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Astron. Astrophys. 341, 527-538 (1999)

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Evidence for large-scale, global mass inflow and flaring on the late-type fast rotator BD+22°4409

M.T. Eibe 1, P.B. Byrne 1, R.D. Jeffries 2 and A.G. Gunn 3

1 Armagh Observatory, College Hill, Armagh BT61 9DG, Ireland
2 Department of Physics, Keele University, Staffordshire ST5 5BG, UK
3 University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire, SK11 9Dl, UK

Received 27 April 1998 / Accepted 21 October 1998

Abstract

We present new results from high-resolution spectroscopic observations of the late-type fast rotator BD+[FORMULA], revealing interesting aspects about its magnetic activity that have not been considered before. Analysis of the extremely variable and rotationally broadened chromospheric H[FORMULA] 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[FORMULA] 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+[FORMULA], [FORMULA], favours the detection of such flow as an asymmetry in chromospheric lines profiles. However, it could make clouds undetectable if they can never be seen in projection on the disk.

Key words: stars: activity – stars: chromospheres – stars: individual: BD+22O 4409 – stars: late-type

Present address: LAEFF, Apdo 50727, E-28080 Madrid, Spain

Send offprint requests to: M.T. Eibe

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© European Southern Observatory (ESO) 1999

Online publication: December 4, 1998
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