Combining asteroseismic data from the Kepler mission with uvby Strömgren photometry, the Strömgren survey for Asteroseismology and Galactic Archaeology (SAGA) will transform the Kepler field into a new benchmark for Galactic studies.
By analyzing oscillation frequencies in stars, asteroseismology can measure fundamental physical quantities, masses, and radii, which otherwise would be inaccessible in single field stars, and which can be used to obtain information on stellar distances and ages. Thanks to space-borne missions such as CoRoT and Kepler global oscillation frequencies are now robustly detected in a few hundreds of main-sequence and subgiant, and several thousands of giant stars. However, until now asteroseismic studies of stellar populations only had coarse information on classical stellar parameters such as Teff and [Fe/H].
Wide-field Strömgren photometry provides reliable stellar parameters, in particular metallicities, over a large magnitude range. By combining asteroseismology from Kepler with Strömgren colors, SAGA provides an unprecedented opportunity to constrain the development and structure of our Galaxy. Furthermore, coupling classical parameters with seismic information improves the derived asteroseismic masses and ages, providing a valuable reference sample to calibrate other metallicity and age-dating techniques.
SAGA is also a natural extension of the Geneva Copenhagen survey (GCS), the only all-sky Strömgren survey currently available and a benchmark for Galactic studies. While the GCS is an all-sky, shallow survey, limited to main-sequence and subgiant stars closer than 100 pc, SAGA observes primarily giants located between 1 and 4 kpc in a specific region of the sky, making the two surveys complementary. The stellar properties estimated by GCS within the solar neighborhood could be stretched across several kpc using kinematics to get a sense of Galactic properties. The larger distance range sampled by SAGA giants provides in situ measurement of stellar and Galactic structure across 5 kpc.
This site provides an overview of the design of SAGA. For more detailed information, please see the SAGA publications. Most importantly, we provide details of and access to the current SAGA data release. This survey is ongoing and updated data sets will be regularly released here.