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Torre, Andrea Dalla; Leeuwen, F. van

doi:10.1023/a:1026215716256

Cited by 8 publications

(5 citation statements)

References 9 publications

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“…2 of ESA 1997;Dalla Torre & van Leeuwen 2003), and the resulting solution instabilities and radiation damage, Hipparcos produced results well exceeding the expectations set for the nominal mission. This was confirmed by a wide range of statistical tests on the final data (Arenou et al 1995;.…”

Section: Introductionmentioning

confidence: 84%

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A new reduction of the raw Hipparcos data

Leeuwen¹,

Fantino

2005

A&A

263

375

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Abstract. We present an outline of a new reduction of the Hipparcos astrometric data, the justifications of which are described in the accompanying paper. The emphasis is on those aspects of the data analysis that are fundamentally different from the ones used for the catalogue published in 1997. The new reduction uses a dynamical modelling of the satellite's attitude. It incorporates provisions for scan-phase discontinuities and hits, most of which have now been identified. Solutions for the final along-scan attitude (the reconstruction of the satellite's scan phase), the abscissa corrections and the instrument model, originally solved simultaneously in the great-circle solution, are now de-coupled. This is made possible by starting the solution iterations with the astrometric data from the published catalogue. The de-coupling removes instabilities that affected great-circle solutions for short data sets in the published data. The modelling-noise reduction implies smaller systematic errors, which is reflected in a reduction of the abscissa-error correlations by about a factor 40. Special care is taken to ensure that measurements from both fields of view contribute significantly to the along-scan attitude solution. This improves the overall connectivity of the data and rigidity of the reconstructed sky, which is of critical importance to the reliability of the astrometric data. The changes in the reduction process and the improved understanding of the dynamics of the satellite result in considerable formal-error reductions for stars brighter than 8th magnitude.

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Section: Introductionmentioning

confidence: 84%

“…Despite a serious problem with the orbit due to a failure of the apogee boost motor (see Volume 2 of ESA 1997;Dalla Torre & van Leeuwen 2003), and the resulting solution instabilities and radiation damage, Hipparcos produced results well exceeding the expectations set for the nominal mission.…”

Section: Introductionmentioning

confidence: 99%

A new reduction of the raw Hipparcos data

Leeuwen¹,

Fantino

2005

A&A

263

375

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“…The Hipparcos team has been well aware of this and has put considerable effort into examining potential sources of systematic error. Their most recent papers (van Leeuwen & Fantino 2003a, 2003bDalla Torre & van Leeuwen 2003;van Leeuwen & Penston 2003;Fantino & van Leeuwen 2003) show, for instance, that noise in the alongscan attitude dominates for H p < 4:5 (where H p is the apparent magnitude as directly measured by Hipparcos) and that this may be especially important for the Pleiades, inter alia (van Leeuwen & Fantino 2003b). This possibility was examined by Makarov (2002), who reanalyzed Hipparcos data to derive d ¼ 129 AE 3, a value that is substantially less discrepant than that reported by van Leeuwen (1999) and Robichon et al (1999).…”

Section: The Distance To the Pleiadesmentioning

confidence: 99%

Confirmation of Errors inHipparcosParallaxes fromHubble Space TelescopeFine Guidance Sensor Astrometry of the Pleiades

Soderblom¹,

Nelan²,

Benedict³

et al. 2005

Astron J

134

136

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We present absolute trigonometric parallaxes and relative proper motions for three members of the Pleiades, obtained with the Hubble Space Telescope's Fine Guidance Sensor 1r, a white-light interferometer. We estimate spectral types and luminosity classes of the stars comprising the astrometric reference frame from R % 2000 spectra, VJHK photometry, and reduced proper motions. From these we derive estimates of absolute parallaxes and introduce them into our model as observations with error. We constrain the three cluster members to have a 1 dispersion in distance less than 6.4 pc and find an average abs ¼ 7:43 AE 0:17 AE 0:20 mas, where the second error is systematic due to member placement within the cluster. This parallax corresponds to a distance of 134:6 AE 3:1 pc or a distance modulus of m À M ¼ 5:65 AE 0:05 for these three Pleiades stars, presuming a central location. This result agrees with three other independent determinations of the Pleiades distance. Presuming that the cluster depth systematic error can be significantly reduced because of the random placement of these many members within the cluster, these four independent measures yield a best-estimate Pleiades distance of abs ¼ 7:49 AE 0:07 mas, corresponding to a distance of 133:5 AE 1:2 pc or a distance modulus of m À M ¼ 5:63 AE 0:02. This resolves the dispute between the main-sequence fitting and the Hipparcos distance moduli in favor of main-sequence fitting. Key words: astrometry -distance scale -open clusters and associations: general -stars: distancestechniques: interferometric 1. THE PROBLEM Our knowledge of the life histories of stars relies on models whose fidelity is ultimately tested by appeal to real stars. The Sun provides the most basic calibration of these models, of course, because it is only for the Sun that an accurate age exists and for which the mass, temperature, composition, and structure are known with precision, accuracy, and completeness. Clusters of stars are also fundamental for constructing models because we can assume that all the cluster's members are of the same age and composition, even if other parameters are more loosely constrained.Preeminent among clusters is the Pleiades, and much effort has gone into determining the absolute parallax of this cluster. ESA's Hipparcos mission brought the benefits of space observing to astrometry to produce precise positions, proper motions, and parallaxes for nearly all stars brighter than V % 9. Before Hipparcos, the distance to the Pleiades was too large for ground-based parallaxes to yield a good distance, so the best estimates were derived by comparing the main sequence of the Pleiades with a main sequence constructed from nearby stars with large parallaxes. A small correction for evolution is necessary ( the Pleiades is about 100 Myr old [ Pinsonneault et al. 1998], whereas the nearby field stars are typically as old as the Sun), but the Pleiades appears to have essentially the same elemental abundances as the Sun ( Boesgaard & Friel 1990), obviating a need for a me...

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“…Background information for the construction of the new catalogue can be found in a series of papers, starting with two papers on torque analysis and attitude modelling (Fantino & van Leeuwen 2003;van Leeuwen & Fantino 2003). In the same volume also the orbit of the satellite was analyzed in detail (Dalla Torre & van Leeuwen 2003), and an overview was presented of the many peculiarities that affected the Hipparcos mission (van Leeuwen & Penston 2003).These papers were followed by a paper on the various peculiarities in the construction and data contents of the 1997 catalogue (van Leeuwen 2005) and a preview of the construction of the new catalogue (van Leeuwen & Fantino 88 F. van Leeuwen 2005). The catalogue has been presented on a DVD, containing also the intermediate astrometric data and various calibration files, as part of a book (van Leeuwen 2007b) describing not only how the new catalogue was derived, but also how these data can be used in astrophysical applications, such as luminosity calibrations, cluster-parameter determinations, and studies of galactic dynamics.…”

Section: Publication Of the New Catalogue And Some Preliminary Resultsmentioning

confidence: 99%

Towards a better understanding of Hipparcos

Leeuwen¹

2007

Proc. IAU

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The formal errors on the astrometric data in the 1997 publication of the Hipparcos catalogue are, for stars brighter than about magnitude 9, largely the result of inaccuracies in the description of the along-scan attitude of the satellite. A detailed study of the dynamics of the Hipparcos satellite has led to a much improved understanding and modelling of the satellite attitude, taking into account peculiarities in the rotation of the payload (scan-phase jumps) as well as the detections of small hits. A new reduction of the Hipparcos data was initiated, in which the attitude modelling is a direct description of the dynamics of the satellite. In this so-called fully-dynamic attitude modelling the underlying torques acting on the satellite are reconstructed, and rates and error angles are obtained through integrations. Both the hits and the scan-phase jumps could be taken into account in the context of this model. The new model, including the provisions for discontinuities, led to a factor five reduction in the attitude noise. A new reduction, based on a global iterative solution like is also planned for Gaia, was started in 2004, and completed, after some 15 iterations, in 2007. In the process of this reduction, also the sensitivity of the solution to optimal connectivity between the data in the two fields of view was exposed and taken care of, as well as a couple of small-scale calibrations. The latter had not been possible to solve for in the original reductions. In the catalogue that resulted from this new reduction, the errors on the astrometric data for all but stars brighter than magnitude 4, are dominated by photon noise. Error-correlation levels in the underlying abscissa data are down by more than an order of magnitude, and play no longer any significant role. This feature very much simplifies the analysis of, for example, wide-binary stars and open cluster data.

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Untitled

Cited by 8 publications

References 9 publications

A new reduction of the raw Hipparcos data

A new reduction of the raw Hipparcos data

Confirmation of Errors inHipparcosParallaxes fromHubble Space TelescopeFine Guidance Sensor Astrometry of the Pleiades

Towards a better understanding of Hipparcos

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