate of any unabsorbed emission, under the hypothesis of spherical symmetry of the coma. The method uses weighted least squares fitting and analytical results. A Tikhonov regularization technique is applied to reduce the possible effects of noise and ill-conditioning, and standard error propagation techniques are implemented. Several theoretical tests of the inversion techniques are carried out to show its validity and robustness, and show that the method is only weakly dependent on any constant offset added to the data, which reduces the dependence of the retrieved emission rate on the background subtraction. We apply the method to observations of three different comets observed using the TRAPPIST instrument: 103P/ Hartley 2, F6/ Lemmon and A1/ Siding spring. We show that the method retrieves realistic emission rates, and that characteristic lengths and production rates can be derived from the emission rate for both CN and C2 molecules. We show that the emission rate derived from the observed flux of CN emission at 387 nm and from the C2 emission at 514.1 nm of comet Siding Spring both present an easily-identifiable shoulder that corresponds to the separation between pre- and post-outburst gas. As a general result, we show that diagnosing properties and features of the coma using the emission rate is easier than directly using the observed flux. We also determine the parameters of a Haser model fitting the inverted data and fitting the line-of-sight integrated observation, for which we provide the exact analytical expression of the line-of-sight integration of the Haser model. [less ▲]

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See detailDistant activity of 67P/Churyumov-Gerasimenko in 2014: Ground-based results during the Rosetta pre-landing phase
Snodgrass, Colin; Jehin, Emmanuel ULiege; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2016), 588

Context. As the ESA Rosetta mission approached, orbited, and sent a lander to comet 67P/Churyumov-Gerasimenko in 2014, a large campaign of ground-based observations also followed the comet. <BR /> Aims ... [more ▼]

Context. As the ESA Rosetta mission approached, orbited, and sent a lander to comet 67P/Churyumov-Gerasimenko in 2014, a large campaign of ground-based observations also followed the comet. <BR /> Aims: We constrain the total activity level of the comet by photometry and spectroscopy to place Rosetta results in context and to understand the large-scale structure of the comet's coma pre-perihelion. <BR /> Methods: We performed observations using a number of telescopes, but concentrate on results from the 8 m VLT and Gemini South telescopes in Chile. We use R-band imaging to measure the dust coma contribution to the comet's brightness and UV-visible spectroscopy to search for gas emissions, primarily using VLT/FORS. In addition we imaged the comet in near-infrared wavelengths (JHK) in late 2014 with Gemini-S/Flamingos-2. <BR /> Results: We find that the comet was already active in early 2014 at heliocentric distances beyond 4 au. The evolution of the total activity (measured by dust) followed previous predictions. No gas emissions were detected despite sensitive searches. <BR /> Conclusions: The comet maintains a similar level of activity from orbit to orbit, and is in that sense predictable, meaning that Rosetta results correspond to typical behaviour for this comet. The gas production (for CN at least) is highly asymmetric with respect to perihelion, as our upper limits are below the measured production rates for similar distances post-perihelion in previous orbits. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 592.C-0924, 093.C-0593, 094.C-0054, and at Gemini South under GS-2014B-Q-15 and GS-2014B-Q-76. [less ▲]

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See detailJoyaux cosmiques - 04/2016
Manfroid, Jean ULiege

Article for general public (2016)

ATLASGAL - IC 2631 - RCW 106

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See detailL'astronomie dans le monde - 04/2016
Manfroid, Jean ULiege

Article for general public (2016)

Planète X - Poussièresprésolaires - Vesta - Chondrites - La glace des comètes - Les « marais salants » de Titan - FRB - Ondes gravitationnelles - Rovers martiens - Mars - Record de distance - Répartition ... [more ▼]

Planète X - Poussièresprésolaires - Vesta - Chondrites - La glace des comètes - Les « marais salants » de Titan - FRB - Ondes gravitationnelles - Rovers martiens - Mars - Record de distance - Répartition des galaxies [less ▲]

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See detailLes observateurs - 04/2016
Manfroid, Jean ULiege; Ponsard, P.

Article for general public (2016)

Transit de Mercure devant le disque solaire - Les nuages terrestres : les cirrus - L’opposition de Mars de 2016

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See detailL'astronomie dans le monde - 03/2016
Manfroid, Jean ULiege

in Ciel (Le) (2016), 78

Disque proto-planétaire - Une galaxie vidée de son gaz - NGC 6240 - Le nuage de Smith - Une galaxie satellite de NGC 253 - V774104 - Pluton

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See detailPremière observation d’ondes gravitationnelles - 03/2016
Manfroid, Jean ULiege

Article for general public (2016)

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See detailUne nouvelle neuvième planète ? - 03/2016
Manfroid, Jean ULiege

Article for general public (2016)

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See detailJoyaux cosmiques - 03/2016
Manfroid, Jean ULiege

Article for general public (2016)

L’amas Trumpler 14 - IC 1613 - NGC 4889

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See detailNew and updated convex shape models of asteroids based on optical data from a large collaboration network
Hanuš, J.; Ďurech, J.; Oszkiewicz, D. A. et al

in Astronomy and Astrophysics (2016), 586

Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. This amount already provided a deep insight into physical ... [more ▼]

Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. This amount already provided a deep insight into physical properties of main-belt asteroids or large collisional families. We aim to increase the number of asteroid shape models and rotation states. Such results are an important input for various further studies such as analysis of asteroid physical properties in different populations, including smaller collisional families, thermophysical modeling, and scaling shape models by disk-resolved images, or stellar occultation data. This provides, in combination with known masses, bulk density estimates, but constrains also theoretical collisional and evolutional models of the Solar System. We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as an input for the convex inversion method, and derive 3D shape models of asteroids, together with their rotation periods and orientations of rotation axes. The key ingredient is the support of more that one hundred observers who submit their optical data to publicly available databases. We present updated shape models for 36 asteroids, for which mass estimates are currently available in the literature or their masses will be most likely determined from their gravitational influence on smaller bodies, which orbital deflection will be observed by the ESA Gaia astrometric mission. This was achieved by using additional optical data from recent apparitions for the shape optimization. Moreover, we also present new shape model determinations for 250 asteroids, including 13 Hungarias and 3 near-Earth asteroids. [less ▲]

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See detailJoyaux cosmiques - 02/2016
Manfroid, Jean ULiege

Article for general public (2016)

La Lune - IDCS J1426 - HH24

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See detailL'astronomie dans le monde - 02/2016
Manfroid, Jean ULiege

Article for general public (2016)

Disques proto-planétaires - Ondes de proue - Supernova Refsdal - M31 - Êta Carinae - Trapèze d’Orion - Le quasar W2246-0526 - Lune - Les ravines de Mars

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See detailCuriosity dans les dunes - 02/2016
Manfroid, Jean ULiege

Article for general public (2016)

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See detailJoyaux cosmiques - 01/2016
Manfroid, Jean ULiege

Article for general public (2016)

NGC 5291 - Sh2-310 et NGC 2362 - Tayna

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See detailNew Horizons - 01/2016
Manfroid, Jean ULiege

Article for general public (2016)

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See detailL'astronomie dans le monde - 01/2016
Manfroid, Jean ULiege

Article for general public (2016)

Couleurs d’une comète- Premières galaxies - Détection du premier pulsar gamma extragalactique - VY Canis Majoris - Le ciel bleu de GJ3470b - HD 106906b - L’amas Pandore

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See detailL'astronomie dans le monde - 05/2016
Manfroid, Jean ULiege

Article for general public (2016)

FRB - Comète 67P - Titan - Mars - G1.9+0.3 - La Lune et le champ magnétique terrestre - Alignements - Trou noir record- Sucre cométaire

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See detailJoyaux cosmiques - 10/2016
Manfroid, Jean ULiege

Article for general public (2016)

Jupiter – M42

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See detailBibliographie - Nous avons lu pour vous - 09/2016
Manfroid, Jean ULiege

in Ciel (Le) (2016), 78

Vous êtes ici - Ce que vous découvririez de la Terre si vous étiez un cosmonaute (Chris Hadfield) ; Les secrets du ciel – dix savants racontent les secrets du cosmos (Mathieu Vidard) ; 45 Years of Heck in ... [more ▼]

Vous êtes ici - Ce que vous découvririez de la Terre si vous étiez un cosmonaute (Chris Hadfield) ; Les secrets du ciel – dix savants racontent les secrets du cosmos (Mathieu Vidard) ; 45 Years of Heck in Professional Astronomy (Joe Hube) [less ▲]

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See detailJoyaux cosmiques - 11/2016
Manfroid, Jean ULiege

Article for general public (2016)

M1 – M18

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