High-resolution spectroscopy of the UMa group
Matthias Ammler (Astrophysical Institute and University Observatory Jena)
Klaus Fuhrmann (Max Planck Institute for Extraterrestrial Physics)
Eike Guenther (Thüringer Landessternwarte Tautenburg)
We are presenting a project to analyse homogeneously Ursa Major (UMa) group members and candidates based on high-resolution, high-signal-to-noise spectroscopy in the optical wavelength regime.
The members of the UMa open cluster and a large number of additional stars form the UMa group with membership assignments still being under dispute. Though all stars show common overall properties, e.g. distinct kinematics, the assessment of firm membership criteria is difficult. Additionally, we just know that the age of the stars is young but age determinations range widely from 100 to 500 Myrs.
Spectra of a large sample of UMa group members and candidates will enable us to address those questions homogeneously and in detail. The spectra not only provide equivalent widths of lines, which are used as age and activity indicators but also allow us to analyse the stellar atmospheres in more detail. This has not been done so far for a larger sample of UMa group members. Taking into account information found in the literature, we intend to assess membership criteria, nature and age of the UMa group more precisely than before.