We stick with a target in the Sigma-Ori region, and have (yet another 😉) look at the object V505Ori. We have so far published two papers where it was discussed in detail: A survey for variable young stars with small telescopes – V. Analysis of TX Ori, V505 Ori, and V510 Ori, the HST ULLYSES targets in the σ Ori cluster, and PENELLOPE: VIII. Veiling and extinction variations of V505 Ori.
In those papers it ha become clear that the object is periodic, with a roughly 7d period. The cause for the periodicity is a warped inner dust disk. Material in the warp orbits in and out of view and causes the brightness changes. Since the amount, properties and distribution of the material in the warp changes, almost no two periods look the same.
In the above image we show just over 2 months of the V, R, and I-band light curve of the source from this winter. One can still see the periodicity, but also that the shape of the light curve is constantly changing. It is data like this that allows us to study the small scale mass movements in the inner disks.
One interesting feature visible are the one-day dimming events of almost one magnitude that occur during maximum light. the first one is visible at JD=2460932. These have the same 7d period, but in total they only show up 7 times and the disappear. This looks like some clump of material at the same position as the warp, but positioned ‘on the other side’ of it. The material survived for 7 orbits before it ‘moved on’. At some point a student should systematically search for these events ….