19.
Evidence for large-scale, global mass inflow and flaring on the
late-type fast rotator BD+22 4409.
Eibe M. T., Byrne P. B., Jeffries R. D., Gunn A. G.,
A & A, 1999, 341, 527-538.
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ABSTRACT.
We present new results from high-resolution spectroscopic observations
of the late-type fast rotator BD+22 4409, revealing interesting
aspects about its magnetic activity that have not been considered
before. Analysis of the extremely variable and rotationally broadened
chromospheric H alpha emission profile provides clear evidence for an
intense and continuous downflow of absorbing material. A high level of
activity was also exhibited in the form of two consecutive flares that
lasted for almost five hours. The decay of the second flare was
accompanied by a dramatic absorption in the blue half of the H alpha
profile that is attributed to the development of cool flare loops. The
observed circulation of material and the presence of magnetic loops in
connection to the chromospheric flare suggest plasma is being
effectively transferred between the chromosphere and the corona.
As opposed to similar active and fast rotators, direct evidence of
cool prominence clouds has not been found in this star. The results
provide strong support for recent theoretical studies by van den Oord
et al. (1997). In that work it was concluded that such prominences are
only stable at some distance from the star in the equatorial
plane. Unstable material would be expected to flow towards the poles
along magnetic lines. The inclination of BD+22 4409, i~50 degrees,
favours the detection of such flow as an asymmetry in chromospheric
line profiles. However, it could make clouds undetectable if they can
never be seen in projection on the disk.
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