Optical spectroscopy of X - ray sources in the old open cluster M 67 ?

We have obtained optical spectra of seven stars in the old galactic cluster M 67 that are unusual sources of X-rays, and investigate whether the X-ray emission is due to magnetic activity or to mass transfer. The two binaries below the giant branch S 1063 and S 1113, the giant with the white dwarf companion S 1040 and the eccentric binary on the subgiant branch S 1242 show magnetic activity in the form of Ca ii H&K emission and Hα emission, suggesting that their X-rays are coronal. The reason for the enhanced activity level in S 1040 is not clear. The two wide, eccentric binaries S 1072 and S 1237 and the blue straggler S 1082 do not show evidence for Ca ii H&K emission. A second spectral component is found in the spectrum of S 1082, most clearly in the variable Hα absorption profile. We interpret this as a signature of the proposed hot subluminous companion.