We present Mn , Co and Eu abundances for a sample of 20 disk F and G dwarfs and subgiants with metallicities in the range -0.8 \leq \mathrm { [ Fe / H ] } \leq + 0.3 .
We investigate the influence of hyperfine structure ( HFS ) on the derived abundances of Mn and Co by using HFS data from different sources in the literature , as well as calculated HFS from interaction factors A and B .
Eu abundances were obtained from spectral synthesis of one Eu ii line that takes into account HFS from a series of recent laboratory measurements .
For the lines analyzed in this study , we find that for manganese , the differences between abundances obtained with different HFSs are no larger than 0.10 dex .
Our cobalt abundances are even less sensitive to the choice of HFS than Mn , presenting a 0.07 dex maximum difference between determinations with different HFSs .
However , the cobalt HFS data from different sources are significantly different .
Our abundance results for Mn offer an independent confirmation of the results from , who favour type Ia supernovae as the main nucleosynthesis site of Mn production , in contrast to trends of Mn versus metallicity previously reported in the literature .
For Co , we obtain \mathrm { [ Co / Fe ] } \sim 0.0 in the range -0.3 < \mathrm { [ Fe / H ] } < +0.3 and [ Co/Fe ] rising to a level of +0.2 when [ Fe/H ] decreases from -0.3 to -0.8 , in disagreement with recent results in the literature .
The observed discrepancies may be attributed to the lack of HFS in the works we used for comparison .
Our results for Eu are in accordance with low-mass type II supernovae being the main site of the r -process nucleosynthesis .