M. Gebran

TL;DR: Gaia as discussed by the authors is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach.

TL;DR: The first Gaia data release, Gaia DR1 as discussed by the authors, consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues.

TL;DR: In this paper, a polynomial expression for the relation between the effective temperature and the colour G BP −−G RP was derived for stars with T eff ǫ≥ 4.5 K. The relation among colours involving Gaia magnitudes (white light G, blue G BP, red G RP and G RVS bands) and colours from other commonly used photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, Hipparcos and Tycho ) was provided.

TL;DR: The POLLUX database of synthetic stellar spectra as mentioned in this paper provides an unprecedented coverage of the entire Hertzsprung-Russell diagram and is used for the construction of theoretical spectral libraries helpful for stellar population synthesis.

TL;DR: The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS) component by means of the astrometric data for open clusters as discussed by the authors, which 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.