With the HDS ( High Dispersion Spectrograph ) on the Subaru telescope , we obtained high resolution optical region spectra of three red giant stars ( cos 4 , cos 82 , and cos 347 ) in the Ursa Minor dwarf spheriodal galaxy .
Chemical abundances in these stars have been analysed for 26 elements including \alpha – , iron–peak , and neutron capture elements .
All three stars show low abundances of \alpha –elements ( Mg , Si , and Ca ) and two stars ( cos 82 and cos 347 ) show high abundance of Mn compared to Galactic halo stars of similar metallicity .
One star ( cos 4 ) has been confirmed to be very metal deficient ( [ Fe/H ] = -2.7 ) and found to show anomalously low abundances of Mn , Cu , and Ba .
In another star cos 82 ( [ Fe/H ] = -1.5 ) , we have found large excess of heavy neutron-capture elements with the general abundance pattern similar to the scaled solar system r –process abundance curve .
These observational results are rather puzzling : low abundances of \alpha – elements and high abundance of Mn seem to sugggest a significant contribution of SNe Ia at low metallicity , while there is no hint of s –process ( i.e. , AGB stars ) contribution even at [ Fe/H ] = -1.5 , suggesting a peculiar nucleosynthetic history of the UMi dSph galaxy .