491 research outputs found
Améliorations des positions des étoiles Hipparcos per l'utilisation des observations 'star-mapper'
No full textSolar System data mining for Gaia and ground-based observational support
No full textInternational audienceThe Gaia mission will observe between 2.5 and 3x105 Solar System objects. Most of them will be asteroids. As described elsewhere (Cellino et al. 2007, Tanga et al. 2007, Mignard et al. 2008) Gaia will provide a complete dynamical and physical characterisation of these bodies, that has no comparisons with the datasets ever obtained by a single groundor spacebased telescope. In fact, high precision astrometry, flux measurements and spectra will be available in an homogeneous set of data. However, in order to fully exploit the scientific potential of the data, a dedicated processing structure is needed. For this reason, a specific data reduction and analysis pipeline is under development. Some aspects of the implementation require solving interesting challenges in Solar System dynamics, consisting in new and more complex formulations of classic problems. We discuss, in particular, the determination of asteroid masses and the measurement of non-gravitational forces. Also, we show that - in the case of Solar System objects - the high astrometric accuracy of Gaia cannot completely rule out the use of ground-based data for increasing the extent of the final mission products. Well planned and focused preand post-mission observational campaigns could thus greatly help to reach goals situated at the edge (or beyond) the reach of Gaia observations alone. References Cellino, A., Tanga, P., Dell'Oro, A., Hestroffer, D. 2007. Asteroid science with Gaia: Sizes, spin properties, overall shapes and taxonomy. Adv. Space Res. 40 (2), 202-208 Mignard, F.,Cellino, A., Muinonen, K., Tanga, P., Delbo, D., Dell'Oro, A., Granvik, M., Hestroffer, D., Mouret, S., Thuillot, W., Virtanen, J. 2008. The Gaia mission: expected applications to asteroid science. Earth Moon and Planets, in press Tanga, P., Hestroffer, D., Cellino, A., Mignard, F. 2007. Gaia observations of Solar System objects: Impact on dynamics and ground-based observations. Adv. Space Res. 40 (2), 209-21
Mass determination of astrometric binaries with Hipparcos
No full textThis paper is the third of a series devoted to the determination of stellar
masses
from Hipparcos data. This is a continuation of Martin et al. (1997), who
introduced the theory and assessed the performance of the method from
simulated data, and of a second paper with the first results for 46
systems, (Martin & Mignard 1998). The orbit file maintained by the CHARA group and
new publications of orbital elements made the processing of 70 additional
candidate systems possible, including 28 of the 145 systems already tested in
the previous work. Significant results were obtained on 22 systems, with
relative accuracy better than 25% for the masses of 17 binaries. New
estimates are also given for 6 systems previously investigated, thanks to
reliable values of the magnitude difference from the Hipparcos catalogue
(ESA 1997). New orbital elements are proposed for HIP 12623 (12 Persei)
from speckle/spectroscopic measurements. Results are discussed for each system,
alongside the mass-luminosity relation based on Hipparcos magnitudes and
distances
Astrometric Properties Of The Hipparcos Catalogue
No full textThe main statistical astrometric properties of the Hipparcos Catalogue are reviewed. This includes the overall figures useful to characterize the content of the Hipparcos Catalogue, meaningful for an average star of 9 mag. The formal errors of the five astrometric parameters are discussed in different coordinate systems as a function of the position on the sky and of the magnitude of the stars. While there is almost no sizeable effect with the ecliptic longitude, the formal errors of the ecliptic longitude and parallax display large variations with the ecliptic latitude. For the other coordinate systems the precision of all the astrometric parameters is a function of both positional coordinates. A more detailed investigation of the distribution of the parallaxes and their expected errors as a function of the magnitude and of the location of the star on the sky is also carried out with a particular emphasis on the relative error oe ß =ß. Keywords: Astrometry, Hipparcos, Parallaxes. 1. I..
Division F commission 53:Extrasolar planets
No full textThe IAU Working Group on Extrasolar Planets (WGESP) was created by the Executive Council as a Working Group of Division III. This decision took place in June 1999, that is only 7 years after the discovery of planets around the pulsar PSR B1257+12 and 4 years after the discovery of 51 Peg b. This working group was renewed for 3 years at the General Assembly in 2003 in Sydney, Australia. It was chaired by Alan Boss from Carnegie Institution of Washington. The WGESP members were Paul Butler, William Hubbard, Philip Ianna, Martin Kürster, Jack Lissauer, Michel Mayor, Karen Meech, Francois Mignard, Alan Penny, Andreas Quirrenbach, Jill Tarter, and Alfred Vidal-Madjar.</p
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