GAIA AND DIVA PHOTOMETRY:

TOWARDS THE FINE STRUCTURE OF THE HR DIAGRAM?

Proceedings of a workshop held in Porto September 3-4 2002

T. Lejeune, J. Fernandes and E. Lastennet (Eds.)

DIVA and GAIA are two space mission satellites planned for launch in 2004 and before 2012, respectively. DIVA will obtain positions, proper motions, parallaxes and magnitudes of about 35 million stars, and dispersed images of about 12 million objects. GAIA will measure more than 1 billion stars in a global stellar census of our Galaxy and its nearest neighbours. As successors of Hipparcos, they are both expected to have an enormous impact on many areas of strophysics, and in particular they will address many key questions of stellar evolution theory.

The observed Hertzsprung-Russell diagram (HRD) is one of the most widely used tools to study and interpret stellar populations, in spite of uncertainties associated with stellar evolution models and calibrations. How well sampled will be the new DIVA and GAIA HRDs in comparison to the Hipparcos HRD? For instance, can we really expect enough stars undergoing rapid evolutionary phases to be detected? How can the DIVA and GAIA measurements help to improve internal structure models and stellar evolution theories? The high-precision positions in the HRD of stars of known surface abundances, provided by Hipparcos and by high resolution spectroscopy, has already shown that there exists a discrepancy between the observed positions and the positions predicted by standard stellar models. Can DIVA and GAIA calibrate the open cluster main-sequences? What improvements can be expected for globular clusters? How strong constraints will DIVA and GAIA place on fundamental stellar parameter determinations for single stars? For double and multiple stars? In which part of the HRD do we need an increased number of objects with extremely accurate data, including masses? Are DIVA and GAIA able to provide them?

Beyond these fundamental questions, the aim of this workshop is twofold:
  1. To give status and performance of the (spectro-)photometric systems of both missions. What are the capabilities of the DIVA dispersed images? As for GAIA, many working groups are actively designing photometric systems, investigating the most efficient one for GAIA. While the definitive choice of this system is still subject of debate, the design of the GAIA photometric system should be fixed by mid-2005 and a more or less definite system is expected by mid-2003.
  2. To summarize the expected accuracy in terms of photometry, radial velocity, distance, position and motions, in order to compare the complementary capabilities of the DIVA and GAIA satellites and to investigate at which level the new data will improve our understanding of the fine structure of the HR diagram.

Manuscript title pages, Preface and Table of contents jad9_8.ps

Author Index: index.ps

Note: papers in these Proceedings have not been refereed

  
Group Photograph