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5. Conclusions

The light variations of the star show, over the last 35 years, a few brief light minima, and frequent light maxima sometimes followed by a long plateau. The three observed plateaus are separated by tex2html_wrap_inline1106 14 and tex2html_wrap_inline1106 19 years. These plateaus represent the longest time spans of permanent strong activity in the star.

Our 1996 observations seem to be situated on a plateau. We do not detect any true long time scale periodicity, but rather time constants of the order of 40 to 80 days. Although sometimes violent, the light fluctuations have been limited to variations of 20 to 30% above and under the plateau level.

The fact that we do not detect here periods of the order of the rotational period (tex2html_wrap_inline1106 2 days) means that the activity is not regionally localized on the stellar surface but rather longitudinally extended around the star, and that it develops very quickly.

Of course such behavior needs a careful simultaneous spectroscopic monitoring, in order to correlate the classical Be emission activity with the present knowledge of the light variations. These observations should be made especially at the phases where the activity increases rapidly, and at the light minima.

The assumption that the periodicities of about 60 days or even the time between plateaus, 5000 and 7000 days, are due to the modulation of the activity by an unseen companion, leads to conclude that this hypothetical companion cannot be detected with the present interferometric techniques. Only devoted spectroscopy could allow the detection of a companion.

Note added in proof: Observations carried out since september 1996 show that OT Gem has reached again its "normal" state luminosity (i.e. around magnitude 6.45). Thus, the 1995-96 plateau has had the same tex2html_wrap_inline1106300 days duration mentioned above for other observed plateaus (between 250 and 340 days). Therefore 300 days seems to be a significant time constant of the plateau phases of the star activity.


The authors acknowledge C. Bourgois, J. Chauville, S. González-Bedolla, J.H. Peña and D. Briot for their help and/or hospitality through the different stages of this investigation. We thank the anonymous referee for his/her help and suggestions to improve the original manuscript. This work was partially supported by CONACYT (Mexico) projects 1219E9203, 458100-5-0464PE and F689E9411 and by the CNRS (France).

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