Neiner, C. ; Hubert, A.-M. ; Frémat, Y. ; Floquet, M.

published in The Three-Dimensional Universe with Gaia, 576, pp. 603 (2005)

Abstract: In this paper, we present the kind of information that can be derived for variable B (ß Cep and SPB) and Be stars from the five-year photometric monitoring and medium resolution near-IR spectra that Gaia will obtain after 2011. First of all, Gaia will provide a deep survey of variability of about one million B and Be stars in young galactic clusters, in the field of the Galaxy and in the Magellanic Clouds. Therefore, we will be able to study the influence of age and metallicity upon variability. Moreover, the high accuracy of photometry will allow us to detect micro-variability predicted in late B stars but undetected with ground-based observations. In addition, we will extend, to a much larger sample, the results regarding the outbursts of bright Be stars derived from Hipparcos photometry. We will then be able to test the hypothesis concerning the origin of the recurrence of Be stars among B-type stars. Finally, Gaia will make a significant contribution for the discovery of new variable stars, in particular SPB stars. Emission in Paschen lines and the use of a medium band filter in the Ha region will also allow us to separate Be stars from B stars. Exotic objects such as B[e], Ae/Be, symbiotic and proto-planetary nebulae stars will be easily distinguished thanks to the presence of iron emission lines combined to the IR emission lines.

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