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 ▲]Detailed reference viewed: 17 (2 ULg) Les observateurs - 04/2016Manfroid, Jean ; Ponsard, P.Article for general public (2016)Transit de Mercure devant le disque solaire - Les nuages terrestres : les cirrus - L’opposition de Mars de 2016Detailed reference viewed: 8 (0 ULg) L'astronomie dans le monde - 03/2016Manfroid, Jean in Ciel (Le) (2016), 78Disque proto-planétaire - Une galaxie vidée de son gaz - NGC 6240 - Le nuage de Smith - Une galaxie satellite de NGC 253 - V774104 - PlutonDetailed reference viewed: 18 (1 ULg) New and updated convex shape models of asteroids based on optical data from a large collaboration networkHanuš, J.; Ďurech, J.; Oszkiewicz, D. A. et alin Astronomy & Astrophysics (2016), 586Asteroid 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 ▲]Detailed reference viewed: 44 (12 ULg) L'astronomie dans le monde - 02/2016Manfroid, Jean 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 MarsDetailed reference viewed: 10 (0 ULg) L'astronomie dans le monde - 01/2016Manfroid, Jean 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 PandoreDetailed reference viewed: 7 (0 ULg) Long-term activity and outburst of comet C/2013 A1 (Siding Spring) from narrow-band photometry and long-slit spectroscopyOpitom, Cyrielle ; Guilbert-Lepoutre, A.; Jehin, Emmanuel et alin Astronomy and Astrophysics (2016), 589In this paper, we present a unique data set of more than one year's worth of regular observations of comet C/2013 A1(Siding Spring) with TRAPPIST in Chile, along with low-resolution spectra obtained with ... [more ▼]In this paper, we present a unique data set of more than one year's worth of regular observations of comet C/2013 A1(Siding Spring) with TRAPPIST in Chile, along with low-resolution spectra obtained with the ESO/VLT FORS 2 instrument. The comet made a close approach to Mars on October 19, 2014 and was then observed by many space and ground-based telescopes. We followed the evolution of the OH, NH, CN, $\mathrm{C_3}$, and $\mathrm{C_2}$ production rates as well as the $Af\rho$ parameter as a proxy for the dust production. We detected an outburst two weeks after perihelion, with gas and dust production rates being multiplied by a factor five within a few days. By modelling the shape of the CN and $\mathrm{C_2}$ radial profiles, we determined that the outburst happened around on November 10 around 15:30 UT ($\pm$ 5h) and measured a gas ejection velocity of $1.1\pm0.2$ km/s. We used a thermal evolution model to reproduce the activity pattern and outburst. Our results are consistent with the progressive formation of a dust mantle explaining the shallow dependence of gas production rates, which may be partially blown off during the outburst. We studied the evolution of gas composition, using various ratios such as CN/OH, $\mathrm{C_2}$/OH, or $\mathrm{C_3}$/OH, which showed little or no variation with heliocentric distance including at the time of the outburst. This indicates a relative level of homogeneity of the nucleus composition. [less ▲]Detailed reference viewed: 35 (11 ULg) An inversion method for cometary atmospheresHubert, Benoît ; Opitom, Cyrielle ; Hutsemekers, Damien et alin Icarus (2016), 277Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight. This integration is the so-called Abel transform of the local emission rate ... [more ▼]Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight. This integration is the so-called Abel transform of the local emission rate. The observation is generally interpreted under the hypothesis of spherical symmetry of the coma. Under that hypothesis, the Abel transform can be inverted. We derive a numerical inversion method adapted to cometary atmospheres using both analytical results and least squares fitting techniques. This method, derived under the usual hypothesis of spherical symmetry, allows us to retrieve the radial distribution of the emission rate of any unabsorbed emission, which is the fundamental, physically meaningful quantity governing the observation. A Tikhonov regularization technique is also applied to reduce the possibly deleterious effects of the noise present in the observation and to warrant that the problem remains well posed. Standard error propagation techniques are included in order to estimate the uncertainties affecting the retrieved emission rate. Several theoretical tests of the inversion techniques are carried out to show its validity and robustness. In particular, we show that the Abel inversion of real data is only weakly sensitive to an offset applied to the input flux, which implies that the method, applied to the study of a cometary atmosphere, is only weakly dependent on uncertainties on the sky background which has to be subtracted from the raw observations of the coma. We apply the method to observations of three different comets observed using the TRAPPIST telescope: 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 retrieved characteristic lengths can differ from those obtained from a direct least squares fitting over the observed flux of radiation, and that discrepancies can be reconciled for by correcting this flux by an offset (to which the inverse Abel transform is nearly not sensitive). The A1/Siding Spring observations were obtained very shortly after the comet produced an outburst, and 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 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, because the Abel transform produces a smoothing that blurs the signatures left by features present in the coma. 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 ▲]Detailed reference viewed: 39 (7 ULg) TRAPPIST photometry and imaging monitoring of comet C/2013 R1 (Lovejoy): Implications for the origin of daughter speciesOpitom, Cyrielle ; Jehin, Emmanuel ; Manfroid, Jean et alin Astronomy and Astrophysics (2015), 584We report the results of the narrow-band photometry and imaging monitoring of comet C/2013 R1 (Lovejoy) with the robotic telescope TRAPPIST (La Silla observatory). We gathered around 400 images over 8 ... [more ▼]We report the results of the narrow-band photometry and imaging monitoring of comet C/2013 R1 (Lovejoy) with the robotic telescope TRAPPIST (La Silla observatory). We gathered around 400 images over 8 months pre- and post-perihelion between September 12, 2013 and July 6, 2014. We followed the evolution of the OH, NH, CN, C[SUB]3[/SUB], and C[SUB]2[/SUB] production rates computed with the Haser model, as well as the evolution of the dust production. All five gas species display an asymmetry about perihelion, since the rate of brightening is steeper than the rate of fading. The study of the coma morphology reveals gas and dust jets that indicate one or several active zone(s) on the nucleus. The dust, C[SUB]2[/SUB], and C[SUB]3[/SUB] morphologies present some similarities, while the CN morphology is different. OH and NH are enhanced in the tail direction. The study of the evolution of the comet activity shows that the OH, NH, and C[SUB]2[/SUB] production rate evolution with the heliocentric distance is correlated to the dust evolution. The CN and, to a lesser extent, the C[SUB]3[/SUB] do not display such a correlation with the dust. This evidence and the comparison with parent species production rates indicate that C[SUB]2[/SUB] and C[SUB]3[/SUB], on one hand, and OH and NH, on the other, could be - at least partially - released from organic - rich grains and icy grains. On the contrary, all evidences point to HCN being the main parent of CN in this comet. [less ▲]Detailed reference viewed: 47 (10 ULg) Joyaux cosmiques - 12/2015Manfroid, Jean Article for general public (2015)NGC 3521 - Le Sac de Charbon - L’Univers jeuneDetailed reference viewed: 16 (0 ULg) L'astronomie dans le monde - 12/2015Manfroid, Jean Article for general public (2015)VFTS 352 - Une nouvelle composante de laVoie lactée - Érosion de l’atmosphère de Mars - Disque autour d’une naine blanche - Éruption du trou noir Mrk 335 - Comète 67P - Sucre et alcool cométaires ... [more ▼]VFTS 352 - Une nouvelle composante de laVoie lactée - Érosion de l’atmosphère de Mars - Disque autour d’une naine blanche - Éruption du trou noir Mrk 335 - Comète 67P - Sucre et alcool cométaires - Géantes rouges magnétiques [less ▲]Detailed reference viewed: 22 (1 ULg)