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Gaia Data Release 1: Astrometry: One billion positions, two million proper motions and parallaxes

Lindegren, L and Lammers, U and Bastian, U and Hernández, J and Klioner, S and Hobbs, D and Bombrun, A and Michalik, D and Ramos-Lerate, M and Butkevich, A and Comoretto, G and Joliet, E and Holl, B and Hutton, A and Parsons, P and Steidelmüller, H and Abbas, U and Altmann, M and Andrei, A and Anton, S and Bach, N and Barache, C and Becciani, U and Berthier, J and Bianchi, L and Biermann, M and Bouquillon, S and Bourda, G and Brüsemeister, T and Bucciarelli, B and Busonero, D and Carlucci, T and Castañeda, J and Charlot, P and Clotet, M and Crosta, M and Davidson, M and De Felice, F and Drimmel, R and Fabricius, C and Fienga, A and Figueras, F and Fraile, E and Gai, M and Garralda, N and Geyer, R and González-Vidal, JJ and Guerra, R and Hambly, NC and Hauser, M and Jordan, S and Lattanzi, MG and Lenhardt, H and Liao, S and Löffler, W and McMillan, PJ and Mignard, F and Mora, A and Morbidelli, R and Portell, J and Riva, A and Sarasso, M and Serraller, I and Siddiqui, H and Smart, R and Spagna, A and Stampa, U and Steele, IA and Taris, F and Torra, J and Van Reeven, W and Vecchiato, A and Zschocke, S and De Bruijne, J and Gracia, G and Raison, F and Lister, T and Marchant, JM and Messineo, R and Soffel, M and Osorio, J and De Torres, A and O'Mullane, W (2016) Gaia Data Release 1: Astrometry: One billion positions, two million proper motions and parallaxes. Astronomy and Astrophysics, 595 (A4). ISSN 0004-6361

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Open Access URL: https://doi.org/10.1051/0004-6361/201628714 (Published version)

Abstract

© ESO, 2016.Context. Gaia Data Release 1 (DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during the first 14 months of its operational phase. Aims. We give a brief overview of the astrometric content of the data release and of the model assumptions, data processing, and validation of the results. Methods. For stars in common with the Hipparcos and Tycho-2 catalogues, complete astrometric single-star solutions are obtained by incorporating positional information from the earlier catalogues. For other stars only their positions are obtained, essentially by neglecting their proper motions and parallaxes. The results are validated by an analysis of the residuals, through special validation runs, and by comparison with external data. Results. For about two million of the brighter stars (down to magnitude ∼11.5) we obtain positions, parallaxes, and proper motions to Hipparcos-type precision or better. For these stars, systematic errors depending for example on position and colour are at a level of ± 0.3 milliarcsecond (mas). For the remaining stars we obtain positions at epoch J2015.0 accurate to ∼10 mas. Positions and proper motions are given in a reference frame that is aligned with the International Celestial Reference Frame (ICRF) to better than 0.1 mas at epoch J2015.0, and non-rotating with respect to ICRF to within 0.03 mas yr-1. The Hipparcos reference frame is found to rotate with respect to the Gaia DR1 frame at a rate of 0.24 mas yr-1. Conclusions. Based on less than a quarter of the nominal mission length and on very provisional and incomplete calibrations, the quality and completeness of the astrometric data in Gaia DR1 are far from what is expected for the final mission products. The present results nevertheless represent a huge improvement in the available fundamental stellar data and practical definition of the optical reference frame.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
Date Deposited: 13 Apr 2017 10:46
Last Modified: 13 Apr 2017 10:46
DOI or Identification number: 10.1051/0004-6361/201628714
URI: http://researchonline.ljmu.ac.uk/id/eprint/6252

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