BD+ is a magnetically active and rapidly-rotating late-type star. A considerable degree of activity in the form of flares and plage regions has been detected in our observations in accordance with previous work by J94. The analysis of photospheric lines has revealed the presence of large spots.
Evidence of an intense downflow of material has also been shown in this paper. Its origin has been discussed in terms of coronal rain and loop prominences phenomena. Based on a recent analysis of the equilibrium and stability of prominence-like cloud in late-type rotators (van den Oord et al. 1997), we conclude that the intense downflow of cool absorbing material is more likely to derive from the interaction between the magnetic field and the stellar plasma in conditions of unstable mechanical equilibrium, thus resembling the loop prominences phenomenon.
Taking into account the results from observations made so far it seems that the loop prominence systems are a common feature in the star BD+. The possibility of condensations as in the case of HK Aqr or AB Dor cannot be ruled out, although a definitive observational proof may be impossible to obtain due to geometrical considerations.
More extended observations are needed to discriminate better between transient phenomena and long-term variations. It would also be interesting to investigate the possible connection of the photospheric variability to chromospheric emission variability.
© European Southern Observatory (ESO) 1999
Online publication: December 4, 1998