We usually look at different stars each week, but this week we make an exception. In last weeks post, we looked at the young star RW Ori which is situated in the sigma-Ori target field of HOYS. We briefly discussed a roughly weekly periodicity of varying, up to 0.5mag amplitude variations, which were overlaid with longer term (~50d), up to one mag variations.

The above images displays last weeks image again, showing the data of the previous observing season. The second image is the new data from this winter. As one can see there are very obvious differences. At the very beginning the roughly weekly variations are still visible. But later on they become more or less undetectable and are overshadowed by the large amplitude longer term variations.

These variations are now of a different timescale and amplitude. The variations during this winter are up to 2.5mag in the B-filter, one magnitude larger than in the last winter. Furthermore, they do not occur with the roughly 50d regularity as seen before. They now occur on shorter time scales and are more irregular.

This source is hence one of the interesting sources that change their behaviour over time. It is most likely caused by evolving structures in the inner part of the disk around this object. Hence, this is a good example why our approach of data taking, high cadence (daily) over long (10s of years) time scales, is important to capture the entire range of variability.