| 1. |
- van Leeuwen, F., et al.
(författare)
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Gaia Data Release 1 : Open cluster astrometry: Performance, limitations, and future prospects
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 601
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Tidskriftsartikel (refereegranskat)abstract
- Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.
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| 2. |
- Jordi, C, et al.
(författare)
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The design and performance of the Gaia photometric system
- 2006
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 367:1, s. 290-314
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Tidskriftsartikel (refereegranskat)abstract
- The European Gaia astrometry mission is due for launch in 2011. Gaia will rely on the proven principles of the ESA Hipparcos mission to create an all-sky survey of about one billion stars throughout our Galaxy and beyond, by observing all objects down to 20 mag. Through its massive measurement of stellar distances, motions and multicolour photometry, it will provide fundamental data necessary for unravelling the structure, formation and evolution of the Galaxy. This paper presents the design and performance of the broad- and medium-band set of photometric filters adopted as the baseline for Gaia. The 19 selected passbands (extending from the UV to the far-red), the criteria and the methodology on which this choice has been based are discussed in detail. We analyse the photometric capabilities for characterizing the luminosity, temperature, gravity and chemical composition of stars. We also discuss the automatic determination of these physical parameters for the large number of observations involved, for objects located throughout the entire Hertzsprung-Russell diagram. Finally, the capability of the photometric system (PS) to deal with the main Gaia science case is outlined.
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| 3. |
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| 4. |
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| 5. |
- Lindegren, L., et al.
(författare)
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The Gaia mission : Science, organization and present status
- 2007
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213. ; 3:S248, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- The ESA space astrometry mission Gaia will measure the positions, parallaxes and proper motions of the 1 billion brightest stars on the sky. Expected accuracies are in the 725 as range down to 15 mag and sub-mas accuracies at the faint limit (20 mag). The astrometric data are complemented by low-resolution spectrophotometric data in the 3301000 nm wavelength range and, for the brighter stars, radial velocity measurements. The scientific case covers an extremely wide range of topics in galactic and stellar astrophysics, solar system and exoplanet science, as well as the establishment of a very accurate, dense and faint optical reference frame. With a planned launch around 2012 and an (extended) operational lifetime of 6 years, final results are expected around 2021. We give a brief overview of the science goals of Gaia, the overall project organisation, expected performance, and some key technical features and challenges.
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| 6. |
- Malbet, F., et al.
(författare)
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Faint objects in motion: the new frontier of high precision astrometry
- 2021
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 845-886
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Tidskriftsartikel (refereegranskat)abstract
- Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles.
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| 7. |
- Perryman, M. A. C., et al.
(författare)
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GAIA: Composition, formation and evolution of the Galaxy
- 2001
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 369, s. 339-363
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Tidskriftsartikel (refereegranskat)abstract
- The GAIA astrometric mission has recently been approved as one of thenext two ``cornerstones'' of ESA's science programme, with a launch datetarget of not later than mid-2012. GAIA will provide positional andradial velocity measurements with the accuracies needed to produce astereoscopic and kinematic census of about one billion stars throughoutour Galaxy (and into the Local Group), amounting to about 1 percent ofthe Galactic stellar population. GAIA's main scientific goal is toclarify the origin and history of our Galaxy, from a quantitative censusof the stellar populations. It will advance questions such as when thestars in our Galaxy formed, when and how it was assembled, and itsdistribution of dark matter. The survey aims for completeness to V=20mag, with accuracies of about 10 mu as at 15 mag. Combined withastrophysical information for each star, provided by on-boardmulti-colour photometry and (limited) spectroscopy, these data will havethe precision necessary to quantify the early formation, and subsequentdynamical, chemical and star formation evolution of our Galaxy.Additional products include detection and orbital classification of tensof thousands of extra-Solar planetary systems, and a comprehensivesurvey of some 105-106 minor bodies in our SolarSystem, through galaxies in the nearby Universe, to some 500 000 distantquasars. It will provide a number of stringent new tests of generalrelativity and cosmology. The complete satellite system was evaluated aspart of a detailed technology study, including a detailed payloaddesign, corresponding accuracy assesments, and results from a prototypedata reduction development.
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| 8. |
- Perryman, M.A.P., et al.
(författare)
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The Hipparcos Catalogue
- 2009
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Ingår i: Astronomy & Astrophysics. ; 500, s. 501-504
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Tidskriftsartikel (refereegranskat)
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