Advancing Double Star Studies in an Age of Space-Based Astrometric Missions

Advancing Double Star Studies in an Age of Space-Based Astrometric Missions

The astrometric study of double stars is over 200 years old, and historically it has been a driver of stellar astrophysics resulting in the determination of the properties of stars, as well as formation and evolution models. Modern, space-based astronomy, from missions such as HIPPARCOS and Gaia, has opened a new sophisticated avenue of binary star studies. These space missions give the astrometric measures of a double star, its angular separation in arcseconds and position angle in degrees, with precisions that are 3 to 4 orders of magnitude more precise than has been available todate from single-aperture ground observations. In this thesis, Paper 1 crossmatches the double stars from the first published catalogue of double stars in the southern hemisphere (the Dunlop Catalogue) with the Gaia Data Release 2 (Gaia DR2) from the Gaia space-based mission and estimates the accuracy of the measures in the Dunlop Catalogue. Overall position angles are within 70°'/separation', separations within 7%, and apparent visual magnitudes are within 1 mag. Paper 2 develops an iteration-based technique for the determination of the first order orbital elements for long period and under-sampled arcs. This technique is then applied to a sample of binary stars from the Dunlop Catalogue. Orbital elements with a mean period and semi-major axis of ~81,000 years and ~76' respectively, were calculated displaying a mean uncertainty of ~37%. Paper 3 confirms the presence of 14 optical double stars within the Dunlop Catalogue and presents and applies an upgraded technique for calculating their rectilinear elements. This upgraded technique results in a minimum one order of magnitude improvement in their one sigma uncertainties over the current method.

Roderick R Letchford, et al., Assessment of the accuracy of measures in the 1829 southern double star catalogue of James Dunlop, Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 4, March 2022, Pages 5330–5347, https://doi.org/10.1093/mnras/stab3777 (This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society©: 2022 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.)

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