Long period variables and Gaia

The period-luminosity (P-L) relation of various types of variable stars is a key tool for determining the distance to an individual object or a whole galaxy. Thus it has a high relevance for stellar and extragalactic astrophysics. The Gaia mission, to be launched in 2011, will provide parallax measurements for a vast number of objects in the Milky Way, which will allow to improve the existing P-L relations considerably.
One of the P-L relations that will profit a lot from this improvement is the one for long period variables. The Hipparcos data did no allow to establish a good relation for the Milky Way in that case. From the Magellanic Clouds we now know that the long period variables are found on several parallel P-L relations. A similar picture could not be established for the Milky Way up to now.
The proposed project aims to provide the preparatory results necessary to produce a P-L diagram with the Gaia data. More specifically, the project will provide the following main output:
(1) a relation for the calculation of a bolometric correction for the Gaia G photometry using Gaia low resolution spectroscopy;
(2) a database of LPVs with well determined periods that will be correlated with the Gaia results for producing accurate P-L diagrams for various parts of the Milky Way;
(3) high quality example light curves for training and optimizing the period finding algorithm of the Gaia data analysis;
(4) improved classification criteria for LPVs according to their pulsation mode;
(5) a better understanding of the global parameters influencing the P-L relations with the help of a study on the LPVs in stellar clusters and pulsation models.
As part of the findings of this project will directly go into the Gaia data analysis the work has to be started in advance of the launch of Gaia. The project is a contribution to the Gaia Data Processing and Analysis Centre, and the applicant is a member of Gaia Coordination Unit 7 (Variable Stars). However, the outcome of the project will be of use also beyond the Gaia mission. Especially the proposed study of the parameters influencing the shape of the P-L diagram will provide new insight into the late stages of stellar evolution of low and intermediate mass stars.