We have shown that the light variations of R 40 look very much like those seen in other Cygni variables and LBVs (at minimum and maximum phase, see van Genderen et al. 1997a,b), another indication that, most likely, all such stars exhibit multi-periodic light variability.
We find evidence that the light variability of R 40 can be separated on the basis of at least 2 frequencies superimposed on a linear trend between JD 2446300 and 2449400. The longest cycle ( 1300 d) represents the SD oscillation (see van Genderen et al. 1997a,b), the shorter cycles describe the microvariations. Note that also for Sco such a long cycle of oscillation was found, and that the latter very likely corresponds to an SD phase as well (Sterken et al. 1997). A strong residual scatter remains; as in Sco it is the stochastic component of the light variation.
Our work indicates that R 40 provides a direct demonstration (based on contemporaneous highly-accurate data) that the so-called normal SD cycle ( 1300 d) does exist, and that the present bright state is a VLT-SD phase.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998