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Astron. Astrophys. 332, 149-154 (1998)

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Activity cycles in UX Arietis

M. Massi 1, 2, J. Neidhöfer 1, G. Torricelli-Ciamponi 3 and F. Chiuderi-Drago 4

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
2 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
3 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
4 Dipartimento di Astronomia, Università di Firenze, Largo E.Fermi 5, I-50125 Firenze, Italy

Received 8 September 1997 / Accepted 1 December 1997


By analysing long term radio observations of the binary system UX Arietis, activity cycles have been discovered which are strongly reminiscent of those present in the Sun. It is well known that the activity cycle in the Sun is 11 years, while the general magnetic field reverses every 11 years, returning to its initial configuration after 22 years, namely after two consecutive cycles of activity. Now we have discovered in UX Arietis an activity cycle of 25.5 days during which the polarization reverses and returns to its initial value after about two consecutive cycles of activity. Moreover as the cycle of 11 years of the Sun is modulated with a period of 90-110 years, poorly estimated due to its long term occurence, we found that the 25.5 days activity cycle in UX Arietis is also modulated with a period of 158 days. The solar activity cycle is related to the dynamo at work in the sun's interior. The fact of having in UX Arietis the same phenomena as in the Sun but at much shorter time scales (i.e. days instead of years) should make possible to acquire better statistics in the future and improve our understanding of the dynamo processes.

Key words: stars: individual: UX Ari – stars: activity – stars: magnetic fields – radio continuum: stars

Send offprint requests to: M. Massi

© European Southern Observatory (ESO) 1998

Online publication: March 10, 1998