Issue |
A&A
Volume 571, November 2014
|
|
---|---|---|
Article Number | A86 | |
Number of page(s) | 9 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361/201424405 | |
Published online | 14 November 2014 |
Analysing weak orbital signals in Gaia data
Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
e-mail: l.lucy@imperial.ac.uk
Received: 15 June 2014
Accepted: 22 August 2014
Anomalous orbits are found when minimum-χ2 estimation is applied to synthetic Gaia data for orbits with astrometric signatures comparable to the single-scan measurement error (Pourbaix 2002, A&A, 385, 686). These orbits are nearly parabolic, edge-on, and their major axes align with the line-of-sight to the observer. Such orbits violate the Copernican principle (CPr) and as such could be rejected. However, the preferred alternative is to develop a statistical technique that incorporates the CPr as a fundamental postulate. This can be achieved in a Bayesian context by defining a Copernican prior. Pourbaix’s anomalous orbits then no longer arise. Instead, the selected orbits have a somewat higher χ2 but do not violate the CPr. The problem of detecting a weak additional orbit in an astrometric binary with a well-determined orbit is also treated.
Key words: binaries: visual / stars: fundamental parameters / methods: statistical
© ESO, 2014
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