Intermediate report 28 Tau campaign
Intermediate Results of the 28 Tau Campaign
The attached overview shows that in spite of a clear increase of Vmag  from approx. HJD 2455000 (Fig. 1), the EW doesn't show such a strong rise (Fig. 2). This can only mean that the rise of Vmag has nothing to do, for that time period, with disk density or disk diameter (indicator for both = EW).
Maybe at present a “new orientation of the disk” takes place, causing less disk coverage of the star surface, which leads to an increase of Vmag. It´s interesting in that context, that our radial velocity measurements (Fig. 3) are showing an increase of the orbital period of the companion from 218 to 254 days.
This could be caused by gravitational interactions of the companion and the disk during each periastron, connected with disturbance of the disk geometry, which leads to the effect of the increase in brightness. Disk disturbances are obviously and clearly observed in the change of V/R ratio during each periastron (Fig. 4).
 from collaboration with Wolfgang Vollmann (Bundesdeutsche Vereinigung Veränderliche Sterne BAV, Berlin)
International Working Group ASPA
Active Spectroscopy in Astronomy