Publications of Jean Manfroid     Results 21-40 of 789.   1 2 3 4 5 6 7 8 9 10 11   L'astronomie dans le monde - 06/2017Manfroid, Jean Article for general public (2017)OMC-1 – LHS1140b – Comète 67P/Churyumov-Gerasimenko – Atmosphères – Cassini (suite) – Astéroïde 2014 JO25Detailed reference viewed: 6 (1 ULiège) Study of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic featuresDias-Oliveira, A.; Sicardy, B.; Ortiz, J. L. et alin The Astronomical Journal (2017), 154(1), 13We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 ... [more ▼]We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ$_{84}$, detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December 2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ$_{84}$'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semi axes $(470 \pm 20) \times (383 \pm 10) \times (245 \pm 8)$~km % axis ratios $b/a= 0.82 \pm 0.05$ and $c/a= 0.52 \pm 0.02$, can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75~h) and the amplitude of its rotation light curve, we derive a density $\rho=0.87 \pm 0.01$~g~cm$^{-3}$ a geometric albedo $p_V= 0.097 \pm 0.009$. A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003~AZ$_{84}$'s limb, that can be interpreted as an abrupt chasm of width $\sim 23$~km and depth $> 8$~km or a smooth depression of width $\sim 80$~km and depth $\sim 13$~km (or an intermediate feature between those two extremes). [less ▲]Detailed reference viewed: 19 (5 ULiège) The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta missionSnodgrass, C.; A'Hearn, M. F.; Aceituno, F. et alin Philosophical Transactions : Mathematical, Physical & Engineering Sciences (2017), 375We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko ... [more ▼]We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively `well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. This article is part of the themed issue 'Cometary science after Rosetta'. [less ▲]Detailed reference viewed: 44 (4 ULiège) L'astronomie dans le monde - 05/2017Manfroid, Jean Article for general public (2017)matière sombre – Abell 2744 vu par ALMA – Bousculade dans Orion – Rotation stellaire – Tsunamis martiens – Planète X ou 9 – Formation d’étoiles dans les jets de trous noirs – Éjection d’un trou noirDetailed reference viewed: 8 (0 ULiège) Joyaux cosmiques - 05/2017Manfroid, Jean Article for general public (2017)NGC 7640 – NGC 1055 – N103BDetailed reference viewed: 7 (0 ULiège) Changements sur le noyau de 67P - 05/2017Manfroid, Jean Article for general public (2017)Detailed reference viewed: 9 (0 ULiège) Joyaux cosmiques - 04/2017Manfroid, Jean Article for general public (2017)Jupiter - La supernova du Grand NuageDetailed reference viewed: 6 (0 ULiège) L'astronomie dans le monde - 04/2017Manfroid, Jean Article for general public (2017)Molécules organiques sur Cérès – Jets bleus – Pulsar lointain – Comète 73P/Schwassmann-WachmannDetailed reference viewed: 8 (1 ULiège) Gas and dust production rates of comets 41P and 45P from TRAPPISTJehin, Emmanuel ; Opitom, Cyrielle; Moulane, Youssef et alPoster (2017, April)Detailed reference viewed: 12 (2 ULiège) Study of comets activity with the TRAPPIST-North telescopeMoulane, Youssef ; Jehin, Emmanuel ; Manfroid, Jean et alPoster (2017, April)TRAPPIST-North (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that was installed in May, 2016 at the Oukaimeden Observatory. The project is led by the University of ... [more ▼]TRAPPIST-North (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that was installed in May, 2016 at the Oukaimeden Observatory. The project is led by the University of Liège (Belgium) and the Caddi Ayad University of Marrakech (Morocco). TRAPPIST-North (TN) is a twin of TRAPPIST-South (TS) telescope which was installed at the ESO La Silla Observatory in 2010. The TRAPPIST telescopes are dedicated to the detection and characterization of planets orbiting stars other than our Sun (exoplanets) and the study of comets and other small bodies in our solar system. These telescopes have a very sensitive CCD camera with complete sets of cometary narrow band filters in order to measure the production rates of several gas species (OH, NH, CN, C3 and C2 ) and the dust. With TRAPPIST-North we can now also observe comets in the Northem hemisphere. Therefore, with the two telescopes, we can now observe continuously the comets around their orbit. We present in this work our strategy to study the evolution of the activity, chemical composition, dust properties, and coma morphology of several comets per year and of different origins over a wide range of heliocentric distances, and on both sides of perihelion. We will measure the production rates of each daughter molecules using a Haser model, in addition to the Afρ parameter to track the activity and the dust properties will be obtained through Monte Carlo models. We present the first measurements of the production rates and Afρ parameter of comet 41P/Tuttle-Giacobini-Kresak before perihelion (r=1.04 AU) and of comet 45P/Honda-Mrkos-Pajdusakova after perihelion (r=0.53 AU), that we observed with TRAPPIST telescopes. [less ▲]Detailed reference viewed: 15 (2 ULiège) L'astronomie dans le monde - 03/2017Manfroid, Jean Article for general public (2017)La Terre et la Lune vues depuis Mars - Pôle nord de Mars - Cérès - Alpha Centauri - Vortex - Vortex au Keck - Subaru - Le Soleil avec ALMA - Le repousseur dipolaireDetailed reference viewed: 10 (0 ULiège) Joyaux cosmiques - 03/2017Manfroid, Jean Article for general public (2017)Orion – NGC 6334 et 6357 - La nébuleuse de la Calebasse - L’Araignée rougeDetailed reference viewed: 6 (0 ULiège) Les observateurs - 03/2017Manfroid, Jean ; Ponsard, P.Article for general public (2017)À l’œil nu - Une autoroute pour satellites géostationnaires - Marathons MessierDetailed reference viewed: 13 (0 ULiège) Joyaux cosmiques - 02/2017Manfroid, Jean Article for general public (2017)NGC 248 - NGC 4449Detailed reference viewed: 10 (0 ULiège) L'astronomie dans le monde - 02/2017Manfroid, Jean Article for general public (2017)Matière noire - Supernova ASASSN-15lh - Tache sur Jupiter - Dioxyde de carbone - Araignées martiennes - Cassini (suite) - Cérès - Bételgeuse - Formation des galaxies - Mars humideDetailed reference viewed: 10 (0 ULiège) Rosetta, l'épilogue - 02/2017Manfroid, Jean Article for general public (2017)Detailed reference viewed: 9 (0 ULiège) Joyaux cosmiques - 01/2017Manfroid, Jean Article for general public (2017)Piliers et nébuleuses – NGC4696Detailed reference viewed: 11 (0 ULiège) L'astronomie dans le monde - 01/2017Manfroid, Jean Article for general public (2017)Disques protoplanétaires– Rondeur naturelle – Galaxie Toile d’Araignée – Les premiers résultats d’ExoMars – Biréfringence du videDetailed reference viewed: 6 (0 ULiège) Trappist-1 et les sept planètesManfroid, Jean ; Désamoré, LucArticle for general public (2017)Detailed reference viewed: 53 (4 ULiège) Observational signatures of past mass-exchange episodes in massive binaries: the case of LSS 3074Raucq, Françoise ; Gosset, Eric ; Rauw, Grégor et alin Astronomy and Astrophysics (2017), 601Context. The role of mass and momentum exchanges in close massive binaries is very important in the subsequent evolution of the components. Such exchanges produce several observational signatures such as ... [more ▼]Context. The role of mass and momentum exchanges in close massive binaries is very important in the subsequent evolution of the components. Such exchanges produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. Aims. We investigated these effects for the close O-star binary LSS 3074 (O4 f + O6-7:(f):), which is a good candidate for a past Roche lobe overflow (RLOF) episode because of its very short orbital period, P = 2.185 days, and the luminosity classes of both components. Methods.We determined a new orbital solution for the system. We studied the photometric light curves to determine the inclination of the orbit and Roche lobe filling factors of both stars. Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars.We then analysed the reconstructed primary and secondary spectra with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. Results. We confirm the apparent low stellar masses and radii reported in previous studies. We also find a strong overabundance in nitrogen and a strong carbon and oxygen depletion in both primary and secondary atmospheres, together with a strong enrichment in helium of the primary star. Conclusions. We propose several possible evolutionary pathways through a RLOF process to explain the current parameters of the system. We confirm that the system is apparently in overcontact configuration and has lost a significant portion of its mass to its surroundings. We suggest that some of the discrepancies between the spectroscopic and photometric properties of LSS 3074 could stem from the impact of a strong radiation pressure of the primary. [less ▲]Detailed reference viewed: 31 (10 ULiège)