Surprising variations in the rotation of the chemically peculiar
stars CU Vir and V901 Ori
Zdeněk Mikulášek (PřF MU Brno)
We studied the stability of the periods of well observed mCP stars CU Vir
and V901 Ori using all accessible data containing phase information. We
found that both stars exhibit alternating intervals of rotational braking
and acceleration. We propose that dynamical interaction between a thin,
outer magnetically-confined envelope, braked by the stellar wind, with an
inner stellar body is able to explain the observed rotational instability. A
theoretically unexpected alternating variability in these stars would remove
the spin-down paradox and brings a new insight into structure and evolution
of some magnetic upper-main sequence stars.
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