2008MNRAS.390..377Z

We have measured the projected rotational velocities (v sini) in a number of symbiotic stars and M giants using high-resolution spectroscopic observations. On the basis of our measurements and data from the literature, we compare the rotation of mass donors in symbiotics with v sini of field giants and find that: (i) the K giants in S-type symbiotics rotate at v sini > 4.5 km/s, which is 2-4 times faster than the field K giants; (ii) the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. Statistical tests show that these differences are highly significant - p-value <10^–3 in the spectral-type bins K2III-K5III, M0III-M6III and M2III-M5III and (iii) our new observations of D'-type symbiotics also confirm that they are fast rotators.

As a result of the rapid rotation, the cool giants in symbiotics should have 3-30 times larger mass-loss rates. Our results suggest also that bipolar ejections in symbiotics seem to happen in objects where the mass donors rotate faster than the orbital period.

All spectra used in our series of papers can be obtained upon request from the authors.