The design and performance of the Gaia photometric system

Abstract

The European Gaia astrometry mission is due for launch in 2011. Gaia will rely on the proven principles of ESA's Hipparcos mission to create an all-sky survey of about one billion stars throughout our Galaxy and beyond, by observing all objects down to 20th magnitude. Through its massive measurement of stellar distances, motions and multi-colour 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 nineteen selected passbands (extending from the ultraviolet 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 to deal with the main Gaia science case is outlined.Comment: MNRAS, accepted 1-Dec-2005; 26 pages, 15 figure

Determination of rotation periods in solar-like stars with irregular sampling: the Gaia case

“…The astrometric measurements will be performed in the G band, i.e. a broad unfiltered passband that covers the wavelength range from about 350 to 1000 nm, with the maximum transmission at ∼715 nm and a full width at half-maximum of 408 nm (Jordi et al 2006). The expected photometric precision for a single measurement is better than 2 mmag for targets brighter than G = 15 and about 10 mmag for the faintest sources (G ∼ 20).…”

“…The sampling at a given sky position has been generated through Astrometry Global Iterative Solution Laboratory (AGISLAB ), a package developed by the Coordination Unit 3 of the Gaia DPAC (Holl, Hobbs & Lindegren 2010). Finally, we degraded the time series accuracy by adding the instrument noise (according to the error model described in Jordi et al 2006) to simulate stellar targets with an average magnitude G = 10.…”

The ilium forward modelling algorithm for multivariate parameter estimation and its application to derive stellar parameters fromGaiaspectrophotometry

“…Particularly desirable is a system which maximizes the separability of the APs (a method for doing this was presented by Bailer-Jones 2004). This opportunity was taken by the Gaia community, which de- signed a multiband photometric system to address the specific Gaia scientific goals (Jordi et al 2006). But this was later replaced with the present (and less desirable) BP/RP spectrophotometry, ultimately for financial reasons.…”

Directed follow-up strategy of low-cadence photometric surveys in search of transiting exoplanets - I. Bayesian approach for adaptive scheduling

“…Such missions, due to their high cadence, will not benefit from the approach since their phase and period coverage are already quite complete. Instead, we aim for all-sky surveys like Hipparcos (van Leeuwen et al 1997), or its successor, Gaia (Jordi et al 2006), in order to use their extensive low-cadence photometric databases for exoplanets search.…”